Gucheng Zhang

Bio: Gucheng Zhang is an academic researcher from Sichuan University. The author has contributed to research in topics: Radical & Pattern recognition (psychology). The author has an hindex of 6, co-authored 13 publications receiving 262 citations.

Degradation of 2,4-dichlorophenol by activating persulfate and peroxomonosulfate using micron or nanoscale zero-valent copper

Abstract: The ability of persulfate (PS) and peroxymonosulfate (PMS) activated by micron or nanoscale zero-valent copper (ZVC or nZVC) to degrade 2,4-dichlorophenol (2,4-DCP) was quantified under various conditions. Mechanism investigation revealed that PS and PMS accelerated the corrosion of ZVC or nZVC to release Cu+ under acidic conditions. The in-situ generated Cu+ further decomposed PS or PMS to produce SO4- and OH, which then dramatically degraded 2,4-DCP. The kobs for 2,4-DCP removal followed pseudo-first-order kinetics, kobs of ZVC/PMS and nZVC/PMS systems were 10∼30 times greater than these in ZVC/PS and nZVC/PS systems. The nZVC/PMS system was most effective to remove 2,4-DCP which even did better than the nZVI/PMS system, with rate constant values ranging from 0.041 to 1.855min-1. At higher pH ZVC is ineffective, but nZVC can activate PS and PMS to significantly degrade 2,4-DCP at pH up to 7.3. The 2,4-DCP degradation pathway was found to involve dechloridation, dehydrogenation, hydroxylation, ring open and mineralization. 56.7% and 45.3% of TOC removals were respectively obtained in the ZVC/PMS and nZVC/PMS systems within 120min. This study helps to comprehend the application of zero-valent metals in reactive radicals-based oxidation processes and the reactivity of Cu+ as an activator of PS and PMS.

Heterogeneous activation of persulfate for Rhodamine B degradation with 3D flower sphere-like BiOI/Fe3O4 microspheres under visible light irradiation

Abstract: This study represents the first investigation on the application of persulfate (PS)/vis-light for the degradation of Rhodamine B (RhB) using bismuth oxyiodide magnetic composites (BiOI/Fe 3 O 4 , BOMCs). The 3D flower sphere-like BOMCs were successfully fabricated via a hydrothermal method, proving to be an excellent photocatalyst under visible light when evaluated by various characterization methods. The results demonstrated that BOMCs had a high photodegradation efficiency at pH 3.0–9.0 and the BiOI/Fe 3 O 4 (5:1) composite displayed the optimal catalytic performance. Inorganic ions such as Cl − showed promotion at a lower concentration, while significant inhibition was observed for higher concentrations of Cl − and HCO − 3 in the Vis/BOMCs/PS process due to the quenching effect. Moreover, 44.9% mineralization efficiency for total organic carbon and the excellent stability of BOMCs were demonstrated with limited iron leaching. Based on the scavenger experiments, the photocatalytic mechanism in the coupled system determined· SO − 4 and OH as the main reactive species. Eventually, the major intermediates are detected by GC/MS, and a possible photocatalytic degradation pathway of RhB is proposed in the Vis/BOMCs/PS process.

Degradation of dimethyl phthalate by activating peroxymonosulfate using nanoscale zero valent tungsten: Mechanism and degradation pathway

Abstract: The oxidation capacity and mechanisms involved in activation of peroxomonosulfate (PMS) by nanoscale zero valent tungsten (nZVW) were investigated with dimethyl phthalate (DMP) as a targeted contaminant. DMP removal was completely achieved by hydroxyl radical ( OH) and sulfate radical ( SO4−) at 50 min in the nZVW/PMS system, and structural and componential changes of nZVW powder before and after reaction were not obvious. Low valence tungsten species were released during nZVW corrosion in oxygenated water via heterogeneous reactions, which was accelerated by PMS. The homogeneous reactions were mainly responsible for radical generation: 1) the stepwise oxidation of nZVW to produce H2O2, which was then activated by low valence tungsten species to generate OH; 2) the activation of PMS by low valence tungsten species to produce SO4− and OH. However, OH− reduced the reactivity of low valence tungsten species due to the formation of tungstate, higher pH thus partly inhibited the DMP removal. Two stages of DMP removal were found, and DMP degraded dramatically in the second stage. The degradation pathways of DMP were proposed, involving the formation of aromatic esters (monomethyl phthalate, methyl benzoate, and methyl salicylate), aromatic acids (phthalic acid, salicylic acid, and benzoic acid), and phenols (catechol, phenol, and hydroquinone) in turn. These results help to comprehend the application of nZVW in reactive radicals-based oxidation processes and the reactivity of low valence tungsten species in water treatment field.

