Target Contaminants Research Articles

Insights into the contrasting effects of sulfidation on dechlorination of chlorinated aliphatic hydrocarbons by zero-valent iron

Contrasting effects of sulfidation on contaminants reduction by zero-valent iron (ZVI) has been reported in literature but the underlying mechanisms remain unclear. Here, under well-controlled conditions, we compared the performance of ZVI and sulfidated ZVI (S-ZVI) toward a series of chlorinated compounds. Results revealed that, although S-ZVI was more reactive than ZVI toward hexachloroethane, pentachloroethane, tetrachloroethylene, and trichloroethene, sulfidation hindered the dechlorination of the other ten tested chlorinated aliphatics by a factor of 1.5–125. Moreover, S-ZVI may lead to an accumulation of toxic partially-dechlorinated products. Analogous to its effects on ZVI reactivity, sulfidation also exerted positive, negligible, or negative effects on the electron efficiency of ZVI. Solvent kinetic isotope effect analysis suggested that direct electron transfer rather than reaction with atomic hydrogen was the dominant reduction mechanism in S-ZVI system. Hence, the sulfidation enhancing effects could be expected only when direct electron transfer is the preferred reduction route for target contaminants. Furthermore, linear free energy relationships analysis indicated one-electron reduction potential could be used to predict the transformation of chlorinated ethanes by S-ZVI, whereas for chlorinated ethenes, their adsorption properties on S-ZVI determined the dechlorination process. All these findings may offer guidance for the decision-making regarding the application of S-ZVI.

Performance evaluation and optimization of a suspension-type reactor for use in heterogeneous catalytic ozonation

Packed fixed-bed reactors are traditionally used for heterogeneous catalytic ozonation. However, a high solid-to-liquid requirement, poor ozone dissolution, ineffective utilization of catalyst surface area, and production of large amounts of catalyst waste impede application of such reactors. In this study, we designed a suspension catalytic ozonation reactor and compared the performance of this reactor with that of a traditional fixed-bed catalytic ozonation reactor employing oxalic acid (OA) as the target contaminant. Our results showed that total O3 dissolved into the suspension reactor (117–134 mg.L−1) was much higher compared to that measured in the fixed-bed reactor (53 mg.L−1) due to a higher O3(g) interphase mass transfer rate in the suspension reactor. In accordance with the higher O3(g) interphase mass transfer, we observed a much higher proportional OA removal (32 %) compared to that achieved in the fixed-bed reactor (10%) employing an Fe-oxide catalyst supported on Al2O3 (Fe-oxide@Al2O3) in both reactors. Use of a double-layered Cu-Al hydroxide (Cu-Al LDHs) catalyst in the suspension reactor further enhanced the performance with nearly 90 % OA removal observed. Given the superior performance of the suspension reactor, we investigated the impact of operating conditions (catalyst dosage, hydraulic retention time and ozone dosage) employing Cu-Al LDHs as the catalyst. We also developed a mathematical kinetic model to describe the performance of the suspension reactor and, through use of the kinetic model, showed that O3(g) interphase transfer rate was the rate-limiting step in OA removal. Thus, improvement in ozone gas diffuser design is required to improve the performance of the suspension reactor. Overall, the present study demonstrated that suspension reactors were more effective than fixed-bed reactors for oxidation of surface-active organic compounds such as OA due to the higher ozone interphase mass transfer rate and effective utilization of the catalyst surface area that can be achieved. As such, further research on suspension reactor design and development of catalysts suitable for use in suspension reactors should facilitate large-scale application of catalytic ozonation processes by the wastewater treatment industry.

Adsorption site identification and regulation to guide design of N-doped porous carbon-based materials for efficient and selective removal of bisphenol a

