Trichloroethylene Degradation Research Articles

Use of carbon-14 labeled trichloroethene to assess degradation potential in rock core microcosms.

In fractured rock aquifers contaminated with trichloroethene (TCE), the extent of groundwater plumes is impacted by degradation occurring within the rock matrix. The objective of this study was to evaluate TCE degradation in rock samples from three sites where in situ conditions may favor natural or enhanced attenuation. Intact rock core microcosms (94 total) were used to assess in situ conditions and enhancement by addition of lactate or lactate + sulfate. A key advance for this study was inclusion of carbon-14 (14C) labeled TCE in the experimental design, which enables monitoring of 14C-labeled products in addition to more readily detectable compounds associated with TCE degradation (i.e., cis-1,2-dichloroethene (cDCE), vinyl chloride, acetylene, ethene, and ethane). 14C-labeled products comprised 35-95 % of the total degradation products recovered over 9-21 months of monitoring, indicating that inclusion of 14C-TCE was essential to capturing the full potential for abiotic and biotic degradation of TCE. Microcosms infused with TCE but not 14C-TCE exhibited enrichment in δ13C-TCE, and enrichment in δ13C-cDCE in microcosms that underwent reductive dechlorination of TCE to cDCE. The results demonstrate the advantages of using diffusion-transport microcosms and 14C-TCE to document degradation of chlorinated ethenes in fractured rock aquifers.

Theoretical analysis and application of immobilized methanotrophs as typical adsorbent materials for adsorption/degradation of trichloroethylene

ABSTRACT Trichloroethylene (TCE) contamination presents a significant environmental challenge, necessitating efficient treatment solutions. This study aimed to develop an optimized immobilized bioreactor using methanotrophs for TCE degradation. Activated carbon fibres were identified as the optimal immobilization material, with an adsorption rate of 6–23 h – significantly faster than over 50 h for other materials – and the highest methane oxidation capacity of 0.970 mL·g−1·h−1. Adsorption kinetics indicated that activated carbon fibres followed a second-order kinetic model with a constant of 0.598 g·mg−1·h−1, suitable for low-concentration bacterial solutions. Thermodynamic analysis confirmed an exothermic process, favouring lower temperatures (288.15 K). The negative interaction energies, as per DLVO theory, suggested electrostatic attraction as a key mechanism. The bioreactor achieved 99% TCE removal within 1 h at an initial concentration of 10 mg·L−1, with visible microbial immobilization within 5 days. This research provides a novel and effective approach for using immobilized methane-oxidizing bacteria in TCE treatment, offering both theoretical and practical advancements for chlorinated hydrocarbon wastewater management.

Kirkendall effect enhanced sustained-release Fe-C composites for long-term reductive dechlorination of trichloroethylene: Interfacial reactions and slow-release degradation

Rebounding and lagging during the process of remediating contaminated sites are challenging problems. A potential solution is developing slow-release materials that could assist in the long-term remediation of contaminated sites. This study synthesised a slow-release Fe-C composite (CSBC-nZVI@β-CD), which exhibits a synergistic effect of encapsulated layers and nanocracks, using a liquid-phase reduction method. Furthermore, the reduction and dechlorination mechanism of trichloroethene (TCE) was systematically investigated. The introduction of β-cyclodextrin (β-CD) intensified the Kirkendall effect, forming nano zero-valent iron (nZVI) with abundant radial nanocracks and a litchi-like appearance on the biochar surface. Additionally, β-CD created an encapsulation layer measuring 5–7 nm on the surface of nZVI, improving its electron transport capacity and hydrophobic properties. The CSBC-nZVI@β-CD nanocomposite successfully removed 99 % of TCE in solution within 2 h and accomplished a degradation efficiency of 98.9 % within 15 d. The synergistic effect of the β-CD encapsulating layer and nanocracks facilitated the reactivity and electron-retarding capacity, resulting in a broad pH tolerance and anti-interference ability. Density-functional theory (DFT) calculations and experimental methods were used to study the mechanism of TCE reduction dechlorination; the unique structure of β-CD tended to bind with Fe as well as adsorb TCE, thereby facilitating electron transfer and the enrichment of TCE at the reaction interface. In addition, the sustained-release Fe-C composites reduced the bonding energy required during the TCE degradation reaction and promoted the complete reaction of the product. Overall, CSBC-nZVI@β-CD exhibited significant potential for the long-term remediation of groundwater.

