Natural Organic Matter Research Articles

Molecular weight fraction-specific transformation of natural organic matter during hydroxyl radical and sulfate radical oxidation

Aquatic natural organic matter (NOM) is one of the main scavengers of reactive species (e.g., •OH and SO4•−) during oxidation processes and undergoes complex transformations. Here, the organic content, optical properties, and redox state in various MW fractions and bulk Suwannee River NOM (SRNOM) were simultaneously evaluated during •OH and SO4•− oxidation processes for the first time. The SRNOM transformation pathways were specific to radical species and MW fractions, which was evidenced by a proportional decrease in electron-donating moieties and chromophores during •OH oxidation but a higher decrease in electron-donating moieties than chromophores during SO4•− oxidation, particularly in lower MW fractions (<3 kDa). The •OH decomposed reactive moieties mainly via aromatic ring opening or depolymerization in all MW fractions. SO4•− oxidation followed a similar pathway in higher MW fractions (>3 kDa) but mainly formed compounds with UV-absorbing properties (e.g., quinones) in lower MW fractions (<3 kDa). With competitive kinetics and depolymerization model, •OH was quantified as approximately 10 times more reactive towards MW fractions than SO4•−. However, the SO4•− concentrations were approximately 10 times those of •OH, resulting in comparable performance to •OH oxidation. SRNOM depolymerization by •OH and SO4•− resulted in formation of more precursors of disinfection byproducts than the parent constituents, especially for •OH. This work improves our understanding of the transformation of specific SRNOM fractions during radical oxidation processes.

Upcycling polystyrene microplastics to Fe/Mo-doped sponge-carbon: Mo5+ enhanced electron transfer for boosting Fenton-like performance

The rate-limiting steps of promoting the conversion of Fe3+ to Fe2+ in Fenton-like systems are crucial for achieving efficient degradation of organic contaminants in aquatic environments. Herein, a novel magnetic Fe/Mo bimetallic doped sponge carbon (Fe/Mo-N-C) derived from polystyrene microplastics was successfully synthesized and the presence of metastable Mo5+ remarkably synergized the electron transfer of Fe2+ in internal microenvironment. In the Fe/Mo-N-C activating peroxymonosulfate (PMS) system, Mo5+ boosted the oxidation of Fe2+, and the conversion of Mo4+/Mo6+ accelerated the restoration of Fe2+ from Fe3+, resulting in nearly 100 % of 17α-ethinylestradiol (EE2) degradation with the kinetic rate constant of 0.343 min−1, which was 8.1 times faster than that of Fe-N-C. Moreover, Fe/Mo-N-C possessed excellent resistance to interference from various coexisting anions (especially chloride, sulfate, and nitrate ions up to 500 mM), natural organic matter, nano-plastics, and different water matrices. Density functional theory analysis demonstrated that Mo centers regulated the electron rearrangement of the Fe 3d orbital, enhancing the activation performance of Fe/Mo-N-C towards PMS. This study lays the groundwork for understanding the mechanism of metastable Mo, which holds significant importance for the up-recycling of polyethylene plastics and environmental remediation.

Identifying Quinones in Complex Aqueous Environmental Media (Biochar Extracts) through Tagging with Cysteine and Cysteine-Contained Peptides and High Resolution Mass Spectrometry Analysis.

Quinones are among the most important components in natural organic matter (NOM) for redox reactions; however, no quinones in complex environmental media have been identified. To aid the identification of quinone-containing molecules in ultracomplex environmental samples, we developed a chemical tagging method that makes use of a Michael addition reaction between quinones and thiols (-SH) in cysteine (Cys) and cysteine-contained peptides (CCP). After the tagging, candidates of quinones in representative aqueous environmental samples (water extractions of biochar) were identified through high-resolution mass spectrometry (HRMS) analysis. The MS and UV spectra analysis showed rapid reactions between Cys/CCP and model quinones with β-carbon from the same benzene ring available for Michael addition. The tagging efficiency was not influenced by other co-occurring nonquinone representative compounds, including caffeic acid, cinnamic acid, and coumaric acid. Cys and CCP were used to tag quinones in water extractions of biochars, and possible candidates of quinones (20 and 53 based on tagging with Cys and CCP, respectively) were identified based on the HRMS features for products of reactions with Cys/CCP. This study has successfully demonstrated that such a Michael addition reaction can be used to tag quinones in complex environmental media and potentially determine their identities. The method will enable an in-depth understanding of the redox chemistry of NOM and its critical chemical compositions and structures.

