Removal Of Organic Pollutants Research Articles

Biomass-based perovskite/graphene oxide composite for the removal of organic pollutants from wastewater

Water pollution is a critical issue that affects both human health and the environment. Biomass-based LaFeO3 is prepared by the microwave-assisted method using rice straw as a cellulose source. Then LaFeO3/graphene oxide (GO) composite is prepared by ultrasonication to facilitate the perovskite-GO binding. Raman and FTIR spectra of the prepared composite identify the presence of the perovskite, biochar, cellulose and GO oxide phases and proves the surface functional groups interactions. Transmission electron microscope image shows that the GO sheets are homogeneous covered with the perovskite nanoparticles. The adsorption performance of the LaFeO3/GO composite for the removal of methylene blue (MB) and congo red (CR) dyes from aqueous solution is optimized. Adsorption follows pseudo 2nd order kinetic model and Freundlich isotherm, with maximum adsorption capacities of 319.5 and 416.7 mg/g for MB and CR, respectively. These values are higher than those reported for magnetic GO composites, indicating the excellent adsorption ability of the proposed perovskite/GO composite. A thermodynamic study shows that the adsorption of MB is exothermic, while it is endothermic for CR and combines physisorption and chemisorption characteristics for both dyes. The proposed adsorbent shows a good performance in the presence of NaCl interferent, with the possibility of regeneration and efficient successive reuse.

Photocatalytic degradation of Rhodamine B dye over oxygen-rich bismuth oxychloride Bi24O31Cl10 photocatalyst under UV and Visible light irradiation: Pathways and mechanism

Photocatalytic removal of organic pollutants from wastewater has recently garnered significant attention due to its environmental and ecological significance. In this study, a bismuth-rich bismuth oxychloride (Bi24O31Cl10) was synthesized using a single-step solid-state reaction and applied as a photocatalyst for the degradation of rhodamine B in aqueous solution. The photocatalyst was prepared through an eco-friendly solid-state method by mixing bismuth oxide (Bi2O3) and bismuth oxychloride (BiOCl), followed by direct annealing at 600 °C. The synthesized material was characterized through various techniques, including X-ray diffraction (XRD), Fourier-transform infrared (FTIR), Raman spectroscopy, scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area analysis, energy dispersive X-ray spectroscopy (EDS), diffuse reflectance, UV–Visible, and photoluminescence (PL) spectroscopies. The electronic structure of the Bi24O31Cl10 bulk material was analyzed using Density Functional Theory (DFT).Rietveld refinement confirmed the formation of a pure monoclinic Bi24O31Cl10 phase with the space group P2/c, and the XRD patterns indicated well-crystallized material. SEM revealed micron-sized crystallites, while BET surface area analysis showed a value of 22.546 m²/g, suggesting that a larger surface area could enhance photocatalytic performance. The band gap of the material was determined to be 2.88 eV, with an absorption edge at 430 nm, indicating a promising response to visible light.The photocatalytic activity of Bi24O31Cl10 was demonstrated by the degradation of rhodamine B (RhB), with complete degradation achieved in 90 min under UV light. Under visible light, 98 % degradation efficiency was reached after 180 min. Kinetic studies showed that the degradation followed a pseudo-first-order model. Optimal conditions for maximum degradation were found at a solution pH of 5, a catalyst concentration of 1 g/L, and a dye concentration of 5 mg/L. Remarkably, the photocatalyst exhibited excellent reusability, maintaining high efficiency over five cycles, with only a slight decrease from 100 % to 90 %.Trapping experiments identified that reactive species such as superoxide radicals (∙O2−) and hydroxyl radicals (∙OH) played key roles in the photocatalytic process. The possible reaction mechanism was proposed, and degradation products were monitored using liquid chromatography-mass spectrometry (LC-MS), allowing for the elucidation of the degradation pathways of RhB. Additionally, the photocatalyst's effectiveness was tested on Methyl Orange (MO) and Methylene Blue (MB), achieving nearly 100 % degradation for MO and 41 % for MB under UV light. This research highlights the significant potential of Bi24O31Cl10 as a photocatalyst for dye degradation in wastewater treatment.

