Degradation Of Contaminants Research Articles

Activation of peroxymonosulfate by CuO-OMS-2 for efficient phenol mineralization: performance, contributions of ROS, and catalytic mechanisms.

In this paper, copper oxide supported manganese oxide octahedral molecular sieves (CuO-OMS-2) composite was successfully synthesized and subsequently investigated for the degradation and mineralization of phenol via peroxymonosulfate (PMS) activation. It was confirmed that the incorporation of CuO significantly promoted multivalent metals transition and oxygen vacancies generation. At initial pH 5.0, CuO-OMS-2 achieved the optimum catalytic activity with 93.6% of phenol degradation efficiency and 87.6% of mineralization rate in 30 min. Additionally, a probe-based kinetic model was developed to simulate the removal of phenol in CuO-OMS-2/PMS system under different pH conditions, which was a decisive factor to affect the transformation of main active radicals and the oxidation capacity. The quantitative results of the active radicals suggested that 1O2 and O2•- played generally a negligible role in the abatement of phenol, while the contribution of SO4•- gradually increased from 25.17 to 75.60% and that of •OH decreased from 69.23 to 22.80% with the rising of pH from 3 to 9. Meanwhile, the CuO-OMS-2 composite showed excellent stability and reusability for contaminant degradation during five consecutive cycles. Finally, the results of probe-based kinetic model and characterization jointly demonstrated the mechanism of phenol degradation by CuO-OMS-2 activating PMS.

Real-time in situ monitoring as a tool for comparison of electrochemical advanced oxidation processes for the decolourisation of azo and indigoid dyes.

The widespread use of synthetic dyes has led to the release of substantial amounts of dye-contaminated wastewater, posing significant environmental and health concerns. This study focuses on the use of anodic and electrochemically activated persulfate oxidation for the degradation of organic contaminants. Specifically, the structural variations of nine dyes in the indigoid and azo families, and their impact on the efficiency of electrochemical oxidation were analysed. An in situ continuous monitoring apparatus with a UV-visible detector was employed to collect data in real-time. The electrochemically activated persulfate system demonstrated higher efficiency compared to the anodic oxidation approach. In both systems the efficiency of decolourisation was highly dependent on the structure of the pollutant. Electron-withdrawing substituents in direct conjugation with the chromophore, bulky auxochromes, and extended aromatic systems significantly decreased the decolourisation efficiency. Conversely, changing the location of electron-withdrawing groups and adding electron-donating substituents increased the decolourisation efficiency, even overcoming the detrimental effects of bulky groups and extended conjugation. This type of systematic structural comparison study is essential for highlighting the interconnected nature of pollutant structure and degradation speed so that efficient electrochemical oxidation systems can be designed for the treatment of genuine wastewater effluent containing more than one pollutant.

Salt-induced anisotropic SrTiO3 to boost piezo-photocatalytic processes

Piezo-photocatalysis materials that can combine the piezoelectric effect in photocatalytic processes are very attractive for promising applications in water splitting and contaminant degradation. The perovskite oxides with adjustable exposed crystal facets are expected to optimize the catalysis activities by exposing the high-energy planes. In this work, we develop a salt-assisted strategy that controllably prepares anisotropic SrTiO3 particles with a large number of surface defects, which exhibit good piezo-photocatalytic features. The exposure of the crystal facets can be tuned by changing the assistants (NaCl or SrCl2). The SrCl2 can lead to the exposure of the (110) plane in one-dimensional SrTiO3 particles and NaCl can induce the cubic SrTiO3 particles with the exposure plane of (200). Attributed to the exposed high-energy facets and abundant oxygen vacancies, the latter show higher activities than the former in both water splitting and dye degradation under light irradiation and ultrasonic vibration. Our work provides an approach to optimize piezo-photocatalytic activities by tuning the exposed crystal facets.

