软铋矿铁酸铋活化过一硫酸盐降解环丙沙星机理及产物研究

运用共沉淀-低温水热技术制备软铋矿铁酸铋（S-BFO）,构建S-BFO非均相活化过一硫酸盐（PMS）降解环丙沙星（CIP）体系。考察了氧化剂浓度、初始pH、催化剂投加量等关键因素对体系的影响,并模拟天然水体,探究了S-BFO/PMS体系稳定性。实验结果表明：在初始pH、25℃条件下,加入0.675 mmol/L PMS,1000 mg/L的催化剂,初始浓度为5.0 mg/L的CIP经反应60 min后去除率为84.8%。通过活性物质淬灭实验结果,发现体系中对目标有机污染物起主要降解作用的活性物质是单线态氧（1O2）,而不是硫酸根自由基（·SO4-）和羟基自由基（·OH）。通过LC/MS/MS技术检测到了9种CIP降解过程中的主要中间产物,并确定了CIP通过羟基加成反应（路径I）及脱羧反应（路径II）被氧化去除的降解路径。     

Enhanced photocatalytic degradation of organic contaminants over CaFe_2O_4 under visible LED light irradiation mediated by peroxymonosulfate

A simple sol-gel approach is proposed herein to fabricate CaFe₂O₄for the degradation of various organic pollutants(rhodamine B(RhB),tetracycline hydrochloride,humic acid,and methylene orange)under LED light irradiation mediated by peroxymonosulfate(PMS).The results indicate that the calcination temperature can significantly influence the performance of CaFe₂O₄for PMS activation,and the CaFe₂O₄sample obtained at 800℃(CaFe₂O₄-800)exhibits the best efficiency in degrading RhB,which is much higher than that of Fe_2o₃-800.This can be attributed to the efficient separation of photogenerated electrons(e^-)and holes(h⁺)by PMS,which is validated by transient photocurrent response and photoluminescence measurements.Results from density functio nal theo ry calculations indicate that the valence band of CaFe₂O₄-800 exhibits a high concentration of carriers and weak localization of electrons,which are favorable for PMS activation.Radical scavenging results confirm that h⁺and O₂^·-are the dominant reactive species.Moreover,CaFe₂O₄-800 not only demonstrated a stable performance during eight cycling runs with negligible iron leaching but also exhibited excellent degradation efficiency under natural water and sunlight.Finally,the mechanism and pathway of RhB degradation by the CaFe₂O₄-800/PMS/LED system are also proposed.This work presents the enormous prospect of CaFe₂O₄as an environmentally benign photocatalyst for PMS activation.     

In situ disinfection of sewage contaminated shallow groundwater: a feasibility study

Sewage-contaminated shallow groundwater is a potential cause of beach closures and water quality impairment in marine coastal communities. In this study we set out to evaluate the feasibility of several strategies for disinfecting sewage-contaminated shallow groundwater before it reaches the coastline. The disinfection rates of Escherichia coli (EC) and enterococci bacteria (ENT) were measured in mixtures of raw sewage and brackish shallow groundwater collected from a coastal community in southern California. Different disinfection strategies were explored, ranging from benign (aeration alone, and aeration with addition of brine) to aggressive (chemical disinfectants peracetic acid (PAA) or peroxymonosulfate (Oxone)). Aeration alone and aeration with brine did not significantly reduce the concentration of EC and ENT after 6 h of exposure, while 4-5 mg L⁻¹ of PAA or Oxone achieved >3 log reduction after 15 min of exposure. Oxone disinfection was more rapid at higher salinities, most likely due to the formation of secondary oxidants (e.g., bromine and chlorine) that make this disinfectant inappropriate for marine applications. Using a Lagrangian modeling framework, we identify several factors that could influence the performance of in-situ disinfection with PAA, including the potential for bacterial regrowth, and the non-linear dependence of disinfection rate upon the residence time of water in the shallow groundwater. The data and analysis presented in this paper provide a framework for evaluating the feasibility of in-situ disinfection of shallow groundwater, and elucidate several topics that warrant further investigation.     