Currently, identification and regulation of adsorption sites of carbon-based materials remain a major challenge. In this study, given the properties of the target contaminant, bisphenol A (BPA), we report a novel method for preparing ultra edge N-doped hierarchically porous carbon-based material with rich vacancy defects (HENDC) via a direct pyrolysis of simultaneous EDTA-4Na and g-C3N4. Interestingly, g-C3N4 kills three birds with one stone, including pore-forming agent, nitrogen configuration regulator, and structural defect former. As such, compared with that of MNDC, which was direct pyrolysis of EDTA-4Na (462.5 mg g−1 for BPA and 551.2 mg g−1 for bisphenol S (BPS)), the adsorption capacity of HENDC for BPA was 870.1 mg g−1, which exceeded that for BPS (793.3 mg g−1). Also, HENDC shortened the adsorption process to 10 min for BPA compared with MNDC (30 min) and displayed a promising environmental application potential. Based on experiments and theoretical calculations, the high adsorption performance of HENDC for BPA originated from edge nitrogen doping, defect inducing, and hierarchically porous structures. Specifically, Lewis acid-base interactions of varying strength occurred between both pyridinic-N (stronger) and pyrrolic-N (weaker) with BPA. A strong π-π EDA interaction between pyridinic-N and BPA, which was further facilitated by vacancy defects in adjacent edge nitrogen. The hydrophobic effect promoted the interaction between pyrrolic-N and BPA. This work offers deep insights into effective and selective removal of BPA, suggesting new strategies for exploring cost-effective carbon-based adsorbents.

Photocatalytic degradation of xanthates under visible light using heterogeneous CuO/TiO2/montmorillonite composites

Due to the significant demand for xanthate treatment in mineral effluents, photocatalytic techniques have emerged as one of the most promising solutions. In this study, a high-performance TiO2/CuO/montmorillonite photocatalyst was prepared. In this configuration, TiO2 was the classic photocatalytic material and CuO and montmorillonite were utilized to broaden the adsorption range of solar light and acted as carriers to support the photocatalyst. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy were employed for the comprehensive characterization of the microstructure of the ternary photocatalyst. The results revealed that fine-sized TiO2 and CuO nanoparticles were uniformly and tightly loaded on the montmorillonite layers. The photocatalytic properties of the photocatalyst were evaluated using sodium butyl xanthate as the target contaminant. For pristine TiO2, ultraviolet (UV) light was required to effectively degrade sodium butyl xanthate. Meanwhile, the degradation reaction could be processed efficiently under visible light using the TiO2/CuO/montmorillonite composite as the photocatalyst. Moreover, UV–visible diffuse reflectance spectroscopy, photoluminescence spectroscopy, and radical quench experiments were performed to elucidate the degradation process, and a possible degradation model and mechanism were proposed.

Comparative efficiency of conventional and green functionalized carbon-based materials for the uptake of priority produced water contaminants

Green chemistry has brought to the spotlight new sets of principles for reducing or eliminating hazardous substances in the synthesis and application of processes and products. Despite its noteworthy growth, this area still lacks studies that compare the potential of greener materials with those conventionally synthesized. Herein, novel materials based on chitosan and reduced graphene oxide were developed via the green (G-Fe/CS/rGO) and conventional routes (C–Fe/CS/rGO). Eucalyptus leaves extract and proanthocyanidin were used in the green approach as reducing/capping and crosslinking agents, respectively, replacing hydrazine and glutaraldehyde, commonly used in conventional synthesis. In addition, carbon nanotubes were also modified with plant extracts. The effect of different rGO contents was evaluated through adsorptive assays. Furthermore, the adsorption potential of C–Fe/CS/rGO, G-Fe/CS/rGO and green CNTs. Priority “Produced Water” contaminants of such as anthracene (ANT), fluoranthene (FLT), phenol (PE), and cyclohexane carboxylic acid (CHA) were used as target contaminants. The best materials were characterized by XRD, FTIR, SEM-EDS and Zeta potential analyses. C–Fe/CS/rGO-3% removed 86.6%, 89.3%, 13.4%, and 33.6%, G-Fe/CS/rGO-7% removed 83.2%, 83.9%, 6.7% and 30.3 % and CNT-E 82.9%, 97.6%, 10.7% and 12.4% of ANT, FLT, PE, and CHA, respectively. Green and conventional beads showed similar performance, indicating the promising use of green synthesis. CNT-E, which demonstrated the best adsorption capacity, was used in reuse assays to assess its feasibility. The material kept FLT removal above 85% after four consecutive adsorption-desorption cycles. Molecular modelling analysis indicated that CHA has greater stability, followed by PE, FLT and ANT, agreeing with the experimental results.

