Search Results (146)

Reverse osmosis (RO) is the key process for textile dyeing wastewater reuse applications. Membrane fouling reduces both permeability and rejection capability, negatively affecting the technological economy of RO process. Membrane cleaning is critical to recovery of the permeability of fouled RO membranes. Based on multi-batch filtration and cleaning experiments, this study systematically evaluated the RO membrane fouling potential of pre-treated textile dyeing wastewater by a membrane bioreactor and the recovery performance of fouled RO membranes after different cleaning methods. A significant decline (more than 15%) in RO membrane permeability occurred after RO membrane permeate production of 625 L/m² at a water recovery ratio of 60%. Protein-like substances and soluble microbial products were identified as the primary organic foulants via three-dimensional fluorescence excitation-emission matrix spectrometry (3D-FEEM). The single forward flushing with either pure water, acid, alkaline, or sodium hypochlorite solutions with a low active chlorine concentration showed very limited recovery of fouled RO membrane permeability. The combined forward flushing with acid followed by alkaline solutions restored fouled membrane permeability by up to 87% of a new RO membrane. The addition of pure water backwashing at a transmembrane pressure (TMP) of 0.5 MPa after both acid and alkaline solutions combined forward flushing restored fouled membrane permeability by up to 97% of a new RO membrane but deteriorated the rejection capability of the RO membrane. The backwashing parameters were further optimized at a TMP of 0.125 MPa and crossflow velocity (CFV) of 0.5 m/s, achieving fouled RO membrane permeability by up to 96% of a new RO membrane, and there were no negative effects on the rejection capability of the RO membrane. Alkaline forward flushing followed by pure water backwashing was the dominant contributor for fouled RO membrane permeability recovery. A preliminary economic analysis showed that the total chemical cost per RO production was 0.763 CNY/m³ and could be further reduced via removing acid cleaning and replacing combined alkaline flushing and pure water backwashing with alkaline backwashing. Full article

The safety of large indoor workspaces hinges on ventilation layout and airflow organization, particularly for dense contaminants that pool near the floor. This qualitative, full-scale case study evaluates chlorine (Cl₂) capture using supporting CFD and visualization experiments in a 20 × 13 × 9 m hall. Four exhaust arrangements—low, mid, high, and all levels combined—were tested under two modes: a single grille at 12,000 m³/h and three co-located grilles at 4000 m³/h each (total 12,000 m³/h), with and without an auxiliary supply (2000 m³/h). Removal performance was sensitive to exhaust elevation: low-level extraction consistently confined the plume near the floor, while distributing the same total flow across three levels achieved comparable or improved capture; mid/high extraction was less effective. A practical extraction radius of ≈5 m was identified, and the auxiliary supply improved outcomes only when steering the plume toward the low grille. CFD results showed that, regardless of the lower grille’s duty, the inlet concentration at the low grille was about twice that at the middle grille and more than four times that at the upper grille; in the three-grille configuration, the upper grille received negligible contaminant. These full-scale findings provide geometry-first guidance for dense-gas control in high-ceiling, large-volume spaces. Full article

The persistence of organochlorine pesticides, such as Aldrin and Dieldrin, in water bodies worldwide necessitates the development of efficient Advanced Oxidation Processes (AOPs) for water treatment or remediation. However, comparative studies evaluating the performance of distinct plasma discharge geometries against acoustic cavitation for the mineralization of these specific chlorinated cyclodienes remain scarce. This study investigates the comparative efficacy of four non-thermal technologies, ultrasound, dielectric barrier discharge (DBD) plasma, glow discharge plasma, and corona discharge plasma, for the simultaneous degradation of Aldrin and Dieldrin in a model contaminated aqueous solution (5 μg/L). All experiments followed a 3²-factorial design, and the residual concentrations of these pesticides were quantified by GC-MS after Solid-Phase Microextraction (SPME). All four methods achieved high degradation efficiencies, ranging from 92.5% to 100% for Aldrin and 92.6% to 99.2% for Dieldrin. Corona discharge plasma achieved the highest performance, resulting in 100% removal of Aldrin. However, ultrasound proved to be the most advantageous, achieving a 98% removal efficiency for both pesticides under its mildest conditions (3125 W/L ultrasonic power density for 3 min). The study confirmed that while Aldrin is highly susceptible to these technologies, Dieldrin remains the limiting factor for regulatory compliance. Chemical analysis did not conclusively identify any organic degradation by-products, suggesting that these AOPs may promote complete mineralization of the pollutants. Full article

