Yunqing Pi

Recent developments in heterogeneous photocatalytic water treatment using visible light-responsive photocatalysts: a review

Visible light-responsive photocatalytic technology holds great potential in water treatment to enhance purification efficiency, as well as to augment water supply through the safe usage of unconventional water sources. This review summarizes the recent progress in the design and fabrication of visible light-responsive photocatalysts via various synthetic strategies, including the modification of traditional photocatalysts by doping, dye sensitization, or by forming a heterostructure, coupled with π-conjugated architecture, as well as the great efforts made within the exploration of novel visible light-responsive photocatalysts. Background information on the fundamentals of heterogeneous photocatalysis, the pathways of visible light-responsive photocatalysis, and the unique features of visible light-responsive photocatalysts are presented. The photocatalytic properties of the resulting visible light-responsive photocatalysts are also covered in relation to the water treatment, i.e., regarding the photocatalytic degradation of organic compounds and inorganic pollutants, as well as photocatalytic disinfection. Finally, this review concludes with a summary and perspectives on the current challenges faced and new directions in this emerging area of research.

Ultrasonic-assisted rational design of uniform rhombus-shaped ZnMoOx on graphene for advanced sunlight-driven photocatalysts, functional supercapacitor electrodes, and antibacterial platforms

To date, growing interest has been devoted to fabricating graphene–metal oxide hybrid composites for a plethora of applications including photocatalysis. However, controllable synthesis of such composite materials by virtue of facile and rational routes still remains challenging. Herein, we report, for the first time, the design of an in situ, ultrasonic-assisted growth strategy for the tailored production of well-dispersed, rhombus-shaped ZnMoOx/reduced graphene oxide (RGO) composites. The resultant composites exhibit a superior and recyclable natural-sunlight-driven photocatalytic activity toward the degradation of Rhodamine B, where the highest photocatalytic degradation efficiency can be achieved for the ZnMoOx/RGO composites with 3 wt% RGO dosage. In addition, the synthesized hybrids possess a high areal capacitance with a good cycling performance, as well as an interesting noticeable antibacterial activity, offering special insights into the usage of such composites for a wide range of applications.

Oxidation of ofloxacin by Oxone/Co 2+ : identification of reaction products and pathways

Oxidative degradation of ofloxacin (OFX) by sulfate free radicals (SO4−•) in the UV/Oxone/Co2+oxidation process was investigated for the first time, with a special focus upon identifying the transformation products as well as understanding the reaction pathways. Thirteen main compounds were identified after the initial transformation of OFX; the detailed structural information of which were characterized by high-performance liquid chromatography–high resolution mass spectrometry and MS fragmentation analysis. The degradation pathways mainly encompassed ring openings at both the piperazinyl substituent and the quinolone moiety, indicating that the usage of SO4−• aided the oxidative degradation of OFX to undergo more facile routes compared to those in previous reports by using OH•/h+ as the oxidant, where the initial transformation attacks were mainly confined to the piperazine moiety. Moreover, in this study, smart control over the pH conditions of the oxidation system via different modes of Oxone dosage resulted in the selective degradation of the functional sites of OFX molecule, where it was shown that the SO4−•-driven destruction of the quinolone moiety of OFX molecule favored the neutral pH conditions. This would be beneficial for the reduction of bacterial resistance against quinolones in the aqueous environment.

Facile green synthetic graphene-based Co-Fe Prussian blue analogues as an activator of peroxymonosulfate for the degradation of levofloxacin hydrochloride

A kind of Co-Fe Prussian blue analogues (Co-Fe PBAs), cobalt hexacyanoferrate Co3[Fe(CN)6]2, and graphene oxide (GO) were combined to synthesize magnetically separable Co-Fe PBAs@rGO nanocomposites through a simple two-step hydrothermal method. The crystalline structure, morphology and textural properties of the Co-Fe PBAs@rGO nanocomposites were characterized. The catalytic performance of the nanocomposites was evaluated by PMS activation, with Levofloxacin Hydrochloride (LVF) as the target contaminant. Synergistic interactions between the Co-Fe PBAs and rGO prevented the aggregation of the Co-Fe PBAs nanoparticles, which resulted in enhanced degradation efficiencies. The influence of several critical parameters was investigated, including the reaction temperature, PMS and Co-Fe PBAs@rGO catalyst concentrations, solution pH and salt content. LVF degradation was favored at higher catalyst and PMS concentrations, high temperatures, and in neutral or weak acidic solutions. Sulphate radicals were the dominant active species in the Co-Fe PBAs@rGO/PMS system. In addition, the Co-Fe PBAs@rGO exhibited no significant decrease in LVF degradation efficiency following five catalytic cycles. Thus, the as-prepared Co-Fe PBAs@rGO nanocomposite catalyst might be applied to the removal of hard-to-degrade organics owing to its high catalytic ability to activate PMS, as well as its good reusability and recyclability.