Photocatalytic Wastewater Treatment Research Articles

Optimization of TiO2/ACF Photocatalytic Continuous Treatment of MB Wastewater Based on Response Surface Methodology

Optimization of TiO2/ACF Photocatalytic Continuous Treatment of MB Wastewater Based on Response Surface Methodology

The enhanced visible-light-driven photocatalytic performance of nanocrystalline TiO2 decorated by quinazolinone-photosensitizer toward photocatalytic treatment of simulated wastewater

Semiconductor-assisted photocatalysis is an efficient, green, low-cost technology employed for wastewater treatment. TiO2-based photocatalysts are the common photocatalysts; however, their large bandgap energy excludes their photocatalytic activities under UV irradiation. Hence, this work investigates the synthesis of quinazolinone photosensitizer to improve the photocatalytic activity of TiO2 in the visible region and efficiently maximize the utilization of solar irradiation. Quinazolinone photosensitizer is a heterocyclic compound exhibits a wide spectrum in the visible region. The prepared samples are characterized by XRD, FE-SEM, FTIR, DRS, and PL. The photocatalytic activity of the Quinazolinone photosensitized-TiO2 catalyst is evaluated toward the degradation of rhodamine B (RB) as a model of organic pollutants in wastewater under UV-A and visible light irradiations. Quinazolinone photosensitized-TiO2 catalyst exhibited a wider absorption spectrum range and lower bandgap of 2.65 eV extending its activity to the visible region compared to bare TiO2 (3.00 eV). Control tests and factors affecting the photocatalytic degradation rate of RB dye such as pH of the medium, dye concentration and catalyst dose are investigated. Degradation of RB follows 1st-order kinetics. The mechanism of degradation is described based on trapping experiments.

CdBi2S4-Decorated Aminated Polyacrylonitrile Nanofiber for Photocatalytic Treatment of Cr(VI) and Tetracycline Wastewater.

The significant threat posed by the high toxicity of heavy metals and antibiotics in water pollutants has prompted a growing emphasis on the development of highly efficient removal methods for these pollutants. In this paper, flexible electrospinning polyacrylonitrile (PAN) nanofiber-supported CdBi2S4 was synthesized via a hydrothermal method, followed by amination treatment with diethylenetriamine (DETA). The as-prepared CdBi2S4/NH2-PAN nanofiber, enriched with sulfur vacancies, demonstrated outstanding visible-light trapping ability and a suitable band gap, leading to efficient separation and transport of photogenerated carriers, ultimately resulting in exceptional photocatalytic capability. The optimal 3-CdBi2S4/NH2-PAN nanofiber achieved impressive reduction rates of 92.26% for Cr(VI) and 96.45% for tetracycline hydrochloride (TCH) within 120 min, which were much higher than those for CdS/NH2-PAN, Bi2S3/NH2-PAN, and CdBi2S4/PAN nanofibers. After five cycles, the removal rate of the CdBi2S4/NH2-PAN nanofiber consistently remained above 90%. Their ease of separation and recovery from the application environment contributes to their practicality. Additionally, compared with conventional suspended particle catalyzers, the composite nanofiber exhibited remarkable flexibility and self-supporting properties.

Synthesis of novel Ag/AgBr/K0.4Y0.7Sb2O6.25 nanocomposite with enhanced photocatalytic properties

Devoloping efficient wastewater treatment photocatalysts capable of improving water quality is undoubtedly one of the main problems of present society. In recent years, novel plasmonic photocatalysts have shown new possible applications in photocatalytic wastewater treatment due to their unique properties. In this work, a novel Ag/AgBr/K0.4Y0.7Sb2O6.25 composite was successfully fabricated by photo-reduction using the pre-prepared AgBr/K0.4Y0.7Sb2O6.25 and K0.4Y0.7Sb2O6.25 (KYSbO). The AgBr/KYSbO and KYSbO were synthesized by deposition-precipitation and precipitation-heating methods. The visible-light photocatalytic performance of parent KYSbO and Ag/AgBr/KYSbO composite was evaluated using methylene blue (MB) as a model organic pollutant. The effects of catalyst dosage, pH and the initial concentration of the MB dye solution on the photocatalytic activity were also investigated in this study. Remarkably, the Ag/AgBr/KYSbO composite exhibited superior visible-light photocatalytic activity for the degradation of MB than that of parent KYSbO. MB was degraded to 91.6% in the presence of parent KYSbO after visible irradiation of 180 min, while 93.2% degraded in merely 30 min in the case of Ag/AgBr/KYSbO composite. The superior improvement in the photocatalytic activity of the Ag/AgBr/KYSbO composite can be credited to the efficient separation of photoinduced electron-hole pairs and the extended visible-light response range. Superoxide radicals are crucial for MB photocatalytic degradation in the Ag/AgBr/KYSbO composite. The possible photocatalytic mechanism was proposed.

