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The use of fly ash for the removal of victoria blue (CI26,44045) from aqueous solution at different concentrations and p H has been investigated. The process follows first order adsorption rate expression and the rate constant was found to be 1*70XlO-' min-l at a victoria blue concentration of l-OX10-4~and25"C. The uptake of victoria blue by fly ash is diffusion controlled and the value of mass transfer coefficient is 1-25 X 1 0-5 cm sec-l. The equilibrium data fit well in the Langmuir model of adsorption. Maximum removal was noted atpH 8.0. Low desorption of dye from adsorbent surface indicates that the process may not be essentially a reversible one.

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The ability of a homogeneous mixture of fly ash and wollastonite (1:1) to remove Cr(V1) from aqueous solutions by adsorption has been investigated. The extent of removal is dependent on concentration, pH and temperature of the solution. The applicability of the Langmuir isotherm for the present system has been tested and the surface mass transfer coefficient at 30°C and pH 2.0 determined. Maximum removal was observed at pH 2.0 and 30°C. The adsorption is first governed by diffusion followed by surface compound formation. The thermodynamic parameters, desorption results and infrared studies indicated that the surface compounds, formed by interaction of adsorbate ions and different constituents of mixed adsorbent, were stable in nature.

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Wollastonite was used as an adsorbent for the removal of Fe(II) at different experimental conditions. The extent of removal is favourable at low concentration and low temperature. Maximum adsorption was noted at pH 4.0. The batch adsorption kinetics has been described by a first order rate expression, and the surface mass transfer coefficients and diffusion coefficients have been calculated at different temperatures. The intraparticle transport of Fe(II) within the pores of wollastonite is found to be the rate limiting step. The applicability of the Langmuir isotherm for the present system has been tested at different temperatures. Thermodynamic parameters indicate the exothermic nature of Fe(II) adsorption on wollastonite. The variation of adsorption with pH has been explained on the basis of interaction of iron species with negatively charged constituents of adsorbent.