Persistent free radicals in natural organic matter activated by iron particles enhanced disinfection byproduct formation

The widespread presence of iron (Fe) particles and natural organic matter (NOM) in drinking water distribution systems (DWDS) can significantly affect tap water quality, contributing to aesthetic issues and potentially generating harmful disinfection byproducts (DBPs). This study revealed that Fe particles, when combined with humic acid (HA), substantially increased DBP formation during chlorination. Fe particles (particularly preformed Fe particles) significantly increased haloacetic acid (HAA) formation by activating the persistent free radicals (PFRs) in the HA. Compared with the control system without Fe particles, greater than 2 times of HAA increase were observed for the system with Fe pariticles. PFRs accumulated on Fe particle surface could generate hydroxyl radicals, facilitating the decomposition of HA into smaller molecules, which were more reactive with chlorine disinfectants, thus elevated the DBP formation including both known and unknown N-DBPs and Cl-DBPs. The DBP promotion effect of in-situ formed Fe particles was much less than that of preformed Fe particles although both in-situ formed and preformed Fe particles could accumulate PFRs from HA. In-situ formed particles primarily accumulated carbon-centered PFRs, while preformed particles accumulated oxygen-centered PFRs. To mitigate the Fe particle induced water quality risks, it is crucial to control iron pipe corrosion and iron release in DWDS. In addtion, the optimization of treatment processes such as coagulation and filtration to more completely remove NOM and Fe particles could help minimize the DBP formation.

Nitrogen-sulfur co-doped magnetic biochar efficiently activates hydrogen peroxide for the degradation of sulfamethazine

To address the issue of low activation efficiency of magnetic biochar (MBC), this research synthesized nitrogen-sulfur co-doped magnetic biochar (NSMBC) using sawdust as the primary material via impregnation pyrolysis method. NSMBC effectively activated hydrogen peroxide and exhibited significant oxidation and degradation capabilities towards sulfamethazine (SMT), a sulfonamide antibiotic. The results demonstrate that under optimal conditions, NSMBC achieves a removal rate of 99.7 % for SMT within 2 h, with a reaction rate constant 8.5 times higher than that of MBC/H2O2 system. Mechanistic investigations unveiled that hydroxyl radicals (·OH) were the primary agents responsible for the degradation of sulfamethazine within the NSMBC/H2O2 system, contributing to 83.26 % of the removal efficiency. Furthermore, the nitrogen-sulfur co-doping facilitates the increase in Fe(II) content, augmentes the defect density, and enriches the number of oxygen-containing functional groups, thereby enhancing the utilization efficiency of H2O2 and consequently boosting the activation performance of magnetic biochar. Notably, the NSMBC/H2O2 system demonstrated excellent degradation efficiency towards various antibiotics, exhibiting potent broad-spectrum activity. Minimal influence on the NSMBC/H2O2 system was observed under conditions of coexisting natural organic matter and anions, rendering it suitable for practical application in the treatment of aquaculture wastewater and providing a novel technology for the application of magnetic biochar in actual water pollution control scenarios.

