Synthesis of Zeolite-Based Cu/Fe–X from Coal Gangue for Fenton-Like Catalytic Degradation of Rhodamine B

In this paper, coal gangue, a solid waste is used as raw material to provide silicon and aluminum sources for synthesis of zeolite. A coal gangue zeolite based Cu/Fe–X catalyst is successfully prepared by immersion-calcination method, which is used to remove Rhodamine B from aqueous solution. The characterization results show that Cu and Fe have been successfully loaded on zeolite, not damaged its structure, and these nanoparticles are highly dispersed and low crystallinity. This special structure will enhance its catalytic ability to activate H2O2. The experiment showed that hydroxyl radical (·OH) was the main active species for catalytic degradation of Rhodamine B, and the circulation of Cu2+ to Cu1+ and Fe3+ to Fe2+ could synergistically produce ·OH. Furthermore, the redox potential of Cu1+ and Cu2+ is lower than Fe2+ and Fe3+, which can promote Fe3+ circulate to Fe2+, further promote Fe2+ to activate H2O2 to decompose into ·OH, and overcome the speed limiting step of Fenton-Like catalytic reaction. The Cu/Fe–X catalyst can activate H2O2 in wide pH range (1–10). Under optimal conditions, the catalytic degradation rate can reach 99.9%, and the TOC removal rate is as high as 98.5%. Therefore, Cu/Fe–X/H2O2 system can effectively remove organic dyes, and has a high industrial application prospect.