Search Results (50)

Microplastics (MPs) and nanoplastics (NPs) can affect microbial abundance and activity, likely by damaging cell membrane components. While their effects on anaerobic digestion are known, less is understood about their impact on microbes involved in contaminant bioremediation. Chlorinated volatile organic contaminants (CVOCs) such as tetrachloroethene (PCE) and explosives like hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) are common in the environment, and their bioremediation is a promising cleanup strategy. This study examined how polystyrene (PS) and polyamide 6 (PA6) MPs and NPs influence CVOC and RDX biodegradation. PS particles did not inhibit the CVOC-degrading community SDC-9, but PA6 MPs impaired the reductive dechlorination of trichloroethene (TCE) to cis-1,2-dichloroethene (cis-DCE), causing a “cis-DCE stall” with no further conversion to vinyl chloride (VC) or ethene. Only 45% of TCE was dechlorinated to cis-DCE, and Dehalococcoides mccartyi abundance dropped 1000-fold in 35 days with PA6 MPs. In contrast, neither PA6 nor PS MPs and NPs affected RDX biotransformation. These results highlight the significant impact of PA6 MPs on CVOC biodegradation and the need to consider plastic pollution in environmental management. Full article

Soil microbial communities are essential for the natural attenuation of organic pollutants, yet their ecological responses under long-term contamination remain insufficiently understood. This study examined the bacterial community structure and the abundance of dechlorinating bacteria at a decommissioned pharmaceutical-chemical site in northern Jiangsu Province, China, where the primary pollutants were dichloromethane, 1,2-dichloroethane, and toluene. Eighteen soil samples from the surface (0.2 m) and deep (2.2 m) layers were collected using a Geoprobe-7822DT system and analyzed for physicochemical properties and microbial composition via 16S rRNA gene amplicon sequencing. The results showed that the bacterial community composition was significantly shaped by the soil pH, moisture content, pollutant type, and depth. Dechlorinating bacteria were detected at all sites but exhibited low relative abundance, with higher concentrations in the surface soils. Desulfuromonas, Desulfitobacterium, and Desulfovibrio were the dominant dechlorinators, while Dehalococcoides appeared only in the deep soils. A network analysis revealed positive correlations between the dechlorinators and BTEX-degrading and fermentative taxa, indicating potential cooperative interactions in pollutant degradation. However, the low abundance of dechlorinators suggests that the intrinsic bioremediation capacity is limited. These findings provide new insights into microbial ecology under complex organic pollution, and support the need for integrated remediation strategies that enhance microbial functional potential in legacy-contaminated soils. Full article

Extensive utilization of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) has resulted in contamination of the aquatic environment; this situation requires effective treatment technology. Ultraviolet-based advanced oxidation processes (UV-AOPs) are widely employed for the removal of organic contaminants from water. This study’s aim was to compare the degradation of the pesticide 2,4-D in UV-C-activated peroxide and peroxydisulfate systems. UV-C irradiation alone exhibited a negligible effect on pesticide degradation, whereas the addition of oxidants significantly enhanced the degradation efficiency relative to 2,4-D. Complete pesticide removal was achieved after 15 min of UV/H₂O₂ treatment, while twice as much time was required with the UV/S₂O₈²⁻ process. COD decreased by 74% and 28% for UV-C-activated peroxide and peroxydisulfate, respectively. Both investigated systems demonstrated good performance for 2,4-D dechlorination. Pesticide degradation rates increased with increasing dosages of the applied oxidants. Acidic conditions were more favorable for degradation of 2,4-D, compared to neutral and basic conditions, for both systems studied. The degradation efficiency relative to 2,4-D decreased in the presence of HA, Cl⁻ and HCO₃⁻ in water matrices. The predominant radical for the UV-C-activated peroxydisulfate was determined to be a sulfate radical. These findings are of fundamental and practical significance in understanding UV-C-activated 2,4-D degradation, paving the way for the selection of preferred processes for the optimal removal of pesticides from various aqueous matrices. Full article