Recent updates on remediation approaches of environmentally occurring pollutants using visible light-active nano-photocatalysts.

Photocatalysis emerges as a potential remedy for the issue of an unreliable light source. Recognized as the most dependable and potent energy source sustaining life on Earth, sunlight offers a promising solution. Sunlight is abundant and free, operational costs associated with running photocatalytic system using nanoparticles are often lower compared to system relying on artificial light source. The escalating problem of water pollution, particularly in highly industrialized nations, necessitates effective wastewater treatment methods. These methods aim to combat elevated pollution levels, encompassing pharmaceuticals, dyes, flame retardants, and pesticide components. Advanced oxidation processes within photocatalytic wastewater treatment exhibit substantial promise for removing complex organic pollutants. Doped nanomaterials, with their enhanced properties, enable efficient utilization of light. Coupled nanomaterials present significant potential in addressing both water and energy challenges by proficiently eliminating persistent pollutants from environment. Photocatalysis when exposed to sunlight can absorb photons and generate e- h + pairs. This discussion briefly outlines the wastewater treatment facilitated by interconnected nanomaterials, emphasizing their role in water-energy nexus. In exploring the capabilities of components within a functional photocatalyst, a comprehensive analysis of both simple photocatalysts and integrated photocatalytic systems is undertaken. Review aims to provide detailed explanation of the impact of light source on photon generation and significance of solar light on reaction kinetics, considering various parameters such as catalyst dosage, pH, temperature, and types of oxidants. By shedding light on these aspects, this review seeks to enhance our understanding of intricate processes involved in photocatalysis and its potential applications in addressing contemporary environmental challenges.

Photocatalytic degradation of methyl orange in water using oyster shell-derived calcium oxide nanoparticles

In response to the Philippine-textile-industry goal of adapting sustainable waste management practices, oyster shells as abundant waste, can be valorized for photocatalytic wastewater treatment. Moreover, aeration and water quality as lesser-known parameters were assessed. Here, a nano-sized calcium oxide (CaO NP) photocatalyst from oyster shells was prepared with a 57 % CaO yield. Instrumental characterization confirmed its nanoparticle size, elemental composition, and narrow bandgap, which favor adsorption-photodegradation. The optimum photocatalyst dose achieved 93.7 % removal efficiency and was significantly maximized to 98.5 % under aerated conditions. CaO NP is reusable with stable performance and has first-order dye degradation kinetics. Aerated photocatalytic treatment of simulated wastewater showed a significant reduction in color and chemical oxygen demand with acceptable final pH. Furthermore, the treated wastewater is dischargeable to Class C waters by Philippine environmental standards, proving its successful remediation and application as a dispersible and recyclable photocatalyst for removing methyl orange in water.

Silver (Ag) doped graphitic carbon nitride (g-C3N4) photocatalyst for enhanced degradation of Ciprofloxacin (CIP) under visible light irradiation

