PBTCA (2-PHOSOPHONOBUTANE-1,2,4-TRICARBOXYLIC ACID)


PBTCA has low content of phosphoric and structural features of both phosphoric acid and carboxylic acid group, which enable its excellent scale and corrosion inhibition properties. 
Its antiscale property under high temperature is far better than that of organophosphines. 
Phosphonobutane tricarboxylic acid can improve zinc salt solubility, has good chlorine oxidation tolerance and good composite synergy.


PBTCA is a high efficient agent as scale and corrosion inhibitor. 
PBTCA is the excellent stabilizer for zinc salt. 
It is widely used in circulating cool water system and oilfield refill water system as scale and corrosion inhibitor, suitable to composite with zinc salt and copolymer. 
PBTCA can be used in situations of high temperature, high hardness, high alkali and high concentration index. 
In lavation fields, phosphonobutane tricarboxylic acid is used as chelating agent and metal detergent.

PBTCA is usually used together with zinc salt, copolymer, organophosphine, imidazole and other water treatment agents. 
When used alone, the dosage of 5-15mg/l is preferred.

EC / List no.: 253-733-5
CAS no.: 37971-36-1
Mol. formula: C7H11O9P

APPLICATIONS: Phosphonates derived from phosphorous (phosphonic) acid are employed in the applications of scale Inhibition, sequestration, dispersion and corrosion inhibition in addition to the main applications of agricultural chemicals such as fertilizers, pesticides, and soil conditioners. 
Phosphonates offer a wide range of sequestrants to control metal ions in aqueous systems. 
By forming stable water soluble complexes with multivalent metal ions, phosphonates prevent undesired interaction by blocking normal reactivity of metal ions. 
This ability contributes to function as threshold industrial water treatment and metal treatment processes (antiscalants, corrosion inhibitors, chelants, sludge conditioners, pulp bleachings, deflocculants, dispersants, metal cleaners, electroplating and crystal growth modifiers). 
Phosphonates are also used in manufacturing detergents, cosmetics and personal care products for special functions such as low levels iron control, stain removal, bleach stabilization, peroxide stabilization and anti-encrustation. 
Phosphonates existing in various compounds as acids or salts are marketed in the form of concentrated solutions.

PBTC or PBTCA or 2-Phosphonobutane-1,2,4-Tricarboxylic Acid has low content of phosphoric, has structural features of both phosphoric acid and carboxylic acid group, which enable its excellent scale and corrosion inhibition properties. 
Its antiscale property under high temperature is far better than that of organophosphines. 
It can improve zinc salt solubility, has good chlorine oxidation tolerance and good composite synergy.

PBTC or PBTCA or Phosphonobutane Tricarboxylic Acid has three carboxy groups in one molecule. 
This multifunctional carboxylic acid provides covalently linked structure with hydroxy group. 
Carboxylic acids form amide derivatives. 
PBTC or Phosphonobutane Tricarboxylic Acid is a raw material to produce aromatic polyimide resins having high resistance to thermal stresses. 
It is a metal chelator. 
It is used as a corrosion inhibitor and a metal-cleaning composition. 
It is used as a chemical intermediate. 
Its derivatives, acyl halides, anhydrides, esters, amides and nitriles, are used in making target products such as flavoring agents, pesticides, cosmetic ingredients, dyes, textile treatment agents, fungicides, and pharmaceuticals through further reactions of substitution, catalytic reduction, metal hydride reduction, diborane reduction, keto formation with organometallic reagents, electrophile bonding at oxygen, and Claisen condensation on carboxylic group.

PBTC or PBTCA or 2-Phosphonobutane-1,2,4-Tricarboxylic Acid is a high efficient agent as scale and corrosion inhibitor. 
PBTC is the excellent stabilizer for zinc salt. 
It is widely used in circulating cool water system and oilfield refill water system as scale and corrosion inhibitor, suitable to composite with zinc salt and copolymer. 
PBTC can be used in situations of high temperature, high hardness, high alkali and high concentration index. 
In lavation fields, it is used as chelating agent and metal detergent.

PBTC or Phosphonobutane Tricarboxylic Acid is usually used together with zinc salt, copolymer, organophosphine, imidazole and other Water Treatment Chemicals. 
When used alone, the dosage of 5-15mg/L is preferred.

PBTC (PBTC 2-phosphonobutane-l,2,4-tricarboxylic acid)is one of the most widely used scale inhibitors in the cooling water treatment industry


2-Phosphonobutane-1,2,4-tricarboxylic acid (PBTCA) 

2-Phosphonobutane-1,2,4-tricarboxylic acid (PBTCA) is an antiscalant that is widely used in reverse osmosis (RO) systems. 
Because of its high concentration in RO concentrate, eutrophication risk and anti-precipitation properties may affect subsequent treatments, therefore treatment strategies are needed to eliminate such substances.

2-Phosphonobutane -1,2,4-Tricarboxylic Acid (PBTCA)

Properties:
PBTCA has low content of phosphoric and structural features of both phosphoric acid and carboxylic acid group, which enable its excellent scale and corrosion inhibition properties. 
Its antiscale property under high temperature is far better than that of organophosphines. 
It can improve zinc salt solubility, has good chlorine oxidation tolerance and good composite synergy.

    
CAS No.37971-36-1
Chemical Name:2-Phosphonobutane-1,2,4-tricarboxylic acid
Synonyms: PBTC;PBTCA;2-Phosphonobutane-1;scale inhibitor PBTCA;PHOSPHONOBUTANETRICARBOXYLIC ACID;2-Phosphonobutane-1,2,4-TricarboxyL;2-Phosphonobutan-1,2,4-tricarbonsure;2-phosphono-1,2,4-butanetricarboxylic;3-Carboxy-3-Phosphonohexanedioic Acid;2-Phosphonobutane-1,2,4-tricarbonicacid

2-PHOSOPHONOBUTANE-1,2,4-TRICARBOXYLIC ACID; 2-PHOSPHONOBUTANE-1,2,4-TRICARBOXYLIC ACID; 2-PHOSPHOBUTANE-1,2,4-TRICARBOXYLIC ACID; 2,4-Butanetricarboxylicacid,2-phosphono-1; PBTC; PBTCA; 2-phosphono-1,2,4-butanetricarboxylic; -Phosphono-1,2,4-butanetricarboxylicacid; 2-phosphono-1,2,4-butanetricarboxylic acid; aqueous 2-Phosphonobutane-1,2,4-tricarbonicacid; 2-Phosphonobutan-1,2,4-tricarbonsure; 4-butanetricarboxylicacid,2-phosphono-2; 
PHOSPHONOBUTANETRICARBOXYLIC ACID; 1,2,4-Butanetricarboxylic acid, 2-phosphono-scale inhibitor PBTCA; 2-Phosphono-1,2,4-butantricarboxylic acid(PBTC); 2-Phosphonobutane-1,2,4-tricarboxylic Acid (ca. 50% in Water); PBTC(2-Phosphonobutane-1,2,4-tricarboxylicacid); 3-Carboxy-3-Phosphonohexanedioic Acid; 2-Phosphonobutane-1,2,4-tricarboxylic acid ; PBTC; Phosphonobutane-1,2,4-Tricarboxylic Acid; 3-Carboxy-3-phosphonohexanedioic Acid;
PBTC; 2-Phosphonobutane -1,2,4-tricarboxylic acid, 50% in water; 2-Phosphonobutane-12-Phosphonobutane-1,2,4-tricarboxylic acid (50% Aqueous solution)Inhibitor 2-Phosphonobutane -1,2,4-Tricarboxylic Acid; PBTCA; 2-Phosphonobutane-1,2,4-TricarboxyL37971-36-137971-63-1; C7H11O9P; Phosphonate antiscalant; Water treatment; Industrial/Fine Chemicals

Usage:
PBTCA is a high efficient agent as scale and corrosion inhibitor. 
PBTCA is the excellent stabilizer for zinc salt. 
It is widely used in circulating cool water system and oilfield refill water system as scale and corrosion inhibitor, suitable to composite with zinc salt and copolymer. 
PBTCA can be used in situations of high temperature, high hardness, high alkali and high concentration index. 
In lavation fields, it is used as chelating agent and metal detergent.
PBTCA is usually used together with zinc salt, copolymer, organophosphine, imidazole and other water treatment agents. 
When used alone, the dosage of 5-15mg/l is preferred.