Laccase immobilized on amino modified magnetic biochar as a recyclable biocatalyst for efficient degradation of trichloroethylene

Bioremediation of trichloroethylene (TCE) contaminated groundwater has recently attracted considerable attention. In this study, laccase was immobilized on amino modified magnetic pine biochar (MBC-NH2) by adsorption-crosslinking-covalent binding method, and its application in the degradation of TCE was evaluated. MBC-NH2 was obtained from pine sawdust by calcination, magnetic modification and amino modification. MBC-NH2 had high specific surface area (71.3 m2/g), rich surface functional groups and good magnetism. Under the conditions of 25 °C, pH = 4, glutaraldehyde (GA) concentration of 7 %, crosslinking time of 1 h, laccase concentration of 0.75 mg/mL, and immobilization time of 7 h, the loading capacity of laccase on MBC-NH2 carrier was as high as 782 mg/g. Compared with free laccase, immobilized laccase showed higher pH stability and thermal stability, and its activity remained 48.5 % after being reused for 10 times, and 80.8 % after being stored at 4 °C for 30 days. The immobilized laccase exhibited a good degradation effect on TCE. At 25 °C, pH = 4, immobilized laccase concentration of 0.35 g/L, and initial TCE concentration of 10 mg/L, the degradation efficiency of TCE by immobilized laccase was as high as 92.1 % within 48 h. In addition, the degradation products of TCE were analyzed, and the results showed that immobilized laccase could degrade TCE into non-toxic products through epoxidation, hydroxylation, and dechlorination. The immobilized laccase biocatalyst prepared in this study can achieve efficient degradation of TCE, which provides a feasible solution for chlorinated pollution of water resources. These research results are of great significance for the synthesis of biocatalysts for the efficient degradation of chlorinated hydrocarbons.

Investigating the Potential of River Sediment Bacteria for Trichloroethylene Bioremediation

Trichloroethylene (TCE) is a prevalent groundwater contaminant detected worldwide, and microbes are sensitive indicators and initial responders to these chemical contaminants causing disturbances to their ecosystem. In this study, microbes isolated from San Marcos River sediment were screened for their TCE degradation potential. Among the twelve isolates (SAN1-12), five isolates demonstrated TCE degradation within 5 days at 25 °C and 40 mg/L of TCE concentration in the following order: SAN8 (87.56%), SAN1 (77.31%), SAN2 (76.58%), SAN3 (49.20%), and SAN7 (3.36%). On increasing the TCE concentration to 80 mg/L, the degradation efficiency of these isolates declined, although SAN8 remained the prominent TCE degrader with 75.67% degradation. The prominent TCE-degrading isolates were identified as Aeromonas sp. SAN1, Bacillus sp. SAN2, Gordonia sp. SAN3, and Bacillus proteolyticus SAN8 using 16S rRNA sequencing. The TCE degradation and cell biomass of Bacillus proteolyticus SAN8 were significantly improved when the incubation temperature was increased from 25 °C to 30 °C. However, both slightly acidic and alkaline pH levels, as well as higher TCE concentrations, lowered the efficacy of TCE degradation. Nevertheless, these conditions led to an increase in bacterial cell biomass.