Pharmaceutical industry wastewater is causing an increased risk of resistant pharmaceutical micropollutants (PMP) e.g. antibiotic resistant bacteria (super bug) in the ecosystem. Amongst variety of wastewater treatment approaches, Advanced oxidation processes (AOPs) employing photocatalysis provides a cost-effective and sustainable approach for fixation of PMP in an economical and efficient manner to counter the potential risks. Until today, tremendous efforts have been made to trig the performance of photocatalytic wastewater treatment, with the key focus on development of cost-effective, efficient and a moderately stable photocatalyst. Such attempts succeeded with different types of photocatalysts using different synthesis techniques. In recent years, graphitic carbon nitride (GCN) has emerged as one of the cost effective, moderately stable, nontoxic and efficient photocatalyst, and has been scarcely studied specifically for pharmaceutical micropollutants (PMPs) degradation. Hence, considering these factors alongside the facile synthesis and moderate optical absorption of GCN, an effort was made in the present work with effective customization of GCN i.e. silver (Ag) doping to extend light absorption in visible light range which may enhance the photocatalytic performance for Ciprofloxacin (CIP) degradation. The optimization of photocatalytic performance was executed with varied Ag dopant content to obtain an optimum sample with supreme photocatalytic activity for the maximum degradation of CIP, a common antibiotic. The best Ag-doped GCN sample (0.1 AGCN) exhibits a photocatalytic degradation efficiency of 84%, which is 2.15 times greater than pure GCN (39%). The obtained results showed that the strategy of Ag doping substantially enhances the photocatalytic performance, thus offering an efficient mean for developing visible light active photocatalyst for PMP removal and encouraging further research. The photocatalytic performance of the prepared samples was evaluated by degradation of CIP under visible light irradiation. Several characterization techniques were used to characterize and analyze the prepared samples, such as X-ray diffraction (XRD), Scanning electron microscopy (SEM), Raman spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, UV Visible absorption, and Photoluminescence (PL) spectroscopy.

2D/2D Ni-MOF/BiOCl S-scheme heterojunction with boosted charge transfer and photocatalytic degradation of tetracycline

Constructing S-scheme heterojunction with boosted charge separation efficiency and high photoredox ability is a promising strategy in photocatalytic wastewater treatment. Herein, we report a novel S-scheme photocatalyst composed of two-dimensional (2D) nanosheets (NSs) of Ni-based metal-organic framework (Ni-MOF) and 2D BiOCl NSs. Such a unique 2D/2D stacking structure affords a large contact area at the interface, which promotes electron transfer and ensures the construction of S-scheme heterojunction between Ni-MOF and BiOCl. Benefitting from the efficient charge transfer and sufficient redox ability, the developed Ni-MOF/BiOCl heterojunctions exhibit enhanced photocatalytic performance for tetracycline (TC) degradation. Especially, the optimum 0.1Ni-MOF/BiOCl catalyst achieves a remarkable TC removal rate constant of 0.00274 min−1, 7.21 folds larger than that of single BiOCl (k = 0.00038 min−1). This study offers an ideal strategy for designing and fabricating novel S-scheme heterojunction photocatalysts with applicability in wastewater treatment

The role of added oxidising agents in assisting the photocatalytic treatment of olive mill wastewater using a metal-free g-C3N4 optical semiconductor

Olive mill wastewaters (OMW) consist of high organic contents and are harmful to aquatic and terrestrial biota. Heterogeneous photocatalysis is a technology that can be operated under mild conditions to remove pollutants in the liquid phase. In the present work, graphitic carbon nitride (g-C3N4, hereafter referred to as GCN) is studied for the first time as a metal-free photocatalyst for OMW treatment. The integration with peroxidation (H2O2), Fenton (Fe2+/H2O2 at both acidic and natural pH), chlorination (HOCl/ClO−) or persulfate (PS) activation is also investigated. This catalyst potentiated the activation of these oxidants, and H2O2 was identified as the best option to achieve high removals of total phenolic content – TPh (87.5 ± 0.3 %), dissolved organic carbon – DOC (63.8 ± 0.4 %) and chemical oxygen demand – COD (87.7 ± 0.6 %), without need to add iron or adjust the pH. The stability and reusability of the GCN material in the H2O2-assisted photocatalytic treatment of OMW give rise to new possibilities for treating these waste waters.

Reusable isotype heterojunction g-C3N4/alginate hydrogel spheres for photocatalytic wastewater treatment.

