Insights into the synergetic mechanism of a combined vis-RGO/TiO2/peroxodisulfate system for the degradation of PPCPs: Kinetics, environmental factors and products

Oxidation effects on Microcystis aeruginosa inactivation through various reactive oxygen species: Degradation efficiency, mechanisms, and physiological properties

The study investigated the inactivation of Microcystis aeruginosa using a combined approach involving thermally activated peroxyacetic acid (Heat/PAA) and thermally activated persulfate (Heat/PDS). The Heat/PDS algal inactivation process conforms to first-order reaction kinetics. Both hydroxyl radical (•OH) and sulfate radical (SO4-•) significantly impact the disruption of cell integrity, with SO4-• assuming a predominant role. PAA appears to activate organic radicals (RO•), hydroxyl (•OH), and a minimal amount of singlet oxygen (1O2). A thorough analysis underscores persulfate's superior ability to disrupt algal cell membranes. Additionally, SO4-• can convert small-molecule proteins into aromatic hydrocarbons, accelerating cell lysis. PAA can accelerate cell death by diffusing into the cell membrane and triggering advanced oxidative reactions within the cell. This study validates the effectiveness of the thermally activated persulfate process and the thermally activated peroxyacetic acid as strategies for algae inactivation.

Using UV/peracetic acid as pretreatment for subsequent bio-treatment of antibiotic-containing wastewater treatment: Mitigating microbial inhibition and antibiotic resistance genes proliferation

UV/peracetic acid (PAA) treatment presents a promising approach for antibiotic removal, but its effects on microbial community and proliferation of antibiotic resistance genes (ARGs) during the subsequent bio-treatment remain unclear. Thus, we evaluated the effects of the UV/PAA on tetracycline (TTC) degradation, followed by introduction of the treated wastewater into the bio-treatment system to monitor changes in ARG expression and biodegradability. Results demonstrated effective TTC elimination by the UV/PAA system, with carbon-centered radicals playing a significant role. Crucially, the UV/PAA system not only eliminated antibacterial activity but also inhibited potential ARG host growth, thereby minimizing the emergence and dissemination of ARGs during subsequent bio-treatment. Additionally, the UV/PAA system efficiently removed multi-antibiotic resistant bacteria and ARGs from the bio-treatment effluent, preventing ARGs from being released into the environment. Hence, we propose a multi-barrier strategy for treating antibiotic-containing wastewater, integrating UV/PAA pre-treatment and post-disinfection with bio-treatment. The inhibition of ARGs transmission by the integrated system was verified through actual soil testing, confirming its effectiveness in preventing ARGs dissemination in the surrounding natural ecosystem. Overall, the UV/PAA treatment system offers a promising solution for tackling ARGs challenges by controlling ARGs proliferation at the source and minimizing their release at the end of the treatment process.

Mechanochemical Degradation of Caffeine and Diclofenac Using Biochar of Fique Bagasse in the Presence of Al: Monitoring by Mass Spectrometry

Much research has been carried out to remove emerging contaminants using diverse materials. Furthermore, studies related to pollutant degradation have increased over the past decade. Mechanochemical degradation can successfully decompose molecules that are persistent in the environment. In this study, the biochar of fique bagasse with mixtures SiO2, Al, Al2O3, and Al-Al2O3 was treated with a mechanochemical technique using a planetary ball mill to investigate the degradation of caffeine and diclofenac. These tests resulted in the transformation of caffeine and diclofenac due to the use of Al employing mechanochemistry. In fact, through the use of liquid chromatography coupled with mass spectrometry, eight and six subproducts were identified for caffeine and diclofenac, respectively. Additionally, analysis of the molecules proposed for caffeine and diclofenac transformation suggested hydroxylation, demethylation, decarboxylation, oxidation reactions, and cleavage of the C-C and C-N bonds in the pollutants studied. The formation of these transformation products could be possible by reductant oxygen species generated from the molecular oxygen in the presence of aluminum and the energy delivered for ball milling. The results obtained show the potential application in the environmental management of mechanochemical treatment in the elimination of emerging contaminants caffeine and diclofenac.