A slow-release reduction material of Escherichia sp. F1 coupled with micron iron powder achieves the remediation of trichloroethylene-contaminated soil

Trichloroethylene (TCE) is a prevalent organic pollutant found in soil. The oxide passivation layer on the surface of micron iron powder inhibits the release of its reducing components, leading to ineffective reduction and purification of TCE in soil. To enhance TCE degradation, a slow-release reduction material "Escherichia sp. F1-micron iron powder" was developed. A novel iron-reducing bacterium, Escherichia sp. F1, was isolated from soil contaminated with chlorinated hydrocarbons. This bacterium demonstrated a sustained iron reduction capability, achieving a reduction rate of 38.7% for Fe(Ⅲ) within 15 days. Genome sequencing revealed that strain F1 harbors 53 functional iron reduction genes and 2 dehalogenation genes. Single-factor experiments identified the optimal conditions for TCE degradation in soil using the coupling material: glucose concentration at 40 mmol/kg, soil water content at 50%, and bacterial inoculum at 1% (v:w). Under these optimal conditions, the coupled material achieved 86.86% degradation of TCE in soil within 28 days. Further analysis using X-ray photoelectron spectroscopy of micron iron powder, soil Fe(Ⅱ) concentration, and soil physicochemical properties demonstrated that the addition of strain F1 to the soil could disrupt the passivation layer of iron oxide on the surface of micron iron powder, promoting the exposure of its reactive sites and internal reducing active components. This resulted in an in situ self-actuated activation of passivated micron iron powder, leading to an improved removal rate and complete dechlorination of TCE in the soil. Soil microbial high-throughput sequencing revealed that the addition of strain F1 regulated the soil bacterial community, significantly enriching of Escherichia-Shigella species associated with iron-reducing functions. This enrichment facilitated the degradation of TCE in the soil through coupling materials. The functional material plays a crucial role in achieving green treatment and risk control of sites contaminated with chlorinated organic pollutants.

Novel phase transfer catalysis coupled with bifunctional oxidation for enhanced remediation of groundwater polluted with multiple NAPL: Performance and mechanisms

Structural differences among non-aqueous phase liquids (NAPLs) result in varying oxidation rates, limiting mass transfer between NAPLs and oxidants and seriously impairing the effectiveness of remediation via traditional in-situ chemical oxidation. To tackle this challenge, a novel approach is proposed for remediating multi-NAPL-polluted groundwater that leverages phase transfer catalysis (PTC) to enhance heterogeneous mass transfer by transferring oxidants from groundwater to NAPLs. Meanwhile, “oxidation-in-situ activation” is achieved through bifunctional oxidation using permanganate and peroxymonosulfate (PP). The proposed approach is referred to PTC-PP in this study. Herein, trichloroethene (TCE) and benzene serve as a representative multi-NAPL system. Experimental results indicated that PP significantly improved degradation efficiency of benzene in multi-NAPL system by at least 60.8% compared to single-oxidant systems, and further enhancement (17.6%) was achieved when PP was combined with PTC compared to PP alone. Dissolved Mn(II) and MnO2 generated by MnO4− reduction effectively activated peroxymonosulfate in PTC-PP system, with colloidal MnO2 being the most effective activator. Consequently, SO4•−, O2•− and 1O2 were formed in both NAPL and aqueous phases, while •OH was formed in aqueous phase, playing a crucial role in benzene oxidation. In phase transfer process of PTC-PP, the proportion of MnO4− transferred to benzene exceeded that to TCE. This finding illustrated that nondirectional phase transfer of oxidants posed a challenge for simultaneous promotion of TCE and benzene degradation. However, TCE and benzene removal efficiencies were both >75.7% by applying peroxymonosulfate after KMnO4 addition. These findings lay the theoretical groundwork for PTC-PP application in groundwater remediation.