Various visible-light-driven photocatalysts have been studied for practical applications in photocatalytic wastewater treatment via solar irradiation. Among them, g-C3N4 has attractive features, including its metal-free and environmentally friendly nature; however, it is prone to charge recombination and has low photocatalytic activity. To solve these problems, isotype heterojunction g-C3N4 was recently developed; however, the methods employed for synthesis suffered from limited reproducibility and efficiency. In this study, isotype heterojunction g-C3N4 was synthesized from various combinations of precursor materials using a planetary ball mill. The isotype heterojunction g-C3N4 synthesized from urea and thiourea showed the highest photocatalytic activity and completely decolorized Rhodamine B (RhB; 10 ppm) in 15 min under visible-light irradiation. Furthermore, to improve recyclability, isotype heterojunction g-C3N4 was immobilized in alginate hydrogel spheres. The isotype heterojunction g-C3N4/alginate hydrogel beads were used in 10 repeated RhB degradation experiments and were able to maintain their initial photocatalytic activity and mechanical strength. These achievements represent an advance towards practical, sustainable photocatalytic wastewater treatment.

Advanced photocatalytic materials based degradation of micropollutants and their use in hydrogen production - a review.

The use of pharmaceuticals, dyes, and pesticides in modern healthcare and agriculture, along with expanding industrialization, heavily contaminates aquatic environments. This leads to severe carcinogenic implications and critical health issues in living organisms. The photocatalytic methods provide an eco-friendly solution to mitigate the energy crisis and environmental pollution. Sunlight-driven photocatalytic wastewater treatment contributes to hydrogen production and valuable product generation. The removal of contaminants from wastewater through photocatalysis is a highly efficient method for enhancing the ecosystem and plays a crucial role in the dual-functional photocatalysis process. In this review, a wide range of catalysts are discussed, including heterojunction photocatalysts and various hybrid semiconductor photocatalysts like metal oxides, semiconductor adsorbents, and dual semiconductor photocatalysts, which are crucial in this dual function of degradation and green fuel production. The effects of micropollutants in the ecosystem, degradation efficacy of multi-component photocatalysts such as single-component, two-component, three-component, and four-component photocatalysts were discussed. Dual-functional photocatalysis stands out as an energy-efficient and cost-effective method. We have explored the challenges and difficulties associated with dual-functional photocatalysts. Multicomponent photocatalysts demonstrate superior efficiency in degrading pollutants and producing hydrogen compared to their single-component counterparts. Dual-functional photocatalysts, incorporating TiO2, g-C3N4, CeO2, metal organic frameworks (MOFs), layered double hydroxides (LDHs), and carbon quantum dots (CQDs)-based composites, exhibit remarkable performance. The future of synergistic photocatalysis envisions large-scale production facilitate integrating advanced 2D and 3D semiconductor photocatalysts, presenting a promising avenue for sustainable and efficient pollutant degradation and hydrogen production from environmental remediation technologies.

GAD plasma-assisted synthesis of ZnO nanoparticles and their photocatalytic activity

In this study we present an efficient method for synthesizing highly pure ZnO nanoparticles using a Gliding Arc Discharge (GAD) plasma system as a non-thermal plasma source. This approach offers distinct advantages over conventional techniques, including simplicity, a short synthesis time, utilization of readily available air as the source gas, and potential scalability, rendering it a promising alternative for sustainable ZnO nanoparticle production. The synthesized nanoparticles physicochemical properties were characterized using various techniques, such as scanning electron microscopy (SEM), energy dispersive x-ray analysis (EDAX), UV-visible spectroscopy (UV–vis), Fourier-transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), Thermogravimetric Analysis (TGA), and Differential Scanning Calorimetry (DSC). Furthermore, we evaluated the effectiveness of the synthesized ZnO nanoparticles for wastewater treatment by assessing their photocatalytic activity against methylene blue (MB), Brilliant Cresyl Blue (BCB), and Congo Red (CR) under UV light irradiation for 2 h and 30 min. The results confirmed the successful synthesis of highly pure ZnO nano-powder with an average size of 27.18 nm and a band gap energy of 3.28 eV in an exceptionally brief duration and through straightforward steps. Additionally, GAD plasma-assisted ZnO nanoparticles exhibited a significant dye removal rate, showcasing their potential as highly effective materials for photocatalytic wastewater treatment. This study contributes new insights into the application of GAD plasma for nanoparticle synthesis.