Package and Storage: 200L plastic drum,IBC(1000L),customers’ requirement. 
Storage for one year in shady room and dry place.

Safety Protection:
Acidity, Avoid contact with eye and skin, once contacted, flush with water.

Keywords:
PBTCA;PBTC;PHOSPHONOBUTANE TRICARBOXYLIC ACID;2-Phosphonobutane -1,2,4-Tricarboxylic Acid;2-Phosphonobutane-1,2,4-tricarboxylic acid PBTC;


Properties:
Water Treatment chemical PBTCA, a good corrosion inhibitors, is widely used in circulating cool water system and oilfield water injection system antifouling treatment.
Water Treatment chemical PBTCA is used as a corrosion inhibitor for industrial water treatment. 
This product has excellent complexing ability with Ca2 +, Zn2 +, Cu2 +, Mg2 +. 
The suitable PH range is from 7.0 to 9.5. 
It can operate at high temperature, high hardness, and high alkalinity conditions. 
It allows coolingwater concentration factor increased to seven or more.

Specification
Appearance: Colorless or Light Yellow Transparent Liquid
Active Acid (PBTCA): % 50.0 Min
Phosphorous Acid (as PO33-): % 0.5Max
Phosphoric Acid (as PO43- ): % 0.5Max
Density (20°C) g/cm3 : 1.25 min
PH (1% Water Solution):2.0 max

Application: Water Treatment chemical PBTCA is a high efficient agent as scale and corrosion inhibitor. 
It is the excellent stabilizer for zinc salt. 
It is widely used in circulating cool water system and oilfield refill water system as scale and corrosion inhibitor, suitable to composite with zinc salt and copolymer. 
It can be used in situationsof high temperature, high hardness, high alkali and high conc-entration index. 
In lavation fields, it isused as chelating agent and metal detergent. 
Water Treatment chemical PBTCA is usually used together with zinc, salt,copolymer, organophosphine, imidazole and other water treatment agents. 
When used alone, the dosage of 5-15mg/L is preferred.

2-phosphonobutane-1,2,4-tricarboxylic acid
EC / List no.: 253-733-5
CAS no.: 37971-36-1
Mol. formula: C7H11O9P

PBTC; PBTCA; (Phosphonobutane Tricarboxylic Acid 50%)
Properties:
Phosphonobutane tricarboxylic acid is excellent as both antiscalants and corrosion inhibitors, because of its structural feature of carboxylic acid and phosphoric acid. 
The PBTC chemical is stable and high efficiency in the condition of high hardness, temperature, pH value, and indexed matter concentration.

While usually building with other organophosphates, PBTC acid also widely works together with zinc salts whose solubility it will increase. 
Phosphonobutane tricarboxylic acid can improve zinc salt solubility. 
PBTC 50% also have a higher tolerance to oxidation agents like chlorine or bromine in the system.

The first reaction for PBTC 50% production is between dialkyl phosphite (usually dimethyl phosphate in China) and maleic acid dimethyl ester under basic catalyst. 
Tetraalkyl ester of phosphonosuccinic acid forms and immediately reacted with methyl acrylate. The following thereupon saponification yields PBTC.

CAS No.: 37971-36-1, from ChemIDplus, EPA Chemicals under the TSCA, EPA DSStox, European Chemicals Agency (ECHA). 40372-66-5, from ChemIDplus, European Chemicals Agency (ECHA).

EC No.: 253-733-5, from the European Chemicals Agency (ECHA). 254-894-4, from the European Chemicals Agency (ECHA).

Molecular Formula: C7H11O9P

Usage:
As an excellent inhibitor to both scale and corrosion, PBTC 50% is an excellent stabilizer for zinc salt. 
It is widely applied in the refilling system and circulated cooling system for oil fields, steel mills, and mines. 
2-Phosphonobutane-1,2,4-tricarboxylic acid can be used in situations of high temperature, high hardness, high alkali, and high concentration index.

Besides, phosphonobutane tricarboxylic acid is used to chelate metal ions in lavation and detergent industries as metal detergent. 
In pH 7-10, 5-15 mg/L is recommended if only PBTC acid. 
PBTC 50% is usually used together with the zinc salt, copolymer, organophosphine, imidazole, and other water treatment agents. 
When used alone, the dosage of 5-15 mg/L is preferred.

Molecular Weight: 270.13
1,2,3-BUTANETRICARBOXYLIC ACID, 2-PHOSPHONOTRIBUTYL
1,2,4-Butanetricarboxylic acid, 2-phosphono
1,2,4-Butanetricarboxylic acid, 2-phosphono-
2-PHOSHONOBUTANE-, 1,2,4-TRICARBOXYLIC ACID
2-PHOSPHOBUTANE-1,2,4-TRICARBOXYLIC ACID
2-Phosphono-1,2,4 butanetricarboxylic acid
2-PHOSPHONO-1,2,4-BUTANETRICARBOXYLIC ACID
2-Phosphono-1,2,4-butanetricarboxylic acid (aerosol), as PBTC
2-phosphono-1,2,4-butanetricarboxylic acid; 2-phosphonobutane-1,2,4-tricarboxylic acid; Dequest 7000
2-PHOSPHONO-1,2,4-BUTANTRICARBONSAEURE 50 % WAESSERIGE LOESUNG
2-Phosphonobutane-1,2,4-tricaboxylic acid
2-phosphonobutane-1,2,4-tricarboxylic acid
2-Phosphonobutane-1,2,4-tricarboxylic acid, >5% in a non hazardous diluent
2-PHOSPHONOTRICARBOXYBUTYL PHOSPHATE
3-CARBOXY-3-PHOSPHONO-ADIPINSAEURE
3-Carboxy-3-phosphonohexanedioic acid
BUTANE-1,2,4-TRICARBOXYLIC ACID, 2-PHOSPHONO-
PBTC
PHOSPHONOBUTANETRICARBOXYLIC ACID
Phosponobutane tricarboxylic acid (PBTCA)

IUPAC names
2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC)

PBTCA
Trade names
Aquacid 101EX
Aquacid 101EX; PBTCA (AM) (50% aqueous solution)PBTCA-AM; PBTCA-AM; PBTCA®AM; PBTC; PBTCA; PHOSPHONOBUTANE TRICARBOXYLIC ACID; Uniphos 100
PBTCA (AM) (50% aqueous solution)
PBTCA
PHOSPHONOBUTANE TRICARBOXYLIC ACID
Uniphos 100

Other identifiers
37971-36-1
CAS number: 94386-13-7
2-PHOSPHONOBUTANE-1,2,4-TRICARBOXYLIC ACID
37971-36-1
1,2,4-Butanetricarboxylic acid, 2-phosphono-
PBTC
2-Phosphono-1,2,4-butanetricarboxylic acid
2-Phosophonobutane-1,2,4-tricarboxylic acid
C7H11O9P
2-Phosphonobutane-1,2,4-tricarbonic acid
EINECS 253-733-5
phosphonobutanetricarboxylic acid
2-Phosphono butane-1,2,4-tricarboxylic acid
EC 253-733-5
3-Carboxy-3-phosphonohexanedioic Acid
Butanetricarboxylic acid, 2-phosphono-1,2,4-
W-2646
(S)-2-phosphonobutane-1,2,4-tricarboxylic acid
2-Phosphonobutane-1,2,4-tricarboxylic acid 50% in water
2- Phosphonobutane -1,2,4-tricarboxylic acid, tetra sodium salt
2-Phosphonobutane-1,2,4-tricarboxylic acid(50% Aqueous solution)
81897-36-1
CAS No.    37971-36-1
EC No.    n/a
Synonyms: 1,2,4-Butanetricarboxylic acid; 2-phosphono-; 2-Phosphono-1,2,4-butanetricarboxylic acid; 2-Phosphonobutane-1,2,4-tricarbonic acid; 1,2,4-tricarboxylic acid; Butanetricarboxylic acid


2-Phosphonobutane-1,2,4,-tricarboxylic acid (PBTC)
​2-Phosphonobutane-1,2,4,-tricarboxylic Acid (PBTC) is a very effective scale inhibitor used in various industrial applications. 
Due to its higher performance properties it is a very cost effective inhibitor compared to standard Phosphonates such as HEDP/ATMP. 
This is mainly due to superior stability to chlorine, bleach and bromine. In cooling water PBTC performs well at high PH or temperatures. 
It further shows high effectiveness in high alkaline solutions such as industrial cleaners.

