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Sulfate radical based photocatalysis is recognized as an effective approach for the photodegradation of organic pollutants in wastewater. To overcome the defects of weak visible light absorptivity and low catalytic efficiency of ZSM-5 based catalysts, MXene (Ti3C2) and a dopant were introduced to develop the multifunctional photocatalyst Metal/MXene/ZSM-5 by a modified in situ hydrothermal method, which was applied to phenol degradation under simulated solar light. The crystal growth, morphology, and structure of the prepared catalysts were systematically characterized by X-ray diffraction, scanning electron microscopy, surface area measurements, and various spectroscopy methods (UV-Raman, X-ray photoelectron, and UV-visible diffuse reflectance spectroscopies). The heterostructure of Fe(II)/Fe(III)/TiO2 in 5%Fe/5%MXene/ZSM-5 reduces the band gap and improves the visible light absorptivity, leading consequently to improved phenol photocatalytic degradation efficiency. The effects of pH, reaction temperature, initial phenol concentration, and peroxymonosulfate dosage on the catalytic performance of 5%Fe/5%MXene/ZSM-5 and the production of free active radicals in the 5%Fe/5%MXene/ZSM-5/PMS system were then investigated. 5%Fe/5%MXene/ZSM-5 achieves an efficient catalytic activity with over 98% removal of phenol within 25 min and 1O2 and ˙O2− radicals are the dominant reactive radicals in the 5%Fe/5%MXene/ZSM-5/PMS system for phenol degradation. This investigation improves the photocatalytic efficiency of the ZSM-5 zeolite-based catalyst under simulated sunlight. [ABSTRACT FROM AUTHOR]

A laboratory scale closed-loop cycle system for the complete regeneration of sodium persulfate/sulfuric acid etching solution (SPS) has been developed by anode oxidation of sulfate paired to cathode reduction of copper. A current-efficient (110%), zero-chemical dosage and zero-emission strategy for complete regeneration of SPS and recovery of copper was achieved. The micro-etching rate of the recycled SPS has no significant difference compared with that of the fresh SPS. On average, the cost of etching in this recycling system is decreased by 100%, compared with that in the current printed circuit boards used in industries. The full utilization of spent SPS realizes waste to wealth conversion in the true sense. The developed recycling system is a techno-economically feasible, environmentally friendly, sustainable, clean and green process for the reuse of SPS and recovery of valuable metal Cu through electrooxidation of sulfate paired to electroreduction of copper. [ABSTRACT FROM AUTHOR]