Effects of Pyrolysis Temperature on ZnCl2 Impregnated Corn Straw-derived Biochar Properties and Vanadium (III, IV, V) Adsorption in Aqueous Solution

In this study, corn straw derived biochars were prepared at different temperatures of 300, 500, 700C, respectively, and the characteristics of corn straw biochars were investigated. Additionally, the adsorption behaviors of vanadium (III, IV, V) on biochars were systematically studied by batch experiments. The absorbents were characterized by ion-exchange capacity (IEC), X-ray Diffraction, N2 adsorption-desorption, and FTIR. The yield of biochar decreases with the increase of pyrolysis temperature. The more ash content is retained, the more alkaline biochar is. The specific area of biochars increased with the rising pyrolysis temperature. With the increase of temperature, the structure became porous and the content of surface functional group elements remained low. Although the content of zinc in biochar is relatively high, the leaching toxicity of biochar does not exceed the Chinese standard. The adsorption capacity of biochars for vanadium (V) decreased under high temperature (700C). In the contrast, The adsorption capacities of biochars for vanadium (IV) and vanadium (III) improved under high temperature. The adsorption mechanisms for vanadium (V), vanadium (IV) and vanadium (III) were surface complexation, which can be proved by FTIR analysis.