Remediation Of Polluted Water Research Articles

RECENT PROGRESS IN THE SYNTHESIS AND PHOTOCATALYTIC DEGRADATION OF ORGANIC POLLUTANTS BY GRAPHENE-BASED TiO2 NANOCOMPOSITE: A REVIEW

Numerous sustainable water processing techniques have been widely investigated and are capable of boosting the quality of water. Among these techniques, photonanocatalysis has stood tall with great promises in the last few decades. Nonetheless, a major challenge in the environmental remediation of photocatalyst technology is to develop an ideal photocatalyst that must have excellent photocatalytic efficiency, large specific surface area, maximum harvesting of solar energy, high durability and recyclability. Due to their stability, low toxicity, low cost and superhydrophilicity TiO2 has been used by researchers as an efficient photocatalyst for the degradation of organic pollutants. Unfortunately, it suffers greatly due to its high band gap with 3.2[Formula: see text]eV, insufficient visible light response, fast photogenerated electrons and holes recombination rate and serious agglomeration. Keeping these views, the present review highlights the principal results of studies on current practical synthesis and photocatalytic activity of graphene-based TiO2 nanocomposite materials for the treatment of water. The amalgamation of graphene oxide (GO) and reduced graphene oxide (rGO) with nanoscale TiO2 particles results in synergistic properties thereby tuning and increasing the functionality of the composite. In this regard, the review also addressed the progress and insight into graphene-based TiO2 nanocomposite in photocatalytic removal of organic pollutants including basis mechanism, possible key strategies of the composite, and an overview of how to elevate efficacy. Finally, brief challenges and future perspectives in this field are also presented. Indeed, this work illustrated that graphene-based TiO2 composite nanomaterials can be a green signal in the future of photocatalysis targeting water pollution remediation.

Advanced cellulose-based hydrogel TiO2 catalyst composites for efficient photocatalytic degradation of organic dye methylene blue

Sustainable cellulose-based hydrogels are used in medicine and environmental science. Hydrogels’ porosity makes them excellent adsorbents and stable substrates for immobilizing photocatalysts to remove organic dyes. Despite their potential, the implementation of hydrogels for this purpose is still limited due to their high synthesis temperature and low cellulose content. To overcome these challenges, this study develops cellulose-based hydrogels, which have a high cellulose content and can be easily synthesized under ambient conditions. Containing a higher cellulose concentration than previous hydrogels, the synthesized hydrogels are more stable and can be reused numerous times in treatment operations. The hydrogel properties were investigated using Fourier transform infrared spectroscopy, X-ray diffraction and thermal analysis. Scanning electronic microscopy revealed that TiO2 nanoparticles were homogeneously distributed throughout the hydrogel's matrices. In addition, transparent hydrogels allow light to pass through, making them suitable substrates to remove organic dye. The results showed that the hydrogel with TiO2 was able to degrade nearly 90% of organic dye within 180 min. Furthermore, the hydrogel with the embedded catalyst exhibits the potential for reusability with a regeneration efficiency of 80.01% after five runs. These findings suggest that this novel hydrogel is a promising candidate for water pollution remediation.

The complete chloroplast genome sequence of Hydrocotyle vulgaris L. (Araliaceae)

Hydrocotyle vulgaris is a perennial wetland clonal plant in the Araliaceae family, which was introduced to China as an ornamental plant in the 1990s. Although H. vulgaris is now considered a potential invasiveness species in China, it also plays a significant role in the remediation of water pollution. Here, we reported its complete chloroplast genome and analyzed the basic characteristics. The chloroplast genome was 153,165 bp in length, including a pair of inverted repeat (IR) regions of 25,072 bp separated by a large single-copy (LSC) region of 84,291 bp and a small single-copy (SSC) region of 18,730 bp. The H. vulgaris chloroplast genome contained 132 predicted genes, and its overall GC content was 37.60%. Phylogenetic analysis revealed that H. vulgaris was closely related to H. verticillata. The H. vulgaris chloroplast genome presented in this study will lay a foundation for further genetic and genomic studies of the genus Hydrocotyle.

