Adsorption behavior of arsenic onto lignin-based biochar decorated with zinc

Abstract

This study evaluated the adsorption properties of arsenic (As) by lignin biochar (LBC) decorated with Zn (Z-LBC) derived from the impregnation reaction of ZnCl2 colloid and the pyrolysis process. The carbon contents of LBC and Z-LBC were 92.8% and 80.2%, respectively. The carbon content in Z-LBC was lower than that of LBC, demonstrating that Zn was clearly deposited in Z-LBC. The surface area of Z-LBC (255 m2/g) was higher than that of LBC (244 m2/g) and showed a more well-developed pore structure. The adsorption amounts of As by pure lignin, LBC, and Z-LBC were 0.44, 1.50, and 18.3 mg/g, respectively, and Z-LBC showed a strong affinity for As. The optimal isotherm and kinetic models for predicting the adsorption of As by Z-LBC were the Langmuir isotherm and pseudo-second order kinetic model, respectively, and the maximum adsorption capacity derived from the Langmuir isotherm was 20.2 mg/g. The adsorption properties of As by Z-LBC were dominantly influenced by the initial pH and Z-LBC dose. In addition, FTIR analysis clearly showed a difference in the functional group of Z-LBC before and after As adsorption, which proved that As was adsorbed on the surface of Z-LBC. Overall, Z-LBC is derived from the impregnation reaction of the ZnCl2 colloid, and the pyrolysis process is adequately utilized as an adsorbent for As removal. However, since the amount of As adsorbed by Z-LBC is greatly affected by the initial pH and Z-LBC dose, a management plan will be necessary.