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The article focuses on a study by Mohamed Ateia and Martin Scheringer that discusses the urgent need to transition away from per- and polyfluoroalkyl substances (PFAS), known as "forever chemicals," due to their severe health and environmental impacts. It highlights the regulatory and legal pressures driving this shift, discusses the complex challenges and trade-offs involved in finding effective PFAS-free alternatives, and emphasizes the importance of a comprehensive, collaborative approach.

This article discusses a special issue of the journal Catalysts that focuses on innovative trends in the field of photocatalytic degradation of environmental pollutants. The issue includes eight articles that cover a range of topics, such as the development of new photocatalysts, the use of sustainable co-catalysts, and the utilization of renewable resources for hydrogen production. The studies presented in the articles contribute to the broader goal of developing sustainable and green technologies. The integration of these innovative approaches into real-world scenarios holds the potential to transform environmental remediation strategies. [Extracted from the article]

PFAS from degrading landfill waste partition into organic matter, leachate, and landfill gas. Driven by the limited understanding of PFAS distribution in landfill organics, we analyzed PFAS across various depths and seven spatially distinct locations within a municipal landfill. The measured PFAS concentrations in organics ranged from 6.71 to 73.06 µg kg−1, a sum of twenty-nine PFAS from six classes. Perfluorocarboxylic acids (PFCAs) and fluorotelomer carboxylic acids (FTCAs) were the dominant classes, constituting 25–82 % and 8–40 % of total PFAS at different depths. PFBA was the most dominant PFCA with a concentration range of 0.90–37.91 µg kg−1, while 5:3 FTCA was the most prevalent FTCA with a concentration of 0.26–17.99 µg kg−1. A clear vertical distribution of PFAS was observed, with significantly greater PFAS concentrations at the middle depths (20–35 ft), compared to the shallow (10–20 ft) and high depths (35–50 ft). A strong positive correlation (r > 0.50) was noted between total PFAS, total carbon, and dissolved organic matter in landfill organics. Multivariate statistical analysis inferred common sources and transformations of PFAS within the landfill. This study underscores the importance of a system-level analysis of PFAS fate in landfills, considering waste variability, chemical properties, release mechanisms, and PFAS transformations. [Display omitted] • PFAS concentrations were highest at mid-depths in the landfill. • Dominant PFAS classes were perfluorocarboxylic acids and fluorotelomer carboxylic acids. • Short-chain PFCAs constituted a significant portion of total PFAS in landfill organics. • Strong correlation between PFAS, total carbon, and dissolved organic matter observed. • Study underscores the need for system-level analysis of PFAS fate in landfills. [ABSTRACT FROM AUTHOR]

Magnetic carbon nanotube (MCNT) composites with titanium dioxide (TiO 2) have an enhanced photocatalytic disinfection efficiency (i.e. higher disinfection rate) and better applicability (i.e. solar light applicability and catalyst separation using its magnetic property) than bare TiO 2 and/or MCNT. However, the role and mechanism of MCNT in the disinfection process are still unclear. Therefore, this study aimed at investigating the disinfection mechanism of Escherichia coli using MCNT-TiO 2 nanocomposites under various conditions (i.e. the presence and absence of light and reactive oxygen species scavengers, and different MCNT-TiO 2 ratio) and photocatalytic disinfection models. The results showed that (i) MCNT and its nanocomposites with TiO 2 had much higher disinfection efficiencies than bare TiO 2 , (ii) the physical bacterial capture was the dominant disinfection mechanism, (iii) the higher disinfection rate was found at an optimum MCNT:TiO 2 ratio of 5:1 under the tested experimental conditions, (iv) hydroxyl radical (OH) was the influencing reactive oxygen species on the photocatalytic disinfection using MCNT-TiO 2 , and (v) good correlation between experimental parameters (i.e. carbon contents, surface area and concentration of MCNT-TiO 2) and the contribution rate of physical and photocatalysis reactions. The finding from this study and the methods proposed herein are essential for understanding the photocatalytic disinfection processes using TiO 2 and its carbonaceous nanocomposites, which can promote the application of photocatalytic disinfection process. Image 1 • CNT and its composites with TiO 2 had much higher disinfection efficiencies than bare TiO 2. • The physical bacterial capture was the dominant disinfection mechanism. • The highest disinfection rate was found at an optimum CNT:TiO 2 ratio of 5:1. • OH was the influencing reactive oxygen species on the photocatalytic disinfection. [ABSTRACT FROM AUTHOR]

The removal of bromide (Br−) and iodide (I−) from source waters mitigates the formation of brominated and iodinated disinfection by-products (DBPs), which are more toxic than their chlorinated analogues. In this study, we report on our recently developed environmental-friendly method for the preparation of novel silver chloride/superfine activated carbon composite (AgCl-SPAC) to rapidly and selectively remove Br− and I− from surface waters. The material characteristics were tracked, before and after treatment, using scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), X-ray diffraction (XRD), and X-ray photoelectron spectra (XPS) spectroscopies. The results showed very fast removal kinetics of Br− and I− by AgCl-SPAC with equilibrium times at 150 s and <10 s, respectively (i.e., 2–3 orders of magnitudes faster than previously tested Ag-based composites). In addition, AgCl-SPAC was evaluated under eight different Cl− concentrations up to 400 mg/L and exhibited high removal efficiencies for I− (i.e., >90% at all tested conditions) and Br− (i.e, >80% at Cl− = 0.5–200 mg/L, and 60–75% at extreme Cl− conditions = 300–400 mg/L). Unlike previous Ag-based composites, AgCl-SPAC performance was not affected by elevated concentrations of two types of natural organic matter (2–16 mg-NOM/L). The superior performance was further confirmed in four different surface waters and one groundwater. After the removal of Br− and I− from all waters by AgCl-SPAC, the subsequent DBPs formation (trihalomethanes, haloacetic acids, and haloacetonitriles), total organic halogens (TOX), bromine substitution factor (BSF), and calculated cytotoxicity under the uniform formation conditions (UFC) decreased significantly. Overall, this novel composite represents a promising alternative approach, to be integrated continuously or seasonally, for controlling the formation of brominated and/or iodinated DBPs at water treatment plants. Image 1 • Novel AgCl-SPAC composite was prepared with environmental-friendly method. • Rapid and selective removal of Br- and I- was demonstrated. • The composite removed Br- and I- from 5 different surface waters and groundwater. • AgCl-SPAC treatment dropped the formation of Br-DBP and I-DBP. [ABSTRACT FROM AUTHOR]