Efficient decolorization of azo dye Reactive Black B involving aromatic fragment degradation in buffered Co/PMS oxidative processes with a ppb level dosage of Co-catalyst

In order to generate powerful radicals as oxidizing species for the complete decolorization and degradation of azo dye Reactive Black B (RBB) at near neutral pH (pH 6), homogeneous activation of peroxymonosulfate (Oxone: PMS) by the trace Co²⁺-catalysts was explored. We not only took advantage of the high oxidation–reduction potential of produced hydroxyl and sulfite radicals but also an opportunity to oxidize RBB to less complex compounds with extremely low dosages, especially the ppb level of the Co²⁺-catalyst (stoichiometric ratio: [Co²⁺]₀/[RBB]₀ = 1.7 × 10⁻⁶–1.7 × 10⁻⁵; [PMS]₀/[RBB]₀ = 8–32). Anion effects and pH effects were also carried out and discussed to simulate an actual application such as that of a textile waste stream. Both the degradations of RBB and its derivative aromatic fragments were illustrated successfully at UV–visable absorptions of 591 and 310 nm, respectively, and the possible relationships between them were also proposed and discussed, based on the experimental results. The RBB degradation in this Co²⁺/PMS oxidative process successfully formulated a pseudo-first-order kinetic model at an isothermal condition of 25 °C with or without different anions present. The initial rate and rate constant were calculated under different comparative conditions, and the results indicate that the activity of both RBB decolorization and its degradation are not obviously dependent on the PMS concentration, but rather are related to the Co²⁺ dosage.     

Heterogeneous activation of peroxymonosulfate by supported cobalt catalysts for the degradation of 2,4-dichlorophenol in water: The effect of support, cobalt precursor, and UV radiation

In order to generate sulfate radicals (SRs) as oxidizing species for the degradation of 2,4-dichlorophenol (2,4-DCP) in water, we explored heterogeneous activation of peroxymonosulfate (PMS) by supported cobalt catalysts. More attention was given to the effect of support materials (Al₂O₃, SiO₂, TiO₂) and cobalt precursors (Co(NO₃)₂, CoCl₂, CoSO₄) on cobalt–support interaction, cobalt leaching, and reactivity of the catalysts. Especially, the feasibility of simultaneous generation of SRs and hydroxyl radicals (HRs) in PMS-Co/TiO₂ systems was first studied under ultraviolet (UV) radiation. Much lower cobalt leaching was observed in Co/Al₂O₃ and Co/TiO₂ systems than that of Co/SiO₂ most probably due to their relatively strong cobalt-support interaction. Co/TiO₂ catalyst prepared with Co(NO₃)₂, compared to CoCl₂ or CoSO₄ (where Cl⁻ and SO₄²⁻, respectively, were not completely removed upon heat treatment at 500 °C), showed strong cobalt–support interaction, and thereby exhibited negligible cobalt leaching. Under UV radiation, Co/TiO₂ at Co/Ti molar ratio of 0.001 showed significant improvement in the degradation of 2,4-DCP due to HRs. The effective generation of HRs in the system can be explained with Co(III)-mediated charge transfer from the photoinduced electrons to PMS, inducing facilitation of photoinduced electron-hole separation. However, high cobalt loading (i.e., Co/Ti molar ratio of 0.1) on TiO₂ surface exhibited negligible enhancement of 2,4-DCP transformation under UV radiation since the penetration of UV light to TiO₂ was prohibited by the cobalt.     