Applications:
Cooling water systems / industrial water treatment
Industrial detergents
Disinfectants
Liquid dishwashing concentrates
Metal surface treatment as corrosion inhibitor for steel
Retardant in concrete
Sequestering agent in textile auxiliaries


(S)-2-phosphonobutane-1,2,4-tricarboxylic acid; 1,2,4-Butanetricarboxylic acid, 2-phosphono-1,2,4-Butanetricarboxylic acid,2-phosphono-2- Phosphonobutane -1,2,4-tricarboxylic acid, tetra sodium salt2-Butanephosphate-1,2,4-tricarboxylic acid (PBTC)2-Phosophonobutane-1,2,4-tricarboxylic acid2-Phosphono butane-1,2,4-tricarboxylic acid2-Phosphono-1,2,4-butanetricarboxylic acid2-Phosphonobutane -1,2,4-Tricarboxylic Acid2-Phosphonobutane 1,2,4-tricarboxylic acid (PBTC)2-Phosphonobutane-1,2,4-tricarbonic acid2-Phosphonobutane-1,2,4-tricarboxylic acid (ca. 50% in water)2-Phosphonobutane-1,2,4-Tricarboxylic acid [PBTCA]2-Phosphonobutane-1,2,4-tricarboxylic acid 50% in water2-Phosphonobutane-1,2,4-Tricarboxylic Acid(PBTCA)37971-36-13-Carboxy-3-phosphonohexanedioic Acid


PBTCA
PBTCA is an aqueous solution of PBTC for water treatment and cleaning agents.  
PBTCA AM can be used in water treatment applications as an effective scale inhibitor in cooling water circuits and process water systems.  
In addition, PBTCA AM is also an excellent corrosion inhibitor for carbon steel.  
PBTCA AM is most effective at neutral to high pH and high hardness, also making it an effective dispersing agent for alkaline cleaning agents and detergents.  
PBTCA AM has outstanding solubility, and can be mixed with strong acid or alkali solutions.

Chemistry:
Acids
Functions:
Corrosion Inhibitor
Dispersant
Markets:
Household, Industrial and Institutional Cleaners
Water Treatment
Market Segments:
Industrial
Institutional
Applications:
Industrial Cleaners and Degreasers
Institutional Cleaners and Degreasers
Municipal Wastewater Treatment

PBTCA

PBTCA is a highly effective scale and corrosion inhibitor, which active ingredient
PBTC was developed by the Bayer AG. Main field of application are the treatment of cooling and process water as well as the area of cleaning formulations.
Chemical name PBTCA is a 50 % solution of 2-Phosphonobutane-1,2,4-tricarboxylic acid (abbreviation: PBTC) in water
CAS Reg. No. 37971-36-1
Empirical formula C7H11O9P
Molecular weight 270.13 g/mol
Physical form clear, colorless to yellowish, low-viscous,almost odorless liquid
Health and safety information Safety data and precautions which must be observed under all circumstances are to be found in EU Safety Data Sheet No. 000969.

Active agent content 50 ± 1 % by mass 2022-2303301-00D Orthophosphate content (as PO43-) ≤ 0.2 % by mass 2022-2303601-00D
Density at 20 °C : 1.285 ± 0.015 g / cm³ DIN 51 757
Turbidity ≤ 10 NTU (= TE/F) DIN 38 404, part 2
Gardner color ≤ 2 - DIN 53 995
Hazen color (at dispatch) ≤ 100 (APHA) ISO 6271
Additional Information
Property Typical Value Unit Test Method
PBTC share *) ca. 84 mol-% 2012-0567802-00D
31P-NMR spectroscopy
Viscosity at 20 °C 17.5 ± 7.5 mPa .s DIN 53 015
Refractive index at 20 °C (n20D) :1.417 - DIN 53 491
pH value of the aqueous solution with 2 % PBTCA:  1.6 ± 0.1 - DIN 38 404, part 5
Iron (as Fe): ca. 5 mg / l AC-F/V/246/03/88
Total chlorine (as Cl): ca. 4 mg / l 2011-0380801-93D
Hazen color (ex works) :10 (APHA) ISO 6271*) referred to phosphorus compounds
These material properties are typical properties and, unless specifically indicated otherwise, are not to be considered as delivery specification.
product data sheet: PBTCA

ISO tank container
1250 kg IBC container
250 kg polyethylene drum

Storage
The product can be stored in tightly sealed original packaging without a deterioration of quality for a period of at least two years in case of appropriate storage. 
Material whichBhas solidified on account of cold (solidifying point approx. – 15 ° C) can be defrosted without a reduction of quality.

Materials
The following materials have proved suitable for the metering tanks, pumps and lines for PBTCA: glass, stainless steel (e.g. DIN W1.4571 = US AISI 316 TI), plastics such as polyethylene, polytetrafluoro ethylene (PTFE) and polyvinyl chloride (PVC). 
Seals should be made form PTFE or graphite.

Peculiarity
No labeling is required for PBTCA under Germany’s regulations on hazardous substances and the equivalent EU Directives.

PBTCA - effects
Scale inhibition

PBTCA® has proved highly effective as a threshold inhibitor. 
Very low additions (ppm range), i.e. in far less than sub-stoichiometric concentrations (calculated on the hardness of the water), prevent the formation of scale and incrustations, respectively. 
Even water which is highly over-saturated with hardness constituents such as calcium
carbonate remain without scale when PBTCA is added. 
The outstanding effectiveness of PBTCA is proofed by a multitude of practically orientated trials, which can be discussed and are available. 

Dispersion The adsorption of the PBTC anion on inorganic particles suspended in water results in a negative charge on their surfaces and thus in an improvement in
dispersibility. 
This is why neutralized PBTCA is used as a dispersion agent /deflocculation agent for inorganic slurries and slips.

Corrosion inhibition: Under the conditions found in cooling water,
PBTCA is a good corrosion inhibitor for carbon steel. 
In the case of relatively soft water, it is common to combine PBTCA® with synergistic substances (phosphates,zinc salts). 
In water of higher hardness or with sufficiently high alkalinity (approx. 300 mg/l or more, calculated as calcium carbonate), formulations containing PBTCA and no inorganic components – known as all-organic formulations – are highly effective. 
In alkaline cleaning agents, the corrosion-inhibiting effects of PBTCA on aluminium can be a benefit.

PBTCA - properties
Solubility
PBTCA can be mixed in any ratio with water. It is soluble in lyes, e.g. sodium hydroxide solution, and in acids, e.g. sulfuric acid. Because of its outstanding solubility,
even formulations which already contain high concentrations of other active substances can be optimized by the addition of PBTCA.
Neutralization
PBTCA is a strong acid. When it is mixed with alkali, a heat of neutralization of around 210 kJ (approx. 50 kcal) is released per mole PBTC. This is why the final
temperature of a solution produced without cooling by neutralizing PBTCA®  AM (commercial product) with 20 % sodium hydroxide solution is around 50 °C higher
than the temperature of the starting solutions. If higher concentrations of sodium hydroxide are used, it must be expected that the solution will begin to boil if it is not
cooled. 

The safety precautions which normally apply for acid-base neutralization must therefore be observed when mixing PBTCA commercial product with concentrated sodium hydroxide solution.