In this study, anodic oxidation (AO) was evaluated using Ti/IrO₂–SnO₂–Sb₂O₅ electrodes in chloride, sulfate, and mixed electrolytes, along with electro-Fenton (EF) and photoelectro-Fenton (PEF) at pH 3.0, for the degradation of alachlor and isoproturon, each 50 mg L⁻¹. Active chlorine species were monitored using UV–Vis, while the removal of both herbicides was quantified using High Performance Liquid Chromatography (HPLC), along with the reduction in Total Organic Carbon (TOC), mineralization current efficiency (MCE), and specific energy per TOC removed (EC_TOC). The results show that electrolyte composition influences AO more than current density. In a chloride medium, isoproturon was eliminated within minutes, whereas alachlor required mixed electrolytes of Cl⁻/SO₄²⁻, allowing simultaneous combination of HClO/ClO⁻, ^●OH, and S₂O₈²⁻/SO₄^●−, or coupling with EF. An optimal current density of ~30 mA cm⁻² limited voltage rise and radical scavenging. EF introduced measurable mineralization (15% TOC), whereas PEF achieved rapid alachlor reduction and TOC reductions of up to 76% at low Fe²⁺. Overall, sequential AO followed by PEF maximized mineralization per unit of energy, and the mixed electrolytes provided a controllable pathway to scale up oxidant speciation generation. Full article

Simultaneous catalytic elimination of nitrogen oxides (NO_x) and volatile organic compounds (VOCs) represents a promising technology for addressing the synergistic pollution of fine particulate matters of <2.5 μm diameter (PM_2.5) and O₃. Nevertheless, it has been maintaining significant challenges in practical implementation, particularly the inherent mismatch in temperature windows between NO_x reduction and VOCs oxidation pathways, coupled with catalyst poisoning and deactivation phenomena. These limitations have hindered the industrial application of bifunctional catalysts for the removal of concurrent pollutant. This review systematically explored the fundamental mechanisms and functional roles of active sites in controlling synchronous catalytic processes. The mechanism of catalyst deactivation caused by multiple toxic substances has been comprehensively analyzed, including sulfur dioxide (SO₂), water vapor (H₂O), chlorine-containing species (Cl*), reaction by-products, and heavy metal contaminants. Furthermore, we critically evaluated the strategies of doping regulation, nanostructure engineering and morphology optimization to enhance the performance and toxicity resistance of catalysts. Meanwhile, emerging regeneration techniques and reactor design optimizations are discussed as potential solutions to improve the durability of catalysts. Based on the above critical aspects, this review aims to provide insights and guidelines for developing robust catalytic systems capable of controlling multi-pollutants in practical applications, and to offer theoretical guidance and technical solutions to bridge the gap between laboratory research and industrial environmental governance applications. Full article

Organic chlorine (Org-Cl) in crude oil poses continuous operational and environmental risks during production, trading, and refining processes. This article reviews the management of Org-Cl from its origin assumptions to analysis and mitigation measures and proposes a practical closed-loop framework. Quantitative merit value indicators (typical detection limit/quantitative limit, accuracy, and repeatability) and greenness indicators are used to compare standard methods and advanced methods, and to guide the selection of applicable methods. Corresponding technical maturity levels (TRLs) are assigned to mitigation measures (protective beds/adsorption, HDC, and emerging electrochemical/photochemical routes). Technical economic indicators with reference values (relative capital expenditure/operating expenditure levels) are summarized to assist decision-making. The main findings are as follows: (i) Evidence of secondary formation of organic chlorine under distillation-related conditions still relies on the matrix and requires independent verification; (ii) MWDXRF can achieve rapid screening (usually only 5 to 10 min), while CIC/D5808 supports quality balance arbitration; (iii) adsorption can remove a considerable portion of organic chlorine in light fractions under laboratory conditions, while the survival ability of HDC related to crude oil depends on the durability of the catalyst and the tail gas treatment capacity; and (iv) minimum viable implementation (MVI) combined with online total-chlorine monitoring and a physical principle-based digital twin technology can provide auditable closed-loop control. The limitations of this review include partial reliance on laboratory-scale data, inconsistent reports among studies, and the lack of standardized public datasets for model benchmarking. Prioritization should be given to analysis quality control, process durability indicators, and data governance to achieve reliable digital deployment. Full article