S-ZVI@biochar constructs a directed electron transfer channel between dechlorinating bacteria, Shewanella oneidensis MR-1 and trichloroethylene

The combination of micron zero-valent iron (mZVI) and microorganisms is an effective method for trichloroethylene (TCE) degradation, but electron transfer efficiency needs improvement. A new chem-bio hybrid process using a composite material (S-ZVI@biochar) was developed, consisting of sulfurized mZVI and biochar as a chemical remover, and Shewanella oneidensis MR-1 and dechlorinating bacteria (DB) as a biological agent for TCE degradation. S-ZVI@biochar showed improved stability, biocompatibility, and TCE removal compared to ZVI and S-ZVI. The hybrid system DB + MR-1 + S-ZVI@biochar exhibited the highest TCE removal efficiency at 96.5% after 30 days, which was 3.7 times higher than that of bare ZVI. The study revealed that the enhanced dechlorination performance was due to improved electron transfer efficiency, adjustment of microbial community structure, and iron recycling. S-ZVI@biochar constructed electron transport channels in the composite system, improving the overall dechlorination capacity. This system shows promise for long-term TCE removal in anaerobic environments.

The enhanced degradation of trichloroethylene in the bioelectrochemical system integrated with iron‑carbon micro-electrolysis

Trichloroethylene (TCE) is one of the most abundant volatile chlorinated hydrocarbons in groundwater which threatens human health and the environment. Utilizing a bioelectrochemical system (BES) to treat TCE is a promising strategy; however, as the ionic strength of the groundwater is low and the extracellular electron transfer of BES is limited, BES degradation of TCE is impeded. In this research, iron and graphite were added to the cathode chamber to form a micro-electrolysis to enhance the degradation of TCE synergistically. The results showed that when the iron and carbon mixture dosage was 70 g/L with the mass ratio (Fe/C) of 1:2 and the initial TCE concentration of 100 mg/L, the degradation efficiency of BES reached 97.8 % at the cathodic potential of −0.3 V (vs.SHE). This was 1.31 times, 1.94 times, and 2.74 times that of Fe/C + open-circuit BES, Fe/C micro-electrolysis, and conventional BES without Fe/C, respectively, which implied that iron‑carbon mediated BES colligated the advantages of microbial degradation and micro-electrolysis, and iron‑carbon provided more electrons and accelerated electron transfer to improve the degradation of TCE significantly. Moreover, through the analysis of the microorganisms of Fe/C + BES, the highest abundances of microorganisms at phylum, class, and genus levels were Proteobacteria, Alphaproteobacteria, and Acetobacterium, respectively. By comparing Fe/C + BES with conventional BES, the addition of iron‑carbon enhanced the microbial diversity and species richness and improved the abundances of Pseudomonas and Geobacter at the genus level. In all, iron‑carbon micro-electrolysis can be integrated with BES to treat TCE and facilitate BES application in the volatile chlorinated hydrocarbon-contaminated sites.

A novel redox synergistic mechanism of peroxymonosulfate activation using Pd-Fe3O4 for ultra-fast chlorinated hydrocarbon degradation

Peroxymonosulfate (PMS)-based heterogeneous advanced oxidation processes for chlorinated hydrocarbons (CHCs) removal in groundwater face the challenge of limited degradation ability. In this work, recyclable catalysts composed of Pd and Fe3O4 nanoparticles were synthesized to activate PMS and generate oxidative HO• and SO4•− and reductive H•, simultaneously. The synergistic attack of different active species led to the ultra-fast degradation and mineralization of multiple CHCs. For trichloroethylene (TCE) degradation, the catalysts mass normalized reaction rate constant of Pd-Fe3O4/PMS system (30.85 L g−1 min−1) was one order of magnitude higher than reported PMS activation systems. The d-band center of Pd in Pd-Fe3O4 was close to the Fermi level, indicating that Pd(0) sites of Pd-Fe3O4 was more conducive to the activation of PMS. In addition, PMS attached Fe3O4 sites caused internal electron transfer to Pd(0) for H• generation. Higher than 97 % of CHCs removal efficiency in continuous flow experiment demonstrated the application potential of Pd-Fe3O4/PMS system.