Attenuation effects of ZVI/PDS pretreatment on propagation of antibiotic resistance genes in bioreactors: Driven by antibiotic residues and sulfate assimilation

Sulfate radical-based advanced oxidation processes (AOPs) combined biological system was a promising technology for treating antibiotic wastewater. However, how pretreatment influence antibiotic resistance genes (ARGs) propagation remains largely elusive, especially the produced by-products (antibiotic residues and sulfate) are often ignored. Herein, we investigated the effects of zero valent iron/persulfate pretreatment on ARGs in bioreactors treating sulfadiazine wastewater. Results showed absolute and relative abundance of ARGs reduced by 59.8%- 81.9% and 9.1%- 52.9% after pretreatments. The effect of 90-min pretreatment was better than that of the 30-min. The ARGs reduction was due to decreased antibiotic residues and stimulated sulfate assimilation. Reduced antibiotic residues was a major factor in ARGs attenuation, which could suppress oxidative stress, inhibit mobile genetic elements emergence and resistant strains proliferation. The presence of sulfate in influent supplemented microbial sulfur sources and facilitated the in-situ synthesis of antioxidant cysteine through sulfate assimilation, which drove ARGs attenuation by alleviating oxidative stress. This is the first detailed analysis about the regulatory mechanism of how sulfate radical-based AOPs mediate in ARGs attenuation, which is expected to provide theoretical basis for solving concerns about by-products and developing practical methods to hinder ARGs propagation.

Thin-wall hollow porous cystic-like graphitic carbon nitride with awakened n→π* electronic transitions and exceptional structural features for superior photocatalytic degradation of sulfamethoxazole

Effective photoexcitation and carrier migration are the essential aspects to strengthen semiconductor-engaged redox reaction. Herein, a three-dimensional thin-wall hollow porous cystic-like g-C₃N₄ (HPCN) with curved layer edge was successfully fabricated via a non-template thermal-condensation strategy. The construction of unique distorted structure can evoke the hard-to-activate n→π* electronic transition to some extent, broadening the absorption spectrum to 800 nm. And benefiting from the multiple reflections of incident light, the effective photoactivation can be further achieved. Moreover, the thin-wall porous framework can shorten the diffusion distance and accelerate migration of photogenerated charge, favouring interfacial redox reactions. The optimized HPCN_1.0 demonstrated an excellent photocatalytic degradation of SMX under blue-LED light irradiation, which was dramatically superior to that of pristine g-C₃N₄ (CN, 11.4 times). Ultimately, in consideration of reactions under several influencing factors with four different water samples, we demonstrated that the HPCN photocatalyst could be utilized far more productively for the elimination of SMX under real-world aqueous conditions. This work provides a straightforward approach for the removal of SMX and has immense potential to contribute to global scale environmental remediation.

AuAg Nanoparticles Grafted on TiO2@N-Doped Porous Carbon: Improved Depletion of Ciprofloxacin under Visible Light through Plasmonic Photocatalysis

TiO2 nanoparticles (NPs) were modified to obtain photocatalysts with different composition sophistication and displaying improved visible light activity. All of them were evaluated in the photodegradation of ciprofloxacin. The band gap of TiO2 NPs was successfully tailored by the formation of an N-doped porous carbon (NPC)-TiO2 nanohybrid through the pyrolysis of melamine at 600 °C, leading to a slight red-shift of the absorption band edge for nanohybrid NPC-TiO2 1. In addition, the in-situ formation and grafting of plasmonic AuAg NPs at the surface of NPC sheets and in close contact with TiO2 NPs leads to AuAg-NPC-TiO2 nanohybrids 2−3. These nanohybrids showed superior photocatalytic performance for the degradation of ciprofloxacin under visible light irradiation, compared to pristine P25 TiO2 NPs or to AuAg-PVP-TiO2 nanohybrid 4 in which polyvinylpyrrolidone stabilized AuAg NPs were directly grafted to TiO2 NPs. The materials were characterized by transmission electron microscope (TEM), High Angle Annular Dark Field—Scanning Transmission Electron Microscopy—Energy Dispersive X-ray Spectroscopy HAADF-STEM-EDS, X-ray photoelectron spectroscopy and solid UV-vis spectroscopy. Moreover, the active species involved in the photodegradation of ciprofloxacin using AuAg-NCS-TiO2 nanohybrids were evaluated by trapping experiments to propose a mechanism for the degradation.

