Preparation and Modification of Rape Straw Biochar and Its Adsorption Characteristics for Methylene Blue in Water: Fid-Bau Portal

Preparation and Modification of Rape Straw Biochar and Its Adsorption Characteristics for Methylene Blue in Water

Jiao Chen / Chenghan Tang / Xiaoyuan Li / Jieyu Sun / Yujie Liu / Wen Huang / Aojie Wang / Yixin Lu

To solve the double problems of methylene blue (MB) pollution in water and waste of straw resources, rape straw biochar (RSB₆₀₀) was made by thermal decomposition of discarded rape residues at 600 °C, and modified RSB600(M-RSB₆₀₀) was prepared after treatment with NaOH for MB adsorption. The physicochemical properties, MB adsorption properties and mechanism of RSB600 and M-RSB600 were studied. According to the experimental findings, M-RSB₆₀₀ has stronger aromaticity, higher hydrophilicity, and more polarity than RSB₆₀₀. Under the same adsorption conditions, M-RSB600 obtained better MB adsorption effect with less dosage. The MB equilibrium adsorption capacity of M-RSB600 reached 268.46 mg/g, which was 65.6% higher than that of RSB600. The quasi-second-order kinetic model better described the adsorption kinetics of MB on RSB₆₀₀ and M-RSB₆₀₀ (R² > 0.98), and the Freundlich and Temkin models better described the adsorption isotherms (R² > 0.95). The adsorption process was spontaneous, internal heat and entropy driven multilayer adsorption, dominated by chemical adsorption, specifically involving multiple interaction mechanisms, including electrostatic adherence, hydrogen-bond, π-π bond and ion-exchange. The results demonstrated that NaOH modification obviously improved the structure of RSB and make it had better adsorption and regeneration performance. M-RSB600 can be utilized as the ideal substance for effectively removing MB from effluent.