Model Organic Contaminant Research Articles

Assessing the electrode configuration in a sandbox system for the removal of sulfanilamide: A pilot study

Electrochemical oxidation has emerged as an effective and straightforward technology for groundwater remediation. While recent studies have investigated parameters such as current, electrolyte composition, and electrode materials, most have been conducted using small-scale batch or flow reactors, limiting their applicability to real-world conditions. In this study, a pilot-scale sandbox reactor was employed to simulate realistic groundwater conditions and assess the removal of sulfanilamide, a model organic contaminant. Various electrode configurations were systematically evaluated to identify the key operational parameters influencing pollutant removal efficiency, providing insights for practical applications in groundwater treatment. This study proposes three configurations, including a single well with the anode and cathode, a double well with the separated anode and cathode, and an e-barrier with electrodes separately mounted inside a permeable barrier. Single well had the lowest removal efficiency (60%) because cathodic reaction inhibited the anodic oxidation. A double well with a separate anode and cathode can achieve 80% removal efficiency. However, effluent pH can reach up to 13.2, which can adversely impact groundwater. Meanwhile, the e-barrier not only achieved complete removal, but also maintained a neutral pH of 7.0 over 30 days. The e-barriers proved to be the most effective configuration based on their removal efficiency (100%) while yielding an effluent with neutral pH. The energy consumption of the e-barrier was most effective at 1.54 kWh/m3, while the other configurations were 5.40 and 22.18 kWh/m3. E-barriers are deemed a very reasonable configuration, both in terms of removal efficiency and practical application in groundwater.

Production of magnetic photocatalysts from TiO2, Fe(NO3)3 and sucrose and their application for the degradation of model organic contaminants

AbstractBACKGROUNDPhotocatalysis is an efficient method for the removal of organic contaminants in wastewater. In this study, different magnetic photocatalysts for the degradation of organic compounds were prepared.RESULTSTi/C/Fe photocatalysts were prepared by supporting TiO2 (20, 40 and 60% w/w) on a carbon/iron oxide (C/Fe) magnetic carrier. Characterization via Raman spectroscopy, X‐ray diffractometry, thermal analysis, X‐ray fluorescence, scanning electron microscopy and energy‐dispersive X‐ray spectroscopy/elemental mapping and magnetic property analysis by vibrating‐sample magnetometry confirmed the presence of TiO2, Fe3O4, Fe3C and char in the photocatalysts as well as their magnetic properties. The results of specific surface area analysis showed that the C/Fe support had a surface area of 183 m2 g−1 and that this area decreased with an increasing amount of supported TiO2, reaching up to 129 m2 g−1. Diffuse reflectance spectroscopy characterization revealed that the bandgap values obtained for the photocatalysts (Ti/C/Fe) were lower than 3.2 eV. The prepared photocatalysts showed high efficiency in degrading the contaminants Remazol Black (RB5) (99%), paracetamol (77%) and phenol (90%). Recovery and reuse experiments using RB5 showed that after the fourth reaction, the photocatalytic efficiency was reduced by 50%, and the recovery reached up to 70%. Sedimentation kinetics showed that while only 6% of the TiO2 was deposited, up to 89% of the photocatalysts were deposited.CONCLUSIONSThese results indicate that the photocatalysts showed excellent photocatalytic efficiency for different contaminants and can be easily and quickly separated from the reaction medium by magnetic separation. © 2024 Society of Chemical Industry (SCI).

Innovative carbon materials from lignocellulosic wastes for electrochemical hydrogen peroxide production: Bridging biomass conversion and material properties