Stability to hydrolysis
PBTCA can be used in aqueous solutions, lyes and acids up to temperatures considerably above 100 °C. 
Investigations of the stability have shown that, for example, the half-life (50 % degradation to orthophosphate) in process water with a pH of 9 and a temperature of 200 °C is around 20 hours.
Inhibitor loss / turbidity region When combined with polyvalent cations, threshold inhibitors can form poorly soluble salts which, when they exceed the solubility limits, often result in turbidity. 
Field experience and special trials have shown that the tendency of the inhibitor to precipitate caused by, for example, Ca2+ and  Fe(III) is much lower in PBTCA than in other phosphonates. 
For this reason, inhibitor losses are low when PBTCA is used. 
 Fig. 1: Tendency of the phosphonates to form undissolved calcium salts
0
20
40
60
80
100
0 5 10 15 20
phosphonate start content [mg/l]
residual phosphonate content [%]
PBTC
HEDP
ATMP
Conditions
Ca2+ concentration = 200 mg/l
pH: 8.5 temperature: 60°C storage time: 24 h
product data sheet: PBTCA

Stability to chlorine, bleaching lye and other oxidizing agents Because of its outstanding stability to chlorine and bleaching lye, PBTCA is often used together with bleaching lye in disinfectant alkaline cleaning agents. 
When manufacturing formulations which contain PBTCA, alkali and bleaching lye, PBTCA must always be neutralized before addition of the latter. 
Like all acids, acidic PBTCA generates toxic chlorine gas when mixed with bleaching lye. 

Under cooling water conditions (neutral to slightly alkaline environment), the high stability of PBTC to chlorine and hypochlorite is also not matched by most other phosphonates. 
The product also has outstanding stability to bromine and hypobromite which are generated by adding chlorine to bromide. 
Bromine does not affect PBTC even after many hours but destroys HEDP, for example very quickly (cp. fig. 2). 
Unlike aminomethylene phosphonates such as ATMP or DTPMP, PBTC is also stable under operating conditions to chlorine dioxide, which is used to prevent reinfection in bottle-washing plants.

Fig. 2: Stability of phosphonates to chlorine and bromine
Conditions for test a): total hardness SE = 3.0 mmol/l (300 mg/l as CaCO3); total alkalinity KS 4.3 = 3.2 mmol/l (160 mg/l as CaCO3);start pH = 8.5; storage temperature 60°C phosphonate concentration: 10 mg/l; chlorine concentration (as bleaching lye): 10 mg/l Conditions for parallel test b):as in a) plus 1 mg/l bromide
The residual phosphonate concentration was calculated from the analytical determined orthophosphate concentration.
0
20
40
60
80
100
0123456
time [h]
residual phosphonate content [%]
PBTC a) b)
HEDP a)
ATMP a)
ATMP b)

PBTCA - ecology and toxicology

Biodegradation
Bacteria which degrade PBTCA were isolated from natural sources (activated sludge, river water and river sediment).
Degradation is rapid if a second carbon source is available to the bacteria and inorganic phosphate is present in concentrations of just a few mg/l.
In pond water, biodegradation was found to take place under natural conditions without isolation and adaptation of the bacterial population. 
The half-life was 28 days. 

Only 0.3 % of radioactively marked PBTC could still be found in the water after 208 days. 
In contrast, in biodegradability tests using standard methods (e.g. OECD 301 D, 302B), PBTC was found to be not easily degradable. 

Degradation by light In water, PBTC is degraded by light. 
The rate of degradation depends on the intensity of the light and on the other constituents in the natural water. 
In the presence of traces of iron or nitrate, the half-life of PBTC is just a few hours.
Adsorption on activated sludge and sediment Trials have shown that more than 95% of PBTC is adsorbed by activated sludge. 
If the water treatment plant has a third treatment stage (phosphate precipitation with aluminium or iron (III) salts) PBTC residues are also precipitated with the consequence that the discharge from the waste water
treatment plant contains virtually no PBTC. 
PBTC is eliminated from standing water over resting sediment through adsorption on the sediment with a half-life of five days. 
If the sediment is kept in suspension, the adsorption process is much quicker (half-life of just a few hours). 
Complex formation PBTC is a much weaker complexing agent than EDTA. 
There is no reason to expect a remobilization of heavy metals from sediment by PBTC. 
This has been confirmed by laboratory trials.
Ecotoxicity
Trials have shown that PBTCA has no harmful effect on aquatic organisms (fish, daphnia, algae, bacteria) or on terrestrial organisms (Earthworms) and sediment organisms (midge larvae).

product data sheet: PBTCA AM


PBTCA has low content of phosphoric, has structural features of both phosphoric acid and carboxylic acid group, which enable its excellent scale and corrosion inhibition properties. 
Its antiscale property under high temperature is far better than that of organophosphines.


SYNONYMS:
PBTCA; PBTC; PHOSPHONOBUTANE TRICARBOXYLIC ACID; 2- Phosphonobutane -1 ,2,4-Tricarboxylic Acid; 2-Phosphonobutane-1,2,4- tricarboxylic acid PBTC
CAS No: 37971-36-1
MOLECULAR FORMULA: C7H11O9P
OTHER TRADE NAME: Belclene 650

PROPERTIES:
PBTC is a 50% aqueous solution of 2-phosphonobutane-1, 2, 4-tricarboxylic acid (PBTC) designed to control calcium scale formation and precipitation in highly stressed alkaline Industrial Water Treatment (IWT) and boiler systems. 
PBTC has been widely used in industry as a sequestering agent and calcium carbonate scale inhibitor for applications in industrial water treatment and industrial cleaning.

SPECIFICATION:
Appearance Clear, Colorless to pale yellow aqueous solution
Active Content (as PBTC) 49.0 - 51.0%
Phosphorous acid (as PO33-) 0.5% max
Phosphoric acid (as Po43-) 0.2% max
pH (1% solution) 1.5 - 1.9
Density (20◦ C) g/cm3: 1.27 - 1.31
Iron(as Fe): 10.0ppm max.
Chlorides (as CL-) 10.0ppm max.

USAGE:
It is mainly used as Scale & Corrosion Inhibitor in Cooling, Boiler & Field Water Treatment .

2-Phosphonobutane-1,2,4-tricarboxylic acid (PBTCA) is an antiscalant that is widely used in reverse osmosis (RO) systems. 
Because of its high concentration in RO concentrate, eutrophication risk and anti-precipitation properties may affect subsequent treatments, therefore treatment strategies are needed to eliminate such substances


Whether PBTCA belongs to an environmentally-friendly scale inhibitor or not, many customers have this question when purchasing. 
Before determining whether PBTC acid is an environmentally friendly scale inhibitor, it is necessary to talk about the types of scale inhibitors.

pbtca-environment friendly scale inhibitor
So far, the types of scale inhibitors that are widely used in the water treatment industry are mainly the following. 
Organic phosphine scale inhibitor (phosphorus), organic phosphonate scale inhibitor (phosphorus), compound scale inhibitor, environmental scale inhibitor (PESA, PASP, etc.), low phosphorus-containing scale inhibitor (such as PBTCA).

Among the organic phosphine type scale inhibitors, PBTCA is one of the lowest scale inhibitors. 
The reason is that its structural characteristics contain only one phosphorus element in the molecular formula. 

PBTC chemical has the characteristics of phosphonic acid and a carboxylic acid, which has good scale inhibition and corrosion inhibition performance and is much better than other organic phosphonic acid scale inhibitors.

PBTCA has low phosphorus content and is ideal for scale inhibition. 
Within the foreseeable range, PBTC acid is still the main product in water treatment chemicals and can be used as a compound or as a separate ingredient.

As the country’s environmental requirements become more stringent, the use of more water treatment agents with higher phosphorus content is limited. 
PBTC acid meets national environmental requirements. 

PBTCA is relatively affordable and is a good choice for most companies.

It is well known that organic phosphine water treatment agents are the most widely used in monomer water treatment agents. 

Faced with more environmental pressures, water treatment agents are moving towards diversification. For example, compounding, copolymer, polymer, and other water treatment agents are more targeted when used.

The full name of PBTCA is 2-phosphonobutane-1 2 4-tricarboxylic acids.

The advantages of 2-phosphonic butane-1 2 4-tricarboxylic acid are as follows.