Facile fabrication of B-rGO/ZnFe2O4 p-n heterojunction-based S-scheme exciton engineering for photocatalytic Cr(vi) reduction: kinetics, influencing parameters and detailed mechanism.

The fabrication of p-n heterostructures was found to be an effective strategy to stimulate the interfacial exciton shipment and photocatalytic reactions. Herein, we report a p-n junction synthesized by combining p-type boron-doped reduced graphene oxide (B-rGO) with an n-type ZnFe2O4 semiconducting material for Cr(vi) reduction under LED light irradiation. The band structures of ZnFe2O4 and B-rGO were evaluated using UV-vis spectroscopy, Mott-Schottky (M-S) plots and photocurrent studies. The results indicated that ZnFe2O4 and B-rGO exhibit a conventional type-II charge transfer, and the Fermi-level (E F) of ZnFe2O4 was found to be much lower than that of the B-rGO material. Based on these investigations, an S-scheme charge-migration pathway was suggested and demonstrated by the photocatalytic activity and nitroblue tetrazolium (NBT) chloride experiments. The optimal 2 wt% B-rGO/ZnFe2O4 heterojunction exhibits the highest photocatalytic performance, i.e. 84% of Cr(vi) reduction in 90 min under 20 W LED light irradiation with a rate constant of 0.0207 min-1, which was 4.6- and 2.15-fold greater than that of ZnFe2O4 (ZnF) and B-rGO, respectively. The intimate interfacial contact, excellent photon-harvesting properties, effective exciton segregation and availability of active electrons are some factors responsible for enhanced photocatalytic Cr(vi) reduction. In order to fulfill the demand of applied waste-water management, the influences of various photocatalyst amounts, pH values and co-exiting ions on photocatalytic activities were evaluated. Finally, this work provides a way to fabricate S-scheme-based p-n-heterostructures for photocatalytic wastewater treatment.

Carbon dots as potential candidate for photocatalytic treatment of dye wastewater.

Water is the utmost important element for the existence of life. In recent decades, water resources have become highly contaminated by a variety of pollutants, especially toxic dyes that are harmful to both living beings and environment. Hence, there is an urgent need to develop more effective methods than traditional wastewater treatment approaches for treatment of hazardous dyes. Herein, we have addressed the various aspects related to the effective and economically feasible method for photocatalytic degradation of these dyes employing carbon dots. The photocatalysts based on carbon dots including those mediated from biomass have many superiorities over conventional methods such as utilization of economically affordable, non-toxic, rapid reactions, and simple post-processing steps. The current study will also facilitate better insight into the understanding of photocatalytic treatment of dye-polluted wastewater for future wastewater treatment studies. Additionally, the possible mechanistic pathways of photocatalytic dye decontamination, several challenges, and future perspectives have also been summarized.

Z-Scheme heterojunction WO3/ZnIn2S4 solar absorber for wastewater remediation

Z-Scheme heterojunction, recognized as one of the optimal methods for the separation of electrons and holes, is extensively applied in the domain of photocatalytic. Leveraging the Z-Scheme heterojunction for photocatalytic and solar interfacial water evaporation presents a promising solution for the purification of dye wastewater and the mitigation of organic pollutant accumulation on traditional solar absorbers. In this study, WO3/ZnIn2S4 heterojunction was synthesized through a two-step solvothermal method, and resulting WO3/ZnIn2S4, which rested on a flexible substrate Ti mesh, possessed the dual functionality of interfacial water evaporation and photocatalytic treatment of dye wastewater, which not only water evaporation rate for WO3/ZnIn2S4 reached 1.26 kgꞏm−2ꞏh−1 but also the Z-Scheme heterojunction WO3/ZnIn2S4 empowered it to effectively degrade dye wastewater, with a degradation rate of Rhodamine B up to 98.6%. The harmonization of these two functionalities effectively circumvented the issue of secondary pollution commonly associated with dye wastewater treatment. This study effectively integrates photocatalysis into a cutting-edge solar-driven interfacial evaporation system, effectively expanding the capabilities of a multifunctional solar absorber and introducing novel applications for zero-discharge dye wastewater treatment.