Preparation of zero-valent iron@Fe3O4 and its removal performance study for trichloroethylene

Trichloroethylene (TCE) is a common organic pollutant with low solubility in water, leading to its accumulation within the soil layer and posing risks to groundwater system. In this study, the zero valent iron@Fe3O4 (nZVI@Fe3O4) with diameters in the range of 500 nm to 1500 nm and thickness between 2 and 3 nm were successfully synthesized by ascorbic acid mediated reduction of FeCl2 in an N2-filled glove box, and proposed to boost the degradation of TCE. Research findings indicate that a starting TCE concentration of 20 mg/L can achieve a removal rate exceeding 80 % after 60 min, with an impressive adsorption capacity of 32.09 mg/g. The acidic environment plays a crucial role in enhancing the elimination of TCE by nZVI. Additionally, it was observed that a high NaCl concentration negatively impacts the effectiveness of nZVI in TCE removal, with the most significant inhibition observed at a NaCl concentration of 1000 mg/L. The adsorption of TCE by nZVI was consistent with the Langmuir model for monolayer adsorption, and the removal process was consistent with the quasi-secondary kinetic model. Importantly, the nanomaterials prepared in this experiment using disproportionation reaction have good economic and environmental benefits.

Enhanced reductive degradation of trichloroethylene by ball milled nitridation of bimetallic Ni-ZVI: Combination effect of electron transfer and catalytic hydrogenation

The performance optimization of zerovalent iron (ZVI) based materials for reductive dechlorination is critical but remains challenging. Combining the advantages of bimetallic and heteroatomic modification may lead to a novel strategy for reductive dechlorination of chlorinated ethenes (CEs) pollution. In this study, three different types of dual-modified micron ZVI (mZVI) composite particles, namely, pre-bimetallic modified mZVI (Ni/mZVI-N), pre-nitrogen modified mZVI (N/mZVI-Ni), and simultaneously modified mZVI (Ni/N-mZVI), were prepared by adjusting the order of ball milling modification of nickel and melamine, in which ball milling mechanical-chemical interactions contributed to the generation of enriched M-N structures. In terms of combined reactivity and selectivity, Ni/N-mZVI exhibited the best performance, with trichloroethylene (TCE) dechlorination rate (kobs,TCE) and electron efficiency (εe) of 0.14 h−1 and 8.9 %, respectively, which were 10.7 and 7.5 times higher than those of mZVI. The distribution and percentage of degradation products further illustrated the reductive dechlorination of nickel-nitrogen dual-modified mZVI via both electron transfer and atomic hydrogen (H*) pathways. A series of characterization and mechanistic analyses showed that the enhancement of TCE reductive dechlorination performance could be attributed to the combined effect of Fe−N to accelerated electron transfer and Ni-N to enhance catalytic hydrogenation. In addition to decreased H2 accumulation, Ni/N-mZVI reduced leaching ions thus mitigating secondary contamination. This double-modification strategy employed to enhance the optimization of mZVI for groundwater remediation establishes a foundation for ongoing progress in the synthesis of reactive materials.

Ultra-efficient peroxymonosulfate utilization and trichloroethylene degradation in heterogeneous catalytic system guided by sheet-like Cu2MnO4 nanoparticles: The role of Cu(III)–O species and free radicals

