Progress in enhancing the remediation performance of microbial fuel cells for contaminated groundwater

Microbial fuel cells(MFCs)have become more prevalent in groundwater remediation due to their capacity for power generation,removal of pollution,ease of assembly,and low secondary contamination.It is currently being evaluated for practical application in an effort to eliminate groundwater pollution.However,a considerable majority of research was conducted in laboratories.But the operational circumstances including anaerobic characteristics,pH,and temperature vary at different sites.In addition,the complexity of contaminants and the positioning of MFCs significantly affect remediation performance.Taking the aforementioned factors into consideration,this reviewsummarizes a bibliography on the application of MFCs for the remediation of groundwater contamination during the last ten decades and assesses the impact of environmental conditions on the treatment performance.The design of the reactor,including configuration,dimensions,electrodes,membranes,separators,and target contaminants are discussed.This review aims to provide practical guidance for the future application of MFCs in groundwater remediation.

Bibliometric analysis and systematic review of electrochemical methods for environmental remediation

Electrochemical methods are increasingly favored for remediating polluted environments due to their environmental compatibility and reagent-saving features.However,a comprehensive understanding of recent progress,mechanisms,and trends in thesemethods is currently lacking.Web of Science(WoS)databases were utilized for searching the primary data to understand the knowledge structure and research trends of publications on electrochemical methods and to unveil certain hotspots and future trends of electrochemical methods research.The original data were sampled from 9080 publications in those databases with the search deadline of June 1st,2022.CiteSpace and VOSviewer software facilitated data visualization and analysis of document quantities,source journals,institutions,authors,and keywords.We discussed principles,influencing factors,and progress related to seven major electrochemicalmethods.Notably,publications on this subject have experienced significant growth since 2007.The most frequently-investigated areas in electrochemical methods included novel materials development,heavy metal remediation,organic pollutant degradation,and removal mechanism identification.“Advanced oxidation process”and“Nanocomposite”are currently trending topics.The major remediation mechanisms are adsorption,oxidation,and reduction.The efficiency of electrochemical systems is influenced by material properties,system configuration,electron transfer efficiency,and power density.Electro-Fenton exhibits significant advantages in achieving synergistic effects of anodic oxidation and electro-adsorption among the seven techniques.Future research should prioritize the improvement of electron transfer efficiency,the optimization of electrode materials,the exploration of emerging technology coupling,and the reduction in system operation and maintenance costs.

New insights on the enhanced non-hydroxyl radical contribution under copper promoted TiO_(2)/GO for the photodegradation of tetracycline hydrochloride

TiO_(2)/graphene oxide(GO)as photocatalyst in the photo-degradation of multitudinous pollutants has been extensively studied.But its low photocatalytic efficiency is attributed to the high band gap energy which lead to low light utilization.Cu-TiO_(2)/GO was synthesized via the impregnation methods to enhance the catalytic performance.The Cu-TiO_(2)/GO reaction rate constant for photo-degradation of pollutants(tetracycline hydrochloride,TC)was about 1.4 times that of TiO_(2)/GO.In 90 min,the removal ratio of Cu-TiO_(2)/GO for TC was 98%,and the maximum degradation ratio occurred at p H 5.After five cycles,the removal ratio of Cu-Ti O_(2)/GO still exceeded 98%.UV-visible adsorption spectra of Cu-Ti O_(2)/GO showed that its band gap was narrower than TiO_(2)/GO.Electron paramagnetic resonance(EPR)spectra test illustrated the generation rate of·O_(2)^(-)and·OH was higher in Cu-TiO_(2)/GO system than TiO_(2)/GO and TiO_(2) system.The contribution sequence of oxidative species was·O_(2)^(-)>holes(h+)>·OH in both TiO_(2)/GO and Cu-Ti O_(2)/GO system.Interestingly,the contribution of·OH in Cu-TiO_(2)/GO was less than that in TiO_(2)/GO during the photo-degradation process.This phenomenon was attributed to the better adsorption performance of Cu-Ti O_(2)/GO which could reduce the accessibility of TC to·OH in liquid.The enhanced non-hydroxyl radical contribution could be attributed to that the more other active species or sites on(nearby)the surface of Cu-TiO_(2)/GO generated after doping Cu.These results provide a new perspective for the tradition metal-doped conventional catalysts to enhance the removal of organic pollutants in the environment.

