Preparation of Kenaf Biochar and Its Adsorption Properties for Methylene Blue

Abstract

The toxic dyestuffs from printing and dyeing wastewater have caused serious damages to the ecological environment, thus exploring effective methods to remove them having become a key topic. Here, a series of biochar samples were synthesized form kenaf to adsorb methylene blue (MB), which was acted as the dye representative for the test of adsorption capacity due to the presence of abundant double bond and aromatic heterocyclic ring. By tuning the raw materials and pyrolysis temperature, a super adsorption capacity about 164.21 mg•g -1 was obtained over the biochar that pyrolyzed at 700°C with the kenaf fiber as raw material. Through the physical adsorption, elemental analysis, FTIR spectra and NH 3 -TPD, it was found the high surface area and pore volume of biochar played a key role in the adsorption of MB, and the acidic sites would also assist the adsorption process. Besides, the adsorption kinetic model was fitted and calculated, implying the MB physically adsorbed on the biochar rapidly and then occurred chemical adsorption on the acidic sites. In addition, through KBC700 recycling experiments, it was found that kenaf biochar had a good binding force to MB, which effectively avoided secondary pollution. This work provides important insights for the adsorption mechanism of MB by biochar, also offers some guidance for the further synthesis of biochar from various biomass.