Cyanuric acid (CYA) is widely used as a chlorine stabilizer in swimming pools, but concentrations above 75 mg L⁻¹ cause overstabilization and loss of disinfection capacity. This study evaluated CYA removal by advanced oxidation processes, including heterogeneous photocatalysis, photo-Fenton, photo-persulfate, and anodic oxidation (AO). AO with boron-doped diamond anodes proved most effective, achieving up to 90% total organic carbon removal in ultrapure water. When applied to real swimming pool samples (118 and 251 mg L⁻¹ CYA), the process achieved significant CYA abatement, demonstrating its potential as a practical strategy to control overstabilization without additional chemicals. Full article

This study reports on green-synthesized zinc oxide nanoparticles (ZnONPs), focusing on their physicochemical characterization, photocatalytic properties, and agricultural applications. Dynamic light scattering (DLS) analysis revealed a mean hydrodynamic diameter of 337.3 nm and a polydispersity index (PDI) of 0.400, indicating moderate polydispersity and nanoparticle aggregation, typical of biologically synthesized systems. High-resolution transmission electron microscopy (HR-TEM) showed predominantly spherical particles with an average diameter of ~28 nm, exhibiting slight agglomeration. Energy-dispersive X-ray spectroscopy (EDX) confirmed the elemental composition of zinc and oxygen, while X-ray diffraction (XRD) analysis identified a hexagonal wurtzite crystal structure with a dominant (002) plane and an average crystallite size of ~29 nm. Photoluminescence (PL) spectroscopy displayed a distinct near-band-edge emission at ~462 nm and a broad blue–green emission band (430–600 nm) with relatively low intensity. The ultraviolet–visible spectroscopy (UV–Vis) absorption spectrum of the synthesized ZnONPs exhibited a strong absorption peak at 372 nm, and the optical band gap was calculated as 2.67 eV using the Tauc method. Fourier-transform infrared spectroscopy (FTIR) analysis revealed both similarities and distinct differences to the pigeon extract, confirming the successful formation of nanoparticles. A prominent absorption band observed at 455 cm⁻¹ was assigned to Zn–O stretching vibrations. X-ray photoelectron spectroscopy (XPS) analysis showed that raw pigeon droppings contained no Zn signals, while their extract provided organic biomolecules for reduction and stabilization, and it confirmed Zn²⁺ species and Zn–O bonding in the synthesized ZnONPs. Photocatalytic degradation assays demonstrated the efficient removal of pollutants from sewage water, leading to significant reductions in total dissolved solids (TDS), chemical oxygen demand (COD), and total suspended solids (TSS). These results are consistent with reported values for ZnO-based photocatalytic systems, which achieve biochemical oxygen demand (BOD) levels below 2 mg/L and COD values around 11.8 mg/L. Subsequent reuse of treated water for irrigation yielded promising agronomic outcomes. Wheat and barley seeds exhibited 100% germination rates with ZnO NP-treated water, which were markedly higher than those obtained using chlorine-treated effluent (65–68%) and even the control (89–91%). After 21 days, root and shoot lengths under ZnO NP irrigation exceeded those of the control group by 30–50%, indicating enhanced seedling vigor. These findings demonstrate that biosynthesized ZnONPs represent a sustainable and multifunctional solution for wastewater remediation and agricultural enhancement, positioning them as a promising candidate for integration into green technologies that support sustainable urban development. Full article

Sonochlorination (US/chlorine) is an emerging sonohybrid advanced oxidation process whose performance reportedly surpasses that of its individual components. However, the underlying oxidant budget is still being debated. We mapped the mechanism by systematically probing the US/chlorine system with selective scavengers (ascorbic acid, nitrobenzene, tert-butanol, 2-propanol, and phenol), competing anions (nitrite), and natural organic matter (humic acid). The kinetic hierarchy US/chlorine > US > chlorine remained consistent across all conditions, though its magnitude depended heavily on the matrix composition. Efficient ^•OH traps, such as alcohols and nitrobenzene, only partially suppressed the US/chlorine system. However, they greatly slowed sonolysis. This reveals a substantial non-^•OH channel in the hybrid process. Ascorbic acid eliminated synergy by stoichiometrically removing free chlorine. Phenol quenched HOCl and chlorine-centered radicals. Nitrite imposed a dual penalty by scavenging ^•OH and consuming HOCl via the nitryl chloride (ClNO₂) pathway. Humic acid acted as a three-way sink for ^•OH, HOCl, and chlorine radicals. These patterns suggest that reactivity is co-controlled by Cl^•, Cl₂^•−, and ClO^•. The results obtained are mechanistically consistent with cavitation-assisted activation of HOCl/OCl⁻ at pH 5–6, where HOCl concentration is maximal. This yields a mixed oxidant suite in which Cl₂^•− is the dominant bulk oxidant, Cl^• provides fast interfacial initiation, and ClO^• offers selective support. Full article

