Preparation and optimization of low-cost red mud based zero-valent iron porous adsorbent by carbothermal reduction and Box-Behnken response method

Red mud is a polluting waste product emitted from the aluminum production industry, which is a potential threat to the environment due to its high yield, strong alkalinity and complex elemental composition. The resource utilization of red mud has also attracted the attention of many researchers. In this study, red mud, straw and bentonite were used as raw materials to prepare granular porous zero valent iron (ZVI) adsorption reaction materials (Fe/GSBR) by carbothermal reduction. Straw was used as pore-forming and reducing agent, bentonite as binder, and red mud as substrate and iron source. The effects of preparation conditions on Fe/GSBR properties were investigated, including raw material ratio, sintering temperature, sintering time and straw particle size. The preparation conditions were optimized by response surface analysis, and the best preparation conditions were determined as follows: raw material ratio was 1:2, sintering temperature was 906℃, sintering time was 60 min, straw particle size was 100 mesh. The Fe/GSBR properties were characterized by SEM, EDS, XRD, and BET to demonstrate the porous and ZVI material. In addition, the regeneration properties and toxic leaching of the materials were evaluated to ensure the environmental safety during use.