Good chemical stability, not easy to decompose, high-temperature resistance, strong acid, and alkali resistance and oxidant resistance. 
It is used together with oxidizing biocides such as sodium hypochlorite and chlorine.
PBTCA has a much higher tolerance for Ca2+. 
It is used under the conditions of high hardness, high alkali, high temperature, high pH and high concentration. 
It can still achieve a good scale inhibition effect.
PBTCA has a high solubility in zinc salts and good stability. 
It can be combined with zinc salt to obtain a very good corrosion inhibition effect.
PBTCA has low phosphorus content (only 11-15%), and it has a low dosage and is not subject to environmental emissions. 
It is one of the more advanced circulating cooling water treatment chemicals in China.
Among the organic phosphine water treatment agents, PBTCA is one of the most suitable organic phosphine monomers for environmentally friendly scale inhibitors due to its own characteristics and low phosphorus content. 
PBTC acid has the structural properties common to phosphonic acids and carboxylic acids.

Therefore, it is relatively superior to other organic phosphonic acids, and it has excellent scale inhibition and corrosion inhibition properties. 
At the same time, PBTC chemical is resistant to high temperature and high alkali, and its scale inhibition performance at high temperature is much higher than other commonly used organic phosphines. 
PBTCA is also used as a special corrosion and scale inhibitor for high temperature.

PBTCA is the most widely used in the combination of high-efficiency corrosion and scale inhibitors. 
It is one of the best performance products among all known scale inhibitors. 
At the same time, PBTC has functional diversity. 

For example, PBTCA can also be used as a stabilizer for zinc salts. 
In addition, PBTCA can also be used as a chelating agent and metal cleaner in the washing industry.

PBTCA is currently mainly used for corrosion and scale inhibition of circulating cooling water systems and oilfield refill systems. 
PBTC acid is compounded with zinc salt and copolymer during use and is used for high temperature, high alkali, high hardness water quality.

If you want to know more about PBTCA, you contact us by email:  info@atamankimya.com


Physicochemical Aspects of 2-Phosphonobutane-l,2,4-Tricarboxylate (PBTC) And Its Effect on CaCO3 Crystal Growth

Industrial water systems often suffer from undesirable inorganic deposits, such as calcium carbonate, calcium phosphates, calcium sulfate, magnesium silicate, and others. 
Synthetic water additives, such as phosphonates and phosphonocarboxylates, are the most important and widely utilized scale inhibitors in a plethora of industrial applications including cooling water, geothermal drilling, desalination, etc. 
The design of efficient and cost-effective inhibitors, as well as the study of their structure and function at the molecular level are important areas of research. 
This study reports various physicochemical aspects of the chemistry of PBTC (PBTC 2-phosphonobutane-l,2,4-tricarboxylic acid), one of the most widely used scale inhibitors in the cooling water treatment industry. 
These aspects include its CaCO3 crystal growth inhibition and modification properties under severe conditions of high CaCO3 supersaturation, stability towards oxidizing microbiocides and tolerance towards precipitation with Ca2+. 
Results show that 15 ppm of PBTC can inhibit the formation of by ,-,35 %, 30 ppm by ,-,40 %, and 60 ppm by ,--44 %. 
PBTC is virtually stable to the effects of a variety of oxidizing microbiocides, including chlorine, bromine and others. 
PBTC shows excellent tolerance towards precipitation as its Ca salt. 
Precipitation in a 1000 ppm Ca2+ (as CaCO3) occurs after 185 ppm PBTC are present.


Calcium carbonate /1/ and calcium phosphate(s) /2/ are the most frequently encountered deposits in industrial water systems. 
Their accumulation greatly diminishes effective heat transfer, interferes with fluid flow, facilitates corrosion processes, and can worsen microbiological fouling. 
These phenomena are most critical in cooling water applications, where incoming water passes through a heat exchanger, cools a "hot" process and is sent back to repeat the same cooling process after it is cooled by forced evaporation. 
This water loss by evaporative cooling results in high supersaturation levels of dissolved ions. 
Eventually, massive precipitation of sparingly soluble mineral salts can occur, either in bulk or on a surface that, in some cases, causes catastrophic operational failures. 
These usually require chemical and/or mechanical cleaning of the adhered scale, in the aftermath of a scaling event. 
Silica and silicate salts are such examples.
Scale growth can be mitigated by use of scale inhibitors. 
They are key components of any chemical water treatment added to process waters in "ppm" quantities and usually work synergistically with dispersant polymers.

Phosphonates belong to a fundamental class of such compounds/8/used extensively in cooling water treatment programs, oilfield applications and corrosion control. 
PBTC, HEDP (hydroxyethylidenediphosphonate) and AMP (amino-tris-methylenephosphonate) are "popular" and effective commercial scale inhibitors. 
Phosphonates are thought to achieve scale inhibition by adsorbing onto specific crystallographic planes of a growing crystal nucleus after a nucleation event. 
This adsorption prevents further crystal growth and agglomeration into larger aggregates.
Study of phosphonates is attracting additional interest due to their potential uses in sequestering toxic metal ions in industrial effluents. 
Moreover, their established use as bone resorption agents and in treatments for osteoporosis makes them desirable from a biological/pharmaceutical perspective.


flow, facilitates corrosion processes, and can worsen microbiological fouling. 
These phenomena are most critical in cooling water applications, where incoming water passes through a heat exchanger, cools a "hot" process and is sent back to repeat the same cooling process after it is cooled by forced evaporation. 
This water loss by evaporative cooling results in high supersaturation levels of dissolved ions. 
Eventually, massive precipitation of sparingly soluble mineral salts can occur, either in bulk or on a surface that, in some cases, causes catastrophic operational failures. 
These usually require chemical and/or mechanical cleaning of the adhered scale, in the aftermath of a scaling event. 
Silica and silicate salts are such examples/5/. Scale growth can be mitigated by use of scale inhibitors. 
They are key components of any chemical water treatment added to process waters in "ppm" quantities and usually work synergistically with dispersant polymers. 
Phosphonates belong to a fundamental class of such compounds used extensively in cooling water treatment programs, oilfield aplications and corrosion control. 
PBTC, HEDP (hydroxyethylidenediphosphonate) and AMP (amino-tris-methylenephosphonate) are "popular" and effective commercial scale inhibitors. 
Phosphonates are thought to achieve scale inhibition by adsorbing onto specific crystallographic planes of a growing crystal nucleus after a nucleation event. 
This adsorption prevents further crystal growth and agglomeration into larger aggregates. 
Study of phosphonates is attracting additional interest due to their potential uses in sequestering toxic metal ions in industrial effluents. 
Moreover, their established use as bone resorption agents and in treatments for osteoporosis makes them desirable from a biological/pharmaceutical perspective.

Phosphonates
Problems arising out of interference of the undesired metallic ions in the processes, the formation of scales and deposits in the equipment like heat exchangers etc. are frequently encountered in the industry. 
Phosphonates offers effective solutions to many of these problems with its array of diverse key properties. 
These products are available in acid form as well as in the form of sodium salts, with each molecule having distinct advantage for specific applications.

Key Properties:
1. Sequestration: The multivalent metal ions like Calcium, Magnesium, Copper, Zinc etc. can be complexed with Phosphonates at stoichometric levels, forming a stable water soluble complex that suppresses unwanted effects of metal ions in various processes.
2. Threshold effect: The scalant mixture can be kept in a solution form by a low concentration of Phosphonates (below the stoichiometric levels), exhibiting a threshold effect.
3. Hydrolytic Stability: Phosphonates are highly stable and resistant to hydrolysis over a wide range of pH and temperatures unlike polyphosphates.
4.Deflocculation (Dispersion): Phosphonates gets adsorbed on the growth sites of scalants. This hinders the growth of crystals from getting cluttered.
5. Corrosion Control: Phosphonates in combination with Zinc Phosphate, Molybdate or Nitrate, offers synergistically enhanced corrosion inhibition in water systems compared to any of the individual components.
6. Chlorine Stability: In the industry, Chlorine is used as an oxidizing agent as well as a biocide. Phosphonates are stable in systems containing chlorine.