Diatomite supported nano zero valent iron with 3D network for peroxymonosulfate activation in efficient degradation of bisphenol A

Diatomite supported nano zero valent iron (nZVI) catalyst (NDA) with complex network structure was prepared via a mild reduction precipitation method in this work.The pore structure and pore distribu-tion of NDA can be regulated and controlled through adjusting the loading amount of nZVI.In general,the nano three-dimensional network formed by nZVI and diatomite channels greatly increase the specific surface area and pore volume of NDA,and further formed more active sites,which made NDA have better performance in activating PMS to degrade BPA than pure nZVI.The pseudo-first-order reaction rate con-stant of 50-NDA (50％-nZVI/diatomite) is almost 3 times higher than that of pure nZVI.Besides,the elec-tron paramagnetic resonance (EPR) and radical quenching experiments showed that the activation process was dominated by the sulfate radical (SO4·-) and hydroxyl radical (OH) produced by Fe0 oxidation.The generated electrons promote the self-decomposition of PMS to produce singlet oxygen (1O2),and then the valence state of iron changes to produce free radicals.In addition,the possible degradation pathway of BPA was inferred from the intermediate products identified by liquid chromatograph-mass spectrom-eter (LC-MS).This study provides a novel strategy for the design and preparation of three-dimensional composite catalysts derived from natural mineral.     

Fabricating an oxygen-vacancy-rich urchin-like Co3O4 nanocatalyst to boost peroxymonosulfate activation to degrade high-concentration crystal violet

Due to the in-situ generation of reactive oxygen species (ROS), sulfate radical-based advanced oxidation processes (SR-AOPs) have emerged for the oxidative degradation of organic contaminants. Developing highly efficient heterogeneous catalysts is of great importance for SR-AOPs. In this work, an urchin-like Co₃O₄ nanocatalyst with oxygen vacancies (V_O) was elaborately fabricated and employed for enhanced peroxymonosulfate (PMS) activation to degrade the high-concentration active dye crystal violet (CV). The obtained sample was characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and N₂ adsorption/desorption isotherms. Characterization results indicated that this unique V_O-rich urchin-like Co₃O₄ nanocatalyst was endowed with a larger surface area and abundant reactive sites for PMS adsorption and activation. The experimental results of CV degradation showed that nearly complete removal of 100 mg L^?1 CV could be realized within 30 min of reaction time under neutral conditions at room temperature, and the degradation process followed retarded-first-order kinetics. Electron paramagnetic resonance (EPR) spectra accompanied by quenching experiments of radicals demonstrated that the contribution of ROS to CV degradation followed this sequence: ¹O₂ > ?OH > SO₄^?- > O₂^?-. The degradation pathways of CV were proposed by a combination of density functional theory (DFT) calculations along with frontier orbit theory while the toxicity of intermediate products was evaluated by quantitative structure-activity relationship (QSAR) prediction.     

Kinetic modeling and synergy quantification in sono and photooxidative treatment of simulated dyehouse effluent

The aim of this work was to explore the application of sulfate radical based advanced oxidation processes: photooxidation (UV/PMS/PS), sonooxidation (US/PMS/PS) and combined sono-photooxidation (US/UV/PMS/PS) for the mineralization of simulated dyehouse effluent (WW); using peroxymonosulfate (PMS) and persulfate (PS) as oxidants. Experiments were performed in a reaction vessel of a defined geometry and axially positioned source of UV-C radiation, all placed in the ultrasonic bath (35 kHz). Mathematical model of the process was developed according to the proposed degradation scheme. Decomposition of dyestuff (C.I. Reactive Violet 2, RV2 and C.I. Reactive Blue 7, RB7), surfactant (linear alkylbenzene sulfonate; hereafter: LAS) and auxiliary organic components was explored in three types of model wastewater: WW, simulated effluent excluding inorganic species (WW-IS) and model solution that consists of a specific compound (hereafter: compound model solutions). The influence of inorganic matrix (Cl⁻, CO₃²⁻/HCO₃⁻) was studied due to the corresponding quenching affinity toward HO and SO₄⁻ radicals. The efficiency of applied processes was evaluated and the response to combined phenomena (cavitation and irradiation) was quantified as synergy index, f_Syn. Sono-photooxidative treatment (US/UV/PMS/PS) of WW resulted in a partial mineralization and partial decolourization; approximately 40% of initial TOC and 30% of initial RB7 remained after 60 min of treatment, while RV2 and LAS molecule were completely decomposed. Circumstantially, the combined process increased the mineralization efficiency by a factor of 3 (f_Syn = 3.026).