Degradation of diclofenac via sequential reduction-oxidation by Ru/Fe modified biocathode dual-chamber bioelectrochemical system: Performance, pathways and degradation mechanisms

A sequential reduction-oxidation for DCF degradation was proposed by alternating anaerobic/aerobic conditions at Ru/Fe-biocathode in a dual-chamber bioelectrochemical system (BES). Results showed that Ru/Fe-electrode was successfully fabricated by in-situ electro-deposition, which was rough and uniformly distributed with Ru⁰ and Fe⁰ particles. The morphologic changing and biocompatibility were favorable to increase the surface area and enhance microbial adhesion on Ru/Fe-electrode. At an applied voltage of 0.6 V, the potential and impedance of Ru/Fe-biocathode were -0.80 V and 26 Ω, respectively, lower than that of carbon-felt-biocathode. It led to a higher DCF degradation efficiency of 93.2% under anaerobic conditions, which was superior to that of 88.0% under aerobic conditions. Using NaHCO₃ as carbon source, DCF removal efficiency increased with increasing applied voltage, but decreased with increasing initial DCF concentration. Thirteen intermediates were measured, and two degradation pathways were proposed, among which sequential reduction-oxidation of DCF was the main pathway, dechlorination intermediates were first generated by [H] attacked under anaerobic conditions, further oxidized by microbes and OH attacked under aerobic conditions, achieving 69.6% of mineralization. After 4 d of reaction, microcystis aeruginosa growth inhibition rate decreased from 22.9 to 8.0%, signifying a significant reduction in biotoxicity. Bacteria (e.g. Nitrobacter, Nitrosomonas, Pseudofulvimonas, Aquamicrobium, Sulfurvermis, Lentimicrobiaceae, Anaerobineaceae, Bacteroidales, Hydrogenedensaceae, Dethiosulfatibacter and Azoarcus) for DCF degradation were enriched in Ru/Fe-biocathode. Microbes in Ru/Fe-biocathode had established defense mechanisms to acclimate to the unfriendly environment, while Ru/Fe-biocathode possessed higher nitrification and denitrification activities than carbon-felt-biocathode, and Ru/Fe-biocathode might be of aerobic and anaerobic biodegradation activities. DCF could be mineralized by the synergistic reaction between Ru/Fe and bacteria under sequential anaerobic/aerobic conditions.

Using Fe-Cu/HGF composite cathodes for the degradation of Diuron by electro-activated peroxydisulfate

An iron-copper graphite felt (Fe-Cu/HGF) electrode was successfully prepared by heat treatment and impregnation of graphite felt as the support followed by calcination, and an electro-activated peroxydisulfate (E-PDS) system with Fe-Cu/HGF as the cathode was constructed to degrade Diuron. This system synergistically activated PDS through electrochemical processes and transition metal catalysis. High-valence metal ions could be converted into low-valence metal ions by reduction at the cathode, and low-valence metal ions continuously activated PDS to generate more sulfate radicals (SO₄^-) and hydroxyl radicals (OH) to accelerate Diuron degradation. The Fe-Cu/HGF composite cathode exhibited a performance superior to graphite felt (RGF) obtained using pretreatment only, including increased hydrophilicity, significantly increased number of defect sites and larger electroactive surface area. Under optimized experimental degradation conditions, Diuron could be completely removed in 35 min, at which time copper ion leaching was not detected in the solution, while the total iron ion concentration was 0.27 mg L^-1. Extending the reaction time to 6 h, the amount of total organic carbon was reduced to 32.2%. In addition, the free radicals that degraded Diuron were identified as mainly SO₄^- and OH with a slightly higher contribution of SO₄^-. The mechanism and pathways of Diuron degradation in the E-PDS system were determined. The E-PDS system was successfully applied to the degradation of other pollutants and the degradation of Diuron in different simulated water environments. In summary, the E-PDS system using Fe-Cu/HGF as the cathode is a promising treatment method for Diuron-containing wastewater.