Decomposition of tetracycline with peroxymonosulfate activated by an ordered hierarchical pores Fe-N/C catalyst rich in FeNx sites: Insights into singlet oxygen mechanism

FeNx sites show significant superiority in the degradation of antibiotic contaminants, but there are difficulties in successfully constructing highly dispersed FeNx sites. In this work, Fe-N/C catalysts doped with hierarchical ordered pores structure and FeNx active sites were prepared by metal node exchange strategy. Among them, Fe-N/C-2 had more excite species for peroxymonosulfate (PMS) owing to the synergy between Fe and N coordination, which achieved 89.36 % tetracycline (TC) removal rate within 20 min, and its reaction kinetic (k = 0.245 min−1) is 7.66 times more than original PMS system. Moreover, the material exhibited excellent activation performance in a variety of complex water environments, such as the coexistence of multiple anions, strong acids and alkalis (pH = 2.90 ∼ 10.73), and natural organic matter interference. Chemical bond detection confirmed the successful formation of FeNx sites, free radical trapping experiments showed that FeNx was the main catalytic site, and 1O2 was the main active component. Furthermore, the reaction principle of the FeNx site catalyzing the production of 1O2 from PMS was revealed in detail through mechanism exploration. Next, the probable pathways of TC decomposition were elaborated in terms of the intermediates identified by Liquid Chromatograph Mass Spectrometer (LC-MS). This study emphasized the significant potential of synthesizing Fe-N/C catalysts with activated FeNx sites, elucidated mechanism of FeNx in PMS activation, and confirmed its feasibility in TC degradation.

Treatability of odorous dioxanes/dioxolanes in source water: How does molecular flexibility and pre-oxidation affect odorant adsorption

Odorous dioxanes and dioxolanes, a class of cyclic acetals often produced as byproducts in polyester resin manufacturing, are problematic in drinking water treatment due to their low odor thresholds and resistance to conventional treatment technology. Our research focuses on the removal of ten dioxane/dioxolane compounds through oxidation and adsorption processes, exploring the key molecular properties that govern the treatmentability. We discovered that both chlorination and permanganate oxidation were largely ineffective at degrading cyclic acetals, achieving less than 20% removal even at high applicable doses. Conversely, powdered activated carbon (PAC) adsorption proved to be a more effective method, with a removal of > 90% at a PAC dosage of 10 mg/L for seven out of ten compounds. The presence of natural organic matter (NOM) reduced PAC adsorbability for all odorants, but the deterioration level substantially varied and mostly affected by structural flexibility as indicated by the number of rotatable bonds. The results of both the experimental investigation and molecular simulation corroborated the hypothesis that more rotatable bonds (from one to three here) are indicative of greater structural flexibility, which in consequence determines the susceptibility of cyclic acetals to NOM competitive adsorption. Increased structural flexibility could facilitate greater entry into silt-like micropores or achieve preferential adsorption sites with more compatible morphology against NOM competition. When pre-oxidation (chlorination and permanganate oxidation) and adsorption were applied sequentially, additional low molecular weight NOM components produced by pre-oxidation resulted in intensified NOM competition and decreased odorant adsorbability. If this combination is inevitably required for algae and odorant control, it would be beneficial to utilize a wise screen for oxidants and a reduced oxidant dose (less than 2 mg/L) to mitigate the deterioration of odorant adsorption. This study elucidates the roles of structural flexibility in influencing the treatability of dioxanes and dioxolanes, extending beyond the solely well-established effects of hydrophobicity. It also presents rational practice guidelines for the combination of pre-oxidation and adsorption in addressing odor incidents associated with dioxane and dioxolane compounds.

Molecular modeling to elucidate the dynamic interaction process and aggregation mechanism between natural organic matters and nanoplastics