This study aims to assess the electrochemical generation of hydrogen peroxide and hydroxyl radicals (*OH) using carbon cathodes synthesized from three different lignocellulosic residues, Phragmites australis (PA), Cladium mariscus (CM) and Typha domingensis (TD). These vegetal species are commonly used in natural wetlands and phytoremediation processes and can accumulate recalcitrant pollutants within these treatment processes, generating a waste that should be properly managed. To convert these residues into valuable carbon materials, they underwent hydrothermal carbonization (HTC) followed by either chemical activation with KOH or pyrolysis at 1000 ºC. The best results were obtained with chemically activated materials, yielding a maximum H2O2 concentration of 313 mg L−1 with the carbon cathode produced from PA. The specific surface area, oxygenated functional groups and presence of structural defects in carbonous structures, were key parameters related to a good performance as catalysts towards the 2e- Oxygen Reduction Reaction (ORR). It was also demonstrated, in comparison with previous studies, that the presence of heavy metals in the structure of the lignocellulosic residue enhanced the decomposition of H2O2 into *OH. However, in the study of the degradation of a model organic contaminant as methylene blue (MB), it was shown that these *OH were not the main contributors to degradation, as direct H2O2 chemical degradation and adsorption on the carbon materials played the most significant role. Therefore, the outstanding capacity of these lignocellulosic residues as catalysts for the electrogeneration of H2O2 was confirmed, suggesting their potential future application in advanced oxidation processes for water decontamination.

Porous sulfur polymers for effective aqueous-phase organic contaminant removal

Sulfur polymers produced through 'inverse vulcanization' exhibit various attributes, such as photocatalytic activity and a high capacity to adsorb heavy metals. Nevertheless, there is a lack of research investigating the use of sulfur polymers as materials for the removal of organic contaminants. In this work, porous sulfur polymers (PSPs) were synthesized from elemental sulfur and 1,3-diisopropenylbenzene, with porosity introduced via salt templating. The result is a material that can strongly adsorb and chemically neutralize a model organic contaminant (caffeine). PSPs show adsorption up to 5 times higher than a leading adsorption material (activated carbon). Furthermore, either the adsorption or degradation processes can govern the removal efficiency depending on the synthesis parameters of PSPs. This is the first-ever report demonstrating sulfur polymers as effective materials for removing emerging contaminants from water. The versatile synthesis of sulfur polymers offers variation, which means that there is much more to explore in this exciting research area.

Microwave-Assisted Synthesis of Flower-like MnMoO4 Nanostructures and Their Photocatalytic Performance.

This article describes an affordable method for the synthesis of MnMoO4 nanoflowers through the microwave synthesis approach. By manipulating the reaction parameters like solvent, pH, microwave power, and irradiation duration along this pathway, various nanostructures can be acquired. The synthesized nanoflowers were analyzed by using a powder X-ray diffractometer (XRD), field emission scanning electron microscopy (FE-SEM) with energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), and UV-vis diffuse reflectance spectroscopy (UV-DRS) to determine their crystalline nature, morphological and functional group, and optical properties, respectively. X-ray photoelectron spectroscopy (XPS) was performed for the examination of elemental composition and chemical states by qualitative and quantitative analysis. The results of the investigations demonstrated that the MnMoO4 nanostructures with good crystallinity and distinct shape were formed successfully. The synthesized MnMoO4 nanoflowers were tested for their efficiency as a photocatalyst in the degradation studies of methylene blue (MB) as model organic contaminants in an aqueous medium under visible light, which showed their photocatalytic activity with a degradation of 85%. Through the band position calculations using the electronegative value of MnMoO4, the photocatalytic mechanism of the nanostructures was proposed. The results indicated that the effective charge separation, and transfer mechanisms, in addition to the flower-like shape, were responsible for the photocatalytic performance. The stability of the recovered photocatalyst was examined through its recyclability in the degradation of MB. Leveraging MnMoO4's photocatalytic properties, future studies may focus on scaling up these processes for practical and large-scale environmental remediation.

A visible light driven photocatalyst Ag/AgBr/SrSb2O6 for removal of model organic contaminants and hexavalent chromium

A single plausible solution to multi-environmental issues is an efficient photocatalyst. The SrSb2O6 with a band gap of 2.72 eV was successfully tailored to 1.99 eV by deposition of Ag/AgBr. The synergistic effect of reduced band gap and surface plasmon resonance (SPR) effect of Ag0 could enhance the photocatalytic efficiency to a greater extent. This work attempts to explore a composite photocatalyst Ag/AgBr/SrSb2O6 for the photodegradation of organic wastes such as dyes, organic solvents, drugs, and antibiotics. In addition, the photo remediation of heavy metal waste such as Cr6+ is also investigated. The propitious results promise Ag/AgBr/SrSb2O6 to be a wide-range photocatalyst that can eliminate both organic and inorganic waste from water. The photodegradation of RhB dye, phenol, and tetracycline reached up to 80.8%, 76.8%, and 64.5%, respectively. Notably, the Ag/AgBr/SrSb2O6 catalyst effectively converted 97.3% of lethal Cr6+ to benign Cr3+. The better electron hole pair separation of the composite was evidenced by PL spectra.

