GLDA

What is GLDA?
GLDA is a chelating agent that is increasingly used as a green alternative to NTA and EDTA in detergents and cleaners for softening water. Water softening is based on the ability to form complexes with calcium and magnesium ions. GLDA is a bio-based chemical derived from glutamic acid, an amino acid found in all organisms as a protein building block. The good chelating properties of GLDA are due to its four carboxyl groups, with which the chelator encloses the central atom.

GLDA is usually present as the sodium salt (GLDA-Na4). The hard-to-pronounce chemical name of GLDA-Na4 is tetrasodium N, N-bis (carboxylatomethyl) -L-glutamate. It is derived from L-glutamic acid-N, N-diacetic acid (GLDA-H4).

Properties
GLDA-Na4 is a white, hygroscopic and highly water-soluble solid. The slightly yellow-looking aqueous solution of the salt reacts slightly alkaline at a pH of 11.5. GLDA-Na4 is very soluble in water in a large pH range from 1 to 12, unlike EDTA and NTA. Its thermal stability also clearly exceeds that of the two complexing agents. While EDTA and NTA already decompose at 150 degrees Celsius, the decomposition of GLDA only starts at 280 degrees Celsius. Furthermore, GLDA-Na4 is characterized by a very good biodegradability and is therefore, in contrast to EDTA, NTA and MGDA an environmentally friendly complexing agent.

Manufacturing
GLDA is produced by cyanomethylation of L-glutamic acid. In the conventional process, hydrogen cyanide (hydrocyanic acid) and formaldehyde react with the sodium salt of L-glutamic acid in the neutral medium to give sodium glutamate-diacetonitrile. After adding sodium glutamate-diacetonitrile with sodium hydroxide solution (NaOH), GLDA-Na4 is formed. In this process, however, NTA always forms as a by-product. As a Solverde product, however, GLDA is NTA-free because it is made by a different process.

Application
As a nature-based complexing agent, GLDA is increasingly replacing the conventional complexing agents NTA, EDTA or MGDA. Fields of application are above all ecological cleaning agents or washing raw materials. The usual complexing agents are still widely accepted today. However, their ecological and toxicological profile is extremely unsatisfactory. Thus, EDTA and NTA are produced on a petrochemical basis. Their biodegradability is also not so good. But GLDA is a bio-based chemical made from renewable resources. In addition, GLDA is also readily biodegradable.

All complexing agents have very good complexing properties with respect to calcium and magnesium, the causative agents of water hardness. But GLDA-Na4, in addition to being an environmentally friendly complexing agent, can prevent the precipitation of lime due to its stability, even at high temperatures.

Environmentally friendly washing raw materials and cleaning agents therefore today contain GLDA-Na4 as a so-called builder. Builders improve the emulsifying action of surfactants as they reduce the surface tension of the water through softening. This also improves the cleaning power of detergents and cleaners.

Today, GLDA-Na4 can also replace phosphates in automatic dishwashers and detergents because it is still highly soluble in water and stable even at high pH levels.

For ecological detergents based on GLDA, the Ecocert seal can be applied for, which is awarded by Ecocert Greenlife. Two of the four criteria, such as the use of bio-based chemicals and biodegradability, have already been met. If green working practices and transparency towards the consumer are also guaranteed, the products can be certified.

Among other things, GLDA-Na4 is also used as a food additive or to increase the effectiveness of biocides.