Chitosan-coated Magnetic Biochar as Adsorbent for Removal of Pb (II) from Aqueous Solution

Abstract

Currently, lead, considered as one of the most hazardous heavy metal species in aqueous phase, has caused world-wide attention due to its toxicity, which potentially risks public health. Treatment methods, such as chemical precipitation facilities, ion exchange units, and electro-chemical and membrane techniques have been widely applied for heavy metal removal from the aqueous phase. However, those treatment methods are usually either uneconomical or inefficient to operate. Biochar, a carbon-rich material, is acquainted with the features of porosity, low cost, and environmentally sustainable. Chitosan is a polysaccharide consisting of copolymer of glucosamine and N- acetylglucosamine that can be obtained from shrimp shell and has been commonly employed to coat other particles such as clay and glass beads. The overarching goal of this research study was to investigate the adsorption performance differences between biochar, magnetic biochar, and chitosan-coated magnetic biochar for lead. To gain an insight on to the adsorption mechanism, kinetic and isotherm models were applied to analyse the data obtained from the corresponding batch adsorption experiments. Results of this work showed that the adsorption capacity altered over initial solution pH adjustment and concentration and the resultant pH increment resulted better adsorption performance of lead ions. Additionally, the adsorbents used showed a relatively better removal performance in lower initial solution concentration of 5mg/L. The adsorption removal performance increased over controlled contact time and a rapid increase could be observed from 30 mins to 360 mins. Afterwards, the 70% - 90% adsorption capacity was achieved, the stage was defined as equilibrium or contact time which was used in the subsequent isotherm studies. Overall, the effect of temperature on the adsorption of lead by the sorbents studied revealed that the process is temperature dependent. The isotherm modelling at 10, 20 and 30oC showed that the adsorbate formed multi-layer onto the adsorbents, and Langmuir model failed to describe the data better. The Freundlich model was found to be more favourable to describe the adsorption process, implying that the lead ions removal process is a heterogeneous system. Key word: Lead, adsorption, biochar, magnetic biochar, chitosan