Organic chelating agents used to control the concentration of metal ions in aqueous systems
The active ingredient contained in the Organic chelating agents types is ethylenediaminetetraacetic acid (EDTA or EDTA-H4) or its salts.
Ethylenediaminetetraacetic acid, C10H16N2O8, is an aminocarboxylic acid with six functional groups.
Ethylenediaminetetraacetic acid (EDTA-H4) in solid form
CAS No. 60-00-4
(Properties of Ethylenediaminetetraacetic acid (EDTA-H4) are below )
Aqueous solution of the tetrasodium salt of ethylenediaminetetraacetic acid (EDTA-Na4)
CAS No. 64-02-8
Tetrasodium salt of ethylenediaminetetraacetic acid (EDTA-Na4) in solid form
CAS No. 64-02-8
Tetrasodium EDTA is the salt resulting from the neutralization of ethylenediaminetetraacetic acid with four equivalents of sodium hydroxide (or an equivalent sodium base).
Tetrasodium EDTA is a white solid that is highly soluble in water.
Commercial samples are often hydrated, e.g. Na4EDTA.4H2O.
The properties of solutions produced from the anhydrous and hydrated forms are the same, provided they are at the same pH.
Tetrasodium EDTA is used as a source of the chelating agent EDTA4-.
A 1% aqueous solution has a pH of approximately 11.3.
When dissolved in neutral water, it converts partially to H2EDTA2-.
Ethylenediaminetetraacetic acid is produced commercially via the intermediacy of tetrasodium EDTA.
Disodium salt of ethylenediaminetetraacetic acid (EDTA-H2Na2) in solid form
CAS No. 139-33-3 (It is a dihydrate and has therefore also been assigned CAS No. 6381-92-6)
Aqueous solution of the triammonium salt of ethylenediaminetetraacetic acid (EDTA-H(NH4)3)
CAS No. 15934-01-7
Aqueous solution of the tetraammonium salt of ethylenediaminetetraacetic acid (EDTA-(NH4)4)
CAS No. 22473-78-5
Aqueous solution of the tetrasodium salt of ethylenediaminetetraacetic acid(EDTA-H4) with added triethanolamine (TEA)
CAS No. 64-02-8/102-71-6
Ethylenediaminetetraacetic acid (EDTA-H4) in solid form
CHEMICAL AND PHYSICAL DATA
CAS No. 60-00-4
Physical form (visual): White powder Clear
Molar mass (DIN 32625) g/mol: 292
expressed as free acid %: approx. 100 (EDTA-H4)
pH approx.: 2.8 approx.
(DIN 19268, 23 °C, 1% in water) (slurry)
Bulk density g/l approx. 820
(ISO 697, 40 mm diam.)
Calcium binding capacity : approx. 340
(mg CaCO3/g t. q.)
Water content %: approx. 0.1
(DIN EN 13268)
Melting point °C approx. 245
(ISO 3146) (decomposes)
Solubility in water (BASF method)
at 25 °C g/l approx. 1
at 80 °C g/l approx. 2
The most important property of the Organic chelating agents is their ability to form water-soluble complexes with polyvalent ions (eg. calcium, magnesium, lead, copper, zinc, cadmium, mercury, manganese, iron, aluminium) over a wide pH range from 2 to 13.5.
EDTA usually forms 1 : 1 complexes, i. e.
1 mol of EDTA chelates binds to 1 mol of metal ions.
The metal ion is completely enclosed by the ligand.
These complexes remain stable, especially in alkali media and even at temperatures of up to 100 °C.
EDTA has six donor groups and it can form octahedral complexes.
From the law of mass action, the equation for the stability constant K can be written as follows:
K = ––––––––––––
[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 EDTA K is the stability constant for the chelate.
Logarithmic stability constants (log K) for complexes of EDTA and selected metal ions
Metal ion log K
EDTA-H4 is a tetrabasic acid that dissociates in four steps. The acid dissociation constants pKa are as follows.
EDTA-H4 pKa1 2.0
EDTA-H3- pKa2 2.6
EDTA-H22- pKa3 6.2
EDTA-H3- pKa4 10.3
In aqueous solutions, EDTA 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.
The high stability of these complexes prevents metal ions from participating in typical chemical reactions.
For instance, manganese, iron and copper are no longer able to catalyse the decomposition of peroxide bleach.
Conditional stability constants [log Kcond] take into account the stability constant K as well as the acid base dissociation equilibria.