Enhanced degradation performance toward para-nitrophenol of adapted immobilized microbial community on coconut coir

Nitrophenol pollutants, including para-nitrophenol (p-NP), are known for their harmful environmental impact due to their persistence, toxicity, and widespread distribution in water sources. While biodegradation generally offers a more effective removal of organic pollutants compared to chemical or physical methods, degrading persistent and toxic compounds like p-NP remains challenging. In this study, a microbial community derived from food processing wastewater was immobilized on coconut coir and adapted to p-NP before being employed for p-NP biodegradation. The spectroscopic analysis demonstrates the effective biodegradation performance of the adapted microbial community, achieving 99% degradation of 50 mg L⁻1 p-NP in 38 min and 250 mg L⁻1 p-NP in 4.65 h. The degradation ability of immobilized cells was determined across a broad range of stirring speeds, temperatures, pH levels, and p-NP solution volumes. Complete mineralization of p-NP was confirmed by chemical oxygen demand (COD) measurements of the treated solution and in-situ CO2 generation. Notably, the p-NP degradation performance of the adapted immobilized microbial community remained stable for the first 40 days, with only a slight decrease observed after 47 days of cold preservation at 4 °C. An average p-NP degradation rate of 0.75 mg L⁻1 min⁻1 was maintained over 54 consecutive runs. Significant alterations in microbial diversity were identified through 16S metabarcoding analysis. The unadapted microbial community comprised a diverse range of genera, while the adapted community showed reduced diversity with an enrichment of specific genera known for p-NP degradation, such as unidentified members of the Micrococcaceae family, Paenarthrobacter spp., and Zoogloea spp.

A tartaric acid (TA)-coated iron-based biochar as heterogeneous fenton catalyst for enhanced degradation of dibutyl phthalate

Iron-biochar composite is a promising catalyst in Fenton-like system for removal of organic pollutants. Nevertheless, low cycling rate of Fe(III)/Fe(II), high iron leaching and low H2O2 utilization efficiency impedes its application. Herein, a iron-based biochar (C-Fe) coated with tartaric acid (TA) was synthesized. The specific structure of inherent graphitized carbon and TA coating improved the removal efficiency of dibutyl phthalate (DBP) to 93%, promoted 2-fold increase in HO• production in H2O2 activation, improved the cycling rate of Fe(III)/Fe(II), and mitigated Fe leaching significantly. The developed HO• and 1O2 dominated Fenton-like system had an excellent pH universality and anti-interference to inorganic ions and real water matrixes. Moreover, C-Fe-TA has been shown to efficiently degrade DBP by using the dissolved oxygen in water to generate HO•. This work provided a novel insight for sustainable and efficient HO• and 1O2 generation, which motivated the development of new water treatment technology based on efficient iron-biochar catalyst.

Bi2MoO6/ZnIn2S4 S-scheme heterojunction containing oxygen vacancies for photocatalytic degradation of organic pollutant

Photocatalytic removal of organic pollutants is a promising strategy to alleviate environmental pollution. In this study, S-scheme heterojunctions Bi2MoO6/ZnIn2S4 (BMO/ZIS) containing oxygen vacancies were synthesized by the solvothermal method. Oxygen vacancies improved the utilization of sunlight and accelerated the separation of charge carriers. The S-scheme charge transfer mechanism provided a channel for the directed migration of photogenerated charges. 10Bi2MoO6/ZnIn2S4 (10BMO/ZIS) efficiently degraded various organic pollutants with a small amount of photocatalyst (15 mg) under visible light irradiation. 10BMO/ZIS presented the highest RhB removal efficiency of 96.52 %, which was 7.02 and 3.67 times greater than Bi2MoO6 containing oxygen vacancies (BMO-Vo) and ZnIn2S4 (ZIS), respectively. Meanwhile, in various inorganic salt ion solutions, 10BMO/ZIS still exhibited high degradation performance. In addition, the photocatalytic degradation pathway was inferred, and the threat of degradation intermediates to the ecological environment was evaluated. This work contributes to a deeper understanding of the photocatalytic mechanisms of oxygen vacancy-modified heterojunction photocatalysts and offers insights for designing efficient environmental remediation photocatalysts.