The interactions of nanoplastics (NPs) with natural organic materials (NOMs) dominate the environmental fate of both substances and the organic carbon cycle. Their binding and aggregation mechanisms at the molecular level remain elusive due to the high structural complexity of NOMs and aged NPs. Molecular modeling was used to understand the detailed dynamic interaction mechanism between NOMs and NPs. Advanced humic acid models were used, and three types of NPs, i.e., polyethylene (PE), polyvinyl chloride (PVC), and polystyrene (PS), were investigated. Molecular dynamics (MD) simulations revealed the geometrical change of the spontaneous formation of NOMs-NPs supramolecular assemblies. The results showed that pristine NPs initially tend to aggregate homogeneously due to their hydrophobic nature, and then NOM fragments are bound to the formed NP aggregates mainly by vdW interaction. Homo- and hetero-aggregation between NOMs and aged NPs occur simultaneously through various mechanisms, including intermolecular forces and Ca2+ bridging effect, eventually resulting in a mixture of supramolecular structures. Density functional theory calculations were employed to characterize the surface properties and reactivity of the NP monomers. The molecular polarity indices for unaged PE, PS, and PVC were 3.1, 8.5, and 22.2 ​kcal/mol, respectively, which increased to 43.2, 51.6, and 42.2 ​kcal/mol for aged NPs, respectively, indicating the increase in polarity after aging. The vdW and electrostatic potentials of NP monomers were visualized. These results clarified the fundamental aggregation processes, and mechanisms between NPs and NOMs, providing a complete molecular picture of the interactions of nanoparticles in the natural aquatic environment.

The potential of palm frond-based magnetic biochar for peat water treatment

Abstract Riau Province has the largest palm plantation in Indonesia. The amount of palm plantation waste is quite large, so it needs to be managed so as not to pollute the environment. Palm plantation waste has a high lignocellulose content, so it has the potential to be used as a raw material for making biochar. Biochar has high effectiveness in removing organic substances from water. Despite its high adsorption capacity, biochar is difficult to separate from water due to its very small particle size. To solve this problem, magnetic biochar can be used. Magnetic biochar is the result of the magnetization of biochar with the addition of chemicals containing metal ions and pyrolyzed with little or no oxygen. The synthesis of magnetic biochar is strongly influenced by the impregnation ratio and pyrolysis temperature. This study aims to synthesize magnetic biochar from palm fronds by varying the impregnation ratio, pyrolysis temperature, and particle size and testing its ability to adsorb color and natural organic matter in peat water. Magnetic biochar was synthesized by FeCl3 impregnation ratios of 0.4, 0.5, 0.6, and 0.7, pyrolysis temperatures 450°C; 500°C with N2 gas flow, and particle size escaped sieves of 0.595 and 0.177 mm. The adsorption test results showed synthetic magnetic biochar with an impregnation ratio of 0.7, pyrolysis temperature of 500°C and particle size of 0.177 mm had the highest efficiency in removing colors and natural organic substances of 71.8% and 78.6%, respectively. From the proximate test, the magnetic biochar moisture content was 0.5%, the ash content was 3.37%, and the volatile content was 12.02%. This result has met the quality of technical activated carbon in SNI 06-3730-1995. The methylene blue absorption was 12.4 mg/g. This value is below the requirements of SNI 06-3730-1995. The results showed that magnetic biochar synthesized from palm frond has the potential to be used as an adsorbent in peat water treatment.

Singlet oxygen dominant-activation by hollow structural cobalt-based MOF/peroxymonosulfate system for micropollutant removal

Despite the keen interest in potentially using the metal-organic framework (MOF) in advanced oxidation processes (AOPs), their application for environmental abatement and the corresponding degradation mechanisms have remained largely elusive. This study explores the use of cobalt-based MOF (CoMOF) for peroxymonosulfate (PMS) activation to remove tetracycline (TC) from water resources. Under optimal conditions, the given catalytic system could achieve a TC removal of 83.3%. Radical quenching tests and EPR analysis revealed that SO4•–, HO•, •O2−, and 1O2 could participate in the catalytic degradation, but the discernible removal mechanism was mainly ascribed to the nonradical pathway induced by 1O2. At only 5 mg/L of CoMOF, the performance of the catalytic system was superior to that of PMS alone for different types of micropollutants. The CoMOF/PMS system could also reliably deal with typical anions in water, such as Cl−, SO42−, HCO3−, and PO43−. The MOF catalyst could last for four cycles with a minor decrease in reactivity of ∼30%. However, the removal performance decreased markedly when aromatic natural organic matter (NOM) were present in the water bodies, and the effectiveness was lower in alkaline or acidic environments. Our work offers insights into the catalytic degradation of CoMOF/PMS applied in contaminated water remediation and serves as a baseline for fabricating an efficient MOF with enhanced catalytic performance and stability.