Properties of Natural Rubber: Magnetite Decorated with Silver Nanoparticles for Catalytic Degradation of Model Organic Contaminant

Properties of Natural Rubber: Magnetite Decorated with Silver Nanoparticles for Catalytic Degradation of Model Organic Contaminant

Effects of Organic Surface Contamination on the Mass Accommodation Coefficient of Water: A Molecular Dynamics Study.

The mass accommodation coefficient (MAC), a parameter that quantifies the possibility of a phase change to occur at a liquid-vapor interface, can strongly affect the evaporation and condensation rates at a liquid surface. Due to the various challenges in experimental determination of the MAC, molecular dynamics (MD) simulations have been widely used to study the MAC on liquid surfaces with no impurities or contaminations. However, experimental studies show that airborne hydrocarbons from various sources can adsorb on liquid surfaces and alter the liquid surface properties. In this work, therefore, we study the effects of organic surface contamination, which is immiscible with water, on the MAC of water by equilibrium and nonequilibrium MD simulations. The equilibrium MD simulation results show that the MAC decreases almost linearly with increasing surface coverage of the organic contaminants. With the MAC determined from EMD simulations, the nonequilibrium MD simulation results show that the Schrage equation, which has been proven to be accurate in predicting the evaporation/condensation rates on clean liquid surfaces, is also accurate in predicting the condensation rate at contaminated water surfaces. The key assumption about the molecular velocity distribution in the Schrage analysis is still valid for condensing vapor molecules near contaminated water surfaces. We also find that under nonequilibrium conditions the adsorption of the water vapor molecules on the organic surface results in an adsorption vapor flux near the contaminated water surface. When the water surface is almost fully covered by the model organic contaminants, the adsorption flux dominates over the water condensation flux and leads to a false prediction of the MAC from the Schrage equation.

Wet‐Chemical Etching and Delamination of MoAlB into MBene and Its Outstanding Photocatalytic Performance

AbstractMBenes are post‐MXene materials that contain boron in their structure instead of carbon and nitrogen. This unique composition offers an opportunity to explore the role of boron in the performance of 2D materials. However, wet‐chemical etching and delamination of the starting MoAlB phase are challenging due to the persistent bonding of aluminum atoms with their neighboring elements. Herein, it is overcome by processing MoAlB for 24, 48, and 72 h with an aqueous HCl/H2O2 solution. The time‐wise etching and delamination delivers individual single‐to‐few layered 48‐MBene flakes. The theoretical‐to‐experimental XRD analysis revealed the best‐delaminated 48‐MBene having Mo2B2 orthorhombic lattice arrangement. The presence of Mo oxide allows direct 1.2 eV and indirect 0.2 eV optical band gaps and outstanding photocatalytic activity in decomposing methylene blue as a model organic contaminant. The 48‐MBene photocatalyst achieves about 90% of MB decomposition under ultraviolet and simulated white light irradiation with three times faster kinetics outperforming even hybridized MXenes. In addition, 48‐MBene appeared best suited to utilize the full spectrum of visible light into reactive oxygen species. Conversely, 24‐MBene and 72‐MBene shows incomplete delamination or oxidation, hampering their photocatalytic activity. The obtained results open an experimental pathway to apply MBenes in environmental remediation.

Enhancement of Photocatalytic Rhodamine B Degradation over Magnesium–Manganese Baring Extracted Iron Oxalate from Converter Slag