Interface coupling induced built-in electric field to regulate the peroxymonosulfate activation over Co3O4/NiO composite for realizing effective degradation of organic contaminants

Interface coupling induced built-in electric field to regulate the peroxymonosulfate activation over Co3O4/NiO composite for realizing effective degradation of organic contaminants

Triggering nanoconfinement effect in advanced oxidation processes (AOPs) for boosted degradation of organic contaminants: A review

Triggering nanoconfinement effect in advanced oxidation processes (AOPs) for boosted degradation of organic contaminants: A review

Coexisting ferrihydrite-enhanced contaminant degradation during pyrite oxygenation

Coexisting ferrihydrite-enhanced contaminant degradation during pyrite oxygenation

Degradation mechanism of organic contaminants in complex contaminated groundwater in landfill sites with oxygen micro-nano-bubbles aeration

Complex contaminated groundwater in landfill sites poses a significant health threat. Oxygen micro-nano-bubbles (MNBO2) aeration shows promise for remediation of such complex contaminated groundwater, while its mechanism for degradation contaminants remained unclear. This study investigated the degradation mechanism of organic contaminants in complex contaminated groundwater in landfill sites with MNB-O2 aeration by contaminants degradation process and efficiency, dissolved organic matter (DOM) transformation as well as enzyme activity and microorganism. The test results indicated that after 105th day of MNB-O2 aeration, the removal efficiencies of 5-day biological oxygen demand, chemical oxygen demand and α(254) in the water sample were 92.64 %, 50.56 % and 77.03 %, respectively. Additionally, the refractory DOM increased by 3 % to 11 %, while biodegradable DOM decreased by 57.63 %. MNB-O2 aeration enhanced the activity of aerobic microorganisms but reduced the diversity, evenness and richness of microbial species in the soil sample. Moreover, it altered the microbial community of the soil sample and enhanced oxidation of organic substance in the water sample. MNB-O2 aeration enhanced the biodegradation of the water sample, and its enhanced volatilization and strong chemical oxidation also contributed to organic contaminants degradation in the water sample. Collectively, the finding of this work will provide theoretical support for the practical application of MNB-O2 aeration in remediation of complex contaminated groundwater in landfill sites.

Application of Micro/Nanomotors in Environmental Remediation: A Review

The advent of self-propelled micro/nanomotors represents a paradigm shift in the field of environmental remediation, offering a significant enhancement in the efficiency of conventional operations through the exploitation of the material phenomenon of active motion. Despite the considerable promise of micro/nanomotors for applications in environmental remediation, there has been a paucity of reviews that have focused on this area. This review identifies the current opportunities and challenges in utilizing micro/nanomotors to enhance contaminant degradation and removal, accelerate bacterial death, or enable dynamic environmental monitoring. It illustrates how mobile reactors or receptors can dramatically increase the speed and efficiency of environmental remediation processes. These studies exemplify the wide range of environmental applications of dynamic micro/nanomotors associated with their continuous motion, force, and function. Finally, the review discusses the challenges of transferring these exciting advances from the experimental scale to larger-scale field applications.

A Novel Synthesis of a Calix [4] Arene, MIL‐101(Fe), and Copper(II) Oxide Nanocomposite (Calix/MIL‐101(Fe)/CuO): Synthesis, Characterization, Degradation, and Pollutant Removal Ability

AbstractDyes are organic compounds. Azo dyes, as the most important dyes, are usually synthesized and reduced after entering the human body, turning into mutagenic and carcinogenic amines. A new efficient composite containing calix [4] arene (Calix), metal‐organic framework (MIL‐101(Fe)), and copper(II) oxide (Calix/MIL‐101(Fe)/CuO) was synthesized and utilized for the degradation of Malachite Green (MG). The dye removal efficiency was 17% for Calix, 56% for CuO, 64% for MIL‐101(Fe), and 98.8% for the Calix/MIL‐101(Fe)/CuO composite using LED visible light. The degradation of MG by Calix/MIL‐101(Fe)/CuO using different doses, including 0, 1, 2, 3, and 4 mg, was 8%, 64%, 75%, 85%, and 98.8%, respectively. The degradation kinetic rate constants for 0, 1, 2, 3, and 4 mg of Calix/MIL‐101(Fe)/CuO were 0.0134, 0.1086, 0.1182, 0.1308, and 0.1727 (zero‐order rate), 5E‐04, 0.007, 0.008, 0.011, and 0.023 (first‐order rate), and 4E‐05, 0.0007, 0.001, 0.0017, and 0.0211 (second‐order rate), respectively. The MG degradation kinetics obeyed the zero‐order model. The Calix/MIL‐101(Fe)/CuO exhibited high reusability for MG degradation. The results suggest that Calix/MIL‐101(Fe)/CuO could serve as an alternative photocatalyst for the degradation of contaminants in aqueous media.