Nanoferrites in photocatalytic wastewater treatment: Advancements, characterization, and environmental implications

Water is the fundamental and indispensable component of every organism on earth.Yet, as a consequence of urbanization and industrialization; sources of clean water have been polluted with dyes that are unsafe to aquatic creatures. Nanoferrites is a photocatalytic material having an incrediblenarrow band gap, physico-chemical equilibrium, a large porosity, excellent separation of carrier’s effectiveness, and paramagnetism, making it easily recoverable. As a result, ferrites act asarole of photocatalyst for wastewater treatment. In this review, the photocatalytic degradation of the dyes using nanoferrites as a host, bimetal, trimetal with doped and composite forms is covered. Characterizations including XRD, FT-IR, SEM, EDAX, TEM, BET, UV-DRS, TGA and Raman spectroscopy are used for investigation and confirm the development and design of nanoferrites. The synthesis of nanoferrites, implemented in photocatalytic research demonstrated their improved ability to degrade cancer-causing dyes and their ability to be recycled for additional cycles of examination has been summarized. Photocatalysis isasimple and ecologically beneficial processprovides the most recent and beneficial concept for cleaning wastewater using specifically manufactured nanoparticles. The fundamental objective of biological approaches, green nanoparticle manufacturing, multiple chemical andgreen synthesis strategies, the benefits of greener chemistry, and its usage in photocatalysis for the degradation of industrial dyes are all addressed in this review article. Overall, this study looks at the manner in which photocatalysis research may be advanced by employing ferritesynthesized using chemical andgreen methods for better environmental monitoring and zero energy waste.Approaches for modification have been emphasized, including elemental doping, composite synthesizing, and morphological modification. By using these modification techniques, ferrite's catalytic activity for the photocatalytic breakdown of organic pollutants in water has been enhanced. The manufacture scale of nanoferrites utilizing inexpensive, energy-efficient, and environmentally conscious methods are referred to as chemical synthesis and biological synthesis in which they are recognized as a potential synthesis approach that employs diverse chemical and biological ingredients respectively. Future study will focus significantly on the combination of various modification strategies to improve ferrites' photocatalytic activity.

Mechanism and performance evaluation of spent-coffee grounds-derived nanocomposite materials for highly efficient photocatalytic degradation of organic pollutant

The study demonstrates a facile and environmentally friendly method for synthesizing crystalline TiO2 nanoparticles on the surface of hydrochar generated from readily available biomass waste, i.e., spent coffee grounds (SCGs), using a simple sol–gel process. The hydrochar served as a support for TiO2, reducing the rate at which electrons and holes recombine during photocatalysis, thereby facilitating the effective binding of TiO2, enhancing its adsorption capacity, and the convenient separation of the photocatalyst after usage. The materials were tested in the photocatalytic degradation of an organic pollutant, methylene blue (MB) dye. TiO2-hydrochar obtained at 210 ⁰C has the best performance, giving a degradation efficiency of 98.5 % and a mineralization efficiency of 87.1 % in 90 min at neutral pH. Radical trapping experiments showed O2.-andh+ being the dominant species, followed by HO.. Besides, it showed superior stability with an activity loss of ∼ 9.2 % after five runs. The superior performance of the HCT210 was ascribed to the enhanced interfacial charge transfer kinetics between the TiO2 and hydrochar through Ti-O-C bond formation, better light absorption, and the high surface area of the materials. Performance metrics show that synthesized nanocomposites are promising photocatalysts, providing a biomass-assisted method for robust photocatalytic wastewater treatment.