Hydroxyl regulating effect on surface structure of BiOBr photocatalyst toward high-efficiency degradation performance

Herein, photocatalytic degradation of levofloxacin hydrochloride (LVF) by a simple surface hydroxyl strategy on BiOBr photocatalyst was studied under simulated visible light irradiation. Interestingly, the BiOBr contained abundant hydroxyl groups following its modification with glucose, which enhanced the photocatalytic degradation of levofloxacin hydrochloride (LVF). The degradation efficiency of LVF over the optimized composite of BiOBr-5 could reach 91.67% in 20 min, which was much higher than that of pristine BiOBr (59.26%). Following, the biotoxicity of antibiotics to Escherichia coli DH5a could be eliminated after LVF photocatalytic degradation. This strategy proposed in this work can provide new ideas for tuning the surface structures of photocatalysts via specific functional groups for the highly efficient degradation and efficient removal of antibiotics in wastewater.

Filter-membrane treatment of flowing antibiotic-containing wastewater through peroxydisulfate-coupled photocatalysis to reduce resistance gene and microbial inhibition during biological treatment

The direct biological treatment of antibiotics containing wastewater brings about a potential risk of antibiotic resistance genes (ARGs) spread. Although advanced oxidation technologies based on photocatalysis generally appear effective at degrading antibiotics in wastewater, the fate of ARGs in succeeding biological treatment system is still unknown. Herein, a filter-membrane-like carbon cloth-immobilized Fe₂O₃/g-C₃N₄ photocatalyst is fabricated through immersion-calcination method. Peroxydisulfate-coupled photocatalysis system is developed to degrade tetracycline (TC, an emerging refractory antibiotic pollutant). The system can produce energetic active species (·OH, SO₄^·-, h⁺, O₂^·- and ¹O₂), exhibiting a superior performance towards TC degradation in static and continuous flow processes under visible-light irradiation. The pretreatment can eliminate the antibacterial activity of antibiotics wastewater, and the chemical oxygen demand removal is greatly enhanced in subsequent anaerobic or aerobic process. The microbial diversity and richness in activated sludge for pretreated water sample are significantly higher than those for the water sample without pretreatment. Meanwhile, the pretreatment can decrease the relative abundance of potential hosts of ARGs and reduce the emergence as well as dissemination risk of ARGs. This study uncovers the effect of pretreatment of antibiotics containing wastewater using advanced oxidation technologies on the treatment efficacy and antibiotic resistome fate in biological treatment system.

Modern Carbon-Based Materials for Adsorptive Removal of Organic and Inorganic Pollutants from Water and Wastewater

Currently, a serious threat for living organisms and human life in particular, is water contamination with persistent organic and inorganic pollutants. To date, several techniques have been adopted to remove/treat organics and toxic contaminants. Adsorption is one of the most effective and economical methods for this purpose. Generally, porous materials are considered as appropriate adsorbents for water purification. Conventional adsorbents such as activated carbons have a limited possibility of surface modification (texture and functionality), and their adsorption capacity is difficult to control. Therefore, despite the significant progress achieved in the development of the systems for water remediation, there is still a need for novel adsorptive materials with tunable functional characteristics. This review addresses the new trends in the development of new adsorbent materials. Herein, modern carbon-based materials, such as graphene, oxidized carbon, carbon nanotubes, biomass-derived carbonaceous matrices-biochars as well as their composites with metal-organic frameworks (MOFs) and MOF-derived highly-ordered carbons are considered as advanced adsorbents for removal of hazardous organics from drinking water, process water, and leachate. The review is focused on the preparation and modification of these next-generation carbon-based adsorbents and analysis of their adsorption performance including possible adsorption mechanisms. Simultaneously, some weak points of modern carbon-based adsorbents are analyzed as well as the routes to conquer them. For instance, for removal of large quantities of pollutants, the combination of adsorption and other methods, like sedimentation may be recommended. A number of efficient strategies for further enhancing the adsorption performance of the carbon-based adsorbents, in particular, integrating approaches and further rational functionalization, including composing these adsorbents (of two or even three types) can be recommended. The cost reduction and efficient regeneration must also be in the focus of future research endeavors. The targeted optimization of the discussed carbon-based adsorbents associated with detailed studies of the adsorption process, especially, for multicomponent adsorbate solution, will pave a bright avenue for efficient water remediation.

