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Introduction |
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Why be concerned? |
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Supplier progress |
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Potential impacts |
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Functional groups |
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Substance list |
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Legislation / REACH |
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FAQs |
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Related Links |
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Wash with care |
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Environmental assessment of laundry detergents |
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Complexing agents |
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General info: Soiling and hard water contain quantities of calcium- and magnesium ions which destroy the effects of the anionic surfactants. This means a lesser cleaning effect with the same amount of detergents. The complexing agents ‘soften’ the water by binding calcium and magnesium ions in a ‘complex’. Another major function of the complexing agents is to stabilise the bleaching system by preventing the metal ions from acting as catalysts. Such catalysts would increase the oxidising effects of the bleaching agents and in a way that damages the textile fibres. Environmental properties Certain complexing agents are slowly biodegradable and it is suspected that strong complexing agents are under suspicion to ‘mobilise’ metals in wastewater treatment plants and in nature. In particular EDTA and phosphonates have been suspected to have this effect, but no scientific evidence has been documented. The obvious alternative to the use of these substances is to soften the water by ionic exchange before laundering. Specific groups: Carboxylates (e.g. Tartrate, Citrate or Gluconate) The substances in this group are weak complexing agents. They are readily degradable and non-toxic to aquatic organisms. Citrate is frequently used in laundry detergents together with other complexing agents or with surfactants not sensitive to water hardness. EDTA (Ethylene Diamine Tetra Acetate) EDTA is used in small amounts in many detergents as a stabiliser for perborate. EDTA is slowly degradable and has been found to pass through the wastewater treatment plants due to its weak settling properties. It has no tendency to bio-accumulate and is low-toxic to fish and crustaceans. EDTA has been under suspicion to be able to ‘mobilise’ and increase the movement of metals but no such effects have been scientifically proved in real scale with the very low concentrations used today. More information: CEFIC / EAC – European Amino-carboxylates producers Committee: EDTA - Favorable results of the European Risk Assessment, March 2003 CEFIC / EAC – European Amino-carboxylates producers Committee: European Risk Assessment on EDTA, March 2003 NTA (Nitrilo TriAcetate) NTA is used in all kinds of cleaning agents and laundry detergents. NTA is considered to be readily degradable and hence the potential mobilisation of metals is considered to have no practical consequence. NTA has very low vertebrate toxicity. In April 2006, the EU Committee for Classification and Labelling of Chemicals decided that NTA will be classified Xi; R36/37, Xn; R22 and R40 (limited evidence of a carcinogenic effect) for products containing more than 5%. More information: www.ecb.jrc.it
Oxalic acid Oxalic acid is used specifically to bleach iron spots (rust) where it binds the iron ions. It is used only for spot removal or re-washing in limited volumes. It is a natural substance in many vegetables – in particular ‘rhubarb’ – and can be considered a harmless substance from an environmental point of view. Oxalic acid has to be stored and handled with care due to strong corrosive and etching effects. Phosphates (e.g. Sodium tri-phosphate or Tetra Potassium pyro-phosphate) Phosphates are the most widely used water softener around the world, due to their simple structure and active effect. Phosphorus is a vital nutrient for all living organisms. Surplus of phosphorus / phosphates in aquatic systems may lead to over-fertilising and consequent uncontrolled growth of algae – the phenomena known as ‘euthrophication’. The consequences of euthrophication can be quite serious, with mass mortality of fish due to oxygen deficiency during the degradation of the algae. It is estimated that approximately 20% of the load of phosphorous substances in municipal waste water treatment plants in Europe are derived from laundry detergents. Treatment plants typically remove 90-95% of phosphates, depending on the type of treatment. Since most industrial laundries discharge to public treatment plants or treat the waste water themselves before discharge, the use of phosphates is not considered a problem. Phosphonates / ‘Phosphone acids’ This group of substances are strong complexing agents. Their main function is to act as stabilisers for bleaching systems e.g. per-carbonates. Phosphonates are generally not readily degradable or slowly degradable and their toxicity to aquatic organisms is low or moderate dependent on the organism. Due to the strong complexing effect, like EDTA, phosphonates have been suspected of mobilising metals, but no concrete evidence has ever been presented. Poly-carboxylates This group consists of weak complexing agents often slowly degradable but are neither bio-accumulating nor toxic to aquatic organisms. It is often necessary to use a stabiliser to prevent poly-carboxylates from degradation in the detergent mixture. Zeolites Zeolites are hydrated alkali aluminium silicate. They are weak complexing agents. The minerals do not dissolve in the liquid but reacts as an ionic-exchange material suspended in the wash liquid. This means that there may be problems with sedimentation of the particles on the surfaces of the textiles leading to greying problems unless rinsing is increased, leading to increased water consumption. Zeolites are an inert material from a biological point of view and hence they have no harmful effects on biological organisms. The use of zeolites may slightly increase the volumes of sludge produced in the waste water treatment plants. More information at: www.zeodet.org
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Function: ‘Soften’ and condition the water for the detergents to be active and stabilise bleaching systems |
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Examples: Phosphates, phosphonates, carboxylates |
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Synonyms: Softeners, complexing agents, builders, chelating agents and sequestering agents. |
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Environmental impacts: Differ greatly between the different chemicals groups used. Please see below. |
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The functional groups:
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Water softening in professional laundries:
Water softening by ionic exchange is a normal procedure in industrial laundries and hence the consumption of complexing agents is significantly reduced compared with household laundering. By softening the water the use of fabric softeners is also reduced. |
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Phased out! EDTA was been phased out of most detergents for professional use several years ago due to its potential negative environmental effects. |
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Valuable fertiliser The phosphates end up in the sludge from the wastewater treatment plants where it is considered a valuable resource when the sludge is used as fertiliser in agriculture. |