Removal of Rhodamine B during the corrosion of zero valent tungsten via a tungsten species-catalyzed Fenton-like system

Abstract: Rhodamine B (RhB) removal in a tungsten species-catalyzed Fenton-like system using nanoscale zero valent tungsten (nZVW) was investigated. The nZVW system can effective remove RhB in oxygenated water, and the nZVW/H2O2 system significantly enhances the RhB removal. Mechanism investigation shows that hydroxyl radical (·OH) is the primary reactive oxidant for removing RhB in both systems. The stepwise oxidation of nZVW can release reactive tungsten species and produce H2O2 by electron transfer from W0 or low valent tungsten species to O2, and ·OH was then formed via a Fenton-like reaction between low valent tungsten species and H2O2. The addition of H2O2 in the nZVW/H2O2 system can increase the RhB removal ratio by accelerating nZVW corrosion and enhancing the Fenton-like reaction. Moreover, higher pH inhibits the RhB removal due to the consumption of reactive tungsten species by OH−, and both higher nZVW and H2O2 dosages can enhance the RhB removal. RhB degradation pathways in the nZVW/H2O2 system are proposed involving N-de-ethylation, chromophore cleavage, ring open, and mineralization. In addition, the present study puts forward a new water treatment technique and contributes to understand the role of tungsten species in advanced oxidation processes.

Ultrasound enhanced heterogeneous activation of peroxymonosulfate by a Co-NiOx catalyst

Abstract: Sulfate radical-based advanced oxidation processes got considerable attention due to the highly oxidizing function of sulfate radicals (SO 4 − ·) resulting in acceleration of organic pollutants degradation in aqueous environments. A Co-Ni mixed oxide nanocatalysts, which was prepared by the sol-gel method, was employed to activate peroxymonosulfate (PMS, HSO 5 − ) to produce SO 4 − · with Acid Orange 7 (AO7) selected as a radical probe. The catalyst was characterized by XRD, XPS, FT-IR and TEM. The characterization results indicated that the ingredient of the catalyst had been changed and the amount of surface hydroxyl increased significantly with the addition of Ni. Therefore, it proved that Co-NiOx catalyst was more effective than CoOx to activate PMS. Moreover, ultrasound (US) can increase the degradation rate of AO7 and US/Co-NiOx/PMS system. This study also focused on some synthesis parameters and the system reached the maximum efficiency under the condition when [PMS] = 0.4 mM, [catalyst] = 0.28 g/L, Pus = 200 W. The AO7 removal in these systems follows first order kinetics. Last but not least, quenching studies was conducted which indicated that the amount of hydroxyl radicals (·OH) increases with the increase of initial pH and SO 4 − · was the primary reactive oxidant for AO7 degradation.

Application of peroxymonosulfate and its activation methods for degradation of environmental organic pollutants: Review

Abstract: The degradation of refractory organic compounds to harmless matters is one of the major concerns of environmentalists. Advanced oxidation processes (AOPs) are promising technologies producing the hydroxyl and sulfate radicals for pollutant degradation. Recently, much attention has been paid to producing sulfate radicals through activation of peroxymonosulfate (PMS). Nowadays, the use of PMS has acquired popularity thanks to its high reactivity and also to its high potential in generating sulfate radical. Actually it is becoming an alternative for hydrogen peroxide and persulfate. PMS is an unsymmetrical oxidant which can be activated to produce both hydroxyl and sulfate radicals. Various methods of PMS activation have been reported in literature including transition metals (homogenous and heterogeneous), ultraviolet, ultrasound, conduction electron, carbon catalysts and so on. PMS activation has been broadly applied for a wide range of pollutants mostly in aqueous solution. A literature review is carried out on environmental application of PMS in degradation of contaminants to clarify the performance of PMS. This review in detail describes the PMS usage in remediation of environmental pollutants with focus on the different methods of activation and the effect of main operational parameters on PMS-based processes. Moreover, the identification of contribution of each radical is discussed based on quenching experiments and electron spin resonance method. Finally, an overview on applying PMS in real wastewater and other matrixes (air, soil and sludge) is conducted and some recommendations are proposed for future studies.

Persulfate-Based Advanced Oxidation: Critical Assessment of Opportunities and Roadblocks.

Abstract: Reports that promote persulfate-based advanced oxidation process (AOP) as a viable alternative to hydrogen peroxide-based processes have been rapidly accumulating in recent water treatment literature. Various strategies to activate peroxide bonds in persulfate precursors have been proposed and the capacity to degrade a wide range of organic pollutants has been demonstrated. Compared to traditional AOPs in which hydroxyl radical serves as the main oxidant, persulfate-based AOPs have been claimed to involve different in situ generated oxidants such as sulfate radical and singlet oxygen as well as nonradical oxidation pathways. However, there exist controversial observations and interpretations around some of these claims, challenging robust scientific progress of this technology toward practical use. This Critical Review comparatively examines the activation mechanisms of peroxymonosulfate and peroxydisulfate and the formation pathways of oxidizing species. Properties of the main oxidizing species are scrutinized and the role of singlet oxygen is debated. In addition, the impacts of water parameters and constituents such as pH, background organic matter, halide, phosphate, and carbonate on persulfate-driven chemistry are discussed. The opportunity for niche applications is also presented, emphasizing the need for parallel efforts to remove currently prevalent knowledge roadblocks.

