Removal of Se(IV) from water with biochar-supported nanoscale zero-valent iron: optimization of preparation conditions and adsorption characteristics

Se(IV) in wastewater is a problem due to its high solubility, mobility, and potential toxicity. The purpose of this study was to develop biochar-supported nanoscale zero-valent iron (BC-nZVI), investigate the preparation conditions and adsorption properties, and explore the removal mechanism of Se(IV). The results illustrated that the adsorption capacity of Se(IV) increased with an increase of pyrolysis temperature. As pyrolysis time rose, the adsorption capacity was increased at low temperature (300°C). Nevertheless, it first increased and then decreased at higher temperatures (400°C and 600°C). The ratio of raw materials also affected the removal of Se(IV). NaOH modification enhanced the adsorption capacity. The –OH had a great influence on the adsorption of Se(IV). With the increase of initial pH, the adsorption capacity increased first and then decreased. The adsorption of Se(IV) fits the pseudo-first-order and pseudo-second-order models, indicating that the adsorption behavior of Se(IV) by BC-nZVI was determined by both physical and chemical mechanisms, of which physical adsorption dominated. The consequence made clear that BC-nZVI synthesized in this experiment had advantages of a simple process and excellent performance. It is a promising material for removing Se(IV) from water.