In this work, iron oxalate from converter slag (FeOX-Slag) was produced by extraction of iron from converter slag using oxalic acid, followed by photo-reduction. The FeOX-Slag sample was subjected to various characterization techniques, including X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX), ultraviolet–visible diffuse reflectance spectroscopy (UV-DRS), photoluminescence spectroscopy (PL), X-ray absorption near-edge structure spectroscopy (XANES), and X-ray photoelectron spectroscopy (XPS), in order to gain insights into its physicochemical properties. Also, to compare the photocatalytic activity of the FeOX-Slag, commercial iron oxide (Fe2O3) was used as a precursor to produce normal iron oxalate (FeOX-Fe2O3). The obtained FeOX-Slag was applied to the photocatalytic degradation of rhodamine B (RhB), a model organic contaminant in wastewater, compared with the FeOX-Fe2O3. Using the produced FeOX-Slag, we were able to degrade RhB more than 98% within 90 min at a reaction rate constant of about 3.6 times faster than FeOX-Fe2O3. Photoluminescence results confirmed the less recombination of the electron–hole pairs in FeOX-Slag, compared to FeOX-Fe2O3, which may be due to the defect structure of iron oxalate by guest metal impurities. The higher separation and transportation of photogenerated electron–hole pairs cause the enhancement of the degradation photocatalytic RhB degradation activity of the FeOX-Slag. In addition, The FeOX-Slag showed higher light absorption ability than FeOX-Fe2O3, resulting in the enhancement of the RhB degradation performance. Thus, the optical properties and the results from the activity tests led to the proposal that FeOX-Slag may be used in a photocatalytic degradation process for RhB under light irradiation.

MoSe2 nanoflakes decorated ZnO nanorods: An effective photoelectrode with S-scheme heterojunction for photoelectrocatalytic degradation of tetracycline and rhodamine B

Photoelectrocatalysis has been extensively used as one of the most widely known advanced oxidation processes (AOPs) owing to its superiority over photocatalytic systems with regards to the reduced recombination of charge carriers. ZnO demonstrates profound performance in PEC systems, and to overcome the obstacle of its limited visible light utilization, heterojunction formation of transition metal dichalcogenides (TMDs) with this classical semiconductor is proposed. Herein, MoSe2 was introduced onto ZnO nanorods to widen its visible light absorption and consequently boost the PEC ability of the proposed composite in omitting model organic contaminants in water. The as-synthesized nanocomposite was immobilized onto FTO by Electrophoretic deposition (EPD) technique which is then represented as the working electrode in the three-electrode PEC system. The characterization of the proposed nanocomposite was attained by techniques including: XRD, FESEM, FTIR, DRS and EDX. Moreover, electrochemical characterization was conducted to study its electrochemical properties. The PEC activity of the samples was studied by the degradation of Rhodamine B dye (62.3%) and tetracycline pharmaceutical (70.2%) under irradiation. The results indicated a much higher PEC ability for ZnO NR/MoSe2/FTO photoelectrode than its bare parent samples as well as its recyclability. To study the impact of the operational parameters, the electrolyte's concentration, initial pH, external bias voltage and initial concentration of the contaminant were investigated. By means of the scavenging tests, electrons and holes have the highest and the lowest importance in the PEC reaction, respectively. The S-scheme mechanism of degradation was proposed based on the cumulative experimental data.

The Impact of Solution Ionic Strength, Hardness, and pH on the Sorption Efficiency of Polychlorinated Biphenyls in Magnetic Nanocomposite Microparticle (MNM) Gels

Environmental conditions of groundwater and surface water greatly vary as a function of location. Factors such as ionic strength, water hardness, and solution pH can change the physical and chemical properties of the nanocomposites used in remediation and the pollutants of interest. In this work, magnetic nanocomposite microparticle (MNM) gels are used as sorbents for remediation of PCB 126 as model organic contaminant. Three MNM systems are used: curcumin multiacrylate MNMs (CMA MNMs), quercetin multiacrylate MNMs (QMA MNMs), and polyethylene glycol-400-dimethacrylate MNMs (PEG MNMs). The effect of ionic strength, water hardness, and pH were studied on the sorption efficiency of the MNMs for PCB 126 by performing equilibrium binding studies. It is seen that the ionic strength and water hardness have a minimal effect on the MNM gel system sorption of PCB 126. However, a decrease in binding was observed when the pH increased from 6.5 to 8.5, attributed to anion-π interactions between the buffer ions in solution and the PCB molecules as well as with the aromatic rings of the MNM gel systems. Overall, the results indicate that the developed MNM gels can be used as magnetic sorbents for polychlorinated biphenyls in groundwater and surface water remediation, provided that the solution pH is controlled.