Chemical stability: EDTA and Salts of EDTA are chemically very stable.
EDTA and Salts of EDTA have been shown to be very stable compared to other organic complexing agents such as citric acid, tartaric acid and gluconates, especially at high temperatures.
Whereas inorganic sequestring agents (eg. phosphates) may hydrolyse at high temperatures, EDTA and Salts of EDTA are stable – even when heated to 200 °C under pressure.
Ethylenediaminetetraacetic acid (EDTA-H4) melt at approx. 245 °C.
Tetrasodium salt of ethylenediaminetetraacetic acid (EDTA-Na4) gradually loseS its water of crystallization at high temperatures and they begin to decompose at approx. 300 °C.
EDTA and Salts of EDTA are resistant to strong acids and bases.
They are 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 EDTA and Salts of EDTA and peroxides in liquid formulations.
Substances that release chlorine, such as sodium hypochlorite, have ahighly detrimental effect on the performance of all of the EDTA and Salts of EDTA types, and some alkaline earth and heavy metal complexes are broken down.
EDTA and Salts of EDTA stabilize polyvalent metal ions, which means that they 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.
With the exception of aluminium, metals that are cleaned with the EDTA and Salts of EDTA types in the slightly alkaline range, which is the optimum pH range for the EDTA and EDTA Salts, are much less prone to corrosion than if they are cleaned with acids.
EDTA and EDTA Salts and great caution should be taken in cases in which resistance to corrosion depends the formation of a passive magnetite layer.
The only type of corrosion that has been observed with EDTA and EDTA Salts types is uniform corrosion: pitting or stress cracking have not been observed in media with a low chloride content.
One of the advantages of EDTA and EDTA Salts is that they can be supplied with a very low chloride content (< 20 mg/kg).
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 EDTA / EDTA Salts with different materials needs to be tested in each individual case.
Austenitic stainless steels such as AISI/SAE 321 are very effective for vessels used to store and transport the Trilon B types even at temperatures of 60 – 100 °C.
Ferritic carbon steels such as ASTM A201 Grade B (European Material No.P265GH) are resistant to Tetrasodium salt of ethylenediaminetetraacetic acid (EDTA-Na4) in liquid form at temperatures up to 60 °C if the liquid is blanketed with nitrogen.
Unalloyed steel is not sufficiently resistant to corrosion by Aqueous solution of the triammonium salt of ethylenediaminetetraacetic acid and Trilon BAQ, which are less alkaline.
Copper and alloys such as brass and bronze must not be treated with Aqueous solution of the triammonium salt of ethylenediaminetetraacetic acid Liquid or Aqueous solution of the tetraammonium salt of ethylenediaminetetraacetic acid (EDTA-(NH4)4), because they contain ammonium compounds.
Here, corrosion is at least partly due to the release of ammonia,and corrosion can be caused by the gas phase above the metal surface.
On the other hand, the use of Disodium salt of ethylenediaminetetraacetic acid (EDTA-H2Na2) in solid form for cleaning copper components in power stations has been documented in the literature and very little corrosion has been detected even at high temperatures.
Aluminium and aluminium alloys such as AL 7075 T6 (European Material No. 3.4365) are not resistant to Tetrasodium salt of ethylenediaminetetraacetic acid (EDTA-Na4), because EDTA-Na4 Liquid is alkaline and aluminium is quickly corroded by strong bases.
The rate of corrosion depends to a large extent on the pH.
The neutral and slightly acidic products such as Aqueous solution of the triammonium salt of ethylenediaminetetraacetic acid and Disodium salt of ethylenediaminetetraacetic acid (EDTA-H2Na2) are much less corrosive to aluminium than the alkaline EDTA types.
Silicon carbide and tungsten carbide are suitable materials for pump seals.
Nickel-bound tungsten carbide seals are resistant to Tetrasodium salt of ethylenediaminetetraacetic acid (EDTA-Na4) liquid at temperatures of up to 100 °C.
EDTA types are used sequester free metal ions in aqueous systems.
They are used to soften water and to remove traces of alkaline earth and heavy metals.
EDTA types are also used to stabilize bleach.
Stoichiometric amounts of EDTA types are required to complex metal ions.
Solutions are clear after they have been treated with chelating agents, and they do not need to be filtered or decanted.
EDTA types can be used to solubilize precipitated metal salts and hydroxides.
Traces of free metal ions are always present in equilibrium with salts, even if these salts are very sparingly soluble.
If the free ions are chelated, the equilibrium is gradually displaced in favour of the soluble chelates.