Lignocellulosic materials extraction from waste baby diaper to prepare light-responsive metal oxide/carbon composite for efficient organic dye pollutant removal

The bimetal oxide comprising nickel incorporated β-Bi2O3 on graphitic carbon in the form of bismuth nickel oxide (BNO@C) was prepared by waste lignocellulosic materials collected from cheap and readily available baby diapers. The prepared BNO@C was used to photocatalytically degrade methylene blue under UV-light irradiation. Prior to the photocatalytic performance analysis, the formation of BNO@C was confirmed by various morphological and structural analysis including SEM, TEM, XRD, and XPS analyses. As a result, the two-dimensional nanosheet morphology and tetragonal primitive lattice-structure with 2+ and 3+ oxidation stated Ni and Bi in BNO@C structural formulation were confirmed. In photocatalysis experimentation examined with BNO@C, the maximum methylene blue removal percentage of 96.7 % was achieved within 16 min. The influence of Ni2+ in BNO@C was identified by performing the photocatalytic performance of bare NiO@C and Bi2O3@C, yielding maximum dye removal of 32.8 % and 64.5 %, respectively. The efficacy of Ni in BNO@C toward increasing catalytic efficiency was identified using DFT analysis, revealing the acting of Ni as active sites for improved light absorption tendency. These findings show a novel strategy to prepare a low-cost BNO@C catalyst with efficient photocatalytic activity, opening a new path for a cost-efficient wastewater treatment approach.

Adsorption, photocatalysis, and sonocatalytic activities of LaFeO3/methylcellulose/multi-walled carbon nanotubes-NiCu2O4/Zn for removal of organic pollutant: preparation, main factor, and mechanism

The primary objective of this study was to create and analyze a new type of LaFeO3/methylcellulose/multi-walled carbon nanotubes-NiCu2O4/Zn nanocomposite, called LFO/MC/MWCNT-NCO/Z, which has multiple functions. Structural investigation using field emission scanning electron microscopy showed that the nanoparticles (40–50 nm) were evenly distributed throughout the nanocomposite, suggesting that they were successfully incorporated without any clumping. FTIR research verified the existence of functional groups that facilitate electrostatic interactions with contaminants, hence strengthening catalytic performance and improving adsorption efficiency. The BET analysis revealed a significantly high specific surface area of 72.61 m2/g, which greatly enhances its ability to adsorb substances. The nanocomposite demonstrated high removal efficiency in adsorption (74.55%), photocatalysis (68.19%), and sonocatalysis (91.22%) procedures, highlighting its potential for effectively removing bisphenol A as organic pollutants. The synthesized LFO/MC/MWCNT-NCO/Z nanocomposite shows great potential in effectively eliminating organic contaminants from water solutions. This offers a sustainable way to address water pollution and protect human health and the environment.

Green synthesis of Z-scheme N-doped g-C3N4/Nd-doped ZnO heterostructure by pomegranate waste peel with enhanced photocatalytic performance for organic pollutants removal and antibacterial activity

Nowadays, the growing global population and increased industrialization have exacerbated water pollution, posing a significant environmental threat. To tackle this issue, there is an urgent need for effective catalysts to remove pollutants. This study developed a novel N-doped g-C3N4/Nd-doped ZnO (NZ) heterostructure using a green approach by incorporating pomegranate peel waste as a stabilizing and capping agent. Characterization techniques confirmed successful NZ nanohybrid preparation. The synthesized NZ displayed high photocatalytic activity in degrading methylene blue (MB) and tetracycline (TC) pollutants found in wastewater, achieving degradation efficiencies of 95.3 % and 98.3 %, respectively. Meanwhile, it demonstrated satisfactory photostability after five-cycle experiments. The radical trapping experiments revealed that superoxide (O2−) and hydroxyl (OH) are the dominant active species and play an essential role in photocatalytic pollutant deterioration. Additionally, it exhibited suitable antimicrobial activity against Staphylococcus aureus and Vibrio cholerae bacterial strains. The enhanced performance is attributed to the abundant reaction sites of porous N-doped g-C3N4, the photo-redox capability of Nd-doped ZnO, and the efficient charge separation process in the Z-type heterojunction. This work advances sustainable and eco-friendly chemistry for the biosynthesis of organic/inorganic heterojunctions used in pollutant degradation and bacterial disinfection of wastewater.

Magnetic Hydrogel Microbots for Efficient Pollutant Decontamination and Self-Catalyzed Regeneration in Continuous Flow Systems.