Photocatalytic decolorization of methyl orange dye using SnO2-TiO2 nanocomposite particles synthesised by Ultrasonic Assisted Co-Precipitation Method

The ultrasonic-aided co-precipitation method was used to create SnO2-TiO2 nanocomposite particles. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and UV-vis spectroscopy were used to characterize the nanocomposite particles. XRD patterns revealed the crystalline structure of particles and the average particle size determined by Debye Scherrer’s equation was found to be 11.355, 4.9577, and 4.333 nm for TiO2 nanoparticles, SnO2 nanoparticles, and SnO2-TiO2 nanocomposites, respectively. The Ti, Sn, and O species were confirmed to exist by energy-dispersive X-ray spectroscopy (EDS). The UV absorption peaks at 288, 305, and 350 nm were attributed to SnO2, TiO2-SnO2, and TiO2 respectively. The photocatalytic aspect was investigated in a model organic contaminant (methyl orange). Data obtained by the above-mentioned characterization methods confirmed the superior photocatalytic activity of SnO2-TiO2 nanostructure than SnO2 or TiO2 alone.

Magnetic Nanocomposites for the Remote Activation of Sulfate Radicals for the Removal of Rhodamine B.

The widespread presence of numerous organic contaminants in water poses a threat to the ecological environment and human health. Magnetic nanocomposites exposed to an alternating magnetic field (AMF) have a unique ability for magnetically mediated energy delivery (MagMED) resulting from the embedded magnetic nanoparticles; this localized energy delivery and associated chemical and thermal effects are a potential method for removing contaminants from water. This work developed a novel magnetic nanocomposite-a polyacrylamide-based hydrogel loaded with iron oxide nanoparticles. For this magnetic nanocomposite, persulfate activation and the contamination removal in water were investigated. Magnetic nanocomposites were exposed to AMF with a model organic contaminant, rhodamine B (RhB) dye, with or without sodium persulfate (SPS). The removal of RhB by the nanocomposite without SPS as a sorbent was found to be proportional to the concentration of magnetic nanoparticles (MNPs) in the nanocomposite. With the addition of SPS, approximately 100% of RhB was removed within 20 min. This removal was attributed primarily to the activation of sulfate radicals, triggered by MNPs, and the localized heating resulted from the MNPs when exposed to AMF. This suggests that this magnetic nanocomposite and an AMF could be a unique environmental remediation technique for hazardous contaminants.

Peroxymonosulfate-based photocatalytic oxidation of tetracycline by Fe2(MoO4)3/Cd0.5Ni0.5S heterostructure; DFT simulation

The current research is meant to develop novel semiconductor photocatalysts, for the decomposition of tetracycline (TC) as a model organic contaminant in the aquatic environment. The fabrication of Fe2(MoO4)3/Cd0.5Ni0.5S (FMO/CNS) composite has proven to be an effective method for improving the sustainability and photocatalytic activity of Cd0.5Ni0.5S (CNS). Under visible light irradiation, FMO/CNS nanocomposite demonstrated significant PMS activation which led to 1.36 and 1.81 times TC removal efficiency as compared to immaculate Fe2(MoO4)3(FMO) and CNS. FMO/CNS composite potentially promotes the segregation of electron-hole pairs (e−-h+) and exemplifies amazing photocatalytic performance for TC degradation. Its significant photocatalytic activity is due to its unique structure, which includes tiny pores on the surface that confine the PMS molecule to the interface. The FMO/CNS composite has significantly greater piezocatalytic activity than pure FMO and CNS, demonstrating the synergistic effect of FMO and CNS. In the degradation of TC, holes and key reactive radicals (•O2−/•OH/SO4−•) played a major role. Computational studies (DFT) estimates, including the determination of intermediates, confirmed that the hydroxyl addition and C–N cleavage pathways were responsible for TC degradation. As a result, this work delivers a new approach to developing novel photocatalysts with high photocatalytic activity for the abatement of organic contaminants in water.