The pesticides carbofuran and picloram alter the diversity and abundance of soil microbial communities.

Many countries widely use pesticides to increase crop productivity in agriculture. However, their excessive and indiscriminate use contaminates soil and other environments and affects edaphic microbial communities. We aimed to examine how the pesticides carbofuran and picloram affect the structure and functionality of soil microbiota using cultivation-independent methods. Total DNA was extracted from microcosms (treated or not with pesticides) for amplification and metabarcoding sequencing for bacteria (16S gene) and fungi (28S gene) using Illumina-MiSeq platform. Data analysis resulted in 6,772,547 valid reads from the sequencing, including 3,450,815 amplicon sequences from the V3-V4 regions of the 16S gene and 3,321,732 sequences from the 28S gene. A total of 118 archaea, 6,931 bacteria, and 1,673 fungi taxonomic operating units were annotated with 97% identity in 24 soil samples. The most abundant phyla were Proteobacteria, Actinobacteria, Acidobacteria, Firmicutes, Chloroflexi, Euryarchaeaota, and Ascomycota. The pesticides reduced the diversity and richness and altered the composition of soil microbial communities and the ecological interactions among them. Picloram exerted the strongest influence. Metabarcoding data analysis from soil microorganisms identified metabolic functions involved in resistance and degradation of contaminants, such as glutathione S-transferase. The results provided evidence that carbofuran and picloram shaped the soil microbial community. Future investigations are required to unravel the mechanisms by which soil microorganisms degrade pesticides.

Biodegradation of Soil Contaminated with Polycyclic Aromatic Hydrocarbons PAHs through Nitrogen Biostimulation

This study evaluated the effect of nitrogen on the biostimulation of microbial load in soil mesocosms contaminated with bunker oil. Urea was used as a nitrogen source, with C/N ratios of 60:1 and 100:10 established to analyze its impact on the biodegradation of polycyclic aromatic hydrocarbons (PAHs). Experiments were conducted in plastic trays containing 2 kg of soil contaminated with 8% bunker oil. Samples were taken on days 15, 30, 60, and 90, and chemical analysis was performed using gas chromatography-mass spectrometry (GC-MS). Results indicated that the treatment with a C/N ratio of 100:10 achieved the highest PAH reduction percentage (99.27%), demonstrating the efficacy of urea biostimulation. This study highlights the importance of optimizing nutrient proportions to enhance biodegradation efficiency in hydrocarbon-contaminated soils. The addition of urea is confirmed as a viable and economical solution for soil remediation, aligning with previous studies emphasizing the crucial role of nitrogen in microbial activity and the degradation of recalcitrant contaminants. In conclusion, incorporating urea as a nitrogen source proved to be an effective strategy for biostimulation and PAH biodegradation in soil mesocosms, offering a sustainable solution to mitigate hydrocarbon contamination.

Electroactive bacteria-established long-distance electron transfer to oxygen facilitates bio-transformation of dissolved organic matter for sediment remediation

Electroactive bacteria (EAB) in sediment commonly establish long-distance electron transfer (LDET) to access O2, facilitating the degradation of organic contaminants, which we hypothesize is mediated by the bio-transformation of dissolved organic matter (DOM). This study confirmed that EAB-established LDET to O2 via a microbial electrochemical snorkel raised the electric potential of sediment by increasing HCl-extracted Fe(III) and NO3− concentrations while reducing DOM concentrations, which further modified microbial diversity and composition, notably reduced the relative abundance of fermentative bacteria. As a result, DOM showed the highest SUVA254 value (3.88) and SUVA280 value (1.61), preliminarily suggesting their enhanced aromaticity, humification and average molecular weight. Additionally, these DOM exhibited the highest electron transfer capacity (174.14±3.62 μmol e− /g C) and redox current. Based on these findings, we propose four possible avenues through which EAB-established LDET to O2 facilitates sediment remediation, mainly including DOM involved affinity, direct and indirect electron transfer, and induced photochemical reaction in degradation or humification process of organic contaminants. Although these proposed avenues require further verification, this work sheds light on deciphering the mechanisms underlying the augmented degradation of organic contaminants facilitated by EAB-established LDET to O2, offering fresh insights into sediment remediation.