Feasibility of phenolic contaminant removal from high-saline wastewater by chloride-mediated activation of peroxymonosulfate (PMS) and peracetic acid (PAA)

Phenolic pollutants are highly toxic and can affect the growth and reproduction of aquatic organisms, as well as contaminate drinking water resources, posing a significant threat to both ecological and human health. However, conventional biological treatment processes are constrained in treating high salinity organic wastewaters due to the potentially lethal effects of high concentrations of dissolved salts on microorganisms. While advanced oxidation processes have shown promise in removing phenolic contaminants from high-saline wastewater, their widespread application is always limited by the high costs associated with energy and chemical usage. In this study, we explored the potential application of directly introducing peroxymonosulfate (PMS) and peracetic acid (PAA) to high-salinity water for the removal of nine phenolic contaminants. By establishing a correlation between the degradation rate constants in the PMS/Cl– (kPMS) and PAA/Cl– (kPAA) systems and various molecule descriptors, two multiple linear regression models were developed to predict the degradation rate constants under investigation. Additionally, we selected bisphenol A (BPA) as the target contaminant and investigated the impact of common ions found in natural water, such as HCO3–, NO3–, and humic acid, on the removal of BPA using two systems. Finally, we conducted experiments using tap water and sewage water to demonstrate the practical application and performance of the two systems. These experiments aimed to provide valuable insights into the influence of background chloride on PMS and PAA activation, as well as the potential of direct PMS/PAA introduction for eliminating phenolic micropollutants from high-saline wastewaters.

Borax Detection Tool in Foodstuffs Using Color Recognition Detection Method on HuskyLens Camera

The use of Borax as a food additive has adverse effects on public health. In an effort to prevent contaminated foodstuffs from becoming public consumption and to detect this contamination quickly and effectively, this research proposes the design of an Internet of Things (IoT)-based borax detection tool using color recognition technology from the HuskyLens Camera. This tool is designed to detect the presence of borax in food with high accuracy and in a short time. This research uses the HuskyLens Camera as a sensor that is sensitive to the target contaminant, and the data obtained from this sensor is transmitted through the IoT network to the MIT App Inventor platform. Optimized detection methods and data processing algorithms are used to accurately interpret the sensor results, providing authorities with immediate information on the safety status of the tested foodstuffs. Experimental test results show that the proposed detection tool has good performance in detecting borax in various types of foodstuffs. It provides an efficient and reliable solution to the challenge of food contamination. With the integration of IoT technology, the detector is able to provide real-time information to authorities, potentially raising awareness about overall food safety. Thus, the design of this IoT-based borax detector has great potential to overcome the problem of food contamination and make a significant contribution to maintaining public health.

Rational design of ionic covalent organic frameworks for PPCPs elimination: Insights into ibuprofen adsorption performance and mechanism

Over the last few years, non-steroidal drugs (including ibuprofen (IBP)) have been used extensively due to the impacts of COVID-19, with the resulting environmental contamination attracting the attention of researchers. For this study, an ionic covalent organic framework (iCOF), synthesized from 1,2,4,5-tetrakis (4-formylphenyl) benzene (TFPB) and 1,3-diaminoguanidine hydrochloride (DgCl) under hydrothermal conditions, was employed for the effective elimination of non-steroidal anti-inflammatory drugs (NSAIDs) from aqueous media. COFs are relatively ordered spherical structures with excellent adsorption capacities for NSAIDs (IBP, diclofenac (DCF), and indomethacin (IDM)) with a removal rate of more than 99%. The adsorption kinetics and isotherm experiments of the COFs were investigated with IBP as a target contaminant, which revealed that its adsorption attained equilibrium within 120 min. Further, increased temperatures promoted the adsorption of IBP, where its maximum adsorption at 45 °C was calculated by the Langmuir isotherm model up to 434.78 mg·g-1. In addition, different pH, ionic influences, and repeated cycling experiments also confirmed the practical applicability of the COFs. Finally, it was demonstrated that the adsorption kinetics of IBP by TFPB-DgCl-COF could be explained by electrostatic and π-π interactions.

