Removal of Pb(II) ions from aqueous solution by manganese oxide coated rice straw biochar A low-cost and highly effective sorbent

Abstract MnOx-coated rice straw biochar was simply synthesized through the reaction of rice straw biochar with KMnO4 in aqueous solution. SEM-EDS analysis confirmed the successful coating of Mn on the surface of the biochar. XPS and FTIR analyses were carried out to study the possible mechanism of Pb(II) binding onto rice straw (RS) biochar and MnOx-coated RS biochar. The work focused mainly on the evaluation of the sorbents for Pb(II) binding. Effect of solution pH, agitating time, Pb(II) initial concentration and co-existing Ca(II) ions on Pb(II) binding were examined. Both for RS biochar and MnOx-coated RS biochar, sorption kinetic data closely follow the pseudo-second-order model. Langmuir isotherm fits well with the experimental data, and the maximum sorption capacity for Pb(II) calculated from Langmuir model were 0.5782 and 1.4732 mmol g−1 for RS biochar and MnOx-coated RS biochar, respectively. This study suggested that KMnO4 modification is a simple and effective method to increase the sorption capacity of RS biochar.