The efficient removal of organic pollutants from water is crucial for protecting human health and the ecosystem. While adsorbent-based approaches offer advantages over traditional chemical and thermal methods, they still suffer from slow adsorption kinetics, high energy demand, and limited material lifespan. Herein, an efficient decontamination platform is introduced, using magnetic hydrogel microbots (MHMs) made from picolitre-sized hydrogel droplets coated with multifunctional magnetic nanoparticles. This approach includes 1) dividing a droplet into smaller microbots to enhance their interaction with sample solution and 2) dynamically spinning these MHMs to generate hydrodynamic flows that actively draw pollutants toward the embedded hydrogel for capture. The MHMs show high decontamination effectiveness in both bulk and continuous flow setups, achieving ≈95% removal efficiency within 3min. Further integrating MHMs with a non-pressurized fluidic platform enables energy-efficient continuous flow decontamination, removing ≥95% total organic carbon from a complex pollutant mixture at a flow rate surpassing other recent designs. Additionally, the MHMs facilitate self-catalyzed regeneration using an environmentally friendly H2O2 precursor, allowing for long-term and repeated usage. By enabling the unique divide-and-arrest decontamination of toxic pollutants, the multifunctional design holds tremendous promise for on-site wastewater treatment to ensure safe water access for everyone, even in resource-limited environments.

A high-flux, photocatalytic wood-derived filter for high-efficiency water purification

Wastewater purification has evolved into a global problem in the face of increasing scarcity of freshwater resources. Photocatalysis technology possesses prominent advantages in treating pollutants in water because of its low cost and mild reaction conditions, which provides an effective way to treat multiple pollutants and reduce membrane fouling. Herein, we combine photocatalysis technology with filtration technology via in situ reduction Bi0 with Bi2SiO5 strategy incorporating a carbonized wood filter to synthesize carbon/Bi2SiO5@Bi bi-functional composite. Thus, simultaneous filtration and photocatalytic degradation of Rhodamine B and tetracycline were achieved. After filtrating for 30 min, the degradation rate of RhB and TC were 94.23 % and 81.39 %, respectively. Especially, the flux of RhB and TC were up to 2162.16 L m−2 h−1 and 1811.32 L m−2 h−1. In addition, the composite filter also has good recyclability and reusability, after 5 cycles, the degradation efficiency of RhB remains at 91 %. This study utilized photocatalytic technology combined with membrane filtration technology to successfully solve the contradiction between catalytic efficiency and water flux, which realized rapid and dynamic removal of organic pollutants from water. Besides, the use of carbonized wood-based materials provides a potential biomass technology for the preparation of bifunctional photocatalytic filters.

Composite of Organo-LDH and biochar for diclofenac sodium removal from aqueous solutions

Classic layered double hydroxides (LDHs) and their composites with biochar are promising adsorbents for removing emerging contaminants like diclofenac sodium (DFS) from water. However, the use of organo-LDHs in these composites remains unexplored and could enhance their adsorption properties for organic molecules. This study investigates the synthesis, characterization, and application of an organo-LDH based on sodium dodecyl sulfate as intercalating agent (SDS-LDH) and its composite with tangerine peel biochar (SDS-LDH/BC) for the removal of DFS from water. The adsorption performance of these materials was compared with those of a composite of SDS-LDH and tangerine peel biomass (SDS-LDH/Bio) and the layered double oxides (LDOs) obtained from the pyrolysis of SDS-LDH and SDS-LDH/Bio, referred to as SDS-LDO and SDS-LDO/Bio, respectively. The materials were characterized by FTIR, XRD, SEM, TG, and pH point of zero charge analyses, and the adsorption of DFS was evaluated in aqueous medium under different conditions. XRD and FTIR demonstrated the successful incorporation of sodium dodecyl sulfate into the interlamellar space of the SDS-LDH, which was preserved in the SDS-LDH/BC and SDS-LDH/Bio composites. SEM analysis revealed that the SDS-LDH structures, with varied shapes and sizes, were dispersed on the matrix of the biochar, while TG analysis showed that the SDS-LDH/BC had similar thermal stability to SDS-LDH. SDS-LDH achieved 90 % DFS removal at pH 8.0 and 25 °C, while SDS-LDH/BC reached 81 % removal under the same conditions, with maximum DFS adsorption capacities of 247 and 169 mg g−1, respectively, outperforming pristine biochar (no removal). Under the same conditions, SDS-LDH/Bio, SDS-LDO/Bio, and SDS-LDO removed 55 %, 36 %, and 36 % of DFS, respectively. These results revealed the pivotal role of the interlamellar structure of SDS-LDH in DFS adsorption, as confirmed by XRD and FTIR, which indicated that DFS interacted with dodecyl sulfate anion in the SDS-LDH interlamellar space, specially through hydrophobic interaction. Kinetics studies revealed that DFS adsorption on SDS-LDH/BC followed the pseudo-first-order model, while adsorption on SDS-LDH followed the pseudo-second-order model, with equilibrium reached in approximately 30 min. The Redlich-Peterson model satisfactorily fitted the adsorption equilibrium isotherms for both SDS-LDH and SDS-LDH/BC. Although no synergistic effect was observed between biochar and SDS-LDH/BC regarding the adsorption capacity, the formation of the SDS-LDH/BC composite improved the preservation of the SDS-LDH structures, allowing for a lower loss of adsorption capacity upon reuse. These findings suggest that the study of such advanced material can contribute to the development of more effective biochar-LDH composite-based adsorbents, specifically for the removal of organic pollutants.