Silver-doped lanthanum nickel oxide decorated Ti3C2Tx MXene nano-composite (Ag–LaNiO3/MXene) for advanced photocatalytic waste-water treatment

Nanomaterials with novel properties and broad potential applications have been widely anticipated in light of recent advances in material science. In this research, Ag-doped LaNiO3/MXene nanocomposite was fabricated by facile routes. Various techniques like XRD, FTIR, SEM and UV–vis absorption spectroscopy were used for the characterization. FTIR results showed different vibrational modes for Ni–O and La–O. Morphological studies were done by SEM analysis. Optical band gap was calculated using UV–vis absorption spectroscopy and the results showed a decrease in bandgap from 2.96 eV to 2.78 eV. The Orthorhombic structure of fabricated Ag–LaNiO3/MXene was confirmed by XRD. To evaluate the photocatalytic efficiency, bromophenol blue (BPB), methyl orange (MO), and benzoic acid (BA) were used as model wastewater contaminants. Photo-catalytic results revealed that Ag–LaNiO3/MXene degraded 84 %, 64 %, and 55 %, of (BPB), (MO), and (BA) respectively. Bromophenol blue highly (84 %) degraded in the whole process. For Ag–LaNiO3/MXene, the rate constants for BPB, MO, and BA were 0.02281 min−1, 0.01142 min−1, and 0.00789 min−1. Hence, this present work revealed that Ag–LaNiO3/MXene enhanced photo-catalytic efficiency at a greater rate.

Performance and mechanism of Al, N co-doped carbon/nano-TiO2 photocatalytic oxidation for the removal of ammonia nitrogen and Ni/Co complexes from ternary precursor wastewater

The process of producing ternary precursors for new lithium batteries produces industrial wastewater containing high concentrations of ammonia nitrogen and metal ammonia complexes, which requires strict treatment. In this study, a simple and efficient photocatalyst (Al, N co-doped carbon/nano-TiO2) with excellent adsorption and photocatalytic properties was developed. The samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), N2 adsorption–desorption test, UV–Vis diffuse reflectance spectroscopy (UV–Vis DRS), Energy Dispersive X-Ray Spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS), which indicated that the catalyst had excellent specific surface area and strong light absorption properties. In addition, the performance of photocatalytic treatment of ternary precursor wastewater was investigated by varying the amount of Al doping, the loading of nano-TiO2, the amount of catalyst input, changing the adsorption and photocatalytic time. The results suggested that the 3.0 g/L of Al, N co-doped carbon/nano-TiO2 composite photocatalyst achieved 91.45% degradation efficiency of ammonia nitrogen and the removal efficiency of nickel and cobalt was 99.11% and 98.34%, respectively. EDS and XPS analyses showed that ammonia nitrogen pollutants in the wastewater were eventually degraded to nitrogen and nitrogen oxides, with nickel and cobalt adsorbed on the catalyst surface in the form of Ni2+ and Co2+.

Incorporating photocatalytic fuel cell with dual S-scheme CuBi2O4/Bi2WO6/ZnO NRA photoanode for energy recuperation from municipal wastewater treatment under sunlight

Photocatalytic fuel cell (PFC) utilized the chemical energy contained in the molecules by combining photocatalytic treatment of wastewater with fuel cell electrochemical reaction. Herein, a PFC system with a novel dual S-scheme heterojunction CuBi2O4/Bi2WO6/ZnO nanorod array (CBO/BWO/ZnO NRA) composite photoanode was first constructed for municipal wastewater treatment accompanied with electricity generation under direct sunlight. The introduction of CBO and BWO not only contributed to the narrowing of the band gap which enabled the ZnO NRA to utilize sunlight more efficiently, but also led to the excellent electron-hole segregating capability. The 10% CBO/BWO/ZnO NRA composite photoanode achieved a significantly ameliorated electrical power with maximum power density of 7.707 µW/cm2, which was superior to those pristine ZnO NRA and BWO/ZnO NRA binary materials. The composite photoanode was then tested for its mineralization activity in the municipal wastewater and 98.4% of COD removal was acquired within 90 min. The main attribution that conducive to its spectacular performance in municipal wastewater treatment came from the one-dimensional nanorod array architecture along with the synergistic relation among the three efficient components in the CBO/BWO/ZnO NRA heterojunction that can effectively hinder the charge carrier recombination rate and facilitated a good route for electron transport. The composite photoanode also manifested good stability in five cyclic runs. The dual S-scheme CBO/BWO/ZnO NRA enabled the free active species partook in the photoelectrocatalytic reaction and the working principle of PFC system was also speculated. Additionally, phytotoxicity findings signified that the comprehensive toxicity of municipal wastewater was eliminated after PFC treatment.