Active packaging films based on the nanoform of chitin, alginate, and layered double hydroxides: characterization, mechanical properties, permeability, and bioactive properties.

Their unique characteristics make plastic films frequently utilised for packaging products. However, this petroleum-derived material has a long history of being linked to environmental contamination and hazardous degradation. Petroleum plastic can be substituted with edible packaging. The objective of this study was to combine sodium alginate with chitin, both in their nanosized form to formulate active packaging films containing different ratios of Zn/Al-layered double hydroxides (LDHs). Subsequently, active packaging films were formulated via a green method with different percentages (0%, 1%, 3%, and 5% w/w) of LDHs. The LDH particles were shaped as rectangular rods with a length of about 60 nm and width of around 20 nm. The films were evaluated for their physicochemical, topological, thermal, mechanical, water vapour, oxygen permeability and antimicrobial properties. Results indicated that active packaging with LDHs (3%) enhanced mechanical properties (tensile strength) by two-fold. Moreover, the addition of LDHs led to decreased permeability properties. Additionally, the antimicrobial study showed that the films with LDHs possessed a broad spectrum of antibacterial and antifungal activities, and the time required for bacterial killing was recorded to be less than 16 hours for films containing 5% LDHs. Thus, the formulated films show potential for use as active packaging.

Enhanced organic pollutant degradation in a two-dimensional Fe-doped crystalline carbon nitride membrane with near 100 % singlet oxygen generation through the Fe–O–N configuration

The singlet oxygen (1O2)-based nonradical AOP process, realized in carbon materials after nitrogen and metal doping, has drawn much attention in recent years. However, the exclusive generation of 1O2 in the specialized two-dimensional (2D) catalytic membranes and the associated contaminant degradation mechanisms remain unclear. Herein, a Fe-doped crystalline carbon nitride (Fe-CCN) material without additional nitrogen doping was developed to preferentially initiate 1O2-based nanoconfined oxidation of organic pollutants in the 2D Fe-CCN membrane/PMS system. Density functional theory calculation revealed that the Fe-O-N configuration formed after Fe doping altered the electronic structure of Fe centers, enhancing PMS adsorption and promoting the thermodynamically favorable generation of the –O* intermediate, leading to fast and highly selective 1O2 generation. EPR characterization and ROS quenching experiment also confirmed that the Fe-CCN activated PMS, generating nearly 100 % 1O2. The Fe-CCN membrane/PMS system exhibited excellent resistance to natural organic matter (NOM) interference and dramatically increased Bisphenol A (BPA) degradation kinetics, approximately 590 times faster than in conventional batch systems. Enhanced 1O2 exposure concentration within the Fe-CCN membrane nanochannels was supported by EPR data and 1O2 exposure simulations. Furthermore, The Fe-CCN membrane/PMS system showed wide pH tolerance, excellent pollutant degradation performance, and high stability. This work underscores the practical significance of 1O2-based oxidation reactions in membrane-confined AOPs for the rapid and efficient removal of organic contaminants from water.

Analytical model for reactive contaminant back-diffusion from low-permeability aquitards with internal source zones

Back diffusion of pollutants from low-permeability aquitards to adjacent high-permeability aquifers is a key issue that hinders site remediation. Previous back diffusion studies have typically assumed that a non-reactive contaminant source zone is located only in the aquifer, with scant attention paid to situations where the source zone resides in aquitards with degradation capacity. This study develops a novel back-diffusion analytical model for rapidly predicting reactive contaminant release from aquitards with internal source zones. The model incorporates the dynamic dissolution of internal sources in a multilayer aquitard with contaminant diffusion, adsorption, and degradation. General solutions were obtained utilizing the Laplace transform, Fourier finite cosine transform, variable substitution, and global matrix methods, validated against experimental data and numerical outcomes. Results reveal that previous back-diffusion models tend to underestimate the spatial extent and depth of aquitard contamination as well as aquifer plume tailing risk when the contaminant source is located within the aquitards. Based on numerous simulations and robust data fitting, the predictive functions for the back-diffusion plume tailing time regarding geometry and release parameters of internal sources were proposed, highly facilitating the risk evaluation of low-permeability sites. Furthermore, accelerating degradation reactions and expanding the degradation zone could efficiently mitigate contaminant back-diffusion from aquitards, implying that active bio-barriers are promising for remediating low-permeability soils.

