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How to understand EDTA in one page?
Apr 07, 2018

1、Briefing


 EDTA (ethylenediaminetetraacetic acid), the abbreviation of four meta carboxylic acid ethylenediamine tetra acetic acid, is an important synthetic organic polybasic acid complexing agent. The most important chemical property is that it can form a highly stable water soluble complex with various metal cations, so it has strong complexing and can prevent metal ion precipitation and prevent it. Catalytic action of metal ions to increase the availability of metal ions in solution or to remove metal ions from the system. Widely used in commercial and domestic detergents, textile and papermaking bleaching process, metal plating process, food industry, medicine and agriculture. At the same time, because it is difficult to be removed by conventional water and wastewater treatment process, it has become the highest concentration of synthetic organic compounds in many surface water and groundwater.


2、 Physicochemical properties


 EDTA is a hexadentate chelating agent, each EDTA molecule can provide four oxygen atoms and two nitrogen atoms, can form six coordination bonds with a metal ion.

 The most important chemical property is the ability to form highly stable water-soluble complexes with various metal cations.

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3、Preparation method


1. chloroacetic acid method: chloroacetic acid reacts with alkali to produce sodium chloroacetate and then condensate with ethylenediamine to produce sodium ethylenediamine tetra acetic acid (four), and EDTA is obtained on the basis of acidification.

2. sodium cyanide method: sodium cyanide and formaldehyde react with ethylenediamine under alkaline conditions to produce ethylenediamine tetra acetic acid four sodium.


4、Action mechanism


EDTA deals with the mechanism of heavy metals in soil: most of the metals in contaminated soil do not exist in the liquid phase, but rather on the solid phase and are strongly adsorbed by soil particles. Therefore, the ability of plant to repair metal is not only related to the rate of absorbing metals from the soil, but also related to the solubility of heavy metals in soil solution. Therefore, the application of heavy metal mobile agent to the soil can promote the absorption and enrichment of heavy metals. For example, the use of chelating agent EDTA can chelate or coordinate some hard moving heavy metals such as Pb, Cu and Cd to form a movable compound, and then to reduce the content of heavy metals in the soil with water leaching or rebuilt plants.