Long-lasting organics removal via •OH adsorbed transition metal flocs: Electron transfer-mediated H-bond and van der Waals force

Homogenous advanced oxidation processes (AOPs) based on transition metal catalysts toward the activation of H2O2 to hydroxyl radical (•OH) have been widely applied to organic pollutants removal, such as Fenton and Fenton-like processes. These transition metal catalysts mostly flocculate as the pH increases. It's worth noting that the formed transition metal flocs are complex heterogeneous aggregations with active substances, providing diverse reaction spaces and interfaces. However, it is a challenge to distinguish the roles of transition metal flocs in the organic pollutants removal from homogeneous catalytic reactions. Herein, we unveiled a pathway for the long-lasting removal of organic pollutants via Cr flocs adsorbed with •OH (HO•-Cr flocs) using a stepwise method. First, adsorbed •OH (•OHads) within the HO•-Cr flocs was proved to be the active site forming hydrogen bond (H-bond) and van der Waals force with organic pollutants. Then, the presence of switchable electron transfer between Cr and OH groups within the HO•-Cr flocs was revealed, contributing to the persistent existence of •OHads and consequently ensuring the long-lasting organics removal. Further, this removal pathway of organic pollutants was confirmed during the leather wastewater treatment. These findings will complement a different pathway for organic pollutants removal via transition metal flocs and extend the lifetime of homogeneous AOPs based on transition metal catalysts, providing significant implications for their design and optimization.

Mechanically robust and anisotropic hydrogel composites for high efficiency steam generation

Solar-driven interfacial evaporation (SDIE) has now become a promising desalination technique to harvest fresh water, and challenges remain to develop high performance solar evaporators that can achieve high performance SDIE while at the same time maintain good mechanical properties. In this work, anisotropic Polydopamine (PDA)/polyvinyl alcohol (PVA)@acidified carbon nanotubes (ACNTs) hydrogels (PPCHs) are prepared for SDIE and dye adsorption. The introduction of PDA and ANCTs improves the overall mechanical properties of the hydrogels and also imparts the hydrogel abundant active adsorption sites. PPCHs possess hierarchically vertical channels and hence powerful water transport capability. The PPCH evaporator with reduced water enthalpy exhibits high evaporation rate and efficiency, up to 3.43 kg m−2 h−1 and 91.6 % even during the long-term evaporation, respectively. In addition, PPCH can also work stably in harsh conditions such as high concentration brine, emulsions, acid and alkali solutions, etc. Due to the electrostatic interaction, PPCHs can effectively adsorb methylene blue (MB) in wastewater. PPCHs show broad application prospects in the field of solar desalination and dye adsorption. This study provides a rational structure design of the hydrogel composites for simultaneous SDIE and organic pollutant removal.

Removing multiple refractory organic pollutants in wastewater by cell bioaugmentation and genetic bioaugmentation with Rhodococcus sp. strain p52

Bioaugmentation is an appealing remediation strategy to treat refractory organic pollutants in contaminated environments. In this study, activated sludge was bioaugmented with Rhodococcus sp. strain p52 to treat synthetic wastewater containing multiple refractory organic pollutants (dibenzofuran, dibenzo-p-dioxin, and phenanthrene). Bioaugmentation of activated sludge reactors with strain p52 alleviated the adverse effects of refractory pollutants on the chemical oxygen demand and ammonia nitrogen removal capacity of the reactors and enhanced the removal of the refractory organic pollutants, especially highly refractory compound dibenzo-p-dioxin. Toxicity of the refractory pollutants to activated sludge bacteria was attenuated due to contaminant degradation by strain p52. Genetic bioaugmentation mediated by catabolic plasmid transfer from strain p52 to activated sludge bacteria and cell bioaugmentation occurred along with successful colonization and proliferation of strain p52. In addition, a potential metabolically mutualistic relationship existed between strain p52 and activated sludge bacteria for refractory pollutants degradation. Both refractory organic pollutants input and strain p52 bioaugmentation profoundly influenced the structure of the activated sludge bacterial community and drove bacterial community shifts in different directions. This study provides insights into the activities of bioaugmented bacteria and bioaugmentation technology for environmental contaminant remediation.