Synthesizing cubic spinel Cu2MnO4 with nanosheet structure (SCMO) aimed to construct a “non-radical-mediated radical-oxidative reaction”, for increasing PMS utilization efficiency, and solving the defects of SO4•− and •OH through indirect PMS activation by electron transfer process. Compared with box-like Cu2MnO4 (11.1%, 0.0035 min−1) and ordinary Cu2MnO4 nanoparticles (21.3%, 0.0070 min−1), SCMO/PMS showed excellent trichloroethylene removal (98.8%, 0.1577 min−1). The pivotal role of Cu(III) was determined based on EPR analysis, quenching experiments, chemical probe experiments, hydrogen temperature-programmed reduction and Raman spectroscopy analysis, in-situ FTIR and Raman analyses. In brief, the interaction between PMS and SCMO could produce surface-bonded reactive complexes and the subsequent breaking of O–O bond in the sub-stable structure allowed the conversion of Cu(II) to Cu(III), which in turn facilitates the generation of •OH and SO4•−. The density functional theory (DFT) calculations provided supporting evidence for the electron donor role of SCMO and the increase of the electron acceptance capacity of PMS. SCMO/PMS system showed good resistance and degradation efficiency to complex composition and combined pollutants in actually contaminated groundwater, respectively. However, the coexistence of high concentrations of arsenic could significantly affect SCMO performance due to their adsorption on –OH groups, which still need in-depth study.

Single-Atom Iron Can Steer Atomic Hydrogen toward Selective Reductive Dechlorination: Implications for Remediation of Chlorinated Solvents-Impacted Groundwater.

Atomic hydrogen (H*) is a powerful and versatile reductant and has tremendous potential in the degradation of oxidized pollutants (e.g., chlorinated solvents). However, its application for groundwater remediation is hindered by the scavenging side reaction of H2 evolution. Herein, we report that a composite material (Fe0@Fe-N4-C), consisting of zerovalent iron (Fe0) nanoparticles and nitrogen-coordinated single-atom Fe (Fe-N4), can effectively steer H* toward reductive dechlorination of trichloroethylene (TCE), a common groundwater contaminant and primary risk driver at many hazardous waste sites. The Fe-N4 structure strengthens the bond between surface Fe atoms and H*, inhibiting H2 evolution. Nonetheless, H* is available for dechlorination, as the adsorption of TCE weakens this bond. Interestingly, H* also enhances electron delocalization and transfer between adsorbed TCE and surface Fe atoms, increasing the reactivity of adsorbed TCE with H*. Consequently, Fe0@Fe-N4-C exhibits high electron selectivity (up to 86%) toward dechlorination, as well as a high TCE degradation kinetic constant. This material is resilient against water matrix interferences, achieving long-lasting performance for effective TCE removal. These findings shed light on the utilization of H* for the in situ remediation of groundwater contaminated with chlorinated solvents, by rational design of earth-abundant metal-based single-atom catalysts.

Uncovering the microbial community structure and physiological profiles of terrestrial mud volcanoes: A comprehensive metagenomic insight towards their trichloroethylene biodegradation potentiality

Mud volcanoes are dynamic geological features releasing methane (CH4), carbon dioxide (CO2), and hydrocarbons, harboring diverse methane and hydrocarbon-degrading microbes. However, the potential application of these microbial communities in chlorinated hydrocarbons bioremediation purposes such as trichloroethylene (TCE) has not yet been explored. Hence, this study investigated the mud volcano's microbial diversity functional potentiality in TCE degradation as well as their eco-physiological profiling using metabolic activity. Geochemical analysis of the mud volcano samples revealed variations in pH, temperature, and oxidation-reduction potential, indicating diverse environmental conditions. The Biolog Ecoplate™ carbon substrates utilization pattern showed that the Tween 80 was highly consumed by mud volcanic microbial community. Similarly, MicroResp® analysis results demonstrated that presence of additive C-substrates condition might enhanced the cellular respiration process within mud-volcanic microbial community. Full-length 16 S rRNA sequencing identified Proteobacteria as the dominant phylum, with genera like Pseudomonas and Hydrogenophaga associated with chloroalkane degradation, and methanotrophic bacteria such as Methylomicrobium and Methylophaga linked to methane oxidation. Functional analysis uncovered diverse metabolic functions, including sulfur and methane metabolism and hydrocarbon degradation, with specific genes involved in methane oxidation and sulfur metabolism. These findings provide insights into the microbial diversity and metabolic capabilities of mud volcano ecosystems, which could facilitate their effective application in the bioremediation of chlorinated compounds.