Monodispersed CuFe2O4 nanoparticles anchored on natural kaolinite as highly efficient peroxymonosulfate catalyst for bisphenol A degradation

Abstract: In this study, CuFe 2 O 4 /kaolinite catalysts were fabricated through a facile citrate combustion method and were evaluated for their efficiency to activate peroxymonosulfate (PMS) towards the destruction of bisphenol A (BPA). The prepared catalysts were systematically characterized to explore the relationship between their characteristics and catalytic activities. In general, higher specific surface area, larger pore volume, more hydroxyl groups, and more accessible reactive sites of 40%-CuFe 2 O 4 /kaolinite contributed to the greater catalytic activity in peroxymonosulfate activation for BPA degradation compared to bare CuFe 2 O 4 . Monodispersed CuFe 2 O 4 nanoparticles were uniformly anchored on the surface of kaolinite with Fe O Al bond, which prevented leaching of metal ions and contributed to the excellent reusability. The sulfate radicals produced in the CuFe 2 O 4 /kaolinite/PMS system were proved as the predominant radical species through electron spin resonance (ESR) and radical quenching experiments. Based on the results of X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance – Fourier transform infrared spectra (ATR-FTIR), two main possible pathways of sulfate radicals generation were proposed: the generation and decomposition of Cu(II)-(HO)OSO 3 − (Cu(II)/Cu(III) and Cu(III)/Cu(II) redox reaction) and the oxidation of Fe(II). Moreover, the BPA degradation pathway was proposed through the identification of transformation products. This work provides an interesting insight for PMS activation by the high-efficient natural mineral-based catalysts for wastewater reclamation.

Scalable synthesis of Ca-doped α-Fe2O3 with abundant oxygen vacancies for enhanced degradation of organic pollutants through peroxymonosulfate activation

Abstract: In this work, a cost-effective and eco-friendly calcium-doped α-Fe2O3 (Ca-Fe2O3) with abundant oxygen vacancies was fabricated using a scalable precipitation-calcination method to activate peroxymonosulfate (PMS) for wastewater purification. Density functional theory calculations revealed that the incorporation of Ca2+ into the α-Fe2O3 structure enhances the electron transfer from α-Fe2O3 to PMS, facilitating the activation of PMS. The degradation of Rhodamine B by 5%Ca-Fe2O3 proceeded with a reaction constant 8 times higher than that of pristine α-Fe2O3. This can be attributed to the increased generation of 1O2 and O2•−, increased specific surface area and enhanced electrical conductivity. The applicability of the 5%Ca-Fe2O3/PMS system was investigated including its operating parameters and stability, and the intermediates involved in the reaction were identified. The 5%Ca-Fe2O3/PMS system exhibited excellent degradation efficiency in natural water samples. This work opens up new perspectives for designing highly efficient catalysts and renders iron oxides potential candidates for environmental remediation.

Tetracycline degradation by persulfate activated with magnetic Cu/CuFe2O4 composite: Efficiency, stability, mechanism and degradation pathway.

Abstract: Magnetically separable Cu/CuFe2O4 composite obtained by a solvothermal method was used to active persulfate (PS) for the removal of tetracycline (TC). Under different pH conditions, Cu/CuFe2O4 catalyst exhibited a higher catalytic activity for PS activation to degrade TC than that of CuFe2O4. The effects of some key parameters including initial pH value, PS concentration, catalyst dosage, reaction temperature and coexisting ions on TC degradation were investigated in Cu/CuFe2O4/PS system. The reuse of Cu/CuFe2O4 catalyst at pH 3.50, 7.00 and 11.00 indicated that the catalyst showed a low stability due to the corrosion of metallic copper (Cu°), but bicarbonate ions could enhance the stability and recyclability of this catalyst through the suppression of copper leaching. Both sulfate and hydroxyl radicals were the main reactive species in Cu/CuFe2O4/PS system. Cu° can not only work as electron donor to active PS to produce the reactive radicals but also act as an electron bridge to facilitate the fast electron transfer between PS and catalyst. The structural cuprous and ferrous ions on the surface of CuFe2O4 participated in the PS activation process through the redox reactions, as confirmed by XPS analysis. The possible degradation pathways of TC were proposed based on the identified intermediates.