Adsorption of lead ions from an aqueous solution onto NaOH-modified rice husk

Abstract

In the current study, the adsorption of toxic lead ions from aqueous solution by NaOH-modified rice husk (MRH) was investigated. The effect of operating factors such as contact time, amount of MRH (adsorbent), initial concentration of metal ions (lead ions) in aqueous solution, temperature and initial solution pH on the adsorptive removal of lead ions from aqueous solution by using MRH was considered. The adsorption results demonstrated that the percentage removal of lead ions was increased with contact time, mass of MRH and pH while declined with initial concentration of lead ions and temperature. Adsorption of lead ions onto MRH was subjected to Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherms. Results represented that adsorption of lead ions fitted well to Langmuir isotherm indicating that surface adsorption and mono-layer coverage of lead ions onto MRH surface. The maximum Langmuir adsorption capacity was 28.6 mg/g. The kinetic study illustrated those lead ions adsorption onto MRH was fitted to pseudo-second-order kinetic model. The thermodynamic parameters investigations revealed that lead ions removal by MRH was an exothermic and spontaneous adsorption process. The MRH demonstrated more than 75% removal of lead ions after 4 adsorption/desorption cycles. Therefore, MRH could be utilized as an extraordinary adsorbent for removal of lead ions from aqueous solution.