Ball-milled biochar-modified zero-valent aluminum activates peroxodisulfate for phenol degradation: Enhancement of catalysis by membrane-breaking effect

Zero-valent aluminum (ZVAl) is a potential activator for peroxodisulfate (PDS), yet the dense oxide film on its surface hampers electron transfer for the O−O bond cleavage of PDS. We synthesized zero-valent aluminum-biochar (BM-ZVAl@BC) composites through ball milling, which effectively disrupted the native oxide layer on BM-ZVAl@BC. Within the BM-ZVAl@BC/PDS system, biochar (BC) not only suppressed the rapid oxidation of BM-ZVAl@BC but also enhanced the dispersion and electron transfer rate of ZVAl, thereby improving the overall catalytic efficiency. Consequently, the phenol removal efficacy in the BM-ZVAl@BC/PDS system was notably improved. Optimal catalytic performance of the prepared BM-ZVAl@BC was achieved at a charcoal-to‑aluminum mass ratio of 2:1, resulting in 95.7 % phenol removal after 180 min. Quenching experiments and electron spin resonance (ESR) analysis revealed that both free radicals (SO4•−, •OH, and O2•−) and non-radical species (1O2) contributed to phenol degradation, with SO4•− and •OH playing predominant roles. In summary, the BM-ZVAl@BC/PDS system represents an effective and promising technology for the remediation of phenolic water pollutants.

New Insights into the pH-Dependent Removal of Sulfamethoxazole in Peracetic Acid Activation Systems: from Mechanistic Exploration to Practical Application Potentials

Peracetic acid (PAA) as emerging oxidant in advanced oxidation processes (AOPs) has attracted widespread attention in purifying water pollution. In this research, the removal of target contaminant (sulfamethoxazole, SMX) was investigated through PAA activation by a facile catalyst (Co@C), and the active sites of catalyst were identified as sp3-C, Oads, and Co0 by correlation analysis. Especially, different pH adjustment strategies were designed, including System A (adjusting pH after adding PAA) and System B (adjusting pH before adding PAA), to investigate the impact of oxidant acidity and alkalinity on solution microenvironment as well as effect and mechanism of pollutant removal. The results showed that HO· and CH3C(O)OO· dominated in System A, while Co(IV)O2+ was also observed in System B. Both systems showed optimal SMX degradation (98%). However, System A exhibited excellent water quality tolerance (efficiency > 78%), superior sustained catalyst activation (efficiency > 80% in 40h), less ion leaching (41μgL-1), and lower products toxicity. Moreover, the pH of solution after reaction in System B was intensely acidic, requiring costly pH adjustments for discharge. This study unveils the strategy of adjusting pH after adding PAA is preferable for water purification, enriching the emerging research of PAA-based AOPs for the remediation of environments. Environmental ImplicationsAs emerging contaminants, the consumption of antibiotics is increasing. Due to their difficult biodegradability, antibiotics have become hazardous substances of great concern as they trigger bacterial resistance and threaten the ecosystem. In this research, two pH adjustment strategies, including System A and System B (adjusting pH after and before adding PAA), were designed to investigate the effective removal of sulfamethoxazole through peracetic acid activation by a facile catalyst (Co@C). In comparison, System A was more suitable for remediation of water pollution owing to its excellent water quality tolerance, superior catalyst sustained activation, less ion leaching, and lower products toxicity.