Electrochemical reduction is a promising strategy for the dechlorination of halogenated organic compounds, offering advantages such as enhanced electron transfer efficiency and increased hydrogen atom concentration. It has garnered significant attention for application in mitigating halogenated disinfection by-products (DBPs) in drinking water, owing to its high efficiency and simple operation. In this study, trichloroacetic acid (TCAA), a representative DBP, was selected as the target contaminant. A novel composite cathode comprising a metal–organic framework MIL-53(Fe)@C supported on an Nd magnet (MIL-53(Fe)@C-MAG) and its dechlorination performance for TCAA were systematically investigated. The innovative aspect of this study is the magnetic attachment of the MOF catalyst to the carbonized cathode surface treated through carbonization, which fundamentally differs from conventional solvent-based adhesion methods. Compared to the bare electrode, the MIL-53(Fe)@C-MAG achieved a TCAA removal efficiency exceeding 96.03% within 8 h of contact time. The structural characterization revealed that the α-Fe⁰ crystalline phase serves as the primary active center within the MIL-53(Fe)@C catalyst, facilitating efficient electron transfer and TCAA degradation. The scavenger experiments revealed that TCAA reduction involves a dual pathway: direct electron transfer and atomic hydrogen generation. The modified MIL-53(Fe)@C-MAG electrode exhibited robust electrolytic performance over a broad pH range of 3–7, with TCAA removal efficiency showing a positive correlation with current density within the range of 10–50 mA/cm². Furthermore, the electrode maintained exceptional stability, retaining more than 90% removal efficiency after five consecutive operational cycles. The versatility of the system was further validated by the rapid and efficient dechlorination of various chlorinated DBPs, demonstrating the broad applicability of the electrode. The innovative magnetic composite electrode demonstrates a significant advancement in electrochemical dechlorination technology, offering a reliable and efficient solution for the purification of drinking water contaminated with diverse halogenated DBPs. These results provide valuable insights into the development of electrolysis for dechlorination in water treatment applications. Full article

The excessive levels of neonicotinoid insecticides, particularly thiacloprid (THI), in the environment have become a significant threat to ecosystems. This study investigates the catalytic degradation of THI using pinewood biochar (PBC), zero-valent iron (ZVI), and ZVI/PBC composite, with a particular focus on the reaction activity modulation mediated by organic acids (humic acid: HA and oxalic acid: OA). Reductive dechlorination dominated THI degradation as observed by Cl⁻ release kinetics. Compared to HA (39.73%), the OA (73.44%) addition markedly increased the THI removal efficiency by ZVI/PBC, which alone has a lower removal efficacy, i.e., 37.29%. The increase in the THI removal rate was attributed to its enhanced electron transfer capacity. As confirmed by electrochemical characterization, the addition of organic acids promotes electron transfer between THI and catalysts (ZVI, PBC, or ZVI/PBC), thereby improving the removal efficiency of THI. XRD/XPS analyses elucidated that OA preferentially converted passivating Fe₂O₃/Fe₃O₄ on ZVI/PBC to reactive FeOOH and formed electron-conductive Fe–COO bonds, thereby suppressing oxide layer formation. PBC amplified these effects through ZVI dispersion and electron shuttling, reducing aggregation-induced activity loss. These findings provide a mechanistic framework for optimizing ligand-engineered iron composites, offering practical strategies to enhance pesticide remediation efficiency in organic acid-rich environmental systems. Full article

The removal of chlorinated organic pollutants from wastewater is a critical environmental challenge, as traditional methods for treating toxic pollutants like phenol and chlorophenols often suffer from high energy consumption and long treatment times, limiting their practical use. Electrocatalytic filtration has emerged as a promising alternative, but efficient, energy-saving electrocatalytic membranes for pollutants like 4-chlorophenol (4-CP) are still underexplored. A new type of electrocatalytic coupling membrane catalyst, ASP/CM (PANI-encapsulated aluminum silicate/ceramic membrane), was prepared using inexpensive silicate and polyaniline as the base materials, with in situ polymerization combined with co-focus magnetron sputtering. Under optimal conditions (25 mA/cm², 10 mM Na₂SO₄, 1.0 mL·min⁻¹ flow rate, and 50 μM 4-CP concentration), the membrane achieved about 95.1% removal of 4-CP and the degradation rate after five cycles was higher than 85%. In addition, O₂^•− and •OH are important active species in the electrocatalytic degradation of 4-CP. The 4-CP electrocatalytic membrane filtration process is a dual process of cathode reduction dechlorination and anodic oxidation. This work offers new insights into developing next-generation electrocatalytic membranes and expands the practical applications of electrocatalytic filtration systems. Full article

