| Persulfate-based advanced oxidation processes（PS-AOPs）have been extensively applied for eliminating aqueous refractory organic pollutants.In PS-AOPs,the key component is the PS activator.However,the existed activation methods still have some demerits.Thus,exploring new energy-saving and high-performance methods for PS-AOPs to decontaminate micropollutants is of great significance.Very recently,the piezoelectric effect in Ba Ti O3piezocatalyst has been reported to be a promising energy-saving and reusable method to effectively activate persulfate for degrading micropollutants.However,the intrinsic piezocatalytic activation mechanisms and the evolution processes of reactive oxygen species（ROS）were not well understood.Moreover,the performances of other types of piezoelectric materials in PS-AOPs were unknown yet,which warrants further investigation.This paper will take the two-dimensional（2D）piezoelectric material Mo S2 as the piezoelectric catalyst model,which is divided into two Part for discussion:（1）Natural mechanical energies,such as wind,tide waves,and water flow,are widely existed in the environment and these inexhaustible natural mechanical energies can be utilized through piezoelectric materials for the degradation of aqueous organic pollutants in the environment.In this work,few-layered molybdenum disulfide nanoflowers（Mo S2 NFs）were adopted as a piezocatalyst to activate peroxymonosulfate（PMS）with ultrasonic wave（US）as the mechanical force for phenol abatement.A much higher degradation efficiency was attained by the integrated US/Mo S2 NFs/PMS system compared to the other single systems,revealing the markedly synergistic effect of US and Mo S2 on PMS activation.Moreover,density functional theory calculations were performed to fundamentally understand the reaction pathways between PMS and carriers on the active edges of Mo S2 for free radical production.It was found that both sulfate radicals(SO4·?)and hydroxyl radicals（·OH）were produced in the US/Mo S2 NFs/PMS system.However,SO4·?was quickly converted into·OH via the hydrolysis reaction under US,enabling·OH to be the primary reactive oxygen species for phenol oxidation.This work offers an efficient piezocatalyst to activate persulfate for water remediation.More importantly,it provides fundamental insights into the piezoelectricity in two-dimensional semiconducting materials and the mechanism in piezocatalytic activation of persulfate.The results prove that the combination of piezoelectricity and advanced oxidation processes is promising for water pollution control,and provides a new idea for the application of inexhaustible natural mechanical energy in the environment for environmental remediation.（2）MoS2-CNT composites was prepared by simple hydrothermal method.The characterization showed that Mo-C bonds are formed between Mo S2 and carbon nanotubes.The catalytic performance of the material was significantly improved after being composited with carbon nanotubes.With benzoic acid as the target pollutant,the degradation efficiency of Mo S2-CNT piezoelectric activated PMS was evaluated.The experiment results indicated that·OH dominated the oxidation process in the US/PMS/Mo S2-CNT system.Experiments have preliminarily proved that the combination of piezoelectric materials and carbon materials accelerates the transmission rate of electrons,which is beneficial to improve the catalytic performance of piezoelectric materials. |
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