Compartmentalization transformation of Fe2+, Mn2+ and NH4+ in groundwater: A comparative research containing experimental medium and functional genera profiling derived from experiment data

Contamination of soluble iron (Fe2+), manganese (Mn2+), and ammonium (NH4+) in groundwater is prevalent, particularly in Northeast China. This study aims to elucidate the intricate biological and physical-chemical reactions involved in the sequential transformation of three target contaminants. Two dynamic column simulations were used to compare quartz sand filtration (QSF) system with riverbank filtration (RBF) system to assess the interactions and respective contributions of the reactions involved in transforming process. Similar pattern of transformation vertical compartmentalization in two systems along the filter depth were founded, and the Fe2+ transformation was mainly distributed in the upper part, while NH4+ and Mn2+ occurred primarily in the downstream sections. The average transformation rate of Fe2+, Mn2+ and NH4+ in RBF system was 84.52 %, 47.68 % and 67.95 %, respectively, which was 5.20 %, 11.43 % and 23.06 % higher than in QSF system. The dominant transformation process for Fe2+ in RBF involved chemical oxidation, bio-oxidation and adsorption. The lower transformation rate for Mn2+ was attributed to abiotic homogenous oxidation limitation and negative affect derived from high concentration of NH4+ with high nitrification rate in RBF system. Nitrification by Nitrosomonas and Nitrospira was critical NH4+ transformation mechanism in RBF system, while the adsorption by iron and manganese oxide and aerobic denitrification were contributed strongly to NH4+ transformation in QSF system. Furthermore, the spatial distribution of functional bacterial genera was in good consistent with the transformation compartmentalization of three target contaminants in both systems, and similar microbial community structure reflected the domestication effect of groundwater chemistry on functional bacteria.

Electrochemical sulfate production from sulfide-containing wastewaters and integration with electrochemical nitrogen recovery

Electrochemical methods can help manage sulfide in wastewater, which poses environmental and health concerns due to its toxicity, malodor, and corrosiveness. In addition, sulfur could be recovered as fertilizer and commodity chemicals from sulfide-containing wastewaters. Wastewater characteristics vary widely among wastewaters; however, it remains unclear how these characteristics affect electrochemical sulfate production. In this study, we evaluated how four characteristics of influent wastewaters (electrolyte pH, composition, sulfide concentration, and buffer strength) affect sulfide removal (sulfide removal rate, sulfide removal efficiency) and sulfate production metrics (sulfate production rate, sulfate production selectivity). We identified that electrolyte pH (3 × difference, i.e., 25.1 to 84.9 μM h−1 in average removal rate within the studied pH range) and sulfide concentration (16 × difference, i.e., 82.1 to 1347.2 μM h−1 in average removal rate) were the most influential factors for electrochemical sulfide removal. Sulfate production was most sensitive to buffer strength (6 × difference, i.e., 4.4 to 27.4 μM h−1 in average production rate) and insensitive to electrolyte composition. Together, these results provide recommendations for the design of wastewater treatment trains and the feasibility of applying electrochemical methods to varying sulfide-containing wastewaters. In addition, we investigated a simultaneous multi-nutrient (sulfur and nitrogen) process that leverages electrochemical stripping to further enhance the versatility and compatibility of electrochemical nutrient recovery.

Deep insight into the effect of bicarbonate on pollutant abatement in the UV/chlorine process

The UV/chlorine process has gained significant attention from researchers and practitioners and is considered as a viable alternative to the UV/H2O2 process. HCO3–, widely spread in natural water, was traditionally perceived to act as a quencher in advanced oxidation processes (AOPs), converting less selective radicals into the more selective CO3·–. Unlike other radical precursors (e.g., persulfate and H2O2), HOCl rapidly reacts with CO3·–, resulting in the formation of ClO·. Consequently, HCO3– introduces complexity to the radical chemistry within the UV/chlorine process. This study comprehensively investigated the role of HCO3– in the UV/chlorine process with regards to pollutant degradation, employing 1,4-dimethoxybenzene (DMOB) as the target contaminant. Adding 2 mM of HCO3− in the UV/chlorine system significantly amplifies the generation of ClO· by ∼ 2 times at pH 7.0, thereby markedly expediting the degradation of DMOB. The reaction rate constant of CO3·− with free chlorine was measured to be 8.82 × 107 M−1 s−1 at pH 7.0, and the rate depends on pH and the species of chlorine. The influence of HCO3− on radical distribution within the UV/chlorine process is also contingent upon other solution conditions, including pH and chlorine doses. Furthermore, this study demonstrates that the HCO3−-mediated radical conversion remains relatively unaffected by background constituents. The experimental data on pollutant degradation via the UV/chlorine process in pure water can be extrapolated to estimate the treatment efficiency in actual water scenarios. These findings enhance our understanding of the intricacies of UV/chlorine chemistry in practical water treatment, thus advancing its potential as an emerging AOP for specialized applications.