Applications: Phosphonates  are used for: Cooling water treatment, Boiler water treatment, Soaps and Detergents, Textile processing, Bottle washing, Industrial & Institutional cleaners, Deflocculation of slurries, Antiscalant formulations for oilfields, Sea water evaporators, Reverse Osmosis & Sugar processing

PBTCA is known as 2-phosphonobutane-1 2 4-tri2carboxylic acid. From a structural point of view, it contains one – PO3H2 and three -COOH.

BTCA is a highly effective scale inhibitor. PBTCA also has a strong scale inhibition effect under the harsh conditions of high temperature, high hardness, and high pH. Especially in the presence of Fe3+, its scale inhibition and corrosion inhibition performance are better than other organic phosphonates.

PBTCA has a good synergistic inhibition effect with zinc salts and polyphosphates.

In addition, PBTCA has a low phosphorus content and is difficult to form insoluble organic calcium phosphonate scale. 
It has good antioxidant properties and good stable zinc action.

PBTCA is stable in nature. 
It is not easily damaged by acid and alkali, is not easy to hydrolyze, and is resistant to high temperatures. 
PBTCA is also resistant to oxidative biocides.

With the improvement of water treatment effect requirements and the increasingly strict requirements of environmental protection regulations, the application of PBTCA has received more and more attention.

PBTCA and HEDP have no difference in appearance and are all colorless or light yellow transparent liquid. 
Their quality control indicators are also very similar.

The most important indicator of the “active component” analysis principle is also the addition of sulfuric acid and decomposer under heating conditions. 
Convert macromolecules to phosphates. After adding the quinoxaline ketone solution, a quinoline phosphomolybdate precipitate is formed. 
After filtration, washing, drying, weighing, minus the content of orthophosphorus and phosphorous, the active component is obtained. 
The two are not only the same analysis principle but also the analysis steps.

The difference is that PBTCA also requires the use of a nuclear magnetic resonance (NMR) spectrometer to measure specific chemical shifts on each 13C NMR spectrum to determine its structure. 
The specific chemical shift on the 13P NMR spectrum was measured to determine its purity.

This cannot be done with existing analytical tools. 
If there is doubt about the sample, the analysis of each indicator alone cannot distinguish between the two.

In this regard, after analysis, it was found that even though the active components of both were 50%. 
However, due to the different molecular structures of HEDP and PBTCA, the phosphorus content of the two is different.

Whether spectrophotometry for determining total phosphorus content in existing circulating water can be utilized. 
They are decomposed under certain conditions to become phosphate. 
The total phosphorus content is then determined, and a preliminary determination can be made based on the difference in total phosphorus content.


2-Phosphonobutane -1,2,4-Tricarboxylic Acid 
PBTCA has low content of phosphoric, has structural features of both phosphoric acid and carboxylic acid group, which enable its excellent scale and corrosion inhibition properties. 
Its antiscale property under high temperature is far better than that of organophosphines. 
It can improve zinc salt solubility, has good chlorine oxidation tolerance and good composite synergy.

CAS No. 37971-36-1

Usage:PBTCA is a high efficient agent as scale and corrosion inhibitor. 
It is the excellent stabilizer for zinc salt. It is widely used in circulating cool water system and oilfield refill water system as scale and corrosion inhibitor, suitable to composite with zinc salt and copolymer. 
It can be used in situations of high temperature, high hardness, high alkali and high concentration index. 
In lavation fields, it is used as chelating agent and metal detergent.


2-Phosphonobutane-1,2,4-tricarboxylic acid (PBTCA) is an antiscalant that is widely used in reverse osmosis (RO) systems.


PBTCA is usually used together with zinc salt, copolymer, organophosphine, imidazole and other Water Treatment Chemicals. 
When used alone, the dosage of 5-15mg/L is preferred.
Package and Storage:Normally In 250kg net Plastic Drum, IBC drum can also be used as required. 
Storage for one year in room shady and dry place.


Properties: 

PBTCA has low content of phosphorus. 
Its structural property of both phosphonic acid and carboxylic acid enables PBTCA to have excellent scale inhibition and corrosion inhibition performance, and to be better than the commonly used organic phosphonic acid, especially at high temperature condition. 
PBTCA can improve the solubility of zinc, and has good chlorine oxidation tolerance and good composite synergy.

Applications:

PBTCA is most widely used in the combination of high efficiency scale and corrosion inhibitors, as one of the best chemicals, and it is also excellent stabilizer of zinc salt. 
PBTCA is widely used as corrosion and scale inhibitors in circulating cooling water system and oilfield water injection systems, and is especially suitable for use with zinc salt and copolymer. 
It can be used in the situation of high temperature, high hardness, high alkali and high concentration times. 
PBTCA can be used as chelating agent and metal cleaning agent in washing industry.


 
1,2,4-Butanetricarboxylic acid, 2-phosphono-
2-phosphonobutane-1,2,4-tricarboxylic acid
2-phosphonobutane-1,2,4-tricarboxylic acid
CAS names
1,2,4-Butanetricarboxylic acid, 2-phosphono-

IUPAC names
1,2,4-Butanetricarboxylic acid, 2-phosphono-
2-phosphobutane-1,2,4-tricarboxylic acid
2-PHOSPHONOBUTANE-1,2,4-TRICARBOXYLIC ACID
2-Phosphonobutane-1,2,4-tricarboxylic acid
2-phosphonobutane-1,2,4-tricarboxylic acid
2-phosphonobutane-1,2,4-tricarboxylic acid
2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC)

PBTC


PBTCA

Trade names
Aquacid 101EX

Aquacid 101 EX
Bayhibit (AM) (50% aqueous solution)
BAYHIBIT-AM
BAYHIBIT-AM
Bayhibit®AM
PBTC
PBTCA
PHOSPHONOBUTANE TRICARBOXYLIC ACID
Uniphos 100
Bayhibit (AM) (50% aqueous solution)
BAYHIBIT-AM
Bayhibit®AM
PBTC
PBTCA
PHOSPHONOBUTANE TRICARBOXYLIC ACID
Uniphos 100


2-phosphonobutane-1,2,4-tricarboxylic acid


The most common use of  PBTC is to act as a scale inhibitor and corrosion inhibitor in water treatment. The water witch used in cooling systems or industrial applications generally has some impurities like calcium carbonate and metal ions. These impurities can cause a lot of problems, creating deposits in the pipes and paths, as well as causing corrosion in the equipment.

For example, in water cooling systems, water will move without interruptions in a cycle and it experiences different temperatures and pressure conditions. The changes in temperature and pressure cause deposits of calcium and other ions to form, which can cause a lot of damage to the system.

Generally, scale control phosphonates are preferred to other materials, due to their excellent properties for dispersing metals and clay, as well as scale inhabitation.

AMP & HEDP have shown their high capabilities, but they also have two major problems: the limited solubility of their salts and their low resistance to oxidizing agents. PBTC is a very strong scale & corrosion inhibitor and is used in many industries. Due to its higher performance, it is very cost-effective than standard phosphates such as HEDP/ATMP.

This material is required to control calcium carbonate and disperse iron and sludge. By blocking the reaction of metallic ions, phosphonates prevent them from reacting unwantedly and produce stable mixtures of water with multiple metal ions. PBTC can be used in environments with high hardness, high temperature, and high alkalinity.

In addition to the use of PBTC in the treatment of water, it can be used as fertilizer and pesticide in agriculture.

Applications of PBTC
Industrial water treatment / Cooling system waters
As previously mentioned, in systems in which water plays a role as cooling fluid, or in boilers, the presence of substances such as calcium ions causes the formation of sediments inside the equipment, this can close the water path and cause fractures and many issues in the process. To solve this problem, the use of PTBC is common and effective.

Industrial detergent
One of the most important uses of sulfonate compounds, such as PBTC, is the use of detergent production, the advantages of which include the following:

Reduce hardness and prevention deposition
Suspend the pollutants and prevent their re-sedimentation
Secondary oil recovery
In the process of oil extraction, oil is extracted from the well in the early stages by the pressure in its reservoir. But after a while, the pressure drops and they have to use some fluids to make enough pressure.

