REMOVAL OF CADMIUM FROM AQUEOUS SOLUTION USING MANGANESE HEXACYANOFERRATES (II)/(III)

Abstract

A series of solid insoluble mixed potassium manganese hexacynoferrates (II) and (III) of the general formula K_yMn_xFe^II/III(CN)₆.zH₂O were prepared by classical precipitation and local growth methods. All synthesized products were thermally stable up to 300 ^oC and were highly insoluble in most mineral acids except hot perchloric acid. The sorption of cadmium ion from 0.1 M HNO₃ solutions on manganese hexacyanoferrates (II) and (III) was investigated. Both sorption kinetics and isotherms were studied. The sorption kinetics for cadmium uptake was observed to follow two steps with fast kinetics in the first step within 5 min. The manganese hexacyanoferrate(III) was found to exhibit higher sorption capacities than manganese hexacynoferrates(II). The highest sorption capacity was achieved with manganese hexacyanoferrate(III) prepared by local growth method. The uptake of cadmium from aqueous solution appeared to follow adsorption mechanism and not ion exchange as characteristic of many other divalent hexacyanoferrates. The sorption data were fitted with Langmuir adsorption isotherm.

KEY WORDS: Cadmium removal, Potassium manganese hexacynoferrates(II)/(III)


Bull. Chem. Soc. Ethiop. 2007, 21(2), 221-228.