Eco-friendly LEDs radiation-assisted photocatalytic mineralization of toxic azure B dye using Bi2MoZnO7 nanocomposite

The present time nanocomposites show highly improved photocatalytic performance in water pollution remediation technology. Herein, BMZ (Bi2MoZnO7) nanocomposite photocatalyst has been synthesized via the co-precipitation method. The structural and morphological studies were interpreted by analytical techniques including X-Ray Diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), Transmission electron microscopy (TEM), and Energy Dispersive X-ray (EDX) analyses. The accomplishment of photocatalysis was determined by the mineralization of toxic azure B dye using a light-emitting diode (LED) as a source of radiation. The characterization studies revealed that the average particle size of BMZ nanocomposite was 28 nm with a flake-like structure having a smooth surface. An EDX spectrum shows the characteristic peaks of Bi, Mo, Zn, and O elements. The parameters such as pH, dye concentration, catalyst weight, reusability of photocatalyst, Fenton’s reagent, CO2, COD, NO3− and SO42− evaluation, and N2 and O2 purging were studied for optimum conditions. Fenton’s reagent test is one of the green approaches in which OH is generated that is utilized for the degradation of toxic azure B dye. The photocatalytic degradation in Fe2+/H2O2/BMZ/Azure B system, high value of the rate constant was recorded as compared to the experiments, performed without BMZ nanocomposite photocatalyst. The eco-friendly LEDs irradiation was applied as a light source material throughout the experiment. The 98 % degradation of toxic azure B dye was observed in 120 min with the highest rate constant (k = 6.1 × 10−4 s−1) in LEDs irradiation.

Biogenic synthesis of reduced graphene oxide and investigation of adsorption isotherm, kinetics, thermodynamics parameters for water pollution remediation

Biogenic synthesis of reduced graphene oxide and investigation of adsorption isotherm, kinetics, thermodynamics parameters for water pollution remediation

Application of artificial wetland technology in Miyun Reservoir water management

In recent years, with the increasing attention to environmental pollution, water quality management has become an important part of protecting water resources and maintaining ecological balance. And as an important means of water pollution remediation, artificial wetlands have gradually received widespread attention. Miyun Reservoir, as an important drinking water source in Beijing, is particularly important for water quality management. As an ecological restoration technology, artificial wetland has significant water quality improvement effect by simulating and improving the function of natural wetland. Therefore, artificial wetland has important scientific research and practical significance in the water management of Miyun Reservoir. In this paper, we will discuss the application of artificial wetland in water management of Miyun Reservoir, and summarise the results and conclusions of the study, highlight the impact and significance of the study, and look forward to the future research direction. By exploring the application of artificial wetlands in reservoir water management, it is expected to provide scientific basis and technical support for water resource management departments and decision makers, and contribute to the improvement of water quality and ecological restoration of Miyun Reservoir.

Investigating dual-functional Al-doped stannic oxide nanorods towards photodegradation of real industry wastes and dye-sensitized solar cell application: An experimental and theoretical interpretation

In this work, we demonstrate a uniquely designed Tin (IV) Oxide (SnO2)-based nanomaterials for energy and environmental applications. Here, the Al-doped SnO2 nanorods (NR) at various concentrations ranging from 3 wt% to 9 wt% carried out following facile co-precipitation technique which induced synergic structural, optical and electrical properties in resulting products. Further, the Al-incorporation induced considerable changes to the structural, optical, and electrical characteristics turning SnO2 nanorods to Al-SnO2 nanocubes (NCs). Resulting changes from nanorod to nanocubes were closely monitored using various characterization techniques, which were then effectively utilized for photocatalytic degradation of important textile industry dyes, encompassing both cationic (MB, CV) and anionic (EBT) types. Optimal Al-doped SnO2 NC (6 wt%) demonstrated significant degradation efficiencies for organic pollutant and textile industry effluents under direct sunlight exposure. On the other hand, combination of optical and electrical properties was utilized in dye-sensitive solar cells (DSSCs) to achieve noteworthy efficiency of 6.33%, surpassing that of previous reported SnO2-based nanostructures. These exceptional performance nanomaterials can be attributed to the optimized morphology of the nanocubes and the reduction of the band gap from 3.24 eV to 2.75 eV facilitated by the introduction of aluminum dopant. Furthermore, synergic combination has also improved visible light excitation, substantially decreased resistance to charge carrier transfer phenomenon, improved the charge carrier concentration, as well as considerably decreased the electron/hole recombination rate. Therefore, presence of Al in SnO2 nanostructure has considerably improved the opto-electrical properties that were interpreted following theoretical studies. Therefore, study gives simple nanomaterials having both the photodegradation and dye-sensitive solar cell (DSSC) performance of the SnO2 nanostructure, as a cost-effective energy conversion and water pollution remediation tool for the near future.

