A study on the modification of rice husk by various carboxylic acids showed that tartaric acid modified rice husk (TARH) had the highest binding capacities for Cu and Pb. The carboxyl groups on the surface of the modified rice husk were primarily responsible for the sorption of metal ions. A series of batch experiments using TARH as the sorbent for the removal of Cu and Pb showed that the sorption process was pH dependent, rapid and exothermic. The sorption process conformed to the Langmuir isotherm with maximum sorption capacities of 29 and 108 mg/g at 27 +/- 2 degrees C for Cu and Pb, respectively. The uptake increased with agitation rate. Decrease in sorbent particle size led to an increase in the sorption of metal ions and this could be explained by an increase in surface area and hence binding sites. Metal uptake was reduced in the presence of competitive cations and chelators. The affinity of TARH for Pb is greater than Cu.
The sorption of cadmium and lead from aqueous solutions by spent grain, a by-product of the brewing process, was investigated. The effects of solution pH, ionic strength, initial concentration, ligands and temperature were studied in batch experiments. The equilibrium process was described well by the 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 sorption was endothermic and the increase in Pb uptake was larger than that of Cd over the same rise in temperature. The initial uptake was rapid and equilibrium was established in less than 120 min. Good correlation coefficients were obtained for the pseudo second-order kinetic model. Equimolar concentrations of Cd and Pb to ethylenediamine tetraacetic acid and nitrilotriacetic acid almost completely suppressed the uptake of metals. Sorption capacities of spent grain for cadmium and lead were compared with some low-cost biological materials.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.