The rate at which precipitates dissolve depends on their crystal structure and age, and on the temperature.
Increasing the temperature can help to increase the rate at which precipitated solids dissolve.
Old, dried-on scale has to be treated with EDTA types over a longer period, and we would recommend applying 1 g/l more than the stoichiometric amount in this case.
EDTA types can be used to stabilize perborate and percarbonate in powder detergents. Small amounts of complexing agents, as little as 0.5 – 1.0 % expressed as the active substance, can be added to prevent traces of heavy metals from catalyzing the decomposition of hydrogen peroxide and other types of bleach.
These heavy metals, which mainly consist of iron, copper and manganese, originate from the walls of pipes, the soil contained in the laundry and the other ingredients of the detergent.
Peroxide bleach can break down fluorescent whitening agents, cause coloured laundry to change shade and damage fabrics in the presence of heavy metal ions.
EDTA types protect fabrics by sequestering heavy metals.
EDTA types play an active role in removing many types of soil and boost the detergency of laundry detergents.
EDTA types can be employed in all types of cleaner and degreaser formulations for industrial and institutional applications.
They prevent hardness ions and heavy metal ions from precipitating.
Inorganic solids of this type can form scale and deposits in tanks, pipes, and nozzles and on hard surfaces.
EDTA types boost the performance of the surfactants contained in cleaner formulations and ensure that their performance remains undiminished during the whole cleaning process.
Scale that consists of calcium carbonate, calcium phosphate or calcium oxalate can be formed in pipes and heat exchangers at high temperatures in various industrial processes.
EDTA types can be added to cleaner formulations remove this type of scale.
The rate at which the scale dissolves can be increased by increasing the cleaning temperature.
Turbidity and precipitation is often a problem when highly concentrated cleaners such as floor cleaners, metal cleaners and bottle-washing formulations are prepared with hard water.
This problem can be overcome in most cases by adding EDTA types.
The excellent solubility of the EDTA types enables them to be used to replace some or all of the phosphates contained in many formulations.
This prevents highly concentrated liquid formulations from precipitating and demixing at low temperatures.
EDTA types can be used to protect lubricants, cleaners and polishes in emulsion form from the damaging effects of hard water and salts of polyvalent metal ions.
EDTA types can be added to curd soap, toilet soap and shaving soap at rates of between 0.3% and 2% to prevent it becoming rancid and discoloured.
The heavy metals responsible for this are usually contained in the tallow, fatty acids and other raw materials, but soap can also be contaminated with metallic particles during drying, milling, plodding or stamping.
Trilon B types
They can also be added at higher rates (1 – 10 %) to prevent lime soaps from being formed, to boost the detergency of the soap and to promote foaming.
EDTA types are employed in the textile industry in pretreatment, aftertreatment and dyeing processes to prevent insoluble substances such as boiler scale and lime soaps from precipitating. They ensure that the treatment process remains effective over the whole working life of the bath.
EDTA types prevent hydroxides of heavy metals and alkaline earth metals from precipitating when cotton, wool and blended fabrics are boiled off with caustic soda.
In bleaching processes, the disruptive heavy metal ions that are washed out of cotton, wool and blended fabrics have to be sequestered with EDTA types to prevent them from catalysing the decomposition of peroxide bleach.
The bleach would otherwise decompose very quickly.
EDTA types enable bleaching costs to be reduced substantially.
EDTA types can also be used to stabilize dyes.
They protect fabrics from incrustation and prevent dyes from being precipitated by calcium or magnesium salts.
EDTA types can be used to suppress turbidity when textiles are washed in hard water after they have been printed.
EDTA types prevent hard water salts from being deposited on fabrics, which endures a brilliant shade and high fastness.
EDTA types can be used to soften the water in order to enhance the whiteness of fabrics when textiles are treated with fluorescent whitening agents.
EDTA types are employed in the production of leather before and during tanning and in dyeing processes.
They prevent solids from being precipitated and staining the leather.
Pulp and paper
EDTA types are used to stabilize peroxide and hydrosulphite bleach by sequestering disruptive metal ions, especially Fe3+, Mn2+ and Cu2+.
These metals are washed out of the pulp in the form of their complexes.
Bleaching mechanical pulp
EDTA types enable substantial savings in the consumption of hydrogen peroxide and hydrosulphite bleach to be made.
Complexing heavy metal ions improves the efficiency of the bleaching process.
