Magnetic Biochar Production from Agricultural Waste and Reactive Blue 19 Removal by Peroxymonosulfate Activation

The conversion of agricultural biomass waste into value-added biochar (BC)-based catalysts is of great interest. Magnetic biochar is an excellent material that facilitates both solid-liquid separation and peroxymonosulfate (PMS) activation. In this study, magnetic biochar was produced from pea pod, an agricultural waste, by pyrolysis, hydrothermal methods, and precipitation. The structure, morphology, and magnetic separation properties of magnetic biochar produced from pea pod (MPPBC) were comprehensively analyzed by different characterization methods. Reactive blue 19 (RB19) was selected as a model pollutant to evaluate the performance of the MPPBC/PMS system. The effect of initial solution pH, MPPBC dosage, PMS concentration, initial RB19 concentration, reusability, and concentrations of anions and natural organic matter concentrations on the removal of RB19 in the MPPBC/PMS system was investigated. The results showed that MPPBC could effectively activate PMS, and RB19 removal reached 85% at an initial solution pH of 3, an MPPBC dosage of 0.20 g/L, a PMS concentration of 0.50 mM, an initial RB19 concentration of 25 mg/L, and an oxidation time of 60 min. The reusability of MPPBC showed an 8% decrease in the removal efficiency of RB19 after four uses. Anions and natural organic matter added to the solution were found to decrease the removal of RB19. The kinetics of RB19 removal in MPPBC/PMS system was determined using first order, second order, and Behnajady-Modirshahla-Ghanbery (BMG) models. As a result of kinetic calculations, the BMG kinetic model was found to be more effective for describing the removal efficiency of RB19.