Regeneration of zero-valent iron powder by the cocatalytic effect of WS2 in the environmental applications

Abstract

One of the biggest problems of microsized iron powder (mZVI) is that with the occurrence of redox reactions, a compact iron oxide shell can be formed on the surface of mZVI, which eventually leads to the catalyst poisoning and inactivation. Here, commercial WS2 is employed for accelerating Fe3+/Fe2+ cycle and foreclosing passivation of mZVI to achieve the regeneration of mZVI for the first time. After 10 cycles oxidation, WS2 cocatalytic effect can make the mZVI/H2O2 maintain the degradation rate of 99% for the remediation of organic pollutants. Moreover, it is found that WS2 can realize the regeneration of mZVI after the reduction of heavy metal ions (Cr6+, Cu2+ and Ni2+), especially, the removal rate of Ni2+ can be recovered from 9.2% back to 30.8%. The enhanced activity and stability can be ascribed to the double active sites on WS2 and mZVI surfaces. The exposed active W4+ sites on WS2 surface can accelerate the Fe3+/Fe2+ cycling reaction, and the active Fe0 active sites can increase the circulation of iron and tungsten ions simultaneously. This research provides a new approach for the regeneration of mZVI during the redox reaction in environmental application, which makes it possible to use mZVI to treat sewage on a large scale.