Substitutes for traditional chelating agents: eco-friendly GLDA - with bactericidal enhancement function

Traditional detergent additives such as EDTA and STPP are widely used in various water-based detergent formulations to control the effects of metal ions (such as calcium, magnesium or heavy metal ions) on the cleaning effect. Although these additives can significantly improve the cleaning effect and are cost-effective, EDTA has poor biodegradability, while STPP will cause eutrophication of rivers and lakes, which is not conducive to consumer health or the ecological environment. Its use is gradually being restricted or banned.

In line with the trend of greening chelating agents, many chemical product manufacturers have launched various green alternatives, mainly including inorganic clays (such as 4A molecular sieves, montmorillonite, etc.), citrates, gluconates and various improved aminopolycarboxylic acid-type green chelating agents. 4A zeolite is generally used to replace phosphates in washing powder: in the process of active sludge treatment of wheat water, phosphonates are easily adsorbed on the surface of active sludge, but are difficult to biodegrade; although citrates and gluconates are easily biodegradable, their chelating ability is usually not as strong as NTA or EDTA. The most promising alternatives are biodegradable aminopolycarboxylic acid chelating agents, such as GLDA, EDG (or HEIDA), MGDA, IDS and EDDS, among which GLDA has attracted much attention due to its green attributes and acceptable performance.

YUANLIAN CHEMICAL GLDA chelating agent is the abbreviation of glutamic acid N,N-diacetic acid (or tetrasodium glutamate diacetate). Its two enantiomers (L- and D-) have different biodegradation characteristics. L-GLDA is easily biodegradable, while D-GLDA is not easily biodegradable. Therefore, only L-GLDA can be used as a green alternative.

GLDA (generally referring to L-GLDA) is mainly prepared from the natural amino acid L-glutamic acid, and does not contain D-GLDA isomers. Pure L-glutamic acid isomers are fermented with carbohydrates (such as sugar, syrup, corn or rice, etc.) as raw materials. L-glutamic acid is a basic raw material for producing L-GLDA, which is sustainable, renewable and has good toxicological properties.

GLDA combines the advantages of easy biodegradation, strong metal chelation ability and convenient use. In the competition test of calcium chelation under harsh conditions (pH>11, HNB is used as a calcium indicator), GLDA's calcium binding efficiency is close to EDTA, better than NTA, and much higher than other biodegradable chelating agents (such as IDS, EDDS, EDG). In the cleaning formula, its function is similar to that of NTA or EDTA. This makes the replacement process relatively easy and avoids major changes to the surfactant system.

GLDA can not only be used as a substitute for traditional chelating agents, but also shows many unique properties.

The solubility of GLDA in aqueous solutions at different pH is higher than that of NTA and EDTA, and the solubility in NaOH solutions of different concentrations is also much higher than that of Na4-EDTA and Na3-NTA. In HCl aqueous solutions with a mass fraction of 5-28%, the solubility of GLDA can be as high as 55% by mass. These unique solubility properties of GLDA facilitate the formulation of highly concentrated formulations, low pH or high NaOH content cleaning products (such as in-place cleaning formulations and strong alkaline hard surface cleaners used in food processing, kitchen cleaning and automatic dishwasher cleaning products).

GLDA's synergistic effect on biocide activity

Biocides are used as disinfectants in many cleaning formulations or as preservatives in personal care products and cosmetics. EDTA is commonly used in biocide formulations to enhance the activity of biocides, but replacing EDTA with biodegradable chelating agents is still innovative. The synergistic effect of chelating agents on biocide activity may be related to their chelation of calcium and magnesium ions in bacterial cell membranes. It is believed that this effect increases the permeability of biocides to cell membranes, thereby reducing the amount of biocide required in the formulation.

Experiments have shown that GLDA, EDTA and NTA all show synergistic effects, that is, the amount of biocide required to kill 99.99% of microorganisms decreases with the addition of chelating agents. The synergistic effect of GLDA is more significant than that of NTA or EDTA. Adding 50ppm of GLDA can reduce the required fungicide concentration to 20ppm.