Biosorption of metal ions on lignocellulosic materials: batch and continuous-flow process studies

Metal adsorption capacities of bioadsorbents, derived from low-cost agricultural waste, were assessed. Batch and column experiments were conducted for evaluation of lead (Pb), cadmium (Cd), and chromium (Cr) sorption kinetics on to modified ( by treating with base and acid) and unmodified sugarcane bagasse and corn cob. Langmuir, Freundlich, and Redlich-Peterson equations were used to understand metal adsorption behavior and Elovich and Lagergren's pseudo-firstorder and pseudo-second-order kinetics equations were used for estimation of adsorption kinetics parameter. The suitability of the models to experimental data was reflected by high r(2) values. Among sorption models, Langmuir and Redlich-Peterson were proved equally good and Cd, Cr, and Pb adsorption process followed the Langmuir isotherm. Batch adsorption experiment showed that the metal adsorption ability of the treated materials was higher than that of untreated. The adsorption sequence was Pb > Cr > Cd. Pseudo-second-order kinetics model was found suitable in describing the obtained data. Result of the column adsorption experiments supplement the batch results and revealed the role of agricultural waste materials in remediation of heavy metal-polluted water.