Mechanistic explanation and influence of molecular structure on chemical degradation and toxicity reduction by hydroxyl radicals.

This study explored the influence of structural characteristics of organic contaminants on the degradation during an advanced oxidation process (AOP). The target contaminants were acetaminophen (ACT), bisphenol A (BPA), and tetracycline (TC). The Fenton process was selected as the model process in which major reactive species of hydroxyl radicals in most AOPs are generated for target compound degradation. The optimal reagent concentration ratio was [Fe2+]/[H2O2] = 0.5 mM/0.5 mM in an acidic condition, resulting in 83.49%, 79.01%, and 91.37% removals of ACT, BPA, and TC, respectively. Contrarily, the mineralization rates were apparently lower compared to their respective removal efficiencies. Experimental observation also suggested that the aromatic structure was rather difficult to degrade since their unsaturated electron clouds would hinder the attack of hydroxyl radicals due to electric repulsion. The preferred attacking sites of an aromatic ring differ due to the functional groups and structure symmetry. However, the electrophilic attack of the hydroxyl radical is the major reaction for decomposing aliphatic structures of cyclic or branched organics, resulting in the highest removal and mineralization of TC among these three tested chemicals. In addition, an apparent removal of a contaminant may not necessarily reduce its toxic impact on the environment.

Distribution and trophodynamics of substituted diphenylamine antioxidants and benzotriazole UV stabilizers in a freshwater ecosystem and the adjacent riparian environment.

Substituted diphenylamine antioxidants (SDPAs) and benzotriazole UV stabilizers (BZT-UVs) are industrial additives of emerging environmental concern. However, little is known about their environmental fate and bioaccumulation. This study investigated the concentrations of SDPAs and BZT-UVs in the water, sediment and biota samples in the freshwater ecosystem and adjacent riparian environment using Hamilton Harbour in the Great Lakes of North America as a study site. The bioaccumulation factors and trophodynamics of these contaminants were studied using field-collected samples. Eight target SDPAs and two BZT-UVs (2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (UV234) and 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol (UV328)) were frequently detected in the sediment, water and biota samples. UV328 showed significantly greater concentrations in water (0.28-2.8 ng L-1) and sediment (8.3-48 ng g-1, dry weight) than other target contaminants, implying greater contamination of UV328 in Hamilton Harbour. SDPAs exhibited trophic dilution in species living in the water, whereas UV234 was biomagnified in the same samples. No clear trophodynamic trend was found for UV328 for water-respiring species. Air-breathing invertebrates had higher concentrations of both SDPAs and BZT-UVs than water-respiring invertebrates, and biomagnification was observed particularly for adult dragonflies. These results suggest that the trophodynamics of SDPAs and BZT-UVs vary depending on whether the food web is terrestrial or aquatic. Future research should investigate the occurrence and partitioning of SDPAs and BZT-UVs in the air-water interface and evaluate the toxicities of these contaminants in air-breathing species.

Comparison of naphthalene degradation by hydrogen peroxide, nano-calcium peroxide, peroxydisulfate, and peroxymonosulfate in the Fe(II)-citric acid catalytic environments

Abstract Naphthalene (NAP) was chosen as a target contaminant due to its increasing environmental concern in this work. Using hydrogen peroxide (H2O2), nano-calcium peroxide (nCP), peroxydisulfate (PDS), and peroxymonosulfate (PMS) as oxidants activated by Fe(II)-citric acid (CA) in aqueous solution, 92.8, 95.0, 97.5, and 99.9% of NAP were removed, respectively, in which CA could significantly enhance NAP degradation. HO• was demonstrated to be the major radical responsible for NAP removal in H2O2/Fe(II)/CA and nCP/Fe(II)/CA processes; both HO• and SO4•− were major radicals in PDS/Fe(II)/CA process, whereas SO4•− was the sole dominant radical in PMS/Fe(II)/CA process. The impacts of water matrices (anions, natural organic matters, and surfactants) and initial solution pH on NAP removal as well as the practicalities of these four systems in groundwater were explored. The efficient NAP degradation of nCP/Fe(II)/CA and PMS/Fe(II)/CA processes in the actual groundwater indicated that these two systems have great potential and advantages in the remediation of NAP-contaminated groundwater.