Abstract Poly- and perfluorinated substances (PFAS) comprise more than 3000 individual compounds; nevertheless, most studies to date have focused mainly on the fate, transport and remediation of long-chain PFAS (C > 7). The main objective of this article is to provide the first critical review of the peer-reviewed studies on the analytical methods, occurrence, mobility, and treatment for ultra-short-chain PFAS (C = 2–3) and short-chain PFAS (C = 4–7). Previous studies frequently detected ultra-short-chain and short-chain PFAS in various types of aqueous environments including seas, oceans, rivers, surface/urban runoffs, drinking waters, groundwaters, rain/snow, and deep polar seas. Besides, the recent regulations and restrictions on the use of long-chain PFAS has resulted in a significant shift in the industry towards short-chain alternatives. However, our understanding of the environmental fate and remediation of these ultra-short-chain and short-chain PFAS is still fragmentary. We have also covered the handful studies involving the removal of ultra-short and short-chain PFAS and identified the future research needs. Graphical abstract Image 1038 Highlights • Comprehensive surveys of the occurrence of short-chain PFAS are needed. • Conventional treatment plants fail to remove short-chain PFAS. • Hybrid sorption systems maybe alternatives to remove short-chain PFAS from water. • Destruction methods are promising but new catalysts and approaches are need. • New selective sorbents for short-chain PFAS must be developed. [ABSTRACT FROM AUTHOR]

The high concentrations of pharmaceuticals and personal care products (PPCP) that found in water in many locations are of concern. Among the available water treatment methods, heterogeneous photocatalysis using TiO 2 is an emerging and viable technology to overcome the occurrence of PPCP in natural and waste water. The combination of carbonaceous materials (e.g., activated carbon, carbon nanotubes and graphene nanosheets) with TiO 2 , a recent development, gives significantly improved performance. In this article, we present a critical review of the development and fabrication of carbonaceous-TiO 2 and its application to PPCP removal including its influence on water chemistry, and the relevant operational parameters. Finally, we present an analysis of current priorities in the ongoing research and development of carbonaceous-TiO 2 for the photodegradation of PPCP. [ABSTRACT FROM AUTHOR]

There is a significant interest in sustainable and eco-friendly methods of regenerating spent nanomaterials in order to use resources more efficiently and minimize the cost of materials and techniques. This paper investigates the feasibility of using ozone to regenerate magnetic carbon nanotubes (MCNTs) after they have been used to remove organic pollutants from water. We ran MCNT through multiple regeneration cycles (i.e. magnetic collection → ozone regeneration → washing with ethanol then water) to adsorb atrazine. The results of our adsorption experiments show that the atrazine removal capacity of the MCNTs decreased from 57.8 to 27.6 mg/g in three cycles if only ozone treatment is used as a regeneration method. However, this capacity increased when MNCTs are washed with ethanol following ozone treatment. MCNTs were seen to retain 85–93% of its original adsorption affinity even after ten consecutive regeneration cycles. Additionally, we used a three layer graphite slab as a model system for CNTs and performed density functional theory (DFT) calculations to determine the free energy of adsorption and the free energy of solvation of atrazine and its byproducts in water and ethanol. The results of X-ray photoelectron spectroscopy (XPS) measurements and DFT calculations showed that π−π interactions of MCNTs were not affected by ozonation and/or washing with ethanol and this procedure could remove the degradation byproducts attached on the surface. Overall, this is the first report that demonstrates the feasibility of regenerating spent MCNTs using ozone assisted by ethanol washing as an efficient and facile treatment. [ABSTRACT FROM AUTHOR]

Current methods for preparing magnetic composites with carbon nanotubes (MCNT) commonly include extensive use of treatment with strong acids and result in massive losses of carbon nanotubes (CNTs). In this study we explore the potential of taking advantage of the inherent magnetic properties associated with the metal (alloy or oxide) incorporated in CNTs during their production. The as-received CNTs are refined by applying a permanent magnet to a suspension of CNTs to separate the high-magnetic fraction; the low-magnetic fraction is discarded with the solvent. The collected MCNTs were characterized by a suite of 10 diffraction and spectroscopic techniques. A key discovery is that metallic nano-clusters of Fe and/or Ni located in the interior cavities of the nanotubes give MCNTs their ferromagnetic character. After refinement using our method, the MCNTs show saturation magnetizations up to 10 times that of the as-received materials. In addition, we demonstrate the ability of these MCNTs to repeatedly remove atrazine from water in a cycle of dispersion into a water sample, adsorption of the atrazine onto the MCNTs, collection by magnetic attraction and regeneration by ethanol. The resulting MCNTs show high adsorption capacities (> 40 mg-atrazine/g), high magnetic response, and straightforward regeneration. The method presented here is simpler, faster, and substantially reduces chemical waste relative to current techniques and the resulting MCNTs are promising adsorbents for organic/chemical contaminants in environmental waters. [ABSTRACT FROM AUTHOR]

