Preparation Of Biochar From Pomelo Peel By Microwave-Chemical Activation And Its Adsorption Properties And Mechanism

Biochar has a wide range of raw material sources,good stability,abundant oxygencontaining functional groups,and easy surface functionalization,which has great potential for the adsorption and removal of pollutants in water.In this paper,biochar(BC)was prepared by microwave carbonization using pomelo peel as raw material.In order to improve the adsorption performance of biochar,two kinds of biochar materialds(The biochar was prepared by mixing the pomelo peel with K2FeO4 through microwave carbonization was named KBCA;The biochar was prepared by mixing pretreating pomelo peel with phosphoric acid and mixing with K2FeO4 through microwave carbonization was named KHBC)were prepared by mixing the pomelo peel with K2FeO4 and pretreating pomelo peel with phosphoric acid and then mixing with K2FeO4,through microwave carbonization.The physicochemical structure characteristics and adsorption mechanism of biochar were characterized by SEM,BET,XRD,FTIR,XPS and Zeta potential analysis.The effects of biochar preparation technology and chemical activation on the adsorption properties of biochar were discussed.The adsorption performance and mechanism of prepared biochar on Cr(VI)and norfloxacin removal in simulated wastewater were studied.The main findings and conclusions are as follows:(1)The optimal preparation of KBCA was obtained by mixing pomelo peel with K2FeO4 in a mass ratio of 5:2 under the microwave power of 700 W for 5 min.While the optimal conditions for preparing the KHBC were pre-treated with 50%H3PO4 and then mixed with K2FeO4 in a mass ratio of 5:1 under microwave power of 600 W for 5 min.(2)The specific surface area and pore volume of KBCA are 49.330 m2·g-1 and 0.030 cm3·g-1,respectively.Many oxygen-containing functional groups were seen on the surface of KBCA,and the pH value of the zero potential point is 4.4.The specific surface area and pore volume of KHBC were 235.100 m·g-1 and 0.320 m3·g-1,respectively.The surface of KHBC biochar contains abundant oxygen-containing functional groups and phosphate group,and the pH value of the zero potential point is 6.4.(3)The adsorption kinetics and thermodynamic studies showed that the adsorption data of Cr(VI)by KBCA and KHBC were in better agreement with the pseudo-second-order kinetic model and the Langmuir adsorption isotherm model.The maximum adsorption capacity of Cr(VI)by KBCA and KHBC was 105.900 and 198.810 mg·g-1,respectively.and after three adsorption-regeneration cycles,80%and 83%of the original adsorption capacity and KBCA and KHBC were retained,respectively.(4)Norfloxacin adsorption data by KBCA is consistent with the pseudo-second-order kinetic model and Langmuir adsorption isotherm model.The thermodynamic process of norfloxacin is spontaneous and endothermic,and the maximum adsorption capacity of norfloxacin was 180.800 mg·g-1 at pH=5.After three adsorption-regeneration cycles,the adsorbent still maintains 82%of the original adsorption capacity.