Citric acid chelating agent

Katoh, M., Influence of Chelating Agent (Citric Acid) and F on Corrosion of Aluminium , Corros. Sci., 8, 423 (1968)... 

Complexing chelating) agents citric acid, tartaric acid, B sodium tartrate), kerosene, segesterene, sodium citrate, oxalic acid, sodium oxalate, or orthophosphoric acid X... 

Preservatives Antimicrobial Benzalkonium chloride Benzyl alcohol Chlorhexidine Imidazolidinyl urea Phenol Potassium sorbate 1 Benzoic acid Bronopol Chlorocresol Paraben esters Phenoxyethanol Sorbic acid Antioxidants a-Tocopherol Ascorbic acid Ascorbyl palmitate Butylated hydroxyanisole Butylated hydroxytoluene Sodium ascorbate Sodium metabisulphite Chelating agents Citric acid Edetic acid... 

The presence of metals in the fat or oil greatly accelerates the oxidation process. Inactivation of the catalytic effect of these metals, e.g., copper, manganese, and iron, can be achieved by the use of a sequestering agent. Citric acid is one of the most common chelating agents used in the fat and oil industry. 

Carboxylic acids are used in the production of polymers, pharmaceuticals, solvents, and food additives. Industrially important carboxylic acids include acetic acid (component of vinegar, precursor to solvents and coatings), acrylic and methacrylic acids (precursors to polymers, adhesives), adipic acid (polymers), citric acid (beverages), ethylenediaminetetraacetic acid (chelating agent), fatty acids (coatings), maleic acid (polymers), propionic acid (food preservative), terephthalic acid (polymers). 

Certain compounds, known as chelating agents (qv), react synergisticaHy with many antioxidants. It is beheved that these compounds improve the functional abiUties of antioxidants by complexing the metal ions that often initiate free-radical formation. Citric acid and ethylenediaminetetraacetic acid [60-00-4] (EDTA), C2QH2gN20g, are the most common chelating agents used (22). 

The lanthanides form many compounds with organic ligands. Some of these compounds ate water-soluble, others oil-soluble. Water-soluble compounds have been used extensively for rare-earth separation by ion exchange (qv), for example, complexes form with citric acid, ethylenediaminetetraacetic acid (EDTA), and hydroxyethylethylenediaminetriacetic acid (HEEDTA) (see Chelating agents). The complex formation is pH-dependent. Oil-soluble compounds ate used extensively in the industrial separation of rate earths by tiquid—tiquid extraction. The preferred extractants ate catboxyhc acids, otganophosphoms acids and esters, and tetraaLkylammonium salts. 

Formulated metal poHshes consist of fine abrasives similar to those involved in industrial buffing operations, ie, pumice, tripoH, kaolin, rouge and crocus iron oxides, and lime. Other ingredients include surfactants (qv), eg, sodium oleate [143-19-1] or sodium dodecylben2enesulfonate [25155-30-0], chelating agents (qv), eg, citric acid [77-92-9], and solvents, eg, alcohols or aUphatic hydrocarbons. 

Addition of secondary chelating agents, eg, polyols such as sorbitol or mannitol and the strongly chelating a-hydroxycarboxyhc acids such as citric or oxahc, prevents development of turbidity outside the pH range of 9—11 (115—117). 

Citric acid is utilized in a large variety of food and industrial appHcations because of its unique combination of properties. It is used as an acid to adjust pH, a buffer to control or maintain pH, a chelator to form stable complexes with multivalent metal ions, and a dispersing agent to stabilize emulsions and other multiphase systems (see Dispersants). In addition, it has a pleasant, clean, tart taste making it useful in food and beverage products. 

Textiles. Citric acid acts as a buffer in the manufacture of glyoxal resins which are used to give textiles a high quaUty durable-press finish (see Amino resins). It has been reported to increase the soil-release property of cotton with wrinkle-resistant finishes and is used as a buffer, a chelating agent, and a non-volatile acid to adjust pH in disperse dying operations (182—193). 

Citric acid is used as a chelating agent in catalyst systems for making resins, and citrate esters are used as plasticizers (qv) in PVC film, especially in food packaging (207). 

These compounds should be dissolvable in a clean-up solution containing a quaternary organic ammonium salt, or simply ammonium chloride [1749]. The solubilities of some selected particulate bridging agents are shown in Table 9-1. A chelating agent such as citric acid or its salts is also included in the clean-up solution. 

Higher phytoextraction coefficients indicate higher metal uptake. The effectiveness of phytoextraction can be limited by the sorption of metals to soil particles and the low solubility of the metals however, metals can be solubilized through the addition of acids or chelating agents and so allow uptake of the contaminant by the plant. Ethylene diamine tetra-acetic acid (EDTA), citric acid, and ammonium nitrate have been reported to help in the solubilization of lead, uranium, and cesium... 

Oxidation Trivalent arsenic citric acid or EDTA Potassium permanganate depending on chelating agent, metal chelate is either strongly sorbed to soil or is highly mobile and can be flumbed usinj water or dilute acid solutions. Oxidizes trivalent arsenic to pentavalent... 

Most divalent and trivalent ions, with the exception of the alkaline-earth metals, are effectively chelated by the hydroxycarboxylates citric and tartaric acid, and citric acid will also sequester iron in the presence of ammonia. Another hydroxycarboxylate, gluconic acid, is especially useful in caustic soda solution and as a general-purpose sequestering agent. 

Copper sulfate is used to control protozoan fish ectoparasites including Ichthyopthirius, Tri-chodina, and Costia. The effectiveness of the treatment diminishes with increasing total alkalinity and total hardness of the water (Straus and Tucker 1993). Copper compounds now used to control protozoan parasites of cultured red drum (Sciaenops ocellatus) include copper sulfate, copper sulfate plus citric acid, and chelated copper compounds (forms of copper bound by sequestering agents, such as ethanolamine) chelated copper compounds are considered less toxic to fish than copper sulfate and at least as effective in controlling parasites (Peppard etal. 1991). 

L-ascorbic acid and, 25 751 as chelating agent, 5 731 in cocoa shell from roasted beans, 6 357t Oxalic-acid-catalyzed novolacs, in molding compounds, 75 786 Oxalic acid esterification, 72 652 Oxaloacetic acid, in citric acid cycle, 6 633 Oxalosuccinic acid, in citric acid cycle, 6 633... 

There have been several investigations of plutonium uptake by plants and several authors have reviewed the various articles (124-126). Based on studies with plant-soil systems direct root uptake into the plant appears to be low. Concentration factors for (pCi/g dry acceptor)/(pCi/g donor) are of the order 10-5 to 10 4 (127). However, variations in the chemical form of plutonium and the presence of chelating agents in the soil can result in the concentration of more plutonium in the plant. Over five years Romney et aL (33) observed that the plutonium concentration in ladino clover increased from 3.1 dpm/g for the first year to 22.6 dpm/g in the fifth year. It should be noted that clovers release citric acid into the soil (113). 

Zhang,Y Kallay, N. Matijevic, E. (1985) Interactions of metal hydrous oxides with chelating agents. VII. Hematite - oxalic and citric acid systems. Langmuir 1 201-206 Zhang, Z. Boxall, C. Kelsall, G.H. (1993) Photoelectrophoresis of colloidal iron oxides. I. Hematite (a-Fe203). Colloids Surfaces. A. Physics Chemical and Engineering Aspects. 73 145-163... 

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