EDTA types make it possible for sodium silicate to be largely dispensed with in peroxide bleaching processes.
In reductive bleaching processes with sodium dithionite, EDTA types are used to sequester Fe3+ ions that would otherwise react with phenolic compounds to form strongly coloured complexes.
EDTA types have also been shown to perform well in two-stage bleaching processes with peroxide and hydrosulphite or peroxide and peroxide.
Bleaching chemical pulp
Tetrasodium salt of ethylenediaminetetraacetic acid (EDTA-Na4) or Pentasodium salt of diethylenetriamine-pentaacetic acid (DTPA-Na5) are often used for bleaching chemical pulp.
They prevent disruptive heavy metal ions from catalyzing the decomposition of oxidative bleach such as hydrogen peroxide by complexing them.
Tetrasodium salt of ethylenediaminetetraacetic acid (EDTA-Na4) types are very pure grades of EDTA, and they allow consumption to be reduced by 10 % compared to standard grades of EDTA or DTPA.
Technological advances in the field of paper production have had the effect that paper machine white water circuits are operated at a higher degree of closure.
This has resulted in the increased formation of scale and deposits in pipes and evaporators, etc., and on the pulp itself.
EDTA and EDTA Salts offer a simple means of softening the water.
EDTA/EDTA Salts, especially Tetrasodium salt of ethylenediaminetetraacetic acid (EDTA-Na4) types, are also capable of dissolving scale that consists of calcium carbonate, calcium sulphate or calcium oxalate in the 9 – 12 pH range.
EDTA / EDTA Salts are very effective for treating water to prevent scale and deposits of calcium carbonate, calcium sulphate and calcium phosphate from forming in boilers, evaporators, reverse osmosis membranes, heat exchangers and filters, etc.
They can also be used to remove scale.
EDTA/EDTA Salts are every effective for cleaning equipment of this type, because they are less corrosive than other cleaners.
They have the advantage over acids that no potentially disruptive CO2 is formed when calcium carbonate is dissolved.
The following table shows the amounts of Tetrasodium salt of ethylenediaminetetraacetic acid (EDTA-Na4) required to soften 1 litre of water containing 1 mmol of Ca2+ ions/l at 20 °C*.
1 mmol Ca2+ ions/l (DIN 53910, Part 1)
Ethylenediaminetetraacetic acid (EDTA-H4) approx. 295 mg
EDTA-Na4 Liquid approx. 955 mg
EDTA-Na4 Powder approx. 450 mg
Disodium salt of ethylenediaminetetraacetic acid (EDTA-H2Na2) approx. 370 mg
* The standard unit of water hardness in Germany according to DIN 53910,Part 1, is mmol of Ca ions per litre of water, but other units are still in use internationally.
1 mmol/l of Ca ions = 5.6° German hardness = 10.0° French hardness = 7.0° English hardness (° Clark) = 100 ppm CaCO3
1° Clark (English hardness) corresponds to 0.01 g CaCO3/0.7 l water (= 0.143 mmol Ca ions/l)
1° German hardness corresponds to 0.01 g CaO/l water (= 0.178 mmol Ca ions/l)
1° French hardness corresponds to 0.01 g CaCO3/l water) (= 0.1 mmol Ca ions/l)
In the United States, water hardness is sometimes expressed in ppm.
1 ppm CaCO3 = 0.001 g CaCO3/l water = 0.01 mmol Ca ions/l.
Example The amount of Trilon B Powder required to soften 100 l of water with a hardness of 2 mmol Ca ions/l (= 200 ppm CaCO3 = approx. 14° Clark) is 450 x 2 x 100 x 0.001 g = 90 g EDTA-Na4 Powder.
Cleaning heat exchangers
Aqueous solution of the triammonium salt of ethylenediaminetetraacetic acid is particularly effective for removing magnetite scale.
Magnetite scale can be formed in the heat exchangers of power stations or in heating circuits if air is allowed to enter.
Aqueous solution of the triammonium salt of ethylenediaminetetraacetic acid causes little corrosion to alloyed and unalloyed steels, and it is much superior to the sodium salt in this respect.
Scale can be removed most efficiently at elevated temperatures.
Magnetite is formed from a mixture of Fe(II) and Fe(III) ions.
Fe(II) forms complexes at a pH of approx. 9, but the pH needs to be in the acid range (pH < 5) for Fe(III) to be complexed.
Adding hydrazine to the cleaning solution can prevent Fe(III) ions from being formed and can reduce these to Fe(II).