Immobilization of MnO2 nanoflowers on coils using direct heating method for organic pollutant remediation

The immobilization of catalysts on supporting substrates for the removal of organic pollutants is a crucial strategy for mitigating catalyst loss during wastewater treatment. This study presented a rapid and cost-effective direct heating method for synthesizing MnO2 nanoflowers on coil substrates for the removal of organic pollutants. Traditional methods often require high power, expensive equipment, and long synthesis times. In contrast, the direct heating approach successfully synthesized MnO2 nanoflowers in just 10 min with a heating power of approximately 40 W·h after the heating power and duration were optimized. These nanoflowers effectively degraded 99% Rhodamine B in 60 min with consistent repeatability. The catalytic mechanisms are attributed to crystal defects in MnO2, which generate electrons to produce H2O2. Mn2+ ions in the acidic solution further dissociate H2O2 molecules into hydroxyl radicals (·OH). The high efficiency of this synthesis method and the excellent reusability of MnO2 nanoflowers highlight their potential as a promising solution for the development of supporting MnO2 catalysts for organic dye removal applications.

Ti3C2TX MXene/loofah-derived carbon aerogel for high-efficiency adsorption of organic pollutants in wastewater

The contamination of wastewater by organic pollutants significantly impacts human health and the environment due to their carcinogenic nature and various adverse effects. To address this issue, this study offers a high-efficiency and low-cost biomass-based carbon aerogel adsorbent, which was prepared through the hydrothermal carbonization of loofah, followed by Ti3C2TX MXene impregnation. The aerogel features a porous three-dimensional network structure and a substantial specific surface area, facilitating broad-spectrum adsorption capabilities for various dyes and drugs. The aerogel achieved impressive adsorption capacities of 175.29 and 75.73 mg/g for cationic methylene blue and Rhodamine B dyes, and 106.33 and 93.29 mg/g for anionic methyl orange and Congo red dyes, as well as 86.25 mg/g for tetracycline hydrochloride, surpassing other reported biomass-based aerogels. Furthermore, it demonstrated effective decolorization ability for wastewater containing mixed dyes. Notably, it exhibited excellent recycling and regeneration properties, maintaining a high removal rate after multiple cycles of adsorption–desorption. The adsorption process of dye/drug by the aerogel followed Langmuir’s monomolecular layer adsorption model, exhibiting spontaneous, endothermic, and disorder-increasing behavior in alignment with the pseudo-second-order kinetic model. This study presents an efficient biomass-based aerogel for the removal of organic pollutants from wastewater.

Electro-Fenton enhanced MBR for fouling alleviation based on MIL-88B-Fe derived carbon membrane with in-situ generated [rad]OH

Porous carbon membrane (PCM) derived from MIL-88B-Fe with the ability of in-situ generation of hydroxyl radical was introduced to electro-enhanced aerobic membrane bioreactor (EMBR) for membrane fouling mitigation and wastewater quality improvement. The resultant PCM obtained with the calcination temperature of 1000 °C owned significant enhancement on hydrophilic and conductive properties, which helped PCM under −1.2 V could completely remove 10 mg/L bovine serum albumin with 2.5 % membrane flux loss rate. During the 76-day operation of EMBR, the extracellular polymeric substances could be suppressed for depositing on the −1.2 V enhanced PCM due to the combined effect of electrostatic barrier and OH oxidation. The pollutant intensity of total cells, polysaccharides and proteins were all reduced on PCM with −1.2 V. After operation, 36.0 % of cake layer pores was blocked in EMBR by total cells, polysaccharides and proteins. However, it was accounted for 69.8 % of the control group. Above results explained why the EMBR owned an always lower transmembrane pressure. Meanwhile, the pollutants removal rates of COD and NH4+-N were as high as 95 % and 98 % with electro-enhanced filtration, respectively, which is attributed to the collaborated effect from electrochemical effect and significantly increased microbial species related to organic pollutants removal, such as Azohydromonas, Thermomonas.