Innovative strategy for the effective utilization of coal waste slag in the Fenton-like process for the degradation of trichloroethylene

In response to environmental concerns at the global level, there is considerable momentum in the exploration of materials derived from waste that are both sustainable and eco-friendly. In this study, CS-Fe (carbon, silica, and iron) composite was synthesized from coal gasification slag (CGS) and innovatively applied as a catalyst to activate PS (persulfate) for the degradation of trichloroethylene (TCE) in water. Scanning electron microscope (SEM), fourier transmission infrared spectroscopy (FTIR), energy dispersive x-ray spectroscopy (EDS), brunauer, emmet, and teller (BET) technique, and x-ray diffractometer (XRD) spectra were employed to investigate the surface morphology and physicochemical composition of the CS-Fe composite. CS-Fe catalyst showed a dual nature by adsorption and degradation of TCE simultaneously, displaying 86.1% TCE removal in 3 h. The synthesized CS-Fe had better adsorption (62.1%) than base material CGS (36.4%) due to a larger BET surface area (770.8 m2 g−1), while 24.0% TCE degradation was recorded upon the activation of PS by CS-Fe. FTIR spectra confirmed the adsorption and degradation of TCE by investigating the used and fresh samples of CS-Fe catalyst. Scavengers and Electron paramagnetic resonance (EPR) analysis confirmed the availability of surface radicals and free radicals facilitated the degradation process. The acidic nature of the solution favored the degradation while the presence of bicarbonate ion (HCO3−) hindered this process. In conclusion, these results for real groundwater, surfactant-added solution, and degradation of other TCE-like pollutants propose that the CS-Fe composite offers an economically viable and favorable catalyst in the remediation of organic contaminants within aqueous solutions. Further investigation into the catalytic potential of coal gasification slag-based carbon materials and their application in Fenton reactions is warranted to effectively address a range of environmental challenges.

Development of a slow-release CO2 absorbent material for alkaline activation of persulfate oxidation of TCE and CO2 capture

Control of carbon dioxide (CO2) emission during chemical oxidation processes of organic-chemical contaminated sites has become a challenge. In this study, a novel slow-release CO2 absorbent material (SCAM) was developed for a slow release of Ca2+ and OH–, which were used for CO2 capture, pH adjustment, and alkaline activation of persulfate (PS) oxidation for trichloroethylene (TCE) degradation. The SCAM was produced using basic oxygen furnace slag (BOFs) and calcium sulfate hemihydrate (CSH) as the components for granulation and modification. Batch experiments were conducted to determine the optimal mass ratio of BOFs to CSH and evaluate CO2 capture capacity and SCAM performance. An increase in BOFs proportion led to a higher CO2 capture capacity, with the maximum capture amount reaching 156 g CO2/kg SCAM. An excessive addition of BOFs resulted in an overly alkaline pH value (pH = 12.4), causing the diminished PS oxidation efficiency. The optimal mass ratio of BOFs to CSH (1 to 1) could capture produced CO2 after TCE oxidation without inhibiting PS oxidation. The SCAM could serve as the catalyst and activate PS oxidation, resulting in 93.1 % of TCE oxidation (initial TCE concentration = 2.32 mM) and 95.4 % of CO2 emission reduction due to the formation of CaCO3 precipitates under alkaline conditions. Produced sulfate and hydroxyl radicals confirmed the PS oxidation of TCE using SCAM as an activator. The developed SCAM is a green catalyst for PS oxidation and it is also an effective CO2 absorbent. SCAM can reduce CO2 emission due to the formation of CaCO3 precipitates under alkaline conditions. The released OH– could also prevent the acidification problem caused by the production of sulfuric acid through PS decomposition.

Biodegradation of Trichloroethylene by Trametes versicolor and its Physiological Response to Contaminant Stress.

