Adsorption of Cd(II) and Pb(II) by Mg-modified straw biochar

Abstract

In this work, magnesium-modified rice straw biochar (MgBC) was prepared by chemical impregnation, and the effects of proportion, initial pH, contact time, temperature and initial concentration on the removal of Cd(II) and Pb(II) by MgBC were investigated. Additionally, scanning electron microscopy, Brunauer–Emmett–Teller, Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) were used for the characterisation of MgBC. The results shown that MgBC surface contained massive Mg-particles and possessed more abundant O-containing groups. Batch adsorption experiments shown that the optimum adsorption efficiency of Cd(II) and Pb(II) by MgBC was achieved at ratio of 1:2 and initial pH of 6.0. The pseudo-second-order kinetic model and the Langmuir isothermal model could better describe the removal of Cd(II) and Pb(II) by MgBC. The maximum adsorption capacity of Cd(II) and Pb(II) by MgBC was 92.68 and 128.06 mg/g at pH 6.0, 35°C and initial concentrations of 10~100 mg/L, respectively. FTIR and XRD analysis shown that the removal mechanism of Cd(II) and Pb(II) by MgBC involved complexation, ions exchange, co-precipitation and electrostatic interaction. After 4 adsorption–desorption experiment, the removal efficiency of Cd(II) and Pb(II) by MgBC remained above 80%. This results indicated that MgBC had great potential for the treatment of wastewater containing Cd(II) and Pb(II).