Simultaneous mineralization of 2-anilinophenylacetate and denitrification by Ru/Fe modified biocathode double-chamber microbial fuel cell

A double-chamber microbial fuel cell (MFC) with Ru/Fe-modified-biocathode was constructed for simultaneous mineralization of 2-anilinophenylacetate (APA) and denitrification. The factors on performance of simultaneous APA degradation and denitrification were explored. The contributions of ROS to APA degradation were evaluated by EPR and quenching experiments. The microbial community of Ru/Fe-modified-biocathode was determined by high-throughput sequencing. Results showed that low resistance accelerated APA degradation by Ru/Fe-modified-biocathode, while higher initial APA concentration inhibited microbial activity of the biocathode. The optimum ammonia concentration was 50 mg L^-1, while too high or too low ammonia concentration did not favor APA degradation. The APA degradation efficiency of Ru/Fe-modified-biocathode-MFC was higher than that of other modified-cathode-MFCs. The APA degradation process confirmed to the pseudo-first-order kinetic model, and APA degradation kinetic constant, the maximum removal efficiency of TOC, ammonia and TN were 2.15d^-1, 59.70%, 99.20% and 44.56% respectively, signifying a simultaneous APA mineralization and denitrification performance of Ru/Fe-modified-biocathode-MFC. The coulombic efficiency decreased with APA concentration increase. OH was the primary radical in APA degradation progress. Eight kinds of intermediates were measured, and two APA degradation pathways were proposed, among which APA hydroxylation was the main pathway. The microbial community of Ru/Fe-modified-biocathode was dominated with Nitrosomonas at genus level, and enriched with various APA-degraders, nitrifiers, and denitrifiers such as Pseudomonas, Nitrospira, Nitrobacter, Paracoccus, Thermomonas, Dechloromonas, and Clostridium_Sutra_stricto_1. COG analysis showed the redox reaction of Ru/Fe might affect signal transduction and environment adaptation, while FAPROTAX analysis suggested that Ru/Fe-modified-biocathode exhibited higher nitrification activity than that of carbon-felt-biocathode. The synergistic mechanism of simultaneous APA mineralization and denitrification was mainly redox reaction of Ru/Fe and supplemented by aerobic biodegradation.

The graceful art, significant function and wide application behavior of ultrasound research and understanding in carbamazepine (CBZ) enhanced removal and degradation by Fe0/PDS/US

Carbamazepine (CBZ) antibiotic organic contamination wastewater poses a huge threat to environmental safety. An advanced oxidation technology (Fe⁰/PDS/US) of using ultrasound (US) enhanced zero-valent iron/potassium persulfate (Fe⁰/PDS) can remove CBZ effectively. The optimal reaction conditions were determined by exploring the effect of single-factor experimental conditions such as ultrasonic power, ultrasonic frequency, CBZ concentration, solution pH, PDS dosage, and Fe⁰ dosage on the removal of CBZ. In addition, we also investigated into the effect of background ions (PO₄^3-, HCO₃^-, Cl^- and HA) on Fe⁰/PDS/US and analyzed the related results. The mechanism of CBZ removal in Fe⁰/PDS/US were explored by analyzing CBZ removal efficiency and reaction rates, the ion concentration of S₂O₈^2-, SO₄^2-, Fe²⁺ and Fe³⁺, pH and the active radicals. The result indicates that US can improve the efficiency of activated PDS and expand the pH range of Fe⁰/PDS. It has prominent performance in catalytically degrading CBZ when the pH is 10.0. SO₄^•-, ^•OH and O₂^•- all coexist in the Fe⁰/PDS/US and make contribution to CBZ removal, whereas the SO₄^•- plays a key role. US can greatly promotes the degradation of target pollutant CBZ by speeding up the dissolution of the outer portion of iron powder, producing sufficient amount of Fe²⁺ with a continuous and stable way, and better activating S₂O₈^2- to generate sufficient SO₄^•- radicals. The degradation of CBZ may embrace three reaction processes, in which organic intermediate products with low molecular weight and biological toxicity is produced, boosting further mineralization and biodegradation of products. The Fe⁰/PDS/US is of great potential application value in removal of organic pollution and environmental purification.

