Adsorption of anionic dyes on to waste Fe (III)/Cr (III).

Waste Fe (III)/Cr (III) hydroxide was investigated for the removal of anionic dyes, namely acid brilliant blue (acidic dye) and procion red (reactive azo dye) from aqueous solution. In batch experiments, parameters studied include contact time, adsorbate concentration, pH, adsorbent dose and temperature. Adsorption followed Langmuir isotherm with adsorption capacity of 10.37 and 3.28 mg/g for acid brilliant blue and procion red, respectively. Adsorption kinetic studies showed second order with respect to acid brilliant blue and first order with respect to procion red. Thermodynamic parameters such as free energy, enthalpy and entropy of adsorption were also evaluated.