Constructing electron-enriched Cu-Mn binuclear sites for enhanced catalytic ozonation toward wastewater purification

Rational construction of electron-enriched active sites in single-atom catalysts to accelerate interfacial electron transfer and boost catalytic ozonation activity is still a challenging task. Herein, electron-enriched Cu-Mn binuclear sites were successfully immobilized onto defect-rich N-doped carbon (Cu-Mn/NvC) in activating O3 for degradation of organic pollutants with high ionization potential from water. The Cu-Mn/NvC with Cu-Nv-Mn sites achieves almost 100 % removal of 4-chlorophenol in 60 min by catalytic ozonation with a degradation rate of 0.067 min−1, which is 3.94 times faster than Mn/NC, exceeding the reported values. The nonradicals of surface atomic oxygen species (*O/*OO) and singlet oxygen (1O2) are the dominant ROS responsible for contaminants degradation. The Cu-Nv-Mn sites can capture electrons from nitrogen vacancies, acting as electron enrichment centers that provide more electrons to O3. The Cu doping elevates Mn d-band center closer to the Fermi energy level and decreases the adsorption energy by 0.494 eV, significantly accelerating electron transfer from the Mn d-bands to the 2p orbital of O3, which enhances the activation of O3 to generate *O/*OO and 1O2 and thus improves the degradation of organic pollutants. Additionally, the excellent catalytic activity towards real wastewater and exceptional reusability after ten cycles demonstrate the superiority of the proposed system for practical application in wastewater treatment. This study provides an efficient pathway for activating O3 by accelerating interfacial electron transfer via the design of electron-rich metal dual-atom sites in carbon-based catalysts.

Mechanistic insights into the pH-driven radical transformation of the Fe(II)/nCP in groundwater remediation

Calcium peroxide nanoparticles (nCP) as a versatile and safe solid H2O2 source, have attracted significant research interst for their application potential in groundwater remediation. Compared to the traditional Fenton system, the nCP-based Fenton-like system has a wider pH-working window for contaminants degradation. This results from the dominant radical transformation under different pH. Unlike the traditional Fenton system which is only effective in acid conditions with hydroxyl radical (•OH) as the main active species, the release of H2O2 and O2 from nCP provides multiple contaminants degradation pathways. In acidic environments, •OH and Fe(IV) predominate as the active species, facilitated by substantial H2O2 production which activates the Fenton reaction. In neutral or alkaline conditions, the production of H2O2 was dramatically decreased. While the O2 released from nCP can be catalyzed by Fe(II) to form superoxide radical (•O2-), which subsequently generate singlet oxygen (1O2). The formation pathway of •O2- was tracked by O18 isotope labeling experiment. The impact of the water matrix on radical generation in the Fe(II)/nCP Fenton-like system was also studied. This research deepens the understanding of the radical formation mechanisms in nCP-based Fenton-like system, offering insights to support their application in remediating contaminated groundwater.

Genome streamlining of Pseudomonas putida B6-2 for bioremediation.

