Cadmium organic complexation

Krishnamurti, G. S. R., Megharaj, M., and Naidu, R. 2004. Bioavailability of cadmium-organic complexes to soil alga an exception to the free ion model. J. Agric. Food Chem. 52, 3894-3899. 

Heavy Metals. Heavy metals of particular concern in the treatment of wastewaters include copper, chromium, 2inc, cadmium, mercury, lead, and nickel. They are usually present in the form of organic complexes, especially in wastewaters generated from textiles finishing and dye chemicals manufacture. 

Organic complexed Cd is not important in arid soil solution. Hirsh and Banin (1990) observed 5-10% of Cd bound to organic ligands in Israeli arid soil solution. Emmerich et al. (1982) found that organic-Cd complexes constituted 1-4% of Cd in California arid soil solution. However, Villarroel et al. (1993) reported that in a California sludge-treated soil, Cd was mainly present in both free ion and organic complex forms (each accounted for 32-40% and 30-45% of total Cd in soil solution, respectively), followed by the chloride complexes (8-20%), S04-complex (3-10%), and P04-Cd complex (1.5-7.7%). The nitrate Cd complexes were the lowest. Cadmium activities and speciation is not significantly affected by P and N treatments. 

Armannsson [659] has described a procedure involving dithizone extraction and flame atomic absorption spectrometry for the determination of cadmium, zinc, lead, copper, nickel, cobalt, and silver in seawater. In this procedure 500 ml of seawater taken in a plastic container is exposed to a 1000 W mercury arc lamp for 5-15 h to break down metal organic complexes. The solution is adjusted to pH 8, and 10 ml of 0.2% dithizone in chloroform added. The 10 ml of chloroform is run off and after adjustment to pH 9.5 the aqueous phase is extracted with a further 10 ml of dithizone. The combined extracts are washed with 50 ml of dilute ammonia. To the organic phases is added 50 ml of 0.2 M-hydrochloric acid. The phases are separated and the aqueous portion washed with 5 ml of chloroform. The aqueous portion is evaporated to dryness and the residue dissolved in 5 ml of 2 M hydrochloric acid (solution A). Perchloric acid (3 ml) is added to the organic portion, evaporated to dryness, and a further 2 ml of 60% perchloric acid added to ensure that all organic matter has been... 

The unstable parent compound, 1,2,4-oxadiazole, was not reported until 1962.39 Moussebois and co-workers treated formamidoxime with the mixed anhydride of formic and acetic acids to get the 0-formyl-formamidoxime, which gave the oxadiazole upon heating. The product, very soluble in water and organic solvents, was isolated as the cadmium chloride complex, from which oxadiazole was obtained by vacuum distillation at 30°. 

This method is for the determination of cadmium, cobalt, copper, iron, manganese, nickel, lead and zinc, which are solvent extracted and concentrated as their diethyldithiocarbamate chelates. After destruction of the organic complexes dissolution of the residue in dilute acid gives a solution suitable for atomic absorption analysis [13]. 

Cadmium, like zinc, binds to a protein, metallothionein, in the body The presence of cadmium increases the production of this protein by many times (the body increases detoxication, when threatened, which may be a reason for the development of tolerance). Although the binding removes the cadmium and effectively detoxifies it, the cadmium-protein complex is deposited in the kidneys and cadmium is eventually released, whereupon it seriously damages the organ. 

Decrystallization of cellulose by swelling agents or solvents can be brought about by concentrated sodium hydroxide amines me-tallo-organic complexes of copper, cadmium, and iron quaternary ammonium bases concentrated mineral acids (sulfuric, hydrochloric, phosphoric) concentrated salt solutions (beryllium, calcium, lithium, zinc) and a number of recently investigated mixed solvents (J6). 

Heavy Metals (e.g.cadmium) Sulfide precipitation Formation of mobile polysulfide and organic complexes under certain conditions with low Fe(0H)3 concentrations strong increase mobility under acidic conditions... 

Phosphoric, sulfuric, nitric acids Zinc chloride, thiocyanates, iodides, bromides Organic amines, aminoxides, CH3NH2 Inorganic complexes of cadmium, copper, iron Organic complexes CH3NH2/DMSO Stable compounds esters, ethers Unstable derivatives of... 

The indirect determination of certain organic substances can be made by complexometric titration methods. Such methods depend on the formation of an insoluble product between the organic material and a metal then, either the excess metal in solution is determined by a suitable titration with EDTA, or the metal-containing precipitate is decomposed and the liberated metal ions titrated. Thus, for example, narcotine, papaverine, codeine, strychnine and brucine have been determined by formation of iodobis-muthate complexes, chlorpromazine and quinine" as cadmium iodide complexes, purines and nicotinic acid derivatives by precipitation with mercury and barbiturates by precipitation with zinc. ... 

The atmospheric pollution by cadmium is a result both of natural and man-made activities, such as the combustion processes based on fossil fuels (in particular coal and oil) and the emission from processes in the pyro-metallurigical non-ferrous metal industries. The deposition, transport, and inhalation processes are controlled predominantly by the size of the atmospheric aerosols, so that the primary type of speciation of interest to atmospheric chemists is the metal size distribution. However, chemical speciation (in terms of the distribution of both the dissolved/ particulate species and the inorganic/organic complexes) is important in governing... 

---