Machine learning models for predicting the rejection of organic pollutants by forward osmosis and reverse osmosis membranes and unveiling the rejection mechanisms

While forward osmosis (FO) and reverse osmosis (RO) processes have been proven effective in rejecting organic pollutants, the rejection rate is highly dependent on compound and membrane characteristics, as well as operating conditions. This study aims to establish machine learning (ML) models for predicting the rejection of organic pollutants by FO and RO and providing insights into the underlying rejection mechanisms. Among the 14 ML models established, the random forest model (R2 = 0.85) and extreme gradient boosting model (R2 = 0.92) emerged as the best-performing models for FO and RO, respectively. Shapley additive explanations (SHAP) analysis identified the length of the compound, water flux, and hydrophobicity as the top three variables contributing to the FO model. For RO, in addition to the length of the compound and operating pressure, advanced variables including four molecular descriptors (e.g., ATSC2m and Balaban J) and three fingerprints (e.g., C=C double bond and carbonyl group) significantly contributed to the prediction. Besides, the associations between these highly ranked variables and their SHAP values shed light on the rejection mechanisms, such as size exclusion, adsorption, hydrophobic interaction, and electrostatic interaction, and illustrate the role of the operating parameters, such as the FO permeate water flux and RO operating pressure, in the rejection process. These findings provide interpretable predictive models for the removal of organic pollutants and advance the mechanistic understanding of the rejection mechanisms in the FO and RO processes.

Dielectric barrier discharge plasma for chlorobenzene removal: Performance optimization, process modeling, and toxicity evaluation

Bio-purification has been recognized as an effective method of removal of volatile organic pollutants (VOCs), yet exist a technical bottleneck of low removal efficiency in the treatment of high toxicity and low water-soluble VOCs, especially chlorobenzene (CB). Herein, dielectric barrier discharge (DBD) technology was used as a pre-treatment technology, and the effect of process parameters (specific input of energy (SIE), inlet concentration of CB, humidity, and discharge length) of DBD on the removal performance of CB was analyzed, in order to investigate the feasibility of DBD as a pre-treatment approach for bio-purification. Taking energy yield, by-product analysis and exhaust evaluation as considerations, an SIE of 1,131.57 J·L-1, an inlet CB concentration of 300 ppm, a humidity of 50 %, and a discharge length of 10 cm were selected as the most suitable experimental conditions for the air DBD reactor. The temperature of gas flow was analyzed. Results suggested that DBD have no adverse thermal effect on the subsequent biotechnology (decreased by about 8 K during the discharge process). The temperature change caused by the degradation of CB (e.g., phenyl ring-opening and other processes) accounts for about 90 % of the total temperature change, where remaining part of temperature decreased caused by the large number of active substances produced by electron excitation, collision and cracking during discharge. The regulation of short-life active substances (e.g., ·NO, ·NO2,·OH, and O2–·) further reduced the toxicity of the outlet gas generated by DBD through affect the contents the long-life active substances (e.g., H2O2, and O3). This study provides a better understanding of the feasibility of DBD as a treatment for bio-purification and a new coupling technology for the effective removal of CB.

Impact of metal doping and non metal loading on the photocatalytic degradation of organic pollutants using tin dioxide catalyst under sunlight irradiation

The goal of this study is to prepare nickel (Ni) doped tin dioxide-loaded activated carbon composite as a catalyst for the removal of dye. Tin dioxide with various (0.050, 0.075, and 0.10 M) Ni doping concentrations and Ni: SnO2/CCAC (corn cob activated carbon) composite was synthesized by the chemical precipitation method and labeled as NS1, NS2, NS3, and NS3/CCAC. XRD spectra revealed that the particle size in NS3/CCAC decreased (12.81 nm) as the NS3 and CCAC content. The absorption spectra reveal that the band gap in NS3/CCAC was reduced (3.50 eV) by the Ni-doping and CCAC-loading. We also used photodegradation of methylene blue (MB) in the presence of sunshine to examine the photocatalytic performance of the NS3/CCAC composite. The NS3/CCAC composite exhibited higher photocatalytic efficiency in comparison to the other samples. The high photodegradation performance (92.30 %) of the composite sample was due to its less average crystallite size, which increased the specific surface area (306.01 m2/g), decreased band gap, and reduced the electron–hole recombination rate resulting in improved photocatalytic efficiency. The findings reported here could benefit the NS3/CCAC photocatalysts for the removal of organic pollutants.