Development of a negative helium ion source with non-metallic charge exchange

Negative helium ion (He−) beams are required for tandem accelerators used at research centers and implanter facilities. The common production method of such beams involves charge exchange between a positive helium ion (He+) source or beam, with a low pressure alkali metal vapour. However, the efficiency of this reaction is poor (only a small percentage) and the alkali metal vapour increases the potential flammability of the interior surfaces of the reaction chamber, as well as contributing to unwanted electrostatic discharge and target contamination downstream. In this paper we describe initial results from experiments using a focused He+ ion microscope (HIM) to measure charge uptake efficiencies after transmission through carbon membranes. The He+ beam (15 keV to 30 keV, 50 fA to 10 pA) collides with a non-metallic foil, and transmitted particles (He+, He0, and He−) are separated electrostatically into discrete beam spots and detected using a radiation camera (AdvaCam MiniPIX). A He− percentage uptake of 0.05 was observed using a 20 nm exfoliated graphite membrane consistent with previous reports. Future work will investigate the efficiency of charge exchange through other suitable membrane materials.

Adsorptive avidity of Prussian blue polypyrrole nanocomposite for elimination of water contaminants: a case study of malachite green and isoniazid.

Persistent water contaminants include a variety of substances that evade natural cleaning processes posing severe risks to ecosystems. Their adsorptive elimination is a key approach to safer attenuation. Herein we present the design and development of Prussian blue incorporated polypyrrole (PPY/PB) hybrid nanocomposite as a high-performance adsorbent for the elimination of malachite green (M.G.), isoniazid (INH) and 4-nitrophenol (4-NP) water contaminants. The nanocomposite synthesis was favored by strong dopant-polymer interactions, leading to a PPY/PB material with enhanced electro-active surface area compared to pristine PPY. The structure-activity response of the nanocomposite for the adsorption of target contaminants was unveiled by evaluating its maximum adsorption capacities under environmentally viable conditions. In-depth analysis and optimization of adsorption influencing factors (pH, temperature, and adsorbent dose) were performed. Using equilibrium studies, kinetic model fitting, aided with FTIR analysis, a multi-step mechanism for the adsorption of target contaminants on the nanocomposite was proposed. Furthermore, the PPY/PB nanocomposite also acts as a catalyst, enabling contaminant elimination following a synergistic scheme that was demonstrated using 4-NP contaminant. The synergetic adsorption and catalytic degradation of 4-NP using PPY/PB as adsorbent and catalyst was demonstrated in the presence of NaBH4 as a reducing agent in absence of light. In summary, this work highlights the targeted design of adsorbent, its optimization for adsorptive avidity, and the synergistic role of adsorption trapping in the catalytic degradation of persistent contaminants.

ENHANCED HEAVY METAL EXTRACTION FROM POST-MINING CONTAMINATED SOIL THROUGH IRON OXIDE NANOPARTICLE ADSORPTION AND SUBSEQUENT PHYTOREMEDIATION

ABSTRACT. In the current paper, the iron oxide nanoparticles (IONPs) have been demonstrated to facilitate the extraction of heavy metals from post-mining contaminated soil due to their water solubility and adsorption capabilities for the target contaminants. Furthermore, IONPs were subsequently removed from the treated soil through phytoremediation and bioaccumulated in the roots and stems of legume plants. For that purpose, 20 nm IONPs coated with an organic shell of humic acid were engineered and their adsorption capacity was assessed to heavy metals as cadmium (Cd2+), lead (Pb2+), zinc (Zn2+), manganese (Mn2+), copper (Cu2+), and nickel (Ni2+), which are common pollutants of acid mine drainage. In the framework of phytoremediation employing legume plants, the IONPs were directly introduced into the experimental soil samples alongside compost. Subsequently, it was noted that the legume roots absorbed the nanoparticles, acting as carriers for the captured heavy metals, thus aiding in their translocation to the aboveground portions of the plants. When introduced into soil environments, humic acid-coated iron oxide nanoparticles in combination with compost may exert positive effects on rhizosphere microbial populations. This can occur through the reduction of toxic metal ion levels and the potential side reaction of degrading or transforming organic pollutants into less harmful substances. Ultimately, the heavy metals become immobilized within the plant biomass, which can subsequently be harvested and removed from the contaminated site. This process leads to soil purification and remediation. The report presented here outlines a promising avenue for practical implementation, combining organic-coated IONPs with select plants to enhance bioaccumulation of heavy metals. This approach aims to develop future cost-effective passive treatment systems for the phytoremediation of soils contaminated postmining sites.