Chlorinated aliphatic hydrocarbons (CAHs) are some of the most widely distributed organic pollutants in underground environments and have high biological toxicity. This research aims to prepare an effective adsorbent comprising biochar and magnetite (MBC) to remove CAH pollution from soil. Optimization of the preparation and adsorption performance of MBC was investigated. The results of the adsorption experiment, combined with scanning electron microscopy (SEM) observations, show that the best raw material and pyrolysis temperature were coconut shell and 500 °C respectively. The Fourier transform infrared (FTIR) and X-ray diffraction (XRD) pattern characterizations, as well as the adsorption results, demonstrated the successful synthesis and enhancement effect of MBC for CAHs. The adsorption of CAHs on Fe₃O₄-loaded biochar was improved by 34.40–222.25% during pyrolysis at 500–900 °C. Additionally, MBC with a 10% Fe₃O₄ content had the best effect on three types of CAHs at low concentrations. A comparative pore analysis of MBC with different doses of Fe₃O₄ was carried out to reveal the relationship between the pore characteristics and adsorption properties. Furthermore, competitive adsorption experiments demonstrated that 4 wt% MBC addition significantly reduced the soil-bound TCE by 48.6%. Overall, these results indicated that MBC was an effective adsorbent for CAH removal from the polluted underground environment. Full article

Nano zero-valent iron (nZVI) particles have received much attention in environmental science and technology due to their unique electronic and chemical properties. While sulfate radical-based advanced oxidation processes (SR-AOPs) activated by nZVI show promise for mono-chlorobenzene (MCB) degradation, their efficiency is severely limited by surface oxidation of nZVI and Fe³⁺ accumulation. This study aims to enhance the nZVI/persulfate (PS) system using L-cysteine (Cys) to achieve effective MCB removal. The work involved synthesizing nZVI via borohydride reduction, followed by comprehensive characterization and batch experiments of the Cys/nZVI/PS degradation system of MCB were carried out to evaluate the key influencing factors and analyze the reaction mechanism of Cys-enhanced MCB degradation. Under optimal conditions (0.1 g/L nZVI, 3 mM PS, 0.1 mM Cys, pH 3), 92.6% of MCB was degraded within 90 min—an 18.7% improvement compared to the Cys-free system. Acidic pH promoted Fe²⁺ release and significantly enhanced degradation, while HCO₃⁻ strongly inhibited the process. Mechanistic studies revealed that sulfate radicals (SO₄^•−) played a dominant role, and Cys served as an electron shuttle that facilitated the Fe³⁺/Fe²⁺ cycle and enhanced Fe⁰ conversion, thereby sustaining PS activation. This study demonstrates that Cys effectively mitigates the limitations of nZVI/PS systems and provides valuable insights for implementing efficient SR-AOPs in treating chlorinated organic contaminants. Full article

The depletion of water resources caused by climate change and human activities is a pressing global issue. Lake Ereen is one of the ten natural landmarks of the Gobi-Altai of western Mongolia is included in the list of “important areas for birds” recognized by the international organization Birdlife. However, the construction of the Taishir Hydroelectric Power Station, aimed at supplying electricity to the western provinces of Mongolia, had a detrimental effect on the flow of the Zavkhan River, resulting in a drying-up and pollution of Lake Ereen, which relies on the river as its water source. This study assesses the pollution levels in Ereen Lake and determines the feasibility of its rehabilitation by redirecting the flow of the Zavkhan River. Field studies included the analysis of water quality, sediment contamination, and the composition of flora. The results show that the concentrations of ammonium, chlorine, fluorine, and sulfate in the lake water exceed the permissible levels set by the Mongolian standard. Analyses of elements from sediments revealed elevated levels of arsenic, chromium, and copper, exceeding international sediment quality guidelines and posing risks to biological organisms. Furthermore, several species of diatoms indicative of polluted water were discovered. Lake Ereen is currently in a eutrophic state and, based on a water quality index (WQI) of 49.4, also in a “polluted” state. Mass balance calculations and box model analysis determined the period of pollutant replacement for two restoration options: drying-up and complete removal of contaminated sediments and plants vs. dilution-flushing without direct interventions in the lake. We recommend the latter being the most efficient, eco-friendly, and cost-effective approach to rehabilitate Lake Ereen. Full article