In offshore drilling, they use seawater to provide the required pressure. The water entering the well has high ion concentrations, which can be deposited after a while and cause clogging in the well, sediment inhibitors such as PBTC to prevent minerals such as calcium carbonate, calcium sulfate, barium sulfate, and strontium sulfate when drilling and in the production line, they are very efficient.

Some of the other applications of 2-Phosphonobutane-1,2,4,-tricarboxylic acid are: Antiseptics, Rust inhibitor in steel, As an inhibitor in concrete

 PBTC MSDS
This substance can cause serious eye problems.
In the case of inhalation, it can cause respiratory irritation and coughing.
It causes skin irritation.
In the case of swallowing, it will cause irritation and pain.

The corrosion properties of steel have been studied in acidic solution containing polymeric inhibitors. 
2-Phosphonobutane-1, 2, 4 tricarboxylic acid (PBTCA) was used as a corrosion inhibitor for carbon steel in cooling water either alone or in combination with polyvinylpyrrolidone (PVP). 
The inhibiting properties of those compounds were investigated with the aid of the weight loss method, open circuit potential measurements and potentiodynamic techniques. 
The inhibition efficiency at various inhibitor concentrations was found to increase with increasing PBTCA concentration. 
A considerable improvement in the protection efficiency was achieved by adding polyvinylpyrrolidone to the PBTCA solution. 
A mixture PBTCA and PVP acts as a synergic inhibitor and found to increase the inhibition efficiency to 96.7%. 

INTRODUCTION 

The control of corrosion in recirculation cooling systems is primarily achieved by maintaining relatively small quantities of chemical additives (corrosion inhibitors) in the cooling water. 
Corrosion inhibitors retard the destruction of metals by chemical or electrochemical reactions with their environment. 
Most of the inhibitors used in cooling water nowadays are based on phosphonates, either alone or in combination with one or more other corrosion inhibitors (1, 2, and 3). 
Phosphonates give better inhibition efficiencies when used in combination with zinc salts. 

Have also studied the inhibition action of 2-phosphonobutane 1, 2, 4-tricarboxylic acid on carbon steel at room temperature and a pH range of 6.5–8. 
They have found that the addition of phosphonocarboxylic acids to water has a considerable effect in preventing corrosion as well as scale formation in water recirculation systems (5). 
Moreover, the efficiency of phosphonocarboxylic acids as corrosion inhibitors has been found to improve by the addition of zinc salts and/or phosphoric acid. 
In spite of the advantage of combining zinc salts with certain inhibitors like the phosphonates, they have been found to adversely affect the water released during the cooling process. 
Therefore, the permissible limit of zinc in water / waste, water has been restricted to a maximum value of 2 mg/l (6). 
As a result of the adverse effects of the salts of the heavy metals, researchers have decided to employ effective corrosion inhibiting compositions that are free from metal ions. 
Such types of inhibitors are highly necessary in industry for the protection of metallic equipments. 
(7) Has described the mechanism of inhibition action of phosphonocarboxylic acid combined with nitrate which was developed to protect ferrous metals used in open evaporative cooling systems. 
This inhibitor has been found to be as effective as zinc chromate or zinc phosphonate. 
Moreover, the passive film formed by this inhibitor has been found to be thinner, more protective, and less prone to pitting corrosion than the passive films formed in the presence of nitrate alone. 
Polymeric compounds consist of large molecules, which can be adsorbed on the surface of a certain metal, hence, these polymers can be considered as corrosion inhibitors. 
For instance, the potentiality of aliphatic polyamines (8), polyvinylpiperidines and polyvinylpyridines (9) as corrosion inhibitors has been investigated. 
The effect of polyvinylpyridine as an inhibitor was attributed to the adsorption of this polymer through several points of each of its molecules. 
Other authors found that the inhibiting properties of phosphonates are enhanced when they are combined with polymers. 
(12) Have described a method for preventing corrosion in water-carrying systems by adding one of the phosphonocarboxylic acids or their salts and other synergistically active substances. 
They have found that enhanced inhibiton action of phosphonocarboxylic acid can be achieved by adding one of the following derivatives: a benzimidozole derivative; polyacrylamide; polyethyleneimine; or lignin sulfonate. 
These inhibitors were found to be highly effective in preventing the corrosion of carbon steel in water-carrying systems. 
Other workers have found that the corrosion rate of steel in cooling water systems was decreased by the addition of 10 ppm hydroxyethylidene-1, 1- diphosphonic acid to the corrosion inhibitor mixtures (13). 
These mixtures consist of 30 ppm gluconate and 30 ppm sodium silicate in the presence of minor acrylic acid–acrylamide copolymer derivatives having a molecular weight of 20000. 
Recently, organophosphorus compounds have been used as corrosion inhibitors for galvanized steel in water cooling systems (14). 
Also, polymers based on 1, 6-hexanediamine has shown superior inhibition efficiencies in compare to the corresponding monomer . 
Al- Mustansiriya J. Sci Vol. 20, No 2, 2009 72 The present investigation describes the results obtained by using 2- phosphonbutene-1, 2, 4-tricarboxylic acid (PBTCA) as an inhibitor for the protection of carbon steel in cooling water systems. 
In addition, the inhibition effect of PBTCA in combination with polyvinylpyrrolidone (PVP) was investigated in cooling water systems at various inhibitor concentrations and temperatures.


It can be concluded that PVP and PBCTA act as corrosion inhibitors in cooling water for carbon steel. 
The inhibiting properties were investigated for PBCTA alone and mixed with PVP. 
The corrosion properties were determined using the weight loss technique, open circuit potential measurements, and potentiodynamic techniques.
The inhibition efficiency at different inhibitor concentrations was found to increase with increasing (PBTCA) concentration.
A synergic effect was observed and a protection efficiency of 96.7% was achieved when the polymeric compound polyvinylpyrrolidone (PVP) was added to the PBTCA solution.


Geothermal energy is a clean and renewable energy source with considerable potential for development. 
In China, low-temperature geothermal resources (≤90 °C) are relatively abundant compared with medium- (90–150 °C) and high-temperature resources (≥150 °C).
While geothermal energy can be used for heating and other applications, a serious problem exists with pipeline scaling in the process of developing and transporting low-temperature geothermal fluid. 
A simple, economical, and effective solution to this problem is to add scale inhibitor.

Two traditional scale inhibitors—polyacrylic acid (PAA) and 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA)—and two green biodegradable inhibitors—polyaspartic acid (PASP) and polyepoxysuccinic acid (PESA)—were selected for the scaling of CaCO3.  
As  reported in the literature, one of the scale inhibitors has been studied over 80 °C.
However, investigations have been lacking on the scale inhibition performance of the above inhibitors at 60–90 °C, the common temperature range of the low-temperature geothermal well. 
The current authors studied the scale inhibition performance of four scale inhibitors at different temperatures and dosages.

Experimental
The scale inhibition performance was analyzed with Fourier transform infrared (FTIR) and a scanning electron microscope (SEM). 
Testing was done using the static scale inhibition method according to the GB/T 16632-2008 standard.
The four scale inhibitors used in this experiment are commercially available PBTCA (50%), PAA (≥30%), PESA (40%), and PASP (40%). 
These were diluted to 0.5 mg/mL. In the GB/T 16632-2008 standard, the heating temperature is 80 °C. 
To investigate the scale inhibition efficiency for geothermal fluids at different temperatures, the researchers changed the heating temperature from 60 °C to 90 °C; temperature gradient was 10 °C.

A solution containing 120 mg Ca2+ and 366 mg HCO3– was prepared. 
Four scale inhibitors were added in 500-mL conical flasks. A solution without inhibitors was also prepared. 
The conical flasks were heated at 60/70/80/90 °C for 10 hr (the level of solutions should not be higher than the water bath level). 
After heating, the solution was cooled to room temperature and filtered. 
Finally, the concentration of Ca2+ in the solutions was measured using EDTA standard solution. 
Performance of scale inhibitors was evaluated by the scale inhibition rate as calculated using Eq. (1):

 Image

(1)

Where ρ2 (mg/mL) is the concentration of Ca2+ in the solution with added scale inhibitors, ρ1 is the concentration of Ca2+ in the solution without scale inhibitors before heating in the water bath, and ρ0 is the concentration of Ca2+ in the solution without scale inhibitors after heating.

