José M. Bisang

Cadmium removal from aqueous sulphate solutions by treatment with iron felts

The possibility of removing cadmium from effluents byelectrochemical treatment using iron felts as three-dimensional electrodes was investigated. It was found that iron felts remove cadmium by three paths: (i) adsorption of cadmium ions by hydrous ferric oxide, (ii) cathodic electrodeposition and (iii) precipitation of cadmium hydroxide due to the localized alkalinity produced by the hydrogen evolution. The adsorption isotherm, at 30°C, of cadmium ions from an aqueous sulphate solution on hydrous ferric oxide is given. The influence of cathodic potential, volumetric flow rate and interelectrode gap on the current, current efficiency and fractional conversion is discussed. The iron felts proved to be efficient in removing cadmium. The highest fractional conversion, ≌25% for single pass operation, with 100% current efficiency was obtained for a volumetric flow rate of 9·57×10−6 m3 s−1 using iron felt cathodes of 4×10−3 m thickness potentiostated at potentials lower than −1·5 V against a saturated calomel electrode.