Unprecedented catalytic activity of coal gangue toward environmental remediation: Key role of hydroxyl groups

Abstract

Heavy metal ions, especially the Cr(VI) ions, cause serious environmental problems, which endows attractive efforts on the Cr(VI) removal with high efficiency. Basically, the Cr(VI) removal in the presence of organic acids under light irradiation presents a relatively slow process. In this regard, this work found that natural coal gangue (CG) without any chemical modification could extraordinarily enhanced the removal rate of Cr(VI) in the presence of tartaric acid (TA) under visible light irradiation. The Cr(VI) removal efficiency could be modulated by calcination treatment. Mechanism investigation uncovered that the abundant hydroxyl groups on natural CG surfaces contributed mostly to the excellent adsorption performance toward O2 and TA and thus facilitated the generation of O2−, which played the dominant role in the photocatalytic process. In addition, Fe species in natural CG also acted as active sites and partially participated the Cr(VI) reduction process. This work would offer persuasive evidence of significant roles for natural solid wastes in catalytic process.