Natural organic matter (NOM) is a heterogeneous mixture of organic compounds that is omnipresent in natural waters. To date, the understanding of the adsorption of NOM components by carbon nanotubes (CNTs) is limited because of the limited number of comprehensive studies in the literature examining the adsorption of NOM by CNTs. In this study, 11 standard NOM samples from various sources were characterized, and their adsorption behaviors on four different CNTs were examined side-by-side using total organic carbon, fluorescence, UV-visible spectroscopy, and high-performance size-exclusion chromatography (HPSEC) analysis. Adsorption was influenced by the chemical properties of the NOM, including aromaticity, degree of oxidation, and carboxylic acidity. Fluorescence excitation-emission matrix (EEM) analysis showed preferential adsorption of decomposed and terrestrial-derived NOM compared to freshly produced and microbial-derived NOM. HPSEC analysis revealed preferential adsorption of fractions in the molecular weight range of 0.5-2 kDa for humic acids but in the molecular weight range of 1-3 kDa for all fulvic acids and reverse-osmosis isolates. However, the smallest characterized fraction (MW < 0.4 kDa) in all samples did not adsorb on the CNTs. [ABSTRACT FROM AUTHOR]

Treatment of greywater by electrocoagulation using aluminum electrodes was studied. The effects of current-density, electrolysis-time, and inter-electrode-gap on turbidity-removal and electrical-energy consumption were investigated. Under the optimal conditions (J= 12.5 mA/cm2,t= 30 min, andl= 0.5 cm), pollutants removal were: CODtotal= 52.8%, CODsoluble= 31.4%, BODtotal= 32.8%, BODsoluble= 27.6%, SS = 64.6%, TN = 30.1%, and TP = 13.6%. The consumed electrical-energy recorded 4.1 kWh/m3with an operating cost 0.25 US $/m3. Artificial intelligence was developed to simulate the influence of variables on the turbidity-removal. A 3–6–1 neural network achievedR-values: 0.99 (training), 0.84 (validation) and 0.89 (testing). An adaptive neuro-fuzzy inference system indicated that current-density is the most influential input. [ABSTRACT FROM AUTHOR]

We investigated the effect of salinity on the removal of organics and ammonium from agricultural drainage wastewater (ADW) using moving bed biofilm reactors (MBBRs). Under the typical salinity level of ADW (total dissolved solids (TDS) concentration up to 2.5 g∙L-1), microorganisms were acclimated for 40 days on plastic carriers and a stable slime layer of attached biofilm was formed. Next, six batch mode MBBRs were set up and run under different salinity conditions (0.2-20 g-TDS∙L-1). The removal efficiency of chemical oxygen demand (COD) and ammonium-nitrogen (NH4-N) in 6 hours decreased from 98 and 68% to 64 and 21% with increasing salt concentrations from 2.5 to 20 g-TDS∙L-1, respectively. In addition, at decreasing salt levels of 0.2 g-TDS∙L-1, both COD removal and nitrification were slightly lowered. Kinetic analysis indicated that the first-order reaction rate constant (k1) and specific substrate utilization rate (U) with respect to the COD removal remained relatively constant (10.9-11.0 d-1 and 13.1-16.1 g-COD-removed.g-biomass-1∙d-1, respectively) at the salinity range of 2.5-5.0 g-TDS∙L-1. In this study, the treated wastewater met the standard criteria of organic concentration for reuse in agricultural purposes, and the system performance remained relatively constant at the salinity range of typical ADW. [ABSTRACT FROM AUTHOR]

Estrone (E1), 17α-estradiol (17α-E2), 17β-estradiol (17β-E2), and estriol (E3) are persistent in livestock manure and present serious pollution concerns because they can trigger endocrine disruption at part-per-trillion levels. This study conducted a global analysis of estrogen occurrence in manure using all literature data over the past 20 years. Besides, predicted environmental concentration (PEC) in soil and water was estimated using fate models, and risk/harm quotient (RQ/HQ) methods were applied to screen risks on children as well as on sensitive aquatic and soil species. The estradiol equivalent values ranged from 6.6 to 4.78 × 104 ng/g and 12.4 to 9.46 × 104 ng/L in the solid and liquid fraction. The estrogenic potency ranking in both fractions were 17β-E2> E1>17α-E2>E3. RQs of measured environmental concentration in the liquid fraction pose medium (E3) to high risk (E1, 17α-E2 & 17β-E2) to fish but are lower than risks posed by xenoestrogens. However, the RQ of PECs on both soil organisms and aquatic species were insignificant (RQ < 0.01), and HQs of contaminated water and soil ingestion were within acceptable limits. Nevertheless, meticulous toxicity studies are still required to confirm (or deny) the findings because endocrine disruption potency from mixtures of these classes of compounds cannot be ignored. • Global manure-borne estrogen occurrence data for 20-year period were synthesized. • Levels in soil and water were estimated based on occurrence data using fate models. • Risk/harm quotient was applied to screen risks on sensitive species and children. • Occurrence levels pose plausible risk but estimated levels have insignificant risks. • Toxicity studies are required on endocrine disruption potency in manure mixtures. [ABSTRACT FROM AUTHOR]