Trichloroethylene (TCE) poses a potentially toxic threat to humans and the environment and widely exists in contaminated sites. White rot fungi effectively degrade refractory pollutants, while a few research studies use white rot fungi to degrade TCE. In this study, we investigated TCE biodegradation by white rot fungi and the potential influencing factors in the environment and attempted to research the effect of TCE on the physiological characteristics of white rot fungi. White rot fungi (Trametes versicolor, Pseudotrametes gibbosa, Pycnoporus sanguines and Pleurotus ostreatus) were added to the liquid medium for shock culture. The results revealed that T. versicolor exhibited the most pronounced efficacy in removing TCE, with a degradation rate of 81.10% within a 7 d period. TCE induces and is degraded by cytochrome P450 enzymes. High pH and Cr(VI) adversely affected the effectiveness of the biodegradation of TCE, but the salinity range of 0-1% had less effect on biodegradation. Overall, the effectiveness of degradation of TCE by T. versicolor has been demonstrated, and it provides a reference for the application prospects of white rot fungi in TCE-contaminated soils.

TCE degradation of modified graphite felt cathode in a flow-through electro-Fenton system and its H2O2 production ability in a real contaminated field

A modified graphite felt (MGF) was prepared with carbon black (CB) and polytetrafluoron (PTFE) for cathodic electrochemical H2O2 production, which was used in a flow-through cathodic electro-Fenton reactor to degrade chlorinated hydrocarbons. Cathode electrode was floating on aqueous surface and 369.1 mg/L H2O2 could be produced after 1 h 150 mA power applied without O2 aeration. The main O2 source for H2O2 production was confirmed from air with this floating position. In a 2.0 L flow-through cathodic electro-Fenton system, 95.97 % degradation efficiency for 5.0 mg/L trichloroethylene (TCE) was achieved in 90 min with 13.4 mL/min influent rate. Reducing the reactor volume to 0.14 L, 5.0 mg/L TCE could be degraded completely in 10 min with continuous 4 L influent. The mixed chlorinated hydrocarbons (TCE, cis-1,1-dichloroethylene, 1,2-dichloroethane, and dichloromethane) were also rapidly degraded in 20 min. The flow-through cathodic electro-Fenton reactor presented excellent degradation ability for chlorinated hydrocarbons with a smaller volume. In the simulated sand tank system, after continuously operated 27 days, H2O2 concentration in electrode well was still remained at 80 mg/L. In the contaminated field in Tianjin, China, H2O2 yield of MGF in groundwater could keep at about 60 mg/L after 220 min operating.

Insight into the role of reactive species on catalyst surface underlying peroxymonosulfate activation by P–Fe2MnO4 loaded on bentonite for trichloroethylene degradation

In this study, bentonite supporting phosphorus-doped Fe2MnO4 (BPF) was synthesized and applied for PMS activation to degrade TCE. Morphology and structure characterization results indicated the successfully synthesized of BPF, and the BPF/PMS system not only featured high TCE removal (97.4%) but also high reaction rate constant (kobs = 0.0554 min−1) and PMS utilization (70.4%, kobs = 0.0228 min−1). According to the results of various experiments, massive oxygen vacancies on P–Fe2MnO4 alter its charge balance and facilitate the electron transfer process named adjacent transfer (direct electron capture by adsorbed PMS from adjacent TCE). Mn(III) is the main adsorption site for PMS, and the hydroxyl groups on the catalyst (Fe sites of P–Fe2MnO4, Si and Al sites of bentonite) can also offer binding sites for PMS. The hydrogen-bonded PMS on Fe(III) and Mn(III) sites will subsequently accept the discharged electrons to generate free radicals and high-valent metal species. Meanwhile, electron loss of HSO5− that chemically bonded to hydroxyl groups on bentonite will generate SO5•−, which will further produce 1O2 through self-bonding. the active species on the catalyst surface contribute 65% of TCE degradation in the heterogeneous catalytic oxidation system.