Trichloroethylene (TCE), a volatile organic compound commonly used as a solvent, is frequently detected in contaminated groundwater. In the zero-valent iron (ZVI) Fenton process, TCE can be eventually dechlorinated into non-toxic products, which is mainly caused by hydroxyl radicals derived from H₂O₂. However, some key factors in the dechlorination of TCE in the zero-valent iron Fenton process have not been studied clearly. In the present study, the effects of the initial TCE concentration, initial H₂O₂ concentration, dosage of ZVI, initial pH, and temperature on TCE degradation in the ZVI Fenton process were studied. In addition, the structure and surface morphology of the ZVI used in this study were analyzed through scanning electron microscopy (SEM), N₂ adsorption–desorption, and X-ray diffractometry (XRD). The experimental results demonstrated that the dosage of ZVI and initial H₂O₂ concentration had obvious impacts on TCE degradation. At a ZVI dosage of 2 g/L and an initial H₂O₂ concentration of 0.53 mol/L, more than 97% of TCE could be degraded within 24 h at 25 °C. We found that the ZVI Fenton process could efficiently degrade TCE at a broad pH range and room temperature, making it applicable to groundwater remediation. TCE degradation was associated with Fe²⁺ concentration. Spectroscopic analyses indicated that the oxide film formed on the ZVI surface was associated with Fe²⁺ concentration in enhanced TCE dechlorination. The ZVI Fenton process could work at a wide range of TCE concentrations (0–200 mg/L). Full article

Actions for improving water quality are critical and include the remediation of polluted groundwater. The effectiveness of the remediation strategy to remove contamination by chlorinated solvents may be increased by combining physicochemical treatments (i.e., adsorption) and biological degradation (i.e., biological reductive dechlorination (BRD)). Recent studies have shown the potentialities of bio-based materials for bioremediation purposes, including polyhydroxybutyrate (PHB), a biodegradable microbial polyester tested as a fermentable source of slow-release electron donors. Further, a low-cost biochar derived from the pyrolysis of pinewood waste (PWB), used as sorbent material, has recently been proposed to accelerate reductive microbial dehalogenation. Here, we propose a coupled adsorption and biodegradation (CAB) process for trichloroethylene (TCE) removal in a mini pilot-scale reactor composed of two reactive zones, the first one filled with PHB and the second one with PWB. This work aimed to evaluate the performance of the CAB process with particular regard to the effectiveness of the PWB in sustaining the biofilm, mostly enriched by Dehalococcoides mccartyi. The main results showed the CAB system treated around 1300 L of contaminated water, removing 102 mg TCE per day. Combining PHB and PWB had a positive effect on the growth of the dechlorinating community with a high abundance of Dhc cells. Full article

The photolysis kinetics of propaquizafop in water under ultraviolet light was investigated in this study, and the effects of different influencing factors (pH, ${\mathrm{N}\mathrm{O}}_3^{-}$, metal ions) on the photolysis of propaquizafop were clarified. Propaquizafop residues in water were determined by a HPLC-UV detector. The results showed that the pH of the aqueous solution had no significant effect on the photolysis of propaquizafop (p < 0.05). The low ${\mathrm{N}\mathrm{O}}_3^{-}$, concentration (0.5~2 mmol/L) had a weak inhibitory effect on the photolysis of the propaquizafop; when the concentration of ${\mathrm{N}\mathrm{O}}_3^{-}$ was 4 mmol/L, the degradation half-life of the propaquizafop was significantly higher than with other treatments (p < 0.05); Different concentrations of Fe³⁺ had varying degrees of inhibitory effects on the photolysis of propaquizafop. The inhibitory effect was stronger at low concentrations (0.5 mmol/L and 1 mmol/L) and weaker at high concentrations (2 mmol/L and 4 mmol/L). As the concentrations of Cu²⁺, Cd²⁺, Mn²⁺, Zn²⁺, and Ni²⁺ increased, their inhibitory effect on the photolysis of propaquizafop in an aqueous solution became stronger. In addition, LC–QTOF-MS was used to identify the photoproducts of propaquizafop in aqueous solution in this study. Five types of photoproducts were identified, and several propaquizafop degradation pathways and mechanisms were proposed, mainly including rearrangement, cracking reactions, dechlorination reactions, and light-induced redox reactions. The results of this study will help us to better understand the photodegradation law of propaquizafop in aqueous solution and provide data support for its safety evaluation in water. Full article

