Sorption of cadmium and lead from aqueous solutions by spent grain

The sorption of cadmium and lead from aqueous solutions by spent grain, a b y-product of the brewing process, was investigated. The effects of solution pH, ionic strength, initial concentration, ligands and temperature were st udied in batch experiments. The equilibrium process was described well by t he Langmuir isotherm model with maximum sorption capacities of 17.3 and 35. 5 mg/g of cadmium and lead on spent grain, respectively. The enthalpy of so rption was endothermic and the increase in Pb uptake was larger than that o f Cd over the same rise in temperature. The initial uptake was rapid and eq uilibrium was established in less than 120 min. Good correlation coefficien ts were obtained for the pseudo second-order kinetic model. Equimolar conce ntrations of Cd and Pb to ethylenediamine tetraacetic acid and nitrilotriac etic acid almost completely suppressed the uptake of metals. Sorption capac ities of spent grain for cadmium and lead were compared with some low-cost biological materials. (C) 2000 Elsevier Science Ltd. All rights reserved.