Modification of Peanut Shell Biochar and Its Adsorption Performance

Abstract

In order to improve the efficient recovery and utilization of agricultural waste, biochar was prepared from peanut shells through oxygen-limited pyrolysis at 240 °C in this work, and biochar was modified with sodium hydroxide solution to explore the adsorption performance of Pb2+ on biochar before and after modification. The specific surface area, pore structure, surface functional groups, microscopic morphology, surface element distribution of the peanut shell biochar before and after modification were analyzed by Brunauer-Emmett-Teller (BET), Fourier transform infrared Spectroscopy (FTIR), and Scanning Electron Microscopy-Energy Dispersive Spectrometer (SEM-EDS). The Pb2+ adsorption experiments on biochar before and after modification were carried out under different conditions, it was found that the suitable solution pH for biochar to adsorb Pb2+ were both 5.5~6.5, the suitable solid-liquid ratio of unmodified biochar was 2.5 g·L−1, the suitable solid-liquid ratio of modified biochar was 2.0 g·L−1, and equilibrium adsorption time of modified biochar was shortened. The adsorption behaviors of the two kinds of biochar conformed to Pseudo-second-order kinetic model and Langmuir isothermal model, thermodynamic parameters were ΔG < 0, |ΔG| < 40 kJ·mol−1, ΔH > 0, ΔS > 0. These adsorption processes were spontaneous endothermic processes including both physical and chemical adsorption.