Low cost bio-sorbent 'wheat bran' for the removal of cadmium from wastewater: kinetic and equilibrium studies

Novel bio-sorbent wheat bran has been successfully utilized for the removal of cadmium(II) from wastewater. The maximum removal of cadmium(II) was found to be 87.15% at pH 8.6, initial Cd(II) concentration of 12.5 mg l-1 and temperature of 20 degrees C. The effect of different parameters such as contact time, adsorbate concentration, pH of the medium and temperature were investigated. Dynamics of the sorption process were studied and the values of rate constant of adsorption, rate constant of intraparticle diffusion and mass transfer coefficient were calculated. Different thermodynamic parameters viz., changes in standard free energy, enthalpy and entropy have also been evaluated and it has been found that the reaction was spontaneous and exothermic in nature. The applicability of Langmuir isotherm showed of monolayer coverage of the adsorbate on the surface of adsorbent. A generalized empirical model was proposed for the kinetics at different initial concentrations.