Preparation and Characterization of Biochar from Four Types of Waste Biomass under Matched Conditions

Abstract

Four contrasting types of waste biomass were subjected to matching treatments to prepare biochar for the potential removal or immobility Cr(VI) in polluted water or soil. Rice straw (RS), rice husk (RH), kraft lignin (KL), and cow dung (CD) were selected. The resulting biochars were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and N2 adsorption-desorption isotherms. The physicochemical properties of biochars, such as pH value, ash, yield, and cation exchange capacity (CEC) were also determined. The results showed that the biochars were alkaline, except for the KL biochar (KLBC), which was weakly acidic. Furthermore, the order of CEC was cow dung biochar (CDBC) > rice straw biochar (RSBC) > rice husk biochar (RHBC) > KLBC. FTIR showed that there are abundant oxygen-containing functional groups on the surface of the biochars, with the total amount almost the same, and the structure was dominated by aromatic ring skeleton. The KLBC with micro-nano structure exhibited higher surface area (111 m2/g) than the other BC samples. The Cr(VI) removal followed the order: KLBC > CDBC > RHBC > RSBC.