Enhanced degradation of trichloroethene by calcium peroxide activated with Fe（III） in the presence of citric acid

Trichloroethene （TCE） degradation by Fe（III）- activated calcium peroxide （CP） in the presence of citric acid （CA） in aqueous solution was investigated. The results demonstrated that the presence of CA enhanced TCE degradation significantly by increasing the concen- tration of soluble Fe（III） and promoting H202 generation. The generation of HO· and O2^-· in both the CP/Fe（III） and CP/Fe（III）/CA systems was confirmed with chemical probes. The results of radical scavenging tests showed that TCE degradation was due predominantly to direct oxidation by HO·, while O2^-· strengthened the generation of HO· by promoting Fe（III） transformation in the CP/Fe （III）/CA system. Acidic pH conditions were favorable for TCE degradation, and the TCE degradation rate decreased with increasing pH. The presence of Cl·-, HCO3·-, and humic acid （HA） inhibited TCE degradation to different extents for the CP/Fe（III）/CA system. Analysis of Cl·- production suggested that TCE degradation in the CP/Fe （III）/CA system occurred through a dechlorination process. In summary, this study provided detailed information for the application of CA-enhanced Fe（III）-activated calcium peroxide for treating TCE contaminated groundwater.

Coupling of bioelectrochemical toluene oxidation and trichloroethene reductive dechlorination for single-stage treatment of groundwater containing multiple contaminants

Bioremediation of groundwater contaminated by a mixture of aromatic hydrocarbons and chlorinated solvents is typically challenged because these contaminants are degraded via distinctive oxidative and reductive pathways,thus requiring different amendments and redox conditions.Here,we provided the proof-of-concept of a single-stage treatment of synthetic groundwater containing toluene and trichloroethene(TCE)in a tubular bioelectrochemical reactor,known as a“bioelectric well”.Toluene was degraded by a microbial bioanode(up to 150 mmol L^(-1) d^(-1))with a polarized graphite anode(t0.2 V vs.SHE)serving as the terminal electron acceptor.The electric current deriving from microbially-driven toluene oxidation resulted in(abiotic)hydrogen production(at a stainless-steel cathode),which sustained the reductive dechlorination of TCE to less-chlorinated intermediates(i.e.,cis-DCE,VC,and ETH),at a maximum rate of 500 meq L^(-1) d^(-1),in the bulk of the reactor.A phylogenetic and functional genebased analysis of the“bioelectric well”confirmed the establishment of a microbiome harboring the metabolic potential for anaerobic toluene oxidation and TCE reductive dechlorination.However,Toluene degradation and current generation were found to be rate-limited by external mass transport phenomena,thus indicating the existing potential for further process optimization.

Biochar-based composites for removing chlorinated organic pollutants: Applications, mechanisms, and perspectives

Chlorinated organic pollutants constitute a significant category of persistent organic pollutants due to their widespread presence in the environment,which is primarily attributed to the expansion of agricultural and industrial activities.These pollutants are characterized by their persistence,potent toxicity,and capability for long-range dispersion,emphasizing the importance of their eradication to mitigate environmental pollution.While conventional methods for removing chlorinated organic pollutants encompass advanced oxidation,catalytic oxidation,and bioremediation,the utilization of biochar has emerged as a prominent green and efficacious method in recent years.Here we review biochar's role in remediating typical chlorinated organics,including polychlorinated biphenyls(PCBs),triclosan(TCS),trichloroethene(TCE),tetrachloroethylene(PCE),organochlorine pesticides(OCPs),and chlorobenzenes(CBs).We focus on the impact of biochar material properties on the adsorption mechanisms of chlorinated organics.This review highlights the use of biochar as a sustainable and eco-friendly method for removing chlorinated organic pollutants,especially when combined with biological or chemical strategies.Biochar facilitates electron transfer efficiency between microorganisms,promoting the growth of dechlorinating bacteria and mitigating the toxicity of chlorinated organics through adsorption.Furthermore,biochar can activate processes such as advanced oxidation or nano zero-valent iron,generating free radicals to decompose chlorinated organic compounds.We observe a broader application of biochar and bioprocesses for treating chlorinated organic pollutants in soil,reducing environmental impacts.Conversely,for water-based pollutants,integrating biochar with chemical methods proved more effective,leading to superior purification results.This review contributes to the theoretical and practical application of biochar for removing environmental chlorinated organic pollutants.