Cellular uptake of multi-walled carbon nanotubes is associated to genotoxic and teratogenic effects towards the freshwater diatom Nitzschia linearis

The increase in industrial production of multi-walled carbon nanotubes (MWCNTs) raises concerns about their potential adverse effects associated to environmental releases, especially in aquatic environments where they are likely to accumulate. This study focuses on the environmental impact of MWCNTs, specifically on a benthic freshwater diatom (Nitzschia linearis), which plays a major role in the primary production of water bodies. The obtained results indicate that exposure to MWCNTs in the presence of natural organic matter (NOM) inhibits diatom's growth in a dose-dependent manner after 72 h of exposure. Interestingly, the photosystem II quantum yield (PSIIQY) in diatoms remains unaffected even after exposure to MWCNTs at 10 mg/L. After 48 h of exposure, MWCNTs are found to bind preferentially to extracellular polymeric substances (EPS) produced by diatoms, which could decrease their toxicity by limiting their interaction with this organism. However, measurement of genotoxicity and teratogenicity in diatoms exposed to MWCNTs revealed that the exposure to MWCNTs increased the occurrence of cells with micronuclei and abnormal frustules. Microscopy analyses including two-photon excitation microscopy (TPEM) revealed the internalization of MWCNTs. Investigations of the diatom's frustule structure using Scanning electron microscopy (SEM) indicated that the presence of pore structures constitutes a pathway allowing MWCNTs uptake. The presence in the diatom's cytoplasm of MWCNTs might possibly induce disturbances of the cellular components, leading to the observed genotoxic and teratogenic effects. In view of previous studies, this work underscores the need for further studies on the interaction between nanomaterials and different diatom species, given the species-specific nature of the interactions.

Seasonal natural organic matter removal and implications for disinfection by-product formation at the Koka water treatment plant: Upper Awash, Ethiopia

ABSTRACT This study evaluated the seasonal performance of the Koka water treatment plant in removing natural organic matter (NOM) and the implications for disinfection by-product (DBP) formation potential. Raw and treated water samples were collected during the dry and wet seasons and analyzed using physicochemical parameters and fluorescence spectroscopy. The results revealed significant seasonal variations in raw water (RW) quality, with higher turbidity, pH, temperature, conductivity, total organic carbon (TOC), dissolved organic carbon (DOC), and UV254 absorbance during both seasons and across treatment processes. The NOM removal efficiency of the treatment plant was poor, with mean TOC removal of 46 and 43% and DOC removal of 15.8 and 15.2% during dry and wet seasons, respectively. The sedimentation unit demonstrated negative TOC removal, indicating NOM accumulation likely due to biochemical reactions in the unit. Fluorescence analysis and the correlation between specific ultraviolet absorbance (SUVA) and DBP formation potential suggest a higher risk of DBP formation in chlorinated drinking water. These findings highlight the influence of seasonal variations, RW quality, and the treatment process dynamics on the plant's performance in removing NOM. There is a need to implement adaptable strategies to enhance NOM removal, accounting for seasonal fluctuations in RW quality.

Nanofiltration membranes in asymmetric flow field-flow fractionation for improved organic matter size fractionation