Regrowth of bacteria after water/wastewater disinfection is a serious risk to public health, particularly when such pathogens carry antibiotic resistance genes. Despite increasing interest in light-based disinfection using ultraviolet or solar radiation, the mechanism of bacterial regrowth and their concentration upon light exposure (i.e., during storage, or after discharge into rivers or lakes) remain poorly understood. Therefore, we present a focused critical review to 1) elucidate regrowth mechanisms, 2) summarize the pros and cons of available experimental designs and detection techniques for regrowth evaluation, and 3) provide an outlook of key research directions for further investigations of post-disinfection bacterial regrowth. Bacterial regrowth can occur through reactivation from a viable but non-culturable state, repair of photo-induced DNA damage, and reproduction of bacteria surviving disinfection. Many studies have underestimated the degree of actual regrowth because of the use of simple experimental designs and plate count methods, which cannot quantify actual abundance of viable bacteria. Further research should investigate the effects of various factors on bacterial regrowth in realistic conditions in regrowth tests and adopt multiplex detection methods that combine culture-based and culture-independent approaches. An accurate understanding of the mechanisms involved in bacterial regrowth following disinfection is critical for safeguarding public health and aquatic environments. Image 1 • Regrowth mechanisms after disinfection are reactivation, repair and reproduction. • More comprehensive regrowth tests at environmentally relevant conditions are needed. • Both culture-base and culture-independent approaches should be adopted. [ABSTRACT FROM AUTHOR]

Pre-chlorination (i.e. dosing chlorine prior to granular activated carbon (GAC) contactors) was recently introduced as a promising method to reduce the formation of disinfection byproducts (DBPs). However, our understanding on the effect of natural organic matter (NOM) and GAC characteristics on pre-chlorination efficiency is still elusive. Thus, we have designed this systematic study to investigate the effects of GAC characteristics (i.e. surface area, pore size, and surface charge) on the subsequent reduction of DBP formation using five well-characterized adsorbents with three different NOM under three initial Br− concentrations. The results revealed that the adsorption of halogenated DBPs precursors mostly occurs in the mesoporous region (i.e. 2 nm < pore size <50 nm) of the adsorbents. Subsequently, pre-chlorination before treatment with HD3000 (i.e. GAC with the highest mesoporous surface area) decreased the formation of DBPs by 58%. Furthermore, oxidation of GAC increased the surface acidity and negatively impacted the adsorption of halogenated DBP precursors, which suggests basic GACs as promising adsorbents when applying pre-chlorination. In addition, experiments with different NOM showed that pre-chlorination was effective with higher aromatic NOM (i.e. high specific ultraviolet absorbance (SUVA 254)). However, pre-chlorination of NOM with low SUVA 254 has decreased the adsorption of some DBP precursors which resulted in increased formations of haloacetic acid (HAA) and total organic halogen (TOX). Also, experiments with effluent organic matter (EfOM) showed that pre-chlorination did not increase the adsorption of DBP precursors in low SUVA 254 wastewater effluents. Besides, increasing initial Br− concentration increased the formation of brominated DBPs (Br-DBPs) and the adsorbed Br-DBP precursors. This study gives in-depth understanding of the mechanisms, advantages, and limitations of pre-chlorination as a potential method to control DBPs formation. Image 1 • Pre-chlorination was tested under various experimental conditions, GACs and fibers. • Halogenated DBP intermediates adsorbed mostly at mesoporous region of the adsorbent. • Pre-chlorination was effective to NOM with high SUVA 254 , but not on low SUVA 254 NOM. • Pre-chlorination increased the adsorption of brominated DBP precursors. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) are prevalent global pollutants that are being detected in aquatic ecosystems and drinking water sources around the world. In addition to plastic polymers, MPs contain various chemical substances (known as "additives") that can leach and risk water quality. In this paper, we investigated for the first time the potential release of disinfection byproducts (DBPs) precursors when MPs are exposed to hydrolysis and/or degradation by simulated sunlight. Seventeen MPs with seven different polymer types were collected either as commercial products (e.g. drinking water bottles, shopping bags, recycled plastics, etc.) or pure/virgin polymers. Results showed high release of dissolved organic carbon (DOC) from five MP samples and a significant increase in bromide concentrations from four MPs. DBPs formation potential (DBPFP) experiments with MPs' leachates showed higher concentrations of chlorinated trihalomethanes (THMs), haloacetonitriles (HANs), and total organic halogens (TOX) in three samples, while a significant shift to brominated DBPs was observed in samples containing bromide. Extending the leaching experiments to four consecutive cycles showed that the leaching of DOC and DBPs' precursor significantly decreased after the second leaching cycle. Further analysis revealed that the reactivity of the leached DOC – indicated by THMFP yields – was comparable to those of several raw waters that supply drinking water treatment plants. The leached THMs and TOX from MPs that were exposed to UVA irradiation were in general higher than MPs that were run under dark conditions. • MP in water released DBPs precursors under both light and dark conditions. • DOC leaching ranges from ∼30 to 1000 mg DOC per kg depending on the composition of MPs. • Reactivity of leached DOC from MP was comparable to natural organic matter. • Some MPs released Br− that shifted the DBPs speciation towards brominated species. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) have been recognized as transport vectors for micropollutants in the natural water environment and the food web; therefore, the sorption behavior of contaminant on MPs has recently gained an increased attention. However, a consensus has not yet been reached and information about the adsorption of water contaminants on real MPs remains elusive. Herein, we raise the question of " Should we continue using pure polymers as surrogates for real MPs ?" This first systematic study compared the adsorption of multiple micropollutants (i.e. a pesticide, a pharmaceutical, and perfluoroalkyl substances (PFAS)) on a large set of MPs (i.e. 20 well-characterized MPs) and kaolin. Material characterizations results showed various physicochemical and compositional differences between real and pure MPs. Pure polymers had lower normalized uptake values than real MPs in most cases. This was attributed to the surface roughness and/or the presence of fillers (e.g. talc and glass fiber) in real samples. Further, preloaded MPs with natural organic matter (NOM) showed an increased uptake of micropollutants due to forming a complex with NOM and/or co-sorption. These findings indicate that employing real MPs in research studies is critical for obtaining environmentally meaningful results, and the evaluation of MPs sorption behavior without NOM preloading can result in a significant underestimation for their actual values. We also provided an outlook the key areas for further investigations. Unlabelled Image • Real MPs have heterogeneous compositions and contain additives and fillers. • MPs exhibited fast sorption kinetics (<24 h). • NOM preloading on MPs increased their adsorption affinity towards micropollutants. • Real MPs show different sorption behavior from pure polymers. • Results from studies on pure polymers shouldn't be generalized for all MPs. [ABSTRACT FROM AUTHOR]