Mechanism and practical application of homogeneous–heterogeneous hybrid catalysts in electrolytic system for high COD chemical waste acid treatment

Treatment of organic contaminants in waste acid via electrochemical oxidation process has drawn sustained attention. Inspired by the electro-generation of persulfate from homogeneous sulfate (SO42-) in waste acid and the catalytic activity of heterogeneous tourmaline, this study aimed to investigate the feasibility of in-situ persulfate electro-generation and activation via utilizing homogeneous–heterogeneous hybrid catalysts system (SO42-/tourmaline) for organic contaminants removal in high chemical oxygen demand (COD) sulfate-containing waste acid. p-Aminodiphenylamine (RT-Base) was selected as a model organic contaminant to explore the mechanism of electrolysis/SO42-/tourmaline system. No RT-Base was detected after 60 min reaction in electrolysis/SO42-/tourmaline system. The formation of •OH and SO4•− in electrolysis/SO42-/tourmaline system made contributions to the RT-Base degradation. Degradation intermediates of RT-Base were identified and possible degradation pathway was proposed. Additionally, the application of electrolysis/SO42-/tourmaline system in treating the real RT-Base waste acid, which contained high COD and SO42-, was explored. Results showed that the COD removal rate was 67.94% under the optimal conditions, and the electrolysis/SO42-/tourmaline system could enhance the biodegradability of RT-Base waste acid. Furthermore, the electrolysis/SO42-/tourmaline system followed by the activated sludge process achieved a high COD removal efficiency (99.09%). Microbial DNA analysis suggested that Bacteroidetes, Proteobacteria, and Actinobacteria were the dominant bacterial phyla in the activated sludge; and metabolism was the predominant microbial function. In-situ electro-generation of persulfate/SO4•− for organics degradation achieved efficient utilization of waste sulfate. Electrochemical oxidation process with activated sludge process as a post-treatment showed great potential in the treatment of organics in high-sulfate waste acid.

Permanganate Oxidation of Organic Contaminants and Model Compounds.

Permanganate oxidation is an attractive environmental remediation strategy due to its low cost, ease of use, and wide range in reactivity. Here, permanganate reactivity trends are investigated for model organic compounds and organic contaminants. Second-order permanganate reaction rate constants were compiled for 215 compounds from 82 references (journal articles, conference proceedings, master's theses, and dissertations). Additionally, we validated some phenol rate constants and contribute a few additional phenol rate constants. Commonalities between contaminant oxidation products are also discussed, and we tentatively identify several model compound oxidation products. Aromatic rings, alcohols, and ether groups had low reaction rate constants with permanganate. Alkene reaction sites had the highest reaction rate constants, followed by phenols, anilines, and benzylic carbon-hydrogen bonds. Generally, permanganate reactivity follows electrophilic substitution trends at the reaction site where electron donating groups increase the rate of reaction, while electron withdrawing groups decrease the rate of reaction. Solution conditions, specifically, buffer type and concentration, may impact the rate of reaction, which could be due to either an ionic strength effect or the buffer ions acting as ligands. The impact of these solution conditions, unfortunately, precludes the development of a quantitative structure-activity relationship for permanganate reaction rate constants with the currently available data. We note that critical experimental details are often missing in the literature, which posed a challenge when comparing rate constants between studies. Future research directions on permanganate oxidation should seek to improve our understanding of buffer effects and to identify oxidation products for model compounds so that extrapolations can be made to more complex contaminant structures.

G-C3N4/rectorite as a highly efficient catalyst for peroxymonosulfate activation to remove organic contaminants in water

In recent years, modification of graphite carbon nitride (g-C3N4) has drawn considerable attention because of its catalytic potential. In this study, rectorite was designed as a carrier for g-C3N4, and g-C3N4/rectorite was synthesized via pyrolysis under nitrogen protection. The efficiency of g-C3N4/rectorite for peroxymonosulfate (PMS) activation was evaluated using acid Orange 7 dye (AO7) as a model organic contaminant. Material characterization suggested the successful synthesis of g-C3N4/rectorite. The removal of AO7 was significantly enhanced by the composite, compared to pure g-C3N4, rectorite, or their physical mixture. The g-C3N4 content in the composite affected its catalytic ability, while the g-C3N4/rectorite with 41% g-C3N4 content showed the highest catalytic efficiency. Furthermore, the removal of AO7 was affected by catalyst concentration, oxidant concentration, and solution pH. Notably, under the optimized condition (i.e., 0.8 g/L of g-C3N4/rectorite, 0.20 mg/L of PMS, and 6.0 of pH), an initial concentration of 50 mg/L AO7 was removed to a level below the detection limit (i.e., 0.25 mg/L) within 8 min. A recycling test demonstrated the reusability of the g-C3N4/rectorite in six repeated reactions. Singlet oxygen played a key role in PMS activation, suggesting that the non-radical degraded process is the dominated AO7 removal pathway. The rectorite has a confined effect preventing g-C3N4 from agglomeration, inhibiting the electron-hole recombination, and improve the exposure of active sites such as CO groups, -OH groups, and pyridinic N. Overall, g-C3N4/rectorite is a low-cost and environment-friendly catalyst exhibiting high catalytic activity for PMS activation to remove organic contaminants in water.

