TRILON AS is organic chelating agent used to control the concentration of metal ions in aqueous systems.

Chemical nature: The active ingredient contained in Trilon AS is nitrilotriacetic acid (NTA-H3) with CAS-No. 139-13-9.

TRILON AS is Nitrilotriacetic acid, C6H9NO6, is an aminocarboxylic acid with four functional groups.

Appearance: Trilon AS is a fine white powder.

Handling and Storage of Trilon AS

The following materials can be used for tanks and drums:
a)    Stainless steel 1.4541 – AISI 321 stainless steel (X6 CrNiTi 1810)
b)    Stainless steel 1.4571 – AISI 316 Ti stainless steel (X6 CrNiMoTi 17122)
c)    Stainless steel 1.4306 – AISI 321 L stainless steel (X2 CrNi 1911)
d)    High-density polyethylene (HDPE)
e)    Low-density polyethylene (LDPE)

Shelf life    
Provided it is stored properly and drums are kept tightly sealed, Trilon AS has a shelf life of at least 36 months in its original packaging.

Some physical properties of Trilon AS are listed in the table below. 
These are typical values only and not all of them are monitored on a regular basis. 
They are correct at the time of publication and do not necessarily form part of the product specification. 

Trilon AS    Unit    Value
Physical form (25 °C): powder
Molecular weight (M.W.)    g/mol: 191

Concentration (pot. Titration with FeCl3-solution) 
calculated as trisodium salt (NTA-Na3 ): approx. 135 %
calculated as free acid (NTA-H3 ) :approx. 100 %

Bulk density (DIN ISO 697, 40 mm diam.)    g/L: approx. 800
pH value(DIN 19268, 1% in water, 23 °C)    :approx. 2.2 (slurry)
Calcium binding capacity (BASF method, pH 11) mg CaCO3/g t.q.: approx. 525
Water content(DIN EN 13267, Karl Fischer)%: approx. 0.2
Melting point (DIN 51004) °C: approx. 245
Solubility in water (BASF method, 25 °C g in 1 litre: approx. 1

Distribution of particles    
The following curve shows the distribution of particles of Trilon AS (all values are approximate):


Complex formation    
The most important property of Trilon AS is its ability to form watersoluble complexes with polyvalent ions (e.g. calcium, magnesium, lead, copper, zinc, cadmium, mercury, manganese, iron) over a wide pH range from 2 to 13.5. 
NTA usually forms 1 : 1 complexes, i. e. 1 mol of NTA chelates binds to 1 mol of metal ions, but it can also form 2 : 1 complexes with some metals if a stoichiometric excess of NTA is present. 
These complexes remain stable, especially in alkaline media and even at temperatures of up to 100 °C.

From the law of mass action, the equation for the stability constant K for 1 : 1 complexes can be written as follows:

[MeZ(m-n)-]K =[Men+] [Zm-]

[MeZ(m-n)-] is the concentration of the chelate that is formed,
[Men+] is the concentration of free, positively charged metal ions, [Zm-] is the concentration of the ligand anion, in this case NTA, K    is the stability constant for the chelate.
Logarithmic stability constants (log K) for complexes of MGDA and selected metal ions:
Metal ion    log K
Fe3+    15.9
Hg2+    14.6
Cu2+    12.9
Ni2+    11.5
Pb2+    11.3
Zn2+    10.7
Co2+    10.4
Cd2+    9.8
Fe2+    8.3
Mn2+    7.5
Ca2+    6.4
Mg2+    5.5
Ba2+    4.8

NTA-H3 is a tribasic acid that dissociates in three steps. 
The acid dissociation constants pKa are as follows.

NTA-H3    pKa1    1.9
NTA-H2-    pKa2    2.5
NTA-H2-    pKa3    9.7

In aqueous solutions, Trilon AS competes for metal ions with other anions, such as hydroxide, sulphate, sulphide, carbonate and oxalate, that form sparingly soluble metal salts. 
The formation of chelates reduces the concentration of free metal ions [Men+] to such an extent that the solubility products of many sparingly soluble metal salts are no longer exceeded. 
The result is that the salts no longer precipitate or may even redissolve.

Conditional stability constants [log Kcond] take into account the stability constant K as well as the acid base dissociation equilibria.

The following curves show the conditional stability constants for selected NTA chelates

Chemical stability: Trilon AS is chemically very stable.

Trilon AS exhibits a higher stability than other organic chelating agents such as citric acid, tartaric acid and gluconates – especially at elevated temperatures.
Whereas inorganic sequestring agents (e.g. phosphates) may hydrolyse at high temperatures, Trilon AS is stable – even when heated to 200 °C under pressure.

Trilon AS melts at approx. 245 °C.

Trilon AS is resistant to strong acids and bases. 
It is gradually broken down by chromic acid, potassium permanganate and other strong oxidizing agents. 
Stability in the presence of hydrogen peroxide, percarbonate and perborate is sufficient for joint application. 
Nevertheless, we do not recommend combining Trilon AS and peroxides in liquid formulations.

Sodium hypochlorite and other substances that release chlorine cause Trilon AS to decompose. 
Alkaline earth and heavy metal complexes are broken down.

Corrosion: Trilon AS stabilizes polyvalent metal ions, which means that it can increase the rate at which metals dissolve. 
Nevertheless, with the exception of aluminium, an oxidizing agent such as air always has to be present for corrosion to take place. 
Unalloyed steel is prone to corrosion in media that contain air, but corrosion can be reduced substantially if the pH is in the alkaline range and can be eliminated almost completely if oxygen and other oxidizing agents are excluded. 
Steel that is cleaned with Trilon AS in the slightly alkaline range, which is the optimum pH range for the Trilon AS, is much less prone to corrosion than if it is cleaned with acids.

The only type of corrosion that has been with Trilon AS is uniform corrosion: pitting or stress cracking have not been observed in media with a low chloride content. 
One of the advantages of Trilon AS is that it can be supplied with very low chloride contents.

The following information on materials is of a very general nature, because corrosion depends on many different factors such as exposure to air, galvanic corrosion caused by the presence of different materials and by the flow patterns of liquids. 
The compatibility of Trilon AS with different materials needs to be tested in each individual case.

Ecology and toxicology: Trilon AS is readily biodegradable in standard OECD tests, it is completely mineralised
and it does not form any persistent metabolites. 
The removal rate for Trilon AS due to biodegradation usually more than in sewage treatment plants is 95%.

Safety: We are not aware of any ill effect that can result from using Trilon AS for the purpose for which it is intended and from processing it in accordance with current practices.
According to the experience that we have gained over many years and other information at our disposal, Trilon AS does not exert harmful effects on health, provided it is used properly, due attention is given to the precautions necessary for handling chemicals, and the information and advice given in our Safety Data Sheets are observed.

Labelling: Please consult the current Safety Data Sheets for information on the classification and labelling of our products and other information relevant to safety.

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