In-situ optical water quality monitoring sensors—applications, challenges, and future opportunities

Water quality issues remain a major cause of global water insecurity, and real-time low-cost monitoring solutions are central to the remediation and management of water pollution. Optical sensors, based on fluorescence, absorbance, scattering and reflectance-based principles, provide effective water quality monitoring (WQM) solutions. However, substantial challenges remain to their wider adoption across scales and environments amid cost and calibration-related concerns. This review discusses the current and future challenges in optical water quality monitoring based on multi-peak fluorescence, full-spectrum absorbance, light-scattering and remotely sensed surface reflectance. We highlight that fluorescence-based sensors can detect relatively low concentrations of aromatic compounds (e.g., proteins and humic acids) and quantify and trace organic pollution (e.g., sewage or industrial effluents). Conversely, absorbance-based sensors (Ultraviolet-Visible-Infra-red, UV-VIS-IR) are suitable for monitoring a wider range of physiochemical variables (e.g., nitrate, dissolved organic carbon and turbidity). Despite being accurate under optimal conditions, measuring fluorescence and absorbance can be demanding in dynamic environments due to ambient temperature and turbidity effects. Scattering-based turbidity sensors provide a detailed understanding of sediment transport and, in conjunction, improve the accuracy of fluorescence and absorbance measurements. Recent advances in micro-sensing components such as mini-spectrometers and light emitting diodes (LEDs), and deep computing provide exciting prospects of in-situ full-spectrum analysis of fluorescence (excitation-emission matrices) and absorbance for improved understanding of interferants to reduce the signal-to-noise ratio, improve detection accuracies of existing pollutants, and enable detection of newer contaminants. We examine the applications combining in-situ spectroscopy and remotely sensed reflectance for scaling Optical WQM in large rivers, lakes and marine bodies to scale from point observations to large water bodies and monitor algal blooms, sediment load, water temperature and oil spills. Lastly, we provide an overview of future applications of optical techniques in detecting emerging contaminants in treated and natural waters. We advocate for greater synergy between industry, academia and public policy for effective pollution control and water management.

Copper nanoclusters-doped novel carrier with synergistic adsorption-catalytic active sites to enable high-performance dye removal

Enhancing the synergistic interplay between adsorption and catalytic oxidation to amplify Fenton-like effects remains a pivotal challenge in advancing water pollution remediation strategies. In this study, a suite of novel carriers (SH) composed of silica (SiO2) and hydroxyapatite (HAp) in different ratios were synthesized through an amalgamation of the sol–gel and co-precipitation techniques. Notably, various forms of copper (Cu) species, including Cu2+ ions and Cu nanoclusters (Cu NCs), could be stably incorporated onto the SH surface via meticulous loading and doping techniques. This approach has engendered a new class of Fenton-like catalysts (Cu NCs-SH1-5) characterized by robust acid-base tolerance stability and remarkable recyclability. Compared with the previously reported Cu NCs-HAp, this catalyst with lower Cu species content could achieve better performance in adsorbing and degrading dyes under the aid of hydrogen peroxide (H2O2). The catalyst's dual action sites, specifically the adsorption sites (SiOH, POH, slit pores) and catalytic centers (multivalent Cu species), had clear division of labor and collaborate with each other. Further, reactive oxygen species (ROS) identification and astute electrochemical testing have unveiled the mechanism underpinning the cooperative degradation of dyes by three types of ROS, spawned through electron transfer between the Fenton-like catalyst (Cu NCs-SH) and H2O2. From these insights, the mechanism of synergistic adsorption-catalytic removal was proposed.