A critical review on bismuth oxyhalide based photocatalysis for pharmaceutical active compounds degradation: Modifications, reactive sites, and challenges

Pharmaceutical active compounds (PhACs), as a kind of widely used pharmaceutical drugs, has attracted much attention. The bismuth oxyhalides (BiOX)-based photocatalysis can remove PhACs efficiently due to its unique layered structure, optical and electronic properties. Nevertheless, the rapid recombination of photogenerated electron-hole pairs, and the inherent instability of structure have limited its practical application. In order to solve these problems, recent modification studies tend to focus on facet control, elemental doping, bismuth-rich strategies, defect engineering and heterojunction. Therefore, the objective of this review is to summarize the recent developments in multiply modified strategies for PhACs degradation. The synthesis methods, photocatalytic properties and the enhancement mechanism are elaborated. Besides, based on theoretical calculation, the reactive sites of typical PhACs attacked by different reactive oxygen species were also proposed. Subsequently, challenges and opportunities in applications are also featured which include factors, viz., dissolution of halogen ions, instability under visible light, applications of real water/wastewater, intermediates and byproducts toxicity analysis of BiOX-based photocatalysis. Finally, the perspectives of BiOX-based photocatalysis for PhACs photodegradation in actual water applications are highlighted.

Diclofenac photodegradation with the Perovskites BaFeyTi1-yO3 as catalysts

Perovskite oxides BaFe_yTi_1-yO₃, with y = 0, 0.6, 0.8 and 1, were prepared by ceramic (CM) and complex polymerization methods (CPM) and utilized in UV-LED (365 nm) photocatalytic degradation assays of 25 mg L^-1 diclofenac (DIC) model solutions. BaTiO₃-CM was also used in the photocatalytic degradation test of a real mineral water for human consumption spiked with 2 mg L^-1 DIC. The XRD patterns of the synthesized perovskites showed cubic structure for those prepared by CPM, with distortions of the cubic lattice to hexagonal or tetragonal when prepared by CM, except for BaTiO₃. All the perovskites showed good catalytic activity, higher than photolysis, except BaFeO₃-CM that presented similar results. BaTiO₃-CM and CPM and BaFeO₃-CPM were also utilized in UV-LED photocatalytic DIC degradation assays with peroxydisulfate addition. BaFeO₃-CPM and BaTiO₃-CPM showed better ability to persulfate activation, but the highest mineralization degree was obtained with BaTiO₃-CM. This last perovskite was also able to perform DIC degradation in a real matrix. The studied oxides show potentiality for photocatalytic degradation of organic compounds, with or without persulfate addition. A degradation mechanism is proposed.

Effective Strategies, Mechanisms, and Photocatalytic Efficiency of Semiconductor Nanomaterials Incorporating rGO for Environmental Contaminant Degradation

The water pollution problems severely affect the natural water resources due to the large disposal of dyes, heavy metals, antibiotics, and pesticides. Advanced oxidation processes (AOP) have been developed using semiconductor nanomaterials as photocatalysts for water treatment as an essential strategy to minimize environmental pollution. Significant research efforts have been dedicated over the past few years to enhancing the photocatalytic efficiencies of semiconductor nanomaterials. Graphene-based composites created by integrating reduced graphene oxide (rGO) into various semiconductor nanomaterials enable the unique characteristics of graphene, such as the extended range of light absorption, the separation of charges, and the high capacity of adsorption of pollutants. Therefore, rGO-based composites improve the overall visible-light photocatalytic efficiency and lead to a new pathway for high-performance photocatalysts’ potential applications. This brief review illustrates the strategies of combining rGO with various semiconductor nanomaterials and focuses primarily on modification and efficiency towards environmental contaminants.

Efficient degradation of typical pharmaceuticals in water using a novel TiO2/ONLH nano-photocatalyst under natural sunlight

Photocatalytic degradation of typical pharmaceuticals in natural sunlight and in actual water is of great significance. In this study, the oxygen or nitrogen linked heptazine-base polymer (ONLH) was successfully incorporated with TiO₂ nanoparticles and formed a TiO₂/ONLH nanocomposite which was responded to the natural sunlight. Under natural sunlight, the TiO₂/ONLH can effectively degrade ten types of pharmaceuticals. In particular, fluoroquinolone containing N-piperazinyl, and cardiovascular drugs containing long aromatic side chains were easily degraded. The half-life of the best degradation performance of propranolol was less than 5 min. The rate constants of propranolol using the TiO₂/ONLH were approximately six- and eight-fold higher than those of pristine TiO₂ and ONLH, respectively. Two reactive species (OH and O₂^-) facilitated the rapid degradation of propranolol, which occurred primarily through the hydroxyl radical addition, ring-opening, and ipso substitution reactions. An acute toxicity test using luminescent bacteria indicated that the toxicity of the propranolol reaction solution gradually decreased with lower total organic carbon (TOC). According to the toxicity evaluation of monomer products, the TiO₂/ONLH also reduced the generation of toxic transformation products. The effects of actual water/wastewater have further shown the TiO₂/ONLH might be applied for the removal of pharmaceuticals in wastewater.

