Efficient removal of organic contaminants in CuS-mediated solid-liquid-interfacial fenton-like system: Role of bimetallic cycle and sulfur species.

The conventional Fenton-like system (Fe(III)/H2O2) is severely limited by the inferior activity of Fe(III) on H2O2 activation to produce highly active species and the sluggish regeneration rate of Fe(II). This work significantly enhanced the oxidative breakdown of the target organic contaminant bisphenol A (BPA) by Fe(III)/H2O2 by introducing cheap CuS at a low dose of 50 mg/L. The BPA removal (20 mg/L) in CuS/Fe(III)/H2O2 system reached 89.5 % within 30 min under the optimal conditions: CuS dosage 50 mg/L, Fe(III) concentration 0.05 mM, H2O2 concentration 0.5 mM and pH 5.6. Compared to CuS/H2O2 and Fe(III)/H2O2 systems, the reaction constants had a 47- and 12.3-fold enhancement, respectively. Even compared with the conventional Fe(II)/H2O2 system, the kinetic constant also increased more than twice, further confirming the distinctive superiority of constructed system. Element species change analyses showed that Fe(III) in solution was adsorbed onto the CuS surface, and then Fe(III) was rapidly reduced by Cu(I) in the CuS lattice. Combining CuS and Fe(III) (in-situ formed CuS-Fe(III) composite) created a robust co-effect on the activation of H2O2. Also, S(-II) and its derivatives, e.g., Sn2- and S0 (as an electron donor), could quickly reduce Cu(II) to Cu(I) and ultimately oxidize to the harmless product SO42-. Notably, a mere 50 μM of Fe(III) was sufficient to maintain enough regenerated Fe(II) to effectively activate H2O2 in CuS/Fe(III)/H2O2 system. In addition, such a system achieved a broad range of pH applications and was more suitable for real wastewater containing anions and natural organic matter. Scavenging tests, electron paramagnetic resonance (EPR), and probes further verified the critical role of •OH. This work provides a new approach to solving the problems of Fenton systems through a solid-liquid-interfacial system design and exhibits considerable application potential in wastewater decontamination.