This makes it easier to remove magnetite scale in the alkaline pH range, and prevents iron(III) hydroxide sludge from being formed.
It is recommended to remove magnetite scale at a pH of approx. 9.
The rate at which the scale dissolves depends to a large extent on the thickness of the scale, its composition and morphology, and the flow of liquid through the equipment to be descaled. Practical experience has shown that the rate at which scale is removed can be speeded up by increasing the concentration of Aqueous solution of the triammonium salt of ethylenediaminetetraacetic acid, the temperature and the rate of flow through the system.
Adding Aqueous solution of the triammonium salt of ethylenediaminetetraacetic acid to the feed water in low concentrations has the advantage that the protective layer of scale that is formed on the bare metal is of a much higher quality than the layer formed in the absence of complexing agents.
The protective layer acts as a patina, protecting the underlying metal from corrosion.
The layer formed in the presence of Aqueous solution of the triammonium salt of ethylenediaminetetraacetic acid is very resistant to corrosion, especially static corrosion when the plant is shut down.
EDTA-Na4 Powder can be used to stabilise phosphonates in neutral and alkaline derusting and descaling baths.
EDTA/EDTA Salts types also prevent lime soaps from precipitating, which prolongs the working life of baths.
Aqueous solution of the tetrasodium salt of ethylenediaminetetraacetic acid (EDTA-H4) with added triethanolamine (TEA) can be added to alkaline degreasing baths that contain polyphosphates to reduce the hydrolysis of polyphosphates in the presence of metal ions, especially alkaline earth and heavy metal ions.
Adding tetrasodium salt of ethylenediaminetetraacetic acid (EDTA-H4) with added triethanolamine (TEA) to degreasing baths helps to inhibit the formation of orthophosphates.
This reduces the danger of the phosphates precipitating, which impairs the complexing power of the bath and its ability to disperse soil and emulsify grease.
Tetrasodium salt of ethylenediaminetetraacetic acid (EDTA-H4) with added triethanolamine (TEA) boosts the detergency of degreasing baths and prevents non-ferrous metals from tarnishing.
Tetrasodium salt of ethylenediaminetetraacetic acid (EDTA-H4) with added triethanolamine (TEA) can be added to passivation and neutralization baths after the metal has been pickled with acid in order to completely remove insoluble iron oxide hydrates from the water and acid.
Tetrasodium salt of ethylenediaminetetraacetic acid (EDTA-H4) with added triethanolamine (TEA) is able to sequester iron(II) and iron(III) in neutral and alkaline media, and especially in highly alkaline solutions, irrespective of the hardness of the water.
Under normal conditions, i. e. in 3 – 10 % caustic soda, 100 g of tetrasodium salt of ethylenediaminetetraacetic acid (EDTA-H4) with added triethanolamine (TEA) sequesters 8.0 – 9.0 g iron ions, 2.15 g calcium ions or 1.3 g of magnesium ions.
Complexing power of tetrasodium salt of ethylenediaminetetraacetic acid (EDTA-H4) with added triethanolamine (TEA) as a function of pH
pH 1 g of tetrasodium salt of ethylenediaminetetraacetic acid (EDTA-H4) with added triethanolamine (TEA) sequesters Fe (mg) at 25 °C
5 approx. 33
6 approx. 33
7 approx. 33
8 approx. 33
9 approx. 46
10 approx. 63
11 approx. 78
12 approx. 100
13 approx. 140
Ethylenediaminetetraacetic acid (EDTA-H4 is employed as a complexing agent in electroplating and electroless plating baths and it is used to regenerate baths by sequestering impurities.
Ethylenediaminetetraacetic acid (EDTA-H4 consists of the free acid of EDTA, and it has the advantage that it can be neutralized with a wide variety of different bases, such as sodium hydroxide, potassium hydroxide or organic amines.
This enables the solubility of the complexing agent to be controlled.
The degree of neutralization can also be varied within wide limits.
Ethylenediaminetetraacetic acid (EDTA-H4) types can be used in applications that demand high standards of purity.
Tetrasodium salt of ethylenediaminetetraacetic acid (EDTA-Na4), types are employed in electroplating and electroless plating baths on account of their high purity.
Electroless copper plating baths are extremely sensitive to organic impurities and heavy metals.
These substances have a very detrimental effect on the effectiveness and stability of the formulation.
Baths based on Tetrasodium salt of ethylenediaminetetraacetic acid (EDTA-Na4) types remain stable.
The high concentration of metal enables the copper to be applied very evenly.