Insights into efficient removal of gaseous p-xylene using cerium-doped ZnO nanoparticles through photocatalytic oxidation

Novel Ce-doped ZnO exhibited excellent photocatalytic activity for decomposing VOCs under VUV light.

Photodegradation of Pharmaceutical and Personal Care Products (PPCPs) and Antibacterial Activity in Water by Transition Metals

The intensity of emerging pollutants such as pharmaceuticals and personal care products (PPCPs) in the aquatic and terrestrial environment is a major source of concern to researchers. The current conventional methods of wastewater treatment plants are considered not efficient enough in the complete removal of the recalcitrant contaminants from water. The use of modified transition metals in visible responsive synthesis to degrade PPCPs and other pollutants (organic and inorganic) is considered as a developing green chemistry and sustainable technology. Hence, this review presents the state-of-the-art discussion on the novel photodegradation of PPCPs, and antibacterial activities of transition metal-modified magnetite materials for wastewater treatment, and suggested directions for the future. Transition metal-modified magnetite nanostructured photocatalysis is identified as one of the best candidates employed in advanced oxidation processes (AOPs) for wastewater treatment and has been found to efficiently destroy bacterial spores and effectively remove recalcitrant pollutants in water. Therefore, this article hopes to contribute scientific knowledge along with existing ones on advanced mechanisms and technology used in wastewater treatment.

Bibliometric approach to the perspectives and challenges of membrane separation processes to remove emerging contaminants from water

The presence of contaminants in water is concerning due to the potential impacts on human health and the environment, and ingested contaminants cause harm in various ways. The conventional water treatment systems are not efficient to remove these contaminants. Therefore, novel techniques and materials for the removal of contaminants are increasingly being developed. The separation process using modified membranes can remove these micropollutants; therefore, they have attracted significant research attention. Among the materials used for manufacturing of these membranes, composites based on graphene oxide and reduced graphene oxide are preferred owing to their promising properties, such as mechanical resistance, thermal and chemical stability, antifouling capacity, water permeability, high thermal and electrical conductivity, high optical transmittance and high surface area. Membrane separation processes (MSP) can be used as secondary or tertiary treatment during the supply of wastewater. However, the efficient and accessible applications of these technologies are challenging. This study aims to demonstrate the main concepts of membrane separation processes and their application in the removal of emerging contaminants. This study reports bibliometric mapping, relevant data on studies using membranes as water treatment processes, and their viability in industrial applications. The main challenges and perspectives of these technologies are discussed in detail as well.

Emerging pollutants-Part II: Treatment

Emerging pollutants (EPs) refer to a class of pollutants, which are emerging in the environment or recently attracted attention. EPs mainly include pharmaceutical and personal care products (PPCPs), endocrine-disrupting chemicals (EDCs), and antibiotic resistance genes (ARGs). EPs have potential threats to human health and ecological environment. In recent years, the continuous detections of EPs in surface and ground water have brought huge challenges to water treatment and also made the treatment of EPs become an international research hotspot. This paper summarizes some research results on EPs treatment published in 2019. This paper may be helpful to understand the current situations and development trends of EP treatment technologies.

Enhanced degradation of diclofenac with Ru/Fe modified anode microbial fuel cell: Kinetics, pathways and mechanisms

