Chelating Agents

Abstract

Chelating agents or chelants are compounds having two or more donor atoms that can form cyclic coordination complexes or chelates with acceptor metals. The complexation is an equilibrium reaction that often strongly favors the complex. Chelating is used to modify or control the behavior of metals and their compounds by controlling the concentration of the metals in solution or to utilize the special properties of the chelation compounds. The active groups in chelants may be linear chains, eg, NCCN, macrocyclic rings, eg [OCC] n , or polycyclic structures, such as the cryptates, eg, X[CCYCC) n ] 3 Y, where X and Y are bridgehead and donor atoms, respectively. Some pH, stability, solubility, and electrochemical relationships among simultaneous equilibria in chelation are shown. A broad range of applications based on concentration control, the special properties, and medical uses of chelation compounds are given. Metal sequestration, solubilization, and buffering are discussed as are metal extraction, precipitation, and displacement. Economic data for industrial chelating agents are given. Use of chelating agents is essentially benign environmentally and presents little or no hazard to health or safety under normal conditions of use and handling.

Hypericum triquetrifolium and H. neurocalycinum as Sources of Antioxidants and Multi-Target Bioactive Compounds: A Comprehensive Characterization Combining In Vitro Bioassays and Integrated NMR and LC-MS Characterization by Using a Multivariate Approach

“…Metal chelation is a crucial antioxidant defence mechanism. In fact, metal chelators can sequester metal ions by forming cyclic coordination complexes ( Howard and Wilson, 2003 ). The participation of metal ions such as iron species in Fenton reaction generate oxidizing species which contribute to oxidative stress and cause oxidative damages to biomolecules ( Zhao, 2019 ).…”

Green Extractants in Assisting Recovery of REEs: A Case Study

“…Therefore, the conditional constant gives the relationship between the concentration of formed complexes and unreacted REE ions and the complexing agent [ 30 ]. The appropriate constant can be found in [ 33 ] compared with sodium tripolyphosphate Na 5 P 3 O 10 (STPP), ethylenediaminetetraacetic acid C 10 H 16 N 2 O 8 (EDTA), and ethylenediaminetetra(methylenephosphonic acid C 6 H 20 N 2 O 12 P 4 (EDTMP). They all increase with the increasing temperature.…”

Pure Metal Chelate Solutions by Ion Exchange

“…Metal chelate solutions are ubiquitous. , For example, iron chelate solutions are used in photography, gas treating, − and plant and human , nutrition. Chelate solutions of calcium, manganese, zinc, and copper, among others, are also used as micronutrients .…”