Photocatalytic nanofiltration (NF) membranes with enhanced flux and anti-fouling properties were prepared from a layered in situ nanocomposite of metal organic framework (i.e., UiO-66) and graphene oxide (UiO-66_GO) on a polyamide NF membrane using a pressure-assisted self-assembly method. For filtering pure water and humic acid, the composite membrane with a 10% UiO-66_GO loading (UiO-66_GO/NF-10%) showed a higher water flux (up to 63 kg/m2 h bar), flux recovery (80%), and total fouling resistance (33%) than the pristine NF membrane. Physical and chemical characterization revealed that this performance was attributed to improvements in hydrophilicity, porosity, surface smoothness, and charge repulsion. The UiO-66_GO/NF-10% composite membrane exhibited better physical stability with a relatively low mass loss (8.64%) after five washes than the membranes with mass loadings of 5 and 15 wt%. Furthermore, the UiO-66_GO/NF-10% composite membrane exhibited considerable photocatalytic activity under ultraviolet (UV) irradiation (bandgap: 3.45 eV), which reduced irreversible fouling from 20.7% to 2.4% and increased flux recovery to 98%. This study demonstrated that surface modification with the UiO-66_GO nanocomposite produced a high-flux anti-fouling photocatalytic NF membrane, which is promising for water purification. [ABSTRACT FROM AUTHOR]

Natural organic matter (NOM) can inhibit the photocatalytic degradation of organic micropollutants (OMPs) through inner filter effect, reactive oxygen species (ROS) scavenging, and competitive adsorption. However, previous studies have focused solely on the bulk properties of NOM and our understanding of the inhibition mechanism by NOM fractions during photocatalytic degradation of OMP is still fragmentary. In this study, five well-characterized different NOM samples (i.e., secondary treated wastewater, river water, and three standard NOM surrogates) were used to elucidate the inhibition mechanisms during photocatalytic degradation of carbamazepine (a model OMP) using TiO 2 and its composites with carbon nanotubes (CNT-TiO 2) under UVC and solar-light irradiation. The results indicated that terrestrially derived NOM with high aromaticity, a low oxygen/carbon atom ratio, and large molecular weight is the major fraction that participates in ROS scavenging, competitive adsorption, and inner filter effect. Furthermore, the modeling analysis suggested that inner filter effect due to NOM and ROS scavenging was the most influential inhibitory mechanism. In the case of secondary treated wastewater, the presence of high concentrations of inorganic species (e.g., PO 4 3−, Cl−, and NO 3 −) together with NOM significantly reduced the photocatalytic degradation of carbamazepine. Overall, the methods and the results of this study provide a comprehensive understanding of the effects of NOM fractions on photocatalysis and highlight the need to further consider the interplay between NOM and background inorganic constituents in photocatalytic degradation of OMP. Image 1 • The inhibition was studied with NOM surrogates, river water, and wastewater. • Aromatic terrestrially derived NOM with high MW inhibit photocatalysis. • Inhibition mechanism: ROS scavenging > inner filter effect > competitive adsorption. [ABSTRACT FROM AUTHOR]

Recently, a series of new photocatalysts have been developed for to combat diverse bio-recalcitrant contaminants and the inactivation of bacteria. Modeling photocatalytic processes is important to assess these materials, and to understand and optimize their performance. In this study, the recent literature is critically reviewed and analyzed to identify and compare methods of modeling photocatalytic performance. The Langmuir–Hinshelwood model (L-H) has been used in many studies to rationalize the degradation kinetics of single contaminants because it is the simplest model including both the adsorption equilibrium and degradation rates. Other studies report the development of more sophisticated variants of the L-H model that include the rates of catalyst excitation, recombination of electron-hole pairs, production of reactive oxygen species (ROS), and formation of by-products. Modified Chick-Watson (C W) and Hom models have been used by many researchers to include lag phases of bacteria in the description of disinfection kinetics. Artificial neural networks (ANNs) have been used to analyze the effects of operational conditions on photocatalyst performance. Moreover, response surface methodology (RSM) has been employed for experimental design, and optimization of operational conditions. We have reviewed and analyzed all available articles that model photocatalytic activity towards water pollution, summarized and put them in context, and recommended future research directions. Unlabelled Image • A large set of articles on photocatalytic modeling have been reviewed. • Current semi-mechanistic models overlook realistic water background components. • Future models need to be based on experiments under low concentration (ng/L–μg/L). • New models on compounds other than dyes and E.coli need to be developed. [ABSTRACT FROM AUTHOR]

