In-situ adsorption-conversion recovery of heavy metal cadmium by natural clay mineral for multi-functional photocatalysis

Pollutant purification, waste recycle and efficient utilization of mineral resources are three main subjects in the environmental fields, while it is hard to achieve simultaneously. Here, we developed a sustainable "adsorbent-to-photocatalyst" strategy for recovering Cd2+ into CdS photocatalyst with clay minerals to simultaneously address the above issues. By comparing the adsorption ability of three natural clay minerals, including sepiolite, attapulgite (ATP) and halloysites, ATP is screened out as a cost-effective adsorbent for the removal of heavy metals Cd2+ from waste water, and then serves as a substrate to allow Cd2+ to be converted into CdS nanoparticles in situ on its surface. The as-prepared CdS/ATP composite materials show multi-functional photocatalytic applications, which are effective in removing heavy metals Cr(VI), tetracycline hydrochloride and killing harmful pathogens in water under visible light. It is demonstrated that the excellent adsorption capacity and production of large number of active species (electrons, holes, hydroxyl radicals and superoxide radicals) are the main reasons for the efficient catalytic activity of CdS/ATP. This study provides a novel reference for the development direction of highly efficient integrated design strategy of heavy metals recovery and high-performance photocatalyst fabrication with cost-effective natural clay minerals.