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In this study, sequential KMnO4-promoted oxidative pyrolysis and H2O2 oxidation were employed to upgrade the adsorption capacities of durian shell biochar for methylene blue (MB) and tetracycline (TC) in an aqueous solution. It was found that the KMnO4/H2O2 co-modification was greatly influenced by pyrolysis temperature and the optimal temperature was 300 °C. Moreover, a low concentration of H2O2 enabled the improvement of the adsorption capabilities greatly with the catalysis of pre-impregnated manganese oxides, addressing the shortcoming of single H2O2 modification. The co-modified biochar exhibited high adsorption capabilities for MB and TC, remarkably surpassed KMnO4- and H2O2- modified biochars as well as pristine biochar. The increase of adsorption capabilities could be mainly contributed to the incorporation of MnOx and carboxyl by KMnO4-promoted oxidative decomposition and Mn-catalyzed H2O2 oxidation. This would provide a novel and efficient method for preparing highly adsorptive biochar using sequential KMnO4-promoted oxidative pyrolysis and H2O2 oxidation. [ABSTRACT FROM AUTHOR]

Catalytic oxidative pyrolysis is a promising method for the preparation of highly adsorptive biochar by introducing oxygen-containing groups. Here, a K 2 FeO 4 -catalyzed oxidative pyrolysis was described for enhancing the adsorption capability of areca leaf biochar toward methylene blue at low temperature. It was shown that the maximum adsorption capacity of the biochar pyrolyzed at 200 °C was greatly improved from 122.67 to 251.95 mg g -1 with the catalysis of K 2 FeO 4 due to the introduction of surface oxygen-containing groups. In addition, a high adsorption capability was observed over a wide pH range for the K 2 FeO 4 -modified biochar and nearly neutral pH was obtained after adsorption, further demonstrating the great advantages of K 2 FeO 4 -catalyzed oxidative pyrolysis. Mechanistic studies revealed that the adsorption of the pristine biochar was mainly determined by hydrogen bonding and electrostatic interaction. Whereas, the adsorption of the K 2 FeO 4 -modified biochar was attributed to cation exchange besides hydrogen bonding and electrostatic interactions., Competing Interests: There are no conflicts of interest to declare., (This journal is © The Royal Society of Chemistry.)