A multi-scale computational investigation of cationic dye interaction with rutile TiO2: An interconnected simulation approach

Metal oxides have increasingly been employed for water pollution remediation. In the present investigation, the adsorptive characteristics of three cationic dyes, rhodamine B (RB), safranin O (SO), and methylene blue (MB), on the (110) surface of rutile titanium dioxide in an aqueous milieu were scrutinized. Utilizing Density Functional Theory (DFT), the reactivity of these organic compounds was evaluated by computing parameters such as molecular frontier orbital energies, energy gap (ΔEgap), electronegativity (χ), chemical hardness (η), chemical softness (σ), electrophilicity (ω), nucleophilicity, electron transfer fraction (ΔN), and Fukui indices. Findings demonstrated that RB exhibited superior reactivity and adsorptive capacity in comparison to MB and SO. Self-Consistent Charge Density-Functional Tight-Binding (SCC-DFTB) simulations revealed that RB engaged in the most potent interactions with the TiO2(110) surface, with interaction energies following the sequence RB (−1.12 eV) > MB (−1.07 eV) > SO (−1.01 eV). Furthermore, the most energetically favorable adsorption configurations for these dyes were elucidated through Molecular Dynamics (MD) simulations. Adsorption energies calculated via MD simulations corroborated that the TiO2 (110) surface possessed high adsorptive capabilities for these cationic dyes, particularly a stronger affinity for RB. The study provides comprehensive insights into the molecular-level interactions between cationic dyes and rutile TiO2, thereby contributing valuable information for the optimization of metal oxide-based water pollution treatment technologies.

Preparation of Ti4O7/h‐BN self‐supported ceramic photoelectrode and its photoelectrocatalytic performance for water purification

AbstractThe construction of high‐efficiency self‐supported ceramic photoelectrode based on ideal semiconductor materials is essential for achieving effective degradation of pollutants by photoelectrocatalysis (PEC) technology. Herein, a Ti4O7/h‐BN composite ceramic photoelectrode with a unique microstructure was fabricated by a step‐by‐step calcination process and used in PEC water pollution remediation. The PEC activity of Ti4O7 ceramic photoelectrode could be enhanced by introducing hexagonal boron nitride (h‐BN) nanoparticles on the surface. The most optimized Ti4O7/h‐BN photoelectrode exhibited the decolorization rate of active brilliant blue KN‐R at about 97.79% in 30 min. The PEC activities could remain stable during five degradation cycles. The excellent photoelectrocatalytic performance of Ti4O7/h‐BN ceramic photoelectrode could be attributed to the low Tafel slope, low charge transfer resistance, large electrochemical active area, and excellent photo‐generated carrier separation efficiency. A type‐II heterojunction was formed between the Ti4O7 and h‐BN, which caused more effective carrier separation and enhanced the generation of dominant active species •O2− and h+. This work provided a mature synthesis strategy of Ti4O7/h‐BN self‐supported ceramic photoelectrodes with excellent practical application prospects to achieve superior PEC performance for water purification.

Thiol-functionalized cellulose for mercury polluted water remediation: Synthesis and study of the adsorption properties

Mercury pollution poses a global health threat due to its high toxicity, especially in seafood where it accumulates through various pathways. Developing effective and affordable technologies for mercury removal from water is crucial. Adsorption stands out as a promising method, but creating low-cost materials with high selectivity and capacity for mercury adsorption is challenging.Here we show a sustainable method to synthesize low-cost sulfhydrylated cellulose with ethylene sulfide functionalities bonded glucose units. Thiol-functionalized cellulose exhibits exceptional adsorption capacity (1325 mg g−1) and selectivity for Hg(II) over other heavy metals (Co, Cu, Zn, Pb) and common cations (Ca++, Mg++) found in natural waters. It performs efficiently across a wide pH range and different aqueous matrices, including wastewater, and can be regenerated and reused multiple times without significant loss of performance. This approach offers a promising solution for addressing mercury contamination in water sources.