Plasmonic silver/silver oxide nanoparticles anchored bismuth vanadate as a novel visible-light ternary photocatalyst for degrading pharmaceutical micropollutants

The degradation of pharmaceutical micropollutants is an intensifying environmental problem and synthesis of efficient photocatalysts for this purpose is one of the foremost challenges worldwide.Therefore,this study was conducted to develop novel plasmonic Ag/Ag2O/BiVO4 nanocomposite photocatalysts by simple precipitation and thermal decomposition methods,which could exhibit higher photocatalytic activity for mineralized pharmaceutical micropollutants.Among the different treatments,the best performance was observed for the Ag/Ag2O/BiVO4 nanocomposites (5 wt.%;10 min’s visible light irradiation)which exhibited 6.57 times higher photodegradation rate than the pure BiVO4.Further,the effects of different influencing factors on the photodegradation system of tetracycline hydrochloride (TC-HCl) were investigated and the feasibility for its practical application was explored through the specific light sources,water source and cycle experiments.The mechanistic study demonstrated that the photogenerated holes (h^+),superoxide radicals (·O2^-)and hydroxyl radicals (·OH) participated in TC-HCl removal process,which is different from the pure BiVO4 reaction system.Hence,the present work can provide a new approach for the formation of novel plasmonic photocatalysts with high photoactivity and can act as effective practical application for environmental remediation.

Air-drying changes the distribution of Hedley phosphorus pools in forest soils

Hedley labile phosphorus(P)pools in soil tend to be several times larger than annual forest requirements,even in highly weathered soils characterized by P limitation.The discrepancy between plant and soil P status could be partly attributable to the frequently adopted air-drying pretreatment that tends to increase soil P solubility.In this study,the effects of air-drying on the distribution of Hedley P fractions were examined using soils collected under 4 forest types at Gongga Mountain,southwestern China.The results showed that the microbial biomass P(Pmic)in the organic horizon decreased markedly after air-drying.The concentrations of Hedley labile P in the air-dried samples were 31%–73%more than those in the field-moist samples.Consequently,the air-drying-induced increments of Hedley labile P pools in the surface soil horizons were 0.8–3.8 times the annual plant P requirements.The organic horizon was more susceptible to the air-drying-induced increases in Hedley labile P than the mineral horizon,probably because of the stronger release of Pmicand disruption of soil organic matter.The quality of P,indexed by the ratio of Hedley labile P to slowly cycling P,shifted in favor of the Hedley labile fractions after air-drying,further revealing that air-drying changed the distribution of Hedley P pools in forest soils.These indicated that the effects of air-drying could not be ignored when interpreting the discrepancy between the P status of plants and the Hedley labile P pools in forest soils.To more efficiently evaluate the P status in forest soils via the Hedley fractionation procedure,the use of field-moist soils is recommended.

Enhanced heterogeneous activation of peroxymonosulfate by boosting internal electron transfer in a bimetallic Fe_(3)O_(4)-MnO_(2) nanocomposite

Transition metal-based bimetallic oxides can effectively activate peroxymonosulfate(PMS) for the degradation of organic contaminants, which may be attributed to the enhanced electron transfer efficiency between transition metals. Here, we investigated the high-efficiency catalytic activation reaction of PMS on a well-defined bimetallic Fe-Mn nanocomposite(BFMN) catalyst. The surface topography and chemical information of BFMN were simultaneously mapped with nanoscale resolution. Rhodamine B(Rh B, as a model pollutant) was used to evaluate the oxidation activity of PMS activation system. The maximum absorption peak of Rh B obviously blue shifted from 554 nm to 501 nm, and decreased sharply to disappear completely within 60 min. The removal performance is better than most of the reported single transition metal oxide. X-ray photoelectron spectroscopy(XPS) imaging of the BFMN electronic structure after catalytic activation confirmed that the accelerated internal electron transfer is mainly caused by the synergy effect of Mn and Fe sites at the catalysis boundary. The outstanding ability of BFMN for PMS chemical adsorption and activation may attribute to the enhanced covalency and reactivity of Mn-O. These results of this study can advance understandings on the origins of bimetallic oxides activity for PMS activation and developing the efficient metal oxide catalysts in real practice.