Size fractionation of organic matter (OM) by asymmetric flow field-flow fractionation (FFFF) with ultrafiltration (UF) is limited by solute loss and peak resolution, particularly for low molecular weight fractions (<10 kDa). Nanofiltration (NF) with a molecular weight cut-off (MWCO) of ≤1 kDa can achieve significant OM retention and may improve OM fractionation. NF membranes with MWCOs ranging from 0.3 to 3 kDa were used to evaluate the retention and fractionation of nine OMs in the humic, polyphenol, biopolymer, and low molecular weight organic classes in stirred cell NF and FFFF. Membranes with an MWCO of 0.2–0.3 kDa (with a pure water permeability of 5–16 L.m−2.h−1.bar−1) with low OM interaction exhibited high peak recovery and resolution and hence improved OM fractionation. Loose NF (MWCO 3 kDa) exhibited a poor peak recovery because of a high OM loss due to both adhesion and permeation, particularly at high ionic strengths (>10 mM). A mixture of nine types of OM and natural organic matter samples from rivers, swamps and lakes achieved good fractionation with a 0.3 kDa (NF270) membrane at low ionic strength. The performance of NF for the analysis of OM and colloids in the smallest size range (≤1 kDa MW) could be further improved by optimizing the salt composition of the mobile phase and by overcoming the pressure limitations of FFFF channels.

Photo-reductive decomposition of perfluorooctane sulfonate (PFOS) and its common alternatives by UV/VUV/sulfite process: Mechanism, kinetic modeling, and water matrix effects

The present study investigated the photo-reduction of perfluorooctane sulfonate (PFOS) and its alternatives, focusing on decomposition mechanisms, active species involvement, the influence of background water constituents, and kinetic model development. The decomposition and defluorination rates followed the order of PFOS > PFHxS > 6:2 FTSA > PFBS, with shorter chains and CH2 linkers enhancing the resistance of PFOS alternatives against the attack of hydrated electrons (eaq−). Two primary pathways were identified during the photodegradation of PFAS: (i) H/F exchange at CF bonds with the lowest bond dissociation energies (BDEs) and (ii) functional group cleavage followed by short-chain PFCAs formation, with OH playing a crucial role in transforming intermediates. Adding iodide and elevated temperatures demonstrated a synergistic effect on PFBS decomposition and defluorination, with high temperatures promoting functional group cleavage as the preferred defluorination pathway. The study examined the impact of background water constituents in different aqueous environments, from surface waters to wastewater streams and ion-exchange brine concentrates. Chloride exhibited a concentration-based dual impact on the UV/VUV/sulfite process: promotive effects at low dosages (1–10 mM) by acting as a secondary eaq− mediator, and adverse effects at high dosages (20–500 mM) due to the scavenging effect of generated chlorine radicals (Cl). High ionic strength adversely affected eaq− quantum efficiency. Additionally, bicarbonate and natural organic matter (NOM) had opposing effects on PFOS photo-reduction, primarily through eaq− scavenging and pH alteration. Kinetic modeling revealed reaction rate constants of the studied PFAS with eaq− ranging from 1.8 × 106 to 1.3 × 109 M−1 s−1, corroborating the concentration profiles of active species and highlighting the reductive nature of sulfite-mediated processes.

Humic acid changes effect of naturally occurring oxidants on the environmental transformation of molybdenum disulfide nanosheets

2H-phase molybdenum disulfide (2H-MoS2) has been considered to be a chemically stable two-dimensional (2D) nanomaterial. Nonetheless, the persistence of 2H-MoS2 in the presence of environmental redox-active matrices, such as naturally occurring oxidants (e.g., manganese dioxide (MnO2)) and natural organic matter (NOM), remains largely unknown. Herein, we examined the interplay between 2H-MoS2, MnO2 (a common natural oxidant), and NOM species (i.e., Aldrich humic acid (ALHA) and Suwannee River natural organic matter (SRNOM)). The results show that MnO2 accelerates the oxidative dissolution of 2H-MoS2, regardless of the presence of dissolved oxygen. The effect of NOM on the MnO2-induced fate of 2H-MoS2 was found to depend on its affinity for 2H-MoS2 and the functionality of NOM. ALHA preferentially adsorbed on hydrophobic 2H-MoS2 nanosheets due to the enrichment of reductive polycyclic aromatics and polyphenolic constituents. The preferential ALHA adsorption counteracted the MnO2-triggered oxidative transformation of 2H-MoS2, as revealed by the cathodic response of 2H-MoS2 (i.e., decreased the open circuit potential by 0.0338 V) and the emergence of reductive Mo‒C bonds at 228.8 and 231.9 eV upon the addition of ALHA. This work evaluated the persistence of 2H-MoS2, illustrating its susceptibility to decomposition by naturally occurring oxidants and the influence of NOM on it. These findings are crucial for revealing the fate and transport of MoS2 in aquatic environments and provide guidelines for related applications in natural or engineered systems for MoS2 and potentially other 2D materials.

