Step 1. Role of Incumbent Chelant

Chelants in bleach-activated powder laundry detergents have a number of key roles to play - bleach stabilization, dye and fabric protection, stain removal, and scale inhibition. 

Laundry powders in Europe use sodium percarbonate and a bleach activator, tetraacetylethylenediamine ( ED), to form peracetic acid in the washing machine that then reacts with bleachable stains such as tea, red wine, coffee, and curry to remove /bleach them from cloth. Transition metal ions, in particular copper, cause first decomposition of peracetic add before it can bleach stains and second react with peroxide to form highly readive hydroxyl radicals that can cause dye and fabric damage [32]. Chelants bind with copper and other metals to prevent these unwanted side readions. 

Chelants can also aid stain removal by removing metal ions from stains to help lift the stain from the cloth and reduce the color of the stain. Additionally, chelants in combination with builders such as zeolite and phosphate bind with hardness ions to keep these in solution and prevent cloth graying, and in the case of phosphonates, also to prevent scale formation in the washing machine, which can lead to blockages and reduced machine performance. 

Phosphonates are commonly used in laundry powders at 0.5-1.0% of the powder, DTPMP and EDTMP for all uses and HEDP mostly for hardness ion control. Wash conditions for powder detergents are usually pH 9-10 and typical temperatures of 40-60 °C, although there is a strong drive to reduce this to 30 °C or even to use a cold water wash. 

Metal ion concentrations in water vary enormously across Europe. The water hardness of the market area can be found fairly easily from water companies hardness maps. Some data on transition metal ion limits and measurements can also be found from water quality data, but even these might not be enough to determine what the consumer uses. For instance, metal ions can dissolve out of pipework into domestic water after it has left the water supplier s plant. Copper is commonly leached out of copper pipes and this can be more acute after leaving for even as short a time as overnight, and so while typical copper levels are much less than 1 ppm [33] there have been measurements up to 5 ppm [34] from domestic taps in European households. 

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