Effect of atom transfer radical polymerization reaction time on PCB binding capacities of Styrene-CMA/QMA Core-Shell iron oxide nanoparticles

Water pollution continues to be one of the greatest challenges humankind faces worldwide. Increasing population growth, fast industrialization and modernization risk the worsening of water accessibility and quality in the coming years. Nanoadsorbents have steadily gained attention as remediation technologies that can meet stringent water quality demands. In this work, core–shell magnetic nanoparticles (MNPs) comprised of an iron oxide magnetic core and a styrene based polymer shell were synthesized via surface initiated atom transfer radical polymerization (SI-ATRP) and characterized for their binding of polychlorinated biphenyls (PCBs), as model organic contaminants. Acrylated plant derived polyphenols, curcumin multiacrylate (CMA) and quercetin multiacrylate (QMA), and divinylbenzene (DVB) were incorporated into the polymeric shell to create high affinity binding sites for PCBs. The affinity of these novel materials for PCB 126 was evaluated and fitted to the nonlinear Langmuir model to determine binding affinities (KD). The KD values obtained for all the MNP systems showed higher binding affinities for PCB 126 that carbonaceous materials, like activated carbon and graphene oxide, the most widely used adsorption materials for water remediation today. The effect of increasing ATRP reaction time on the binding affinity of MNPs demonstrated the ability to tune polymer shell thickness by modifying the reaction extent and initial crosslinker concentrations in order to maximize pollutant binding. The enhancement in binding affinity and capacity for PCB 126 was demonstrated by the use of hydrophobic, aromatic rich molecules like styrene, CMA, QMA and DVB, within the polymeric shell provides more sites for π-π interactions to occur between the MNP surface and the PCB molecules. Overall, the high affinities for PCBs, as model organic pollutants, and magnetic capabilities of the core–shell MNPs synthesized provide a strong rationale for their application as nanoadsorbents in the environmental remediation of specific harmful contaminants.

Effects of seasonal biofouling on diffusion coefficients through filter membranes with different hydrophilicities in natural waters

Biofouling is a major issue for the diffusive gradients in thin films (DGT) passive samplers during long-term deployment. Although biofilms have a negative effect on DGT samplers, the effects of seasonal biofilms on the flux of targets through different membranes are poorly understood. Herein, we evaluated the relationship between the biofilm growth and diffusion coefficients' decline rate through two membranes with different hydrophilicities during the four seasons in natural waters. Cu2+ and tetracycline were selected as the model metal and organic contaminant, respectively. Rapid biofilm growth on the membrane surface was observed, and the fouling growth rate increased in the order: winter < spring < autumn < summer. Biofouling had a negative effect on the diffusion coefficients of Cu2+ and tetracycline. Generally, the decreasing tendency of diffusion coefficients agreed with the increasing tendency of the fouling growth rate. Biofilms in a lag phase with little bacterial colonies had insignificant effect on the diffusion coefficients. After 30 days, the decline ratios of diffusion coefficients were in the range of 38.14%–53.05%, 69.63%–83.19%, 51.57–68.42%, and 19.43–35.84%, respectively, during the spring, summer, autumn and winter. The flux through the membrane with higher hydrophilicity was greater. Both the hydrophilicity of membrane and structure of target analytes had important effects on the diffusion coefficients through biofouled membranes. Owing to similar physical and chemical characteristics, there was insignificant difference in diffusion coefficients decline trend between the Yalu River water and Hunhe River water in the summer.