CuCo2S4/sulfite reaction for efficient removal of tetracycline in water

Water pollution by antibiotics is an increasing concern, which may be addressed by advanced oxidation processes using sulfites as precursors of sulfate radicals (SO4 center dot-), yet the efficiency of sulfite activation is limited. Here, we tested copper cobalt sulfide (CuCo2S4) to activate sulfite, based on the synergy among transition metals and the facilitation of transition metal redox circulation by reductive sulfur species. We analyzed CuCo2S4 structure by X-Ray photoelectron spectroscopy, and we studied the effect of pH and radical scavengers. Results show 90-100% abatement of tetracycline concentration at pH 8.0-10.0, with SO4 center dot- and HO center dot as the main reactive radicals. This finding is explained by the accelerated redox recycling of copper and cobalt by sulfur, and by the synergetic effect between active cobalt and copper sites.