The emerging classes of perfluorinated alkyl substances (PFAS) (e.g., Perfluorobutanoic acid (PFBA), perfluorobutane sulfonic acid (PFBS), GenX, ADONA, and F–53B) are persistent and recalcitrant to removal by conventional treatment techniques. Herein, we report on poly (N -[3-(dimethylamino)propyl]acrylamide, methyl chloride quaternary, DMAPAA-Q) hydrogel matrix as an effective sorbent for sequestering PFAS from different water matrices. The selective removal of 16 PFAS from different classes using DMAPAA-Q polymer was confirmed in surface waters and treated wastewater at environmentally relevant concentration (i.e., <1000 ng/L). The results showed fast removal kinetics with equilibrium time of 60–120 min and a higher removal of sulfonated than carboxylic PFAS, regardless of their chain lengths. These observations were in agreement with adsorption energy calculations of short- and long-chain PFAS on poly DMAPAA-Q hydrogel using density functional theory (DFT). No desorption was observed when the experimental time was extended to 24 h, which gives an added advantage of poly DMAPAA-Q hydrogel over previously reported adsorbents in the literature. In addition, the removal efficiency was not affected under a varying pH range of 4–10. The impact of background anions on PFAS removal by poly DMAPAA-Q hydrogel was tested and found to follow an order of SO 4 2− > Cl− > NO 3 −. The performance of poly DMAPAA-Q hydrogel was maintained in six consecutive adsorption/regeneration cycles to remove PFAS. The unique fast kinetics and high adsorption activity of poly DMAPAA-Q hydrogel towards PFAS exhibits a great potential for being a promising material for PFAS control. Image 1 • The cationic polymer show fast removal of short and long chain PFAS and GenX. • The polymer maintains high removal at pH range of 4–10. • Selective removal of 16 PFAS was confirmed in surface water and wastewaters. • The performance was maintained in ten consecutive adsorption/regeneration cycles. • Calculated adsorption energies by DFT matched the experimental results. [ABSTRACT FROM AUTHOR]

Periodic mesoporous organosilica nanoparticles (PMO SiNPs) were developed for the targeted capture of specific volatile organic compounds (VOCs). The removal kinetics for adsorbing VOCs were fast and the maximum removal could be achieved within less than 30 min. PMO SiNPs removed >99% of VOCs at a low sorbent dose (i.e. >0.5 mL analyte per g PMO SiNPs). They also showed good recyclability and maintained reasonable removal efficiencies after five cycles (i.e. 77% and 65% for hexanal and butyric acid vapors, respectively). [ABSTRACT FROM AUTHOR]

We have comprehensively compared the molecular sieving of natural organic matter (NOM) by adsorption on activated carbon (AC) and multi-walled carbon nanotubes (CNT) using different types of NOM. All water samples were characterized using UV–visible and fluorescence spectroscopies as well as high-performance size-exclusion chromatography (HPSEC) before and after adsorption. Adsorption isotherm results fitted well with Freundlich model ( R 2  = 0.95–0.99) and the model parameters indicated higher adsorption of NOM on CNT than AC. Fluorescence index (FI) and freshness index (BIX) showed preferential adsorption of microbial derived and fresh NOM on AC, whereas, terrestrial derived and decomposed NOM were preferentially adsorbed on CNT. Further, HPSEC revealed that AC adsorbed NOM fractions with small molecular weight (MW) (<0.4 kDa) faster than the fractions with higher MW. In contrast, CNT adsorbed NOM fractions characterized by high MW (>1 kDa) while the smallest fraction (<0.4 kDa) was not adsorbed, possibly due to its hydrophilic character. Our results also demonstrated a good correlation between FI and average MW of NOM ( R 2  > 0.93). These findings illustrate the influence of the adsorbent's type and characteristics (i.e., porosity and pore size distribution) on the preferential adsorption of different NOM fractions. [ABSTRACT FROM AUTHOR]

Significant progress has been made in developing fluorine-free firefighting foams (F3) as alternatives to perfluoroalkyl substances (PFAS)-containing aqueous film-forming foams (AFFF) to help eliminate the health and environmental concerns linked to PFAS exposure. However, developing viable F3 options hinges on a thorough assessment of potential risks alongside the technical performance evaluations. This study showcases the capability of a zebrafish-based platform to discern the developmental and behavioral toxicities associated with exposure to one AFFF and two F3 formulations. To facilitate direct exposure to the chemicals, embryos were enzymatically dechorionated and then exposed to the diluted formulations (6–120 hours post fertilization (hpf)) at concentrations folding from 0.1% of the manufacturer-recommended working concentrations. The exposure regimen also included daily automated media changes (50%) and mortality assessments (24 and 120 hpf). At 120 hpf, a comprehensive assessment encompassing overall development, prevalence of morphological defects, and behavioral responses to acute stressors (visual, acoustic, and peripheral irritant) was conducted. Exposure to both F3s significantly increased larval mortalities to percentages exceeding 90%, whereas AFFF exposures did not cause any significant effect. Overall development, marked by total larval length, was significantly impacted following exposures to all foams. Behavioral responses to acute stressors were also significantly altered following exposures to both F3s, whereas the AFFF did not alter behavior at the concentrations tested. Our findings demonstrate toxicities associated with tested F3 formulations that encompass several endpoints and highlight the utility of the proposed platform in evaluating the developmental toxicities of current and future foam formulations. [Display omitted] • F3s are potential alternatives, but risk assessment is crucial. • F3s more toxic than PFAS-containing AFFFs in acute and developmental toxicity assessments. • F3s significantly affect activity and behavioral stress responses. • Our findings highlight the utility of the proposed toxicity assessment platform. [ABSTRACT FROM AUTHOR]