Hexachlorobenzene (HCB) is one of the most persistent environmental pollutants of global concern. Ni/Fe nanoparticles, with their small particle size, large surface area, and high reactivity, are a promising candidate for HCB degradation. In this work, we investigated the kinetics and products of the dechlorination of HCB by Ni/Fe nanoparticles and how the presence of heavy metal ions Cd(Ⅱ) and Zn(Ⅱ) influences the reaction. It is found that 400 μg/L HCB can be rapidly removed by 7.5 g/L Ni/Fe nanoparticles and the removal percentage reaches 99% in 48 h. The removal is facilitated by adsorption and sequential dechlorination of HCB, producing PCB, 1,2,3,4-TeCB, and 1,2,3-TCB as the main products, with 1,2,3,5/1,2,4,5-TeCB, 1,2,4-TCB, and 1,2-DCB as the minor products. The addition of heavy metal ions Cd(Ⅱ) and Zn(Ⅱ) does not significantly affect the removal rate of HCB but hinders the adsorption and degradation of the byproducts through competitive adsorption. Additionally, the concentration of both Cd(Ⅱ) and Zn(Ⅱ) decreases rapidly and achieves over 98% removal in 4 h. Our study reveals that Ni/Fe nanoparticles can remove HCB and heavy metals Cd(Ⅱ) and Zn(Ⅱ) concurrently, with the extent of HCB dechlorination reduced compared to that without heavy metal. These findings may inform the application of Ni/Fe nanoparticles in the treatment of water bodies and soil contaminated by both halogenated aromatics and heavy metal. Full article

Organic saline wastewater has become a concern in recent decades due to its resistance to biological treatment and potential harm to municipal wastewater treatment plants. While photocatalytic methods have been used for treatment, they often lead to catalyst deterioration. The use of salt-tolerant catalysts presents a viable solution for treating organic saline wastewater. In this study, a Zn-rich g-C₃N₄ was synthesized, demonstrating excellent performance in removing 2,4-DCP and its derivatives from saline wastewater. More than 75.6% of 2,4-DCP was effectively removed with the addition of Zn-rich g-C₃N₄, nearly doubling the removal rate compared to pure g-C₃N₄ and those doped with Co, Ag, Mo, and Bi. Notably, the removal efficiency of 2,4-DCP slightly increased as salinity rose from 0.1 to 2.3 wt.%. Adding 0.1 g L⁻¹ of Zn-rich g-C₃N₄ resulted in the removal of 2,4-DCP, 2-chlorohydroquinone, chloroacetophenone, and 2-chloropropionic acid by 99.3%, 99.8%, 98.2%, and 99.9%, respectively, from a real saline wastewater sample with 2.2 wt.% salinity, corresponding to a 67.7% removal of TOC. The EPR results indicated that Zn-rich g-C₃N₄ generated more free radicals compared to pure g-C₃N₄, such as·OH and Cl, to degrade organic contaminants. The degradation pathway revealed that 2,4-DCP was first dechlorinated into p-phenol and catechol, which were subsequently degraded into maleic acid/fumaric acid, trihydroxyethylene, acetic acid, oxalic acid, and other products. Furthermore, Zn-rich g-C₃N₄ demonstrated excellent stability and holds promising potential for applications in saline wastewater treatment. Full article

The removal of pesticides and other organic pollutants from water through advanced oxidation processes (AOPs) holds great promise. The main advantage of these technologies is that they remove, or at least reduce, pesticide levels by mineralization rather than transfer, as in conventional processes. This study first evaluated the effectiveness of UV/S₂O₈⁼ compared to heterogeneous photocatalysis using UV/TiO₂ processes on the degradation of two commonly used herbicides (terbuthylazine and isoproturon) in aqueous solutions using a laboratory photoreactor. In addition, the effect of the UV wavelength on the degradation efficiency of both herbicides was investigated. Although the degradation rate was greater under UV(254)/S₂O₈⁼ nm than under UV(365)/S₂O₈⁼ nm, complete degradation of the herbicides (0.2 mg L⁻¹) was achieved within 30 min under UV-366 nm using a Na₂S₂O₈ dose of 250 mg L⁻¹ in the absence of inorganic anions. To assess the impact of the water matrix, the individual and combined effects of sulfate (SO₄⁼), bicarbonate (HCO₃⁻), and chloride (Cl⁻) were evaluated. These can react with hydroxyl (HO^•) and sulfate (SO₄^•−) radicals generated during AOPs to form new radicals with a lower redox potential. The results showed negligible effects of SO₄⁼, while the combination of HCO₃⁻ and Cl⁻ seemed to be the key to the decrease in herbicide removal efficiency found when working with complex matrices. Finally, the main intermediates detected during the photodegradation process are identified, and the likely pathways involving dealkylation, dechlorination, and hydroxylation are proposed and discussed. Full article