Microbial transformation is a favored approach for environmental remediation. However, the effectiveness of microbial remediation has been limited by the lack of chassis cells with satisfactory contaminant degradation performance. Pseudomonas putida B6-2, with a wide substrate spectrum and high solvent tolerance, is a chassis strain with great potential for application in environmental remediation. Here, guided by bioinformatic analyses and genome-scale metabolic model (GEM) predictions, we successfully optimized P. putida B6-2 by rationally reducing its nonessential genetic components and generating a more robust genome-streamlined strain, P. putida BGR4. Several improvements were observed compared with the original P. putida B6-2 strain, including a 1.4 × 105-fold increase in electroporation efficiency, an 8.3-fold increase in conjugation efficiency, improved glycerol utilization capability, and increased phenol utilization after heterologous expression of the phenol monooxygenase encoded by dmpKLMNOP. Additionally, P. putida BGR4 exhibited enhanced tolerance to several stressors, including starvation, oxidative stress, and DNA damage. Transcriptomic analysis revealed that genome streamlining led to the upregulation of genes involved in the "carbon metabolism" and "tricarboxylic acid cycle" pathways in P. putida BGR4, which likely contributed to the superior phenotype of P. putida BGR4 in terms of carbon source utilization and contaminant degradation capabilities. Furthermore, the absence of four prophages was identified as a potential cause of the enhanced stress resistance observed in P. putida BGR4. Overall, we developed a combined genome-streamlining strategy involving bioinformatic analyses and GEM predictions and generated a more robust chassis strain, P. putida BGR4, which expands the repertoire of chassis cells for environmental remediation.IMPORTANCEDespite the development of many chassis cells, there is still a lack of robust chassis cells with satisfactory contaminant degradation performance. Targeted genome streamlining is an effective way to provide powerful chassis cells. However, genome streamlining does not always lead to the improved phenotypes of genome-streamlined chassis cells. In this research, a novel procedure that combined bioinformatic analyses and GEM predictions was proposed to guide genome streamlining and predict the effects of genome streamlining. This genome streamlining procedure was successfully applied to Pseudomonas putida B6-2, which was a chassis cell with great potential for application in environmental remediation and resulted in the generation of a more robust chassis cell, P. putida BGR4, thereby providing a superior chassis cell for efficient and sustainable environmental remediation and a valuable framework for guiding the genome streamlining of strains for other applications.

Carbazolyl-Decorated Metal-Organic Framework with a High Fluorescent Quantum Yield for Detection and Photocatalytic Degradation of Organic Contaminants.

A carbazolyl-based fluorescent metal-organic framework with deep-blue light emission and a high quantum yield (88%) has been screened out by changing the ratio of mixed ligands, named Cz-MOF-2, which was constructed by ZrO4(OH)4 clusters, 3-(9-ethyl-9H-carbazol-3-yl)-4-methylthieno[2,3-b]thiophene-2,5-dicarboxylate (H2ECMTDC) and 3,4-dimethyl-dihydrothieno[2,3-b]thiophene-2,5-dicarboxylate (H2DMTDC). Cz-MOF-2 has excellent sensitivity in fluorescent sensing of 2,6-dichloro-4-nitroaniline (DCN), nitrofurazone (NZF), and nitrofurantoin (NFT) with detection limits of 3.37 × 10-7, 1.64 × 10-5, and 1.76 × 10-5 M, respectively. The quenching mechanisms involving electron transfer and competitive absorption were comprehensively elucidated through DFT calculations and UV absorption experiments. Cz-MOF-2 has been fabricated into a rapidly regenerated composite membrane with PVDF as a visualized fluorescent sensor for DCN. Furthermore, the carbazolyl groups covalently modified in the framework endowed Cz-MOF-2 with a suitable band gap (2.58 eV) for photocatalytic degradation of organic contaminants. It demonstrated superior photocatalytic efficiency compared to UiO-66 and NH2-UiO-66 in the degradation of tetracycline (TC), and the removal efficiency was up to 85% (20 mg of catalyst, 50 mL, 20 mg/L TC solution and 180 min) under simulated sunlight irradiation using a 300 W Xe lamp. Photoelectrochemical tests demonstrate that Cz-MOF-2 exhibits high photocurrent density and low charge transfer resistance, which provide evidence for the efficient charge separation capability. Radical trapping experiments and ESR detection have substantiated that ·O2- and h+ are the primary active species involved in this photocatalytic reaction. This work highlights the potential of MOFs in the targeted design and development of fluorescent sensors and photocatalysts for environmental detection and remediation.

Cellulose acetate membrane doped with silver-reduced graphene oxide nanocomposites to enhance the visible-light photocatalytic degradation of organic contaminants

Cellulose acetate membrane doped with silver-reduced graphene oxide nanocomposites to enhance the visible-light photocatalytic degradation of organic contaminants