Per- and polyfluoroalkyl substances (PFAS) are persistent, bioaccumulative pollutants found in water resources at concentrations harmful to human health. Whereas current PFAS destruction strategies use nonselective destruction mechanisms, we found that perfluoroalkyl carboxylic acids (PFCAs) could be mineralized through a sodium hydroxide-mediated defluorination pathway. PFCA decarboxylation in polar aprotic solvents produced reactive perfluoroalkyl ion intermediates that degraded to fluoride ions (78 to ~100%) within 24 hours. The carbon-containing intermediates and products were inconsistent with oft-proposed one-carbon-chain shortening mechanisms, and we instead computationally identified pathways consistent with many experiments. Degradation was also observed for branched perfluoroalkyl ether carboxylic acids and might be extended to degrade other PFAS classes as methods to activate their polar headgroups are identified. [ABSTRACT FROM AUTHOR]

Removal and destruction of perfluorooctanoic acid (PFOA) are challenging due to its extreme persistence and dilute concentrations. This study investigated dual-function adsorptive-photocatalytic zeolite materials to selectively adsorb and degrade PFOA via tuning pore structures and doping transition metals. It is found that the pore opening is critical in the size-selective trapping of PFOA, while the iron doped zeolites present excellent adsorption of PFOA (>80 mg g−1) combining hydrophobic and electrostatic interactions. The formation of PFOA-iron complexes has reduced bond dissociation energy of C−F, calculated from density functional theory, for favorable stepwise defluorination (over 60% defluorination in 4 hours) by superoxide radicals and ligand-to-metal charge transfer. This mechanistic investigation extends the potential of the concentrate-and-degrade concept to remove PFOA selectively and effectively from contaminated water. [Display omitted] • Zeolites with comparable pore opening to PFOA favor its adsorption and degradation. • PFOA adsorption on Fe-BEA is driven by hydrophobic and electrostatic interactions. • PFOA molecule activation by Fe complexes decreases the decarboxylation energy. • Ligand-to-metal charge transfer and superoxide radical contribute to PFOA degradation. [ABSTRACT FROM AUTHOR]

• f TMP are higher in coastal seawater than in inland freshwater. • Proportion of high-energy 3DOM* varies greatly in coastal seawater. • f TMP estimation models are available for both freshwater and seawater. • E 2 :E 3 is more reliable than spectral slopes for modeling f TMP. • Different freshwater catchment characteristics affect f TMP. The excited triplet-state of dissolved organic matter (3DOM*) is a major reactive intermediate in sunlit waters. Its quantum yield is important in understanding the fate of organic micropollutants. The degradation efficiency of its chemical probe, 2,4,6-trimeythlphenol (f TMP), is generally used as a proxy of the quantum yield. However, f TMP has been described and modelled only for freshwater systems. Therefore, this study quantified f TMP in inland freshwater and coastal seawater sampled in Japan by conducting steady-state photochemical experiments. Optical properties of water were then used to model f TMP. Results indicated that the inland freshwater DOM originated mainly from terrestrial sources, while the coastal seawater DOM were microbial-dominated. On average, inland freshwater exhibited lower f TMP (61.2 M−1) than coastal seawater (79.7 M−1) and the coastal seawater exhibited significant variations in the proportion of high-energy 3DOM* (> 250 kJ/mol). In addition, E 2 :E 3 (ratio of absorbance at 254 to 365 nm) was positively correlated with f TMP of inland freshwater, coastal seawater, and the overall dataset. Catchment conditions such as forest coverage also influenced the production of 3DOM* and high-energy 3DOM* in inland freshwater. Furthermore, the developed models estimated f TMP based on the optical properties of both freshwater and seawater, providing valuable insights about 3DOM* photochemistry in the aquatic environment. [Display omitted] [ABSTRACT FROM AUTHOR]

The performance of photocatalytic advanced oxidation must be improved in order for the technology to make the jump from academic research to widespread use. Research is needed on the factors that cause photocatalysis to become self-limiting. In this study, we introduced, for the first time, nanobubbles continuously into a running photocatalytic reactor. Synthetic air, O2, and N2 bubbles in the size range of 40 to 700 nm were added to a reaction system comprising P25 TiO2 photocatalyst in stirred aqueous solution excited by UV-A lamps, with methyl orange as a target contaminant. The removal of methyl orange was tested under conditions of changing pH and with the addition of different radical scavengers. Results indicated that the oxygen and air nanobubbles improved the photocatalytic degradation of methyl orange—the removal efficiency of methyl orange increased from 58.2 ± 3.5% (N2 aeration) to 71.9 ± 0.6% (O2 aeration). Dissolved oxygen (DO) of 14.93 ± 0.13 mg/L was achieved using O2 nanobubbles in comparison to 8.43 ± 0.34 mg/L without aeration. The photodegradation of methyl orange decreased from 70.8 ± 0.4% to 53.9 ± 0.5% as pH increased from 2 to 10. Experiments using the scavengers showed that O2− was the main reactive species in photocatalytic degradation under highly dissolved oxygen conditions, which also accounted for the observation that the removal efficiency for methyl orange decreased at higher pH. However, without photocatalyst, nanobubbles alone did not improve the removal of methyl orange, and nanobubbles also did not increase the degradation of methyl orange by only photolysis. These experiments show that oxygen and air nanobubbles can act as environmentally friendly catalysts for boosting the performance of photocatalytic water treatment systems. [ABSTRACT FROM AUTHOR]