The utility of ultraviolet beam in advanced oxidation-reduction processes: a review on the mechanism of processes and possible production free radicals.

Advanced oxidation processes (AOPs) and advanced reduction processes (ARPs) are a set of chemical treatment procedures designed to eliminate organic (sometimes inorganic) contamination in water and wastewater by producing free reactive radicals (FRR). UV irradiation is one of the factors that are effectively used in oxidation-reduction processes. Not only does the UV beam cause the photolysis of contamination, but it also leads to the product of FRR by affecting oxidants-reductant, and the pollutant decomposition occurs by FRR. UV rays produce active radical species indirectly in an advanced redox process by affecting an oxidant (O3, H2O2), persulfate (PS), or reducer (dithionite, sulfite, sulfide, iodide, ferrous). Produced FRR with high redox potential (including oxidized or reduced radicals) causes detoxification and degradation of target contaminants by attacking them. In this review, it was found that ultraviolet radiation is one of the important and practical parameters in redox processes, which can be used to control a wide range of impurities.

Enhanced removal of sulfamethoxazole by Mn(II)/bisulfite in presence of nitrilotriacetic acid: Role of Mn(III)

Currently, the research on bisulfite (BS) activation by Mn(II) is very limited probably because of the low catalytic efficiency of Mn(II). Adding ligands to Mn(II)/BS system is likely to improve the BS activation, but the relative information is very rare. Therefore, the effect of nitrilotriacetic acid (NTA) on Mn(II)/BS system was investigated in this work using sulfamethoxazole (SMX) as the target contaminant. The results showed that the addition of NTA enhanced SMX removal in Mn(Ⅱ)/BS system through forming Mn(Ⅱ/III)-NTA complexes driving Mn(III)/Mn(II) cycle and stabilizing Mn(III). Alcohol scavenging experiments and competitive kinetic experiments indicated that sulfate radical (SO4•−) and hydroxyl radical (HO•) were not the main reactive species in Mn(II)/NTA/BS system. Mn(Ⅲ) was the primary oxidant for SMX elimination in this system and its existence was proved by UV-Vis absorption spectrum of reaction solution. Mn(Ⅱ)/NTA/BS system could greatly degrade SMX in near-neutral conditions, while nearly no SMX removal was observed at pH 3.0. The decrease of dissolved oxygen concentration significantly inhibited BS autocatalytic stage, thus suppressing the removal of SMX. Due to the competitive complexation of HCO3− and FA with NTA for Mn(II), their addition in Mn(Ⅱ)/NTA/BS system obviously inhibited SMX degradation. Four intermediates were detected during SMX degradation in Mn(Ⅱ)/NTA/BS system, and the possible SMX transformation pathways were speculated as N-S bond breaking, hydroxylation, amino oxidation and coupling reaction.

Synergistic catalysis degradation of amoxicillin by DBD plasma-catalyst system constructed by DBD plasma and Ce0.5Bi0.5VO4/HCP coating

A highly catalytic activity dielectric barrier discharge (DBD) plasma-catalyst synergistic system was constructed by DBD plasma and Ce0.5Bi0.5VO4/honeycomb ceramic plate (Ce0.5Bi0.5VO4/HCP) catalytic coating. Various characterization techniques were employed to analyze the physicochemical properties of the prepared photocatalysts. The catalytic activity of different catalytic systems was evaluated using amoxicillin (AMX) as the target contaminant. The DBD plasma-catalyst synergistic system exhibited significantly enhanced catalytic capacity compared to the single DBD plasma system. H2O2 and O3 concentrations in the solution during the reaction were monitored, and their formation process and roles were analyzed. The TOC results indicated that AMX exhibits a good mineralization rate in the synergistic system, and the 3D EEMs further revealed the changes in organic pollutant types during the mineralization process. The possible degradation pathways of AMX were inferred through mass spectra results and theoretical calculations. Additionally, the LC50 results for fathead minnow and daphnia show a significant downward trend of the main degradation intermediates. A possible synergistic mechanism was discussed based on the characterization results, experimental data, and relevant literature. This study offers a straightforward technical approach and theoretical backing for the synergistic wastewater treatment using DBD plasma combined with photocatalysts.