A microbial fuel cell (MFC) was constructed with a Ru/Fe-modified-anode prepared by reduction and coating for enhancing diclofenac (DCF) degradation. Results showed that Ru⁰ and Fe⁰ were dispersed uniformly on Ru/Fe-modified-electrode surface, and Ru/Fe existed as an alloy structure. Due to catalysis of Ru/Fe, both electrochemical activity and DCF-degradation performance of Ru/Fe-modified-anode-MFC (Ru/Fe-MFC) were enhanced compared to carbon-felt-anode-MFC (CF-MFC). The maximum power density of Ru/Fe-MFC reached 0.600 W m^-2, and DCF-degradation in Ru/Fe-MFC followed the pseudo-first-order-kinetic model with k_obs of 0.711 d^-1 which was 1.08, 1.34 and 2.21 times higher than that of Ru-modified-anode-MFC (Ru-MFC), Fe-modified-andoe-MFC (Fe-MFC) and CF-MFC, respectively. Results also showed that DCF-degradation and power generation would compete for electrons in Ru/Fe-MFC. Ru/Fe-modified-anode accelerated the enrichment of electro-active bacteria and DCF-degrading bacteria such as Geobacter, Clostridium, Sedimentibacter, Pseudomonas and Desulfovibrionaceae. Stepwise dechlornation occurred for DCF-degradation mainly due to synergistic reaction of Ru/Fe and DCF-degrading bacteria within Ru/Fe-MFC.

Photocatalytic degradation of cephalexin by ZnO nanowires under simulated sunlight: Kinetics, influencing factors, and mechanisms

Increasing concentrations of anthropogenic antibiotics and their metabolites in aqueous environments has caused growing concerns over the proliferation of antibiotic resistance and potential adverse impacts to agro-environmental quality and human health. Photocatalysis using novel engineered nanomaterials such as ZnO nanowires may be promising for removing antibiotics from waters. However, much remains to be learned about efficiency and mechanism for photocatalytic degradation of antibiotics by ZnO nanowires. This study systematically investigated photodegradation of cephalexin using ZnO nanowires under simulated sunlight. The degradation efficiency of cephalexin was substantially increased in the presence of ZnO nanowires especially at circumneutral and alkaline condition (solution pH of 7.2-9.2). The photodegradation followed the first-order kinetics with degradation rate constants (k) ranging between 1.19 × 10^-1 and 2.52 × 10^-1 min^-1 at 20-80 mg L^-1 ZnO nanowires. Radical trapping experiments demonstrated that hydroxyl radicals (OH) and superoxide radicals (O₂^-) predominantly contributed to the removal of cephalexin. With the addition of HCO₃^- (1-5 mM) or Suwannee River natural organic matter (SRNOM, 2-10 mg L^-1), the k values were substantially decreased by a factor of 1.8-70 to 1.69 × 10^-3-6.67 × 10^-2 min^-1, probably due to screening effect of HCO₃^- or SRNOM sorbed on ZnO nanowires and scavenging of free radicals by free HCO₃^- or SRNOM in solution. Combining product identification by mass spectrometry and molecular computation, cephalexin photodegradation pathways were identified, including hydroxylation, demethylation, decarboxylation, and dealkylation. Overall, the novel ZnO nanowires have the potential to be used for removing antibiotics from contaminated waters.

Photocatalytic Degradation of Pharmaceuticals Carbamazepine, Diclofenac, and Sulfamethoxazole by Semiconductor and Carbon Materials: A Review

The presence of pharmaceutical compounds in the environment is a reality that calls for more efficient water treatment technologies. Photocatalysis is a powerful technology available but the high energy costs associated with the use of UV irradiation hinder its large scale implementation. More sustainable and cheaper photocatalytic processes can be achieved by improving the sunlight harvesting and the synthesis of semiconductor/carbon composites has proved to be a promising strategy. Carbamazepine, diclofenac, and sulfamethoxazole were selected as target pharmaceuticals due to their recalcitrant behavior during conventional wastewater treatment and persistence in the environment, as properly reviewed. The literature data on the photocatalytic removal of carbamazepine, diclofenac, and sulfamethoxazole by semiconductor/carbon materials was critically revised to highlight the role of the carbon in the enhanced semiconductor performance under solar irradiation. Generally it was demonstrated that carbon materials induce red-shift absorption and they contribute to more effective charge separation, thus improving the composite photoactivity. Carbon was added as a dopant (C-doping) or as support or doping materials (i.e., nanoporous carbons, carbon nanotubes (CNTs), graphene, and derived materials, carbon quantum dots (CQDs), and biochars) and in the large majority of the cases, TiO₂ was the semiconductor tested. The specific role of carbon materials is dependent on their properties but even the more amorphous forms, like nanoporous carbons or biochars, allow to prepare composites with improved properties compared to the bare semiconductor. The self-photocatalytic activity of the carbon materials was also reported and should be further explored. The removal and mineralization rates, as well as degradation pathways and toxicity of the treated solutions were also critically analyzed.