Antimony(V) Adsorption and Partitioning by Humic Acid-Modified Ferrihydrite: Insights into Environmental Remediation and Transformation Processes.

Antimony (Sb) migration in soil and water systems is predominantly governed by its adsorption onto ferrihydrite (FH), a process strongly influenced by natural organic matter. This study investigates the adsorption behavior, stability, and mechanism of FH and FH-humic acid (FH-HA) complexes on Sb(V), along with the fate of adsorbed Sb(V) during FH aging. Batch adsorption experiments reveal that initial pH and concentration significantly influence Sb(V) sorption. Lower pH levels decrease adsorption, while higher concentrations enhance it. Sb(V) adsorption increases with prolonged contact time, with FH exhibiting a higher adsorption capacity than FH-HA complexes. Incorporating HA onto FH surfaces reduces reactive adsorption sites, decreasing Sb(V) adsorption. Adsorbed FH-HA complexes exhibit a higher specific surface area than co-precipitated FH-HA, demonstrating stronger Sb(V) adsorption capacity under various conditions. X-ray photoelectron spectroscopy (XPS) confirms that Sb(V) adsorption primarily occurs through ligand exchange, forming Fe-O-Sb complexes. HA inhibits the migration of Sb(V), thereby enhancing its retention within the FH and FH-HA complexes. During FH transformation, a portion of Sb(V) may replace Fe(III) within converted iron minerals. However, the combination of relatively high adsorption capacity and significantly lower desorption rates makes adsorbed FH-HA complexes promising candidates for sustained Sb adsorption over extended periods. These findings enhance our understanding of Sb(V) behavior and offer insights for effective remediation strategies in complex environmental systems.

Molecular characterization of nontarget brominated disinfection byproducts formed during the ozonation in the presence of bromide and ammonium and their potential toxicity implications

While there is extensive literature covering byproducts formed during various water treatment processes, there is limited research focusing on the generation of brominated disinfection byproducts (Br-DBPs) specifically during ozonation in the presence of bromide (Br−) and ammonium (NH4+). This study used Orbitrap mass spectrometry and a custom halogen extraction code to selectively pinpoint 109 Br-DBPs generated during the ozonation of Suwannee River natural organic matter (SRNOM) containing Br− and NH4+. The Br-DBPs are predominantly distributed ranging from m/z 190 to 320, with elemental compositions consisting of CHOBr and CHONBr. They mainly fell within the H/C (0.5–1.5) and O/C (0.2–1.0) zones, with 16 % being aromatic compounds. NH4+ suppressed Br-DBP formation in CHOBr1-2 subgroups but promoted it in CHONBr1-2 subgroups compared to Br−-containing SRNOM ozonation. Kendrick mass defect diagram revealed 64 identical Br-DBP formulas in the CHOBr1-2 subgroups in both systems, and among them, 13 brominated carboxylic acids were identified, whose formation was suppressed by the addition of NH4+. Moreover, bromonitrophenol and bromobenzonitrile were identified in CHONBr1-2 subgroups, and their formation pathways were proposed. Nitrogen-containing Br-DBPs, especially the aromatic nitrogen-containing ones, exhibited higher toxicity. Caution is necessary to minimize toxic Br-DBPs formation during Br− and NH4+-involved ozonation. This study offers insights into Br-DBP characterization, formation mechanisms and toxicity, guiding enhanced water treatment strategies.

