Effect of carbon type on the detoxification mechanism of hexavalent chromium [Cr(VI)] by carbothermal reduction

Abstract

Carbon powders were used to detoxify [Cr(VI)] in metallurgical solid waste was investigated, since the presence of [Cr(VI)] had a very serious impact on the environment. Five types of carbon powders were selected as carbon sources and soluble CrO3 was used as a hexavalent chromium source in metallurgical solid waste. Ultra-fine Cr3C2 powders (about 80 nm) were synthesized by carbothermal reduction reaction to achieve the detoxification of [Cr(VI)]. The temperature plays a crucial role in the synthesis of Cr3C2 according the experimental and thermodynamic results, illustrating that the synthesis temperature was in the range of 900 ℃–1200 ℃. Surface area, morphology, and surface chemistry of carbon powders were investigated to analyze the effect of carbon type on the mechanism of detoxification of hexavalent chromium [Cr(VI)] and the formation of chromium carbide. The results show that nano carbon powder with finer particle size (30–50 nm), higher specific surface area (101.5 m2/g) and fewer chemical bonds with carbon atoms formed by sp2 orbital hybridization are more suitable as a carbon source for carbothermal reduction of [Cr(VI)]. Therefore, nano Cr3C2 powder was achieved at the lowest synthesis temperature (900 ℃), when nano carbon powder was selected as the carbon source.