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ABSTRACT:The removal of toxic metal ions (iron and manganese) from aqueous solution by adsorption was studied. The batch process was used either to remove each metal ion singly or both metals as a multi-component system. The adsorbents used were low-cost materials, viz. palm fruit bunch and maize cob. The adsorption isotherms demonstrated that the adsorbents behaved in a favourable manner towards metal ion adsorption. The adsorption capacities for iron ions on palm fruit bunch and maize cob were in the 57-80% range and for the manganese ion in the 50-79% range for initial concentrations between 1 ppm and 10 ppm. With mixtures of both metal ions, removal of iron ions from the mixture was in the 54-79% range and for the manganese ion in the 54-76% range. The extended Langmuir model gave poor agreement with the data for the adsorption of mixtures of the two metal ions while the P-factor model yielded good agreement.

Tannery effluent is characterized not only by heavy loads but also with toxic heavy metals especially chromium ions. Chromium is considered an important source of contamination due to large volume of exhaust liquid discharged and solid sludge produced. Details on adsorption studies were carried out using synthetic chromium salts (chromium chloride) as adsorbate, and cement kiln dust (a waste from white cement industry) as adsorbent. Equilibrium isotherms have been determined for the adsorption of chromium ions on cement kiln dust. Kinetic study provided that the adsorption process is diffusion controlled. The experimental results have been fitted using Freundlich, Langmuir, and Redlich Peterson isotherms. The maximum adsorption capacity of cement kiln dust was found to be 33 mg/g. Industrial tannery effluent (22-mg/L chromium and COD 952 mg/L) was also treated by cement dust. The treated effluent (using 20 g cement dust per 1 L) contains only 0.6 mg/L chromium and COD 200 mg/L.