Baths based on the Tetrasodium salt of ethylenediaminetetraacetic acid (EDTA-Na4) types are distinguished by their long working life and the high quality of the copper deposits.
EDTA-Na4 makes it easier to separate metals that are difficult to isolate, such as rare earths.
EDTA-Na4 is used in the production of rubber as a complexing agent for iron(II) catalysts.
The latex can be washed with EDTA-Na4 to remove traces of heavy metals, especially copper and manganese, that originate from the bark of trees.
This prevents the rubber from ageing prematurely.
All products that come into contact with rubber have to be free of heavy metal ions.
Articles that are intended to be treated, coated, or impregnated with rubber can be washed by boiling them for 1 – 2 hours in water that contains 1 – 2 g EDTA-Na4 Powder per litre.
Disodium salt of ethylenediaminetetraacetic acid (EDTA-H2Na2) prevents lithographic inks from scumming and piling.
It sequesters the polyvalent metal ions in the fountain solution and prevents them from forming salts.
Depending on the hardness of the water and the type of binder, Disodium salt of ethylenediaminetetraacetic acid (EDTA-H2Na2) is applied at a rate of between 0.5 % and 2 %, expressed as a proportion of the printing ink.
It can be added in solid form to the pigment before it is dispersed or it can be dissolved and added to the fountain solution.
Disodium salt of ethylenediaminetetraacetic acid (EDTA-H2Na2) can cause some inks to dry more slowly. This problem can be overcome by increasing the drier content or changing over to other driers.
We know of no ill effects that could have resulted from using the EDTA types for the purpose for which they are intended and from processing them in accordance with current practice.
According to the experience we have gained over many years and other information at our disposal, EDTA types do not exert any harmful effects on health, provided that they are 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.
EDTA-Na4 Liquid should not be stored at temperatures below 0 °C, because this can cause them to precipitate. It can be reconstituted by heating it briefly to 40 – 50 °C and stirring.
EDTA-Na4 Liquid, Aqueous solution of the triammonium salt of ethylenediaminetetraacetic acid and tetraammonium salt of ethylenediaminetetraacetic acid (EDTA-(NH4)4) are easily capable of being pumped at temperatures down to – 10 °C.
EDTA-Na4 Powder is hygroscopic, and so it should be kept in tightly sealed containers.
EDTA/EDTA Salts types supplied in powder form have a shelf life of two years, provided they are stored in their original packaging and kept tightly sealed.
EDTA/EDTA Salts in liquid form have a shelf life of one year in their tightly sealed original packaging.
We would recommend storing EDTA/EDTA Salts supplied in liquid form in tanks made from AISI 316 Ti or AISI 321 stainless steel.
Ecology and toxicology
EDTA can be broken down and removed from the environment by biotic and abiotic processes.
EDTA is quickly broken down by photochemical degradation.
In particular, EDTA-iron complexes readily decompose on exposure to sunlight into substances that are readily biodegradable.
EDTA is inherently biodegradable, provided that the bacteria are sufficiently adapted and the residence time is long enough.
Both of these conditions can be present in the environment.
EDTA can be broken down quickly by UV oxidation, which can be made use of in industrial wastewater treatment plants.
However, this biodegradation process takes a relatively long time, with the result that the removal rates that are measured with methods such as the Zahn-Wellens test or in treatment plants are generally low. EDTA is not persistent in the environment.
The interaction between the various different mechanisms ensures that the rates of removal are high enough that only a fractional amount of the EDTA that is used finds its way into the environment.
The information given above has been confirmed by experts from EU member states in the EU EDTA Risk Assessment, which was completed in 2004.
No problems affecting consumers were identified in any of the applications for EDTA or in the production of EDTA.
EDTA was found to have low toxicity to aquatic organisms in the environment.
No risks were identified that could be attributed to the influence of EDTA on the mobility of heavy metals.
Please refer to the latest Safety Data Sheets for detailed, up-to-date information on classification, labelling and product safety.
The data contained in this publication are based on our current knowledge and experience.
In view of the many factors that may affect processing and application of our product, these data do not relieve processors from carrying out their own investigations and tests; neither do these data imply any guarantee of certain properties, nor the suitability of the product for a specific purpose.
Any descriptions, drawings, photographs, data, proportions, weights etc. given herein may change without prior information and do not constitute the agreed contractual quality of the product.
It is the responsibility of the recipient of our products to ensure that any proprietary rights and existing laws and legislation are observed.