Results and discussion
Scale inhibition rate
Figure 1a–d shows the scale inhibition rates of PBTCA, PASP, PAA, and PESA with different additions at 60/70/80/90 °C, respectively. 
The scale inhibition rate of the four scale inhibitors increased with increase in dosage. 
Scale inhibitors at low dosage have poor scale inhibition performance, which is most pronounced in PESA. 
At 80 °C, compared with the blank group, there was no change in Ca2+ content of PESA with 2-, 4-, and 6-mg/L dosages after heating for 10 hr, and the scale inhibition rate was 0. 
At 90 °C, the scale inhibition rate was also close to 0 when the addition of PESA was 2 mg/L and 4 mg/L. 
At 60–90 °C, when the dosage of inhibitors was ≥6 mg/L, the scale inhibitor maintained a high and stable inhibition rate.

ImageZoom In
Figure 1 – Scale inhibition rate of PAA, PBTCA, PASP, and PESA at different dosages at 60 ° (a), 70 ° (b), 80 ° (c), and 90 ° (d).
When the heating temperature was 60 °C, 70 °C, and 90 °C, the scale inhibition effects of the four scale inhibitors were PBTCA>PASP>PAA>PESA. 
However, the scale inhibition performance of PASP was greatly reduced at 80 °C. 
The scale inhibition performance of the four scale inhibitors was PBTCA>PAA>PASP>PESA, and the inhibition rate of PASP was only 1.71–15.38%. 
At 60 °C, when PBTCA dosages were 6 mg/L, 8 mg/L, and 10 mg/L, the scale inhibition rates were 64.44%, 67.13%, and 66.23%, respectively. 
PASP inhibition rate increased to 61.31% when the dosage was 8 mg/L. 
The scale inhibition rate of PBTCA and PASP at 70 °C increased to 81.82% and 73.74% when the dosage was 10 mg/L. 
PBTCA showed good scale inhibition performance at 80 °C. 
When the dosage was 10 mg/L, the scale inhibition rate was 64.1%. 
The highest scale inhibition rates of PAA, PASP, and PESA were only 48.72%, 15.38%, and 21.37%, respectively. 
At 90 °C, the scale inhibition rates of PBTCA and PASP were 65.73% and 61.54% when the dosage was 10 mg/L.

The above analysis demonstrates that the scale inhibition performance of PBTCA and PASP is better than PAA and PESA at 60 °C, 70  °C, and 90 °C. 
It is worth mentioning that PASP is a nontoxic, environmentally friendly scale inhibitor that was developed based on studying the metabolic processes of marine animals. 
It can be completely degraded into an end product that is harmless to the environment. 
PBTCA, on the other hand, is an organic phosphate, which easily forms into organic phosphoric acid scale. 
Considering the environmental impact, PASP is a better choice.

As can be seen in the above analysis, when the dosage of scale inhibitor is above 6 mg/L, the inhibition effect tends to be stable. 
The effect of temperature on the scale inhibition rate of the four inhibitors when the addition was 10 mg/L is shown in Figure 2. 
With the increase in temperature, the scale inhibition rate of PESA and PAA gradually decreased, and the scale inhibition rate at 90 °C decreased to 12.59% and 43.36%, respectively. 
The temperature resistance of PESA and PAA was poor, while PBTCA had good temperature resistance. 
Scale inhibition rates at 60/70/80/90 °C were 66.23%, 81.82%, 64.1%, and 65.73%, respectively. 
PASP also showed good temperature resistance at 60 °C, 70 °C, and 90 °C; scale inhibition rates were 56.38%, 73.74%, and 61.54%, respectively. 
However, the scale inhibition rate was only 15.38% at 80 °C. The reason for this will be the subject of future research.

ImageFigure 2 – Scale inhibition rate of 10-mg/L inhibitors at different temperatures.
Scaling inhibition mechanism of inhibitors FTIR
There are three common crystalline structures of CaCO3: calcite, aragonite, and is the most stable crystalline structure of CaCO3. 
Vaterite is the most unstable structure, and the stability of aragonite is somewhere in between.5

Figure 3 shows the FTIR spectra of precipitated scale products in the absence and presence of PAA, PESA, PBTCA, and PASP. 
The absorption peak of CaCO3 without scale inhibitor  is 712 cm-1 and 876 cm-1, revealing that the main crystal structure of calcium carbonate is calcite.
Except for the absorption peaks at 712 cm-1 and 876 cm-1, the characteristic band at ~1085 cm-1 was also found in the samples in the presence of PAA, PBTCA, and PESA; ~1085 cm-1 is a characteristic band of vaterite.
This confirmed that calcite has the tendency to transform into vaterite in the presence of PAA, PBTCA, or PESA. 
However, the current authors did not find the characteristic band of vaterite in the FTIR analysis of the CaCO3 sample with the addition of PASP, so they used SEM for further analysis.

ImageFigure 3 – FTIR analysis of CaCO3 samples in the absence and presence of PAA, PESA, PBTCA, and PASP.
SEM
Figure 4a and b is an SEM image of CaCO3 without inhibitor, and 4c–f shows CaCO3 with PAA, PBTCA, PESA, or PASP. 
The three crystal structures of CaCO3 have different microstructures—the morphology of calcite is cubic, aragonite is acicular, and vaterite is spherical.8,9

Figure 4 – SEM graphs of CaCO3 samples with different scale inhibitors: CaCO3 without inhibitor (a, b), PAA-CaCO3 (c), PBTCA-CaCO3 (d), PESA-CaCO3 (e), and PASP-CaCO3 (f).

 

When the scale inhibitor was not added to the system (Figure 4a and b), the crystal structure of CaCO3 was mainly regular hexahedron, and crystal size was about 5–7 μm. 
The structure cell stacks closely and the shape is regular. 
This is a typical calcite structure. In the SEM analysis of the CaCO3 sample with PAA (Figure 4c), the morphology of the crystals changed—the original hexagonal structure gradually lost its edges and corners. 
The CaCO3 sample with PBTCA (Figure 4d) shows that the crystal surface gradually became smooth and the corners almost disappeared. Crystal size is about 3 μm.
The CaCO3 scale sample with PESA (Figure 4e) has no hexagonal structure. 
Its scale structure is loose with no obvious angularity. Compared with the blank group, the above results confirm that the addition of PAA, PESA, or PBTCA causes CaCO3 to transform from calcite to vaterite, which is consistent with the FTIR results.

Unlike the other three scale inhibitors, a large number of acicular structures with a length of about 20 μm was observed in the CaCO3 scale sample in the presence of PASP (Figure 4f). 
This is a crystal structure of CaCO3 between calcite and vaterite called aragonite. 
Compared to the stable cubic structures of calcite, aragonite is also an unstable crystal structure  of CaCO3. 
At the same time, this also explains the phenomenon that the FTIR image of CaCO3 adding PASP does not show the characteristic peak of vaterite.

Conclusion
Increasing the dosage of the scale inhibitor and heating temperature causes the scale inhibition rate to increase, and, when the dosage is ≥6 mg/L, the four scale inhibitors achieve stable inhibition performance. 
At 60 °C, 70 °C, and 90 °C, the scale inhibition efficiency is PBTCA>PASP>PAA>PESA; at 80 °C, PBTCA>PAA>PASP>PESA. 

PBTCA is an efficient scale inhibitor with good temperature resistance. 

Taking into account environmental factors, PASP is a better choice at 60 °C, 70 °C, and 90 °C.

Based on the results of FTIR and SEM analyses, the scale inhibition mechanisms of the four scale inhibitors can be summarized as follows: the addition of scale inhibitors changes the CaCO3 structure from dense and stable calcite to loose, irregular change in crystal morphology makes CaCO3 less likely to adhere to the surface of the device and is more likely to be present in water in a suspended state, making it easier for circulat- ing water to wash away the calcium scale.

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