Insights into the controlling factors of the transport of tire wear particles in saturated porous media: The facilitative role of aging and fulvic acid

The widespread distribution and potential adverse effects of tire wear particles (TWPs) on soil and groundwater quality pose a growing environmental concern. This study investigated the transport behavior of TWPs in saturated porous media and elucidated the underlying mechanisms influenced by environmental factors. Additionally, the effects of key environmental factors, such as aging, ionic strength, cation species, medium type, and natural organic matter (NOM), on the transport of TWPs were evaluated. The results showed that aging processes simulated through O3 and UV irradiation altered the physicochemical properties of TWPs, increased the mobility of TWPs at low ionic strengths. However, the high ionic strengths and the presence of Ca2+ significantly inhibited the mobility of TWPs due to enhanced aggregation. The transport mechanism of the original and aged TWPs shifted from blocking to ripening under favorable retention conditions (i.e., high ionic strengths, divalent cations, and fine sands). Interestingly, the presence of fulvic acid (FA) inhibited the ripening of the three TWPs, significantly promoting their transport through a spatial site resistance mechanism. The two-site kinetic attachment model (TSKAM), extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory, and colloid filtration theory (CFT) were applied to describe the transport behavior of the TWPs. The study provided a comprehensive understanding of the transport behavior of TWPs in groundwater environments, highlighting the environmental risks associated with their widespread distribution.

Comparative analysis of Cr(VI) oxyanions adsorption on aged polyamide microplastics: Evaluating UV irradiation versus chemical aging

Microplastics (MPs) commonly undergo aging in various environmental media, affecting both their environmental behavior and Trojan-horse effect for contaminants. However, the mechanisms underlying the different impact of various aging processes on the Trojan-horse effect of polyamide (PA) MPs towards metal oxyanions remain unclear. This study explored how chemical aging and UV irradiation impact the structural characteristics and Cr(VI) adsorption of PA MPs under various influencing factors. Results showed that both aging processes enhanced the negative surface charge, surface oxygen content, and roughness of PA MPs, with FTIR correlation spectroscopy confirming an increase in O-containing functional groups. Cr(VI) adsorption onto aged PA sharply increased by 17.4 % (14 days of UV irradiation), 39.4 % (42 days of UV irradiation), and 21.7 % (chemical aging) compared to original PA. Salinity and natural organic matter had adverse effects on Cr(VI) adsorption. Spectroscopic analyses highlighted the crucial role of hydrophilic amide groups in controlling Cr(VI) adsorption onto aged PA, involving hydrogen bonding, electrostatic interactions, and reduction. Aged PA exhibited higher adsorption capacities but also greater desorption under simulated seawater and intestinal fluid, suggesting increased migration potential for Cr(VI). This study provides helpful insights into assessing the environmental risk of co-existing PA MPs and metal oxyanions, particularly considering the effect of aging processes.

Based on size-exclusion effect of selective removal of organic pollutants in complex water quality by low temperature plasma: Degradation behavior and selective mechanism analysis

The presence of natural organic matters (NOMs) will have a negative effect on the removal of small molecule organic contaminants in complex water quality, therefore, it’s very important to design a catalyst with size-exclusion function to achieve the selective removal of targeted pollutant. Herein, a novel ZIF-L catalyst precursor with lamellar stack structure is designed, and iron as heteroatom is doped in ZIF-L gaps named ZIF-L@Fe. After pyrolysis, Fe ions are transformed into Fe nanoparticles, and act as the active sites of catalyst. In order to verify the selective removal ability of resulted NSC@Fe in dielectric barrier discharge (DBD), tetracycline hydrochloride (TTCH) and humic acid (HA) is selected as the target pollutant and coexistence macromolecular interferent, respectively. In the presence of HA (50 mg/L), the degradation rate of TTCH in the system is not significantly affected (with HA, k = 0.037 min−1; without HA, k 0.036 min−1), which is mainly due to the layered material stacking characteristics (size-exclusion). The degradation mechanism and pathway are further confirmed by radical quenching experiments and liquid chromatography−mass spectrograph (LC−MS), respectively. This study is believed to shed new light on how to rationally design catalyst with selective removal of organic pollutants in complex water quality for water remediation.