The presence of bromide (Br−) in water results in the formation of brominated disinfection byproducts (DBPs) after chlorination, which are much more cytotoxic and genotoxic than their chlorinated analogs. Given that conventional water treatment processes (e.g., coagulation, flocculation, and sedimentation) fail to remove Br− effectively, in this study, we systematically tested and compared the performance of different anion exchange resins, particularly two novel Br-selective resins, for the removal of Br−. The resins performance was evaluated under both typical and challenging background water conditions by varying the concentrations of anions and organic matter. The overall Br− removal results followed the trend of Purolite-Br ≥ MIEX-Br > IRA910 ≥ IRA900 > MIEX-Gold > MIEX-DOC. Further evaluation of Purolite-Br resin showed Br− removal efficiencies of 93.5 ± 4.5% for the initial Br− concentration of 0.25 mg/L in the presence of competing anions (i.e., Cl−, NO 3 −, NO 2 −, SO 4 2−, PO 4 3−, and a mixture of all five), alkalinity and organic matter. In addition, experiments under challenging background water conditions confirmed the selectivity of the resins (i.e. Purolite-Br and MIEX-Br) in removing Br−, with SO 4 2− and Cl− exhibiting the greatest influence upon the resin performance followed by NOM concentration, regardless of the NOM characteristic. After Br− removal, both the subsequent formation of brominated DBPs (trihalomethanes, haloacetic acids, and haloacetonitriles), and the total organic halogens (TOX), decreased by ∼90% under the uniform formation conditions. Overall, Br-selective resins represent a promising alternative for the efficient control of Br-DBPs in water treatment plants. Image 1 • Br-selective resins were tested under typical and challenging conditions. • Performance of Br-resins was better than conventional resins. • Characteristics of natural organic matter did not affect Br-resin performance. • Formations of Br-DBPs and total DBPs were reduced by 90% and 85% with Br-resin. [ABSTRACT FROM AUTHOR]

Perfluorooctanoic acid (PFOA) is a toxic and recalcitrant perfluoroalkyl substance commonly detected in the environment. Its low concentration challenges the development of effective degradation techniques, which demands intensive chemical and energy consumption. The recent stringent health advisories and the upgrowth and advances in photocatalytic technologies claim the need to evaluate and compare the state-of-the-art. Among these systems, chemical-free photocatalysis emerges as a cost-effective and sustainable solution for PFOA degradation and potentially other perfluorinated carboxylic acids. This review (I) classifies the state-of-the-art of chemical-free photocatalysts for PFOA degradation in families of materials (Ti, Fe, In, Ga, Bi, Si, and BN), (II) describes the evolution of catalysts, identifies and discusses the strategies to enhance their performance, (III) proposes a simplified cost evaluation tool for simple techno-economical analysis of the materials; (IV) compares the features of the catalysts expanding the classic degradation focus to other essential parameters, and (V) identifies current research gaps and future research opportunities to enhance the photocatalyst performance. We aim that this critical review will assist researchers and practitioners to develop rational photocatalyst designs and identify research gaps for green and effective PFAS degradation. [Display omitted] • State-of-the-art of chemical-free photocatalysts families for PFOA degradation. • Evaluation of the performance and practical limitations of the photocatalysts. • Discussion of the strategies to enhance the material's performance. • A cost evaluation tool estimates the material cost and compares the performance. • Identification of current research gaps and future research opportunities. [ABSTRACT FROM AUTHOR]

This study reports on an easy and scalable synthesis method of a novel magnetic nanocomposite (GO/ZIF-8/γ-AlOOH) based on graphene oxide (GO) nanosheets decorated with zeolitic imidazolate framework-8 (ZIF-8), pseudo-boehmite (γ-AlOOH), and iron oxide (Fe 3 O 4) nanoparticles by combining solvothermal and solid-state dispersion (SSD) methods. The nanocomposite was successfully applied to remove of diclofenac sodium (DCF) – a widely used pharmaceutical – from water. Response Surface Methodology (RSM) was used to optimize the adsorption process and assess the interactions among the influencing factors on DCF removal efficiency; including contact time, adsorbent dosage, initial pH, solution temperature, and DCF concentration. Adsorption isotherm results showed a good fitting with the Langmuir isotherm model with an exceptional adsorption capacity value of 2594 mg g−1 at 30 °C, which was highly superior to the previously reported adsorbents. In addition, kinetic and thermodynamic investigations further illustrated that the adsorption process was fast (equilibrium time = 50 min) and endothermic. The regeneration of GO/ZIF-8/γ-AlOOH nanocomposite using acetic acid solution (10% v/v) after a simple magnetic separation was confirmed in five consecutive cycles, which eliminate the usage of organic solvents. The nanocomposite has also shown a superior performance in treating a simulated hospital effluent that contained various pharmaceuticals as well as other organic, and inorganic constituents. [Display omitted] • Magnetic GO/ZIF-8/γ-AlOOH-NC was synthesized for DCF removal from aqueous effluents. • The reaction fitted pseudo-second-order kinetic model with an endothermic reaction. • GO/ZIF-8/γ-AlOOH-NC showed high adsorption capacity of 2594 mg g−1 for DCF. [ABSTRACT FROM AUTHOR]