In this study, the degradation system of Shewanella oneidensis MR-1 and goethite was constructed with chlorpyrifos as the target contaminant. The effects of initial pH, contaminant concentration, and temperature on the removal rate of chlorpyrifos during the degradation process were investigated. The experimental conditions were optimized by response surface methodology with a Box–Behnken design (BBD). The results show that the removal rate of chlorpyrifos is 75.71% at pH = 6.86, an initial concentration of 19.18 mg·L⁻¹, and a temperature of 30.71 °C. LC-MS/MS analyses showed that the degradation products were C₄H₁₁O₃PS, C₇H₇Cl₃NO₄P, C₉H₁₁Cl₂NO₃PS, C₇H₇Cl₃NO₃PS, C₉H₁₁Cl₃NO₄P, C₄H₁₁O₂PS, and C₅H₂Cl₃NO. Presumably, the degradation pathways involved are: enzymatic degradation, hydrolysis, dealkylation, desulfur hydrolysis, and dechlorination. The findings of this study demonstrate the efficacy of the goethite/S. oneidensis MR-1 complex system in the removal of chlorpyrifos from water. Consequently, this research contributes to the establishment of a theoretical framework for the microbial remediation of organophosphorus pesticides in aqueous environments. Full article

A new membrane-less bioelectrochemical reactor configuration was developed for contaminated groundwater remediation. The new bioelectrochemical reactor configuration was inspired by the utilisation of a permeable reactive barrier (PBR) configuration with no separation membrane. The corresponding reactive zones were created by using graphite granules and mixed metal oxide (MMO) electrodes to stimulate the reductive and oxidative biological degradation of chlorinated aliphatic hydrocarbons. In the present study, the PBR-like bioelectrochemical reactor has been preliminarily operated with synthetic contaminated groundwater, testing the reductive dechlorination activity on cis-dichloroethylene (cisDCE). Moreover, to assess the effects of competing anions presence for the electron donor (i.e., the cathode), the synthetic wastewater contained sulphate and nitrate anions. In the PBR-like reactor operation, nearly all cisDCE was removed in the initial sampling port, with only VC detected as the observable RD product. During the same biotic test of the PRB reactor, the presence of both the reductive dechlorination and anions reduction was confirmed by the complete nitrate reduction in the cathodic chamber of the PRB reactor. On the contrary, sulphate reduction showed a lower activity; indeed, only 25% of the influent sulphate was removed by the PRB reactor. Full article

In this study, an electrochemical-assisted ferric ion/persulfate (EC/Fe³⁺/PS) process was proposed to degrade bezafibrate (BZF), a widespread hypolipidemic drug, in water. By promoting the reduction of Fe³⁺ to Fe²⁺ at the cathode, the introduction of an electric field successfully overcomes the limitation of non-regenerable Fe²⁺ inherent in Fe²⁺/PS systems, significantly improving the degradation efficiency of BZF. The predominant reactive species identified were •OH and SO₄^●−, with ¹O₂ also playing a role. Various key operational parameters were investigated and optimized, including the current intensity, Fe³⁺ dosage, PS concentration, and initial pH. With a current intensity of 50 mA, an Fe³⁺ concentration of 50 μΜ, a PS dosage of 50 μM, and an initial pH of 3, the degradation efficiency of BZF demonstrated an exceptional achievement, reaching up to 98.8% within 30 min. The influence of anions and humic acid was also assessed. An LC/TOF/MS analysis revealed four major degradation pathways of BZF: hydroxylation, amino bond cleavage, dechlorination, and fibrate chain removal. The acute and chronic toxicities of BZF and its degradation intermediates were then assessed using the ECOSAR program. These findings highlight the wide-ranging applications of the EC/Fe³⁺/PS system and its potential for remediating water contaminated with micropollutants. Full article