Iopamidol (IPM), as a typical recalcitrant emerging pollutant and precursor of iodinated disinfection by-products (I-DBPs), is unsuccessfully removed by conventional wastewater treatment processes. This study comprehensively evaluated the ozone/peracetic acid (O₃/PAA) process for IPM degradation, focusing on degradation kinetics, environmental impacts, transformation products, ecotoxicity, disinfection byproducts (DBPs), and microbial inactivation. The O₃/PAA system synergistically activates PAA via O₃ to generate hydroxyl radicals (^•OH) and organic radicals (CH₃COO^• and CH₃CO(O)O^•), achieving an IPM degradation rate constant of 0.10 min⁻¹, which was significantly higher than individual O₃ or PAA treatments. The degradation efficiency of IPM in the O₃/PAA system exhibited a positive correlation with solution pH, achieving a maximum degradation rate constant of 0.23 min⁻¹ under alkaline conditions (pH 9.0). Furthermore, the process demonstrated strong resistance to interference from coexisting anions, maintaining robust IPM removal efficiency in the presence of common aqueous matrix constituents. Furthermore, quenching experiments revealed ^•OH dominated IPM degradation in O₃/PAA system, while the direct oxidation by O₃ and R-O^• played secondary roles. Additionally, based on transformation products (TPs) identification and ECOSAR predictions, the primary degradation pathways were elucidated and the potential ecotoxicity of TPs was systematically assessed. DBPs analysis after chlorination revealed that the O₃/PAA (2.5:3) system achieved the lowest total DBPs concentration (99.88 μg/L), representing a 71.5% reduction compared to PAA alone. Amongst, dichloroacetamide (DCAM) dominated the DBPs profile, comprising > 60% of total species. Furthermore, the O₃/PAA process achieved rapid 5–6 log reductions of E. coli. and S. aureus within 3 min. These results highlight the dual advantages of O₃/PAA in effective disinfection and byproduct control, supporting its application in sustainable wastewater treatment. Full article

This review explores current knowledge on the environmental, oxidative, and genomic effects of sucralose (E955), an artificial sweetener widely used in food products, including those for children, and known to cross both the placental barrier and into breast milk. Although initially considered safe, research conducted over the past two decades has presented conflicting evidence regarding its long-term impact, particularly on ecosystems and biological systems. Structurally similar to chlorinated compounds such as perfluoralkyl substances (PFAS), sucralose is highly persistent in the environment, which complicates its degradation and removal, especially from aquatic systems. Several studies have reported behavioral, metabolic, and even genomic alterations in aquatic organisms exposed to sucralose, raising concerns about its broader ecological safety. In addition, its presence has been linked to shifts in microbiota composition in both environmental and human contexts. Reports of sucralose-induced oxidative stress further highlight the need for caution in its continued use, particularly in sensitive formulations. Given its widespread presence and resistance to degradation, further investigation into the environmental and biological safety of sucralose is urgently needed. Full article

Natural organic matter (NOM) in surface waters is a major challenge for drinking water treatment due to its role in the formation of disinfection byproducts (DBPs) during chlorination. This study evaluated the performance of chitosan, a biodegradable coagulant, dissolved in acetic, lactic, and L-ascorbic acids for NOM removal under three turbidity levels (403, 1220, and 5038 NTU). Jar tests were conducted using raw water from the Río Grande de Añasco (Puerto Rico), and TOC, DOC, and UV₂₅₄ were measured at multiple time points. TOC removal ranged from 39.8% to 74.3%, with the highest performance observed in high-turbidity water treated with chitosan–L-ascorbic acid. DOC and UV₂₅₄ reductions followed similar trends, with maximum removals of 76.4% and 76.2%, respectively. Estimated THM formation potential (THMFP) was reduced by up to 81.6%. Across all acids, flocculation efficiencies exceeded 95%. Compared to conventional aluminum-based coagulants, chitosan demonstrated comparable performance, while offering environmental benefits. These results confirm the potential of chitosan–acid systems for effective organic matter removal and DBP control, supporting their application as sustainable alternatives in drinking water treatment. Full article