Adsorption behavior of 2,4-DCP by rice straw biochar modified with CTAB.

In this study, rice straw was used as the raw materials of biomass carbon to prepare biochar at different temperatures (400°C, 500°C, 600°C, 700°C, and 800°C). In addition, cetyl trimethyl ammonium bromide (CTAB) modified biochar was used to treat 2,4-dichlorophenol (2,4-DCP) in water. The influences of adsorbent dosage, solution pH, adsorption time, and initial solubility of the 2,4-DCP solution on the adsorption properties were investigated. The physicochemical properties of biochar were investigated using SEM, FT-IR, BET surface area, and pore size analysis. The results showed that the pyrolysis temperature had a great influence on the biochar structure. CTAB provided hydrophilic and hydrophobic groups to the modified biochar, which had increased adsorption capacity comparing to unmodified biochar. The pH also had a significant effect on the adsorption performance of biochar, and the adsorption performance of biochar decreased significantly under alkaline conditions. The maximum adsorption capacities of modified biochar and unmodified biochar were 59.81 and 20.89 mg/g, respectively, indicating that the adsorption capacity of modified biochar was significantly higher than that of unmodified biochar. The adsorption process of 2,4-DCP by rice straw biochar conformed to the Second-order kinetic model and the Freundlich isotherm adsorption model.