Chinese yam-derived aerogel as a versatile platform for efficient freshwater production and pollution remediation

Water scarcity and pollution have become major obstacles to sustainable global development. The development of a versatile platform that can simultaneously produce clean water and remediate pollutants from water is highly desirable but still difficult to realize. Herein, to address this challenge, we have developed a CY@PPy@Ag aerogel with excellent photothermal and photocatalytic capabilities through a freeze-drying process, followed by polypyrrole coating and Ag deposition. The excellent characteristics, including broad-spectrum light absorption (97.2%), localization of converted heat, rapid water transport, and porous open microchannels, enabled it to act as an advanced solar evaporator for efficient and continuous steam generation without salt crystallization. Moreover, the high evaporation rate (1.51 kg m−2 h−1) was maintained even in high concentrations of brine and real seawater. Taking advantage of its enhanced photocatalytic performance, organic dyes in water could be rapidly and completely decomposed by the CY@PPy@Ag aerogel under solar irradiation, and this photodegradation process was significantly accelerated with the help of NaBH4. This work is expected to provide a one-stone-two-birds strategy to simultaneously achieve clean water harvesting and pollution remediation, which holds great promise in the fields of solar energy harvesting, wastewater treatment, and seawater desalination.

Contrasting piezocatalytic and tribocatalytic behavior of BaTiO3

In this work, BaTiO3 with different morphologies is obtained by controlling the Ba/Ti ratio in the precursor, reaction temperature, and reaction time. The effects of the morphology and the specific surface area of samples, as well as friction conditions on piezocatalytic and tribocatalytic performance, are investigated. BaTiO3 exhibits the best piezocatalytic performance when it is composed of a mixed-shape of BaTiO3 rod and particle because in this case there is a balance between the specific surface area and the piezopotetial. However, the tribocatalytic performance is majorly dependent on friction conditions such as the roughness of the reaction vessel and the rotation speed of the stirring rod. Both ⋅O2− and ⋅OH play important roles in the piezocatalytic and tribocatalytic degradation of dyes. Therefore, this work gains significant factors in piezocatalytic and tribocatalytic degradation of dyes and provides a reference for remediation of water pollution in the future.

Efficient and Selective Removal of Heavy Metals and Dyes from Aqueous Solutions Using Guipi Residue-Based Hydrogel.

The presence of organic dyes and heavy metal ions in water sources poses a significant threat to human health and the ecosystem. In this study, hydrogel adsorbents for water pollution remediation were synthesized using Guipi residue (GP), a cellulose material from Chinese herbal medicine, and chitosan (CTS) through radical polymerization with acrylamide (AM) and acrylic acid (AA). The characteristics of the hydrogels were analyzed from a physicochemical perspective, and their ability to adsorb was tested using model pollutants such as Pb2+, Cd2+, Rhodamine B (RhB), and methyl orange (MO). The outcomes revealed that GP/CTS/AA-co-AM, which has improved mechanical attributes, effectively eliminated these pollutants. At a pH of 4.0, a contact duration of 120 min, and an initial concentration of 600 mg/L for Pb2+ and 500 mg/L for Cd2+, the highest adsorption capabilities were 314.6 mg/g for Pb2+ and 289.1 mg/g for Cd2+. Regarding the dyes, the GP/CTS/AA-co-AM hydrogel displayed adsorption capacities of 106.4 mg/g for RhB and 94.8 mg/g for MO, maintaining a stable adsorption capacity at different pHs. Compared with other competitive pollutants, GP/CTS/AA-co-AM demonstrated a higher absorption capability, mainly targeted toward Pb2+. The adsorption processes for the pollutants conformed to pseudo-second-order kinetics models and adhered to the Langmuir models. Even after undergoing five consecutive adsorption and desorption cycles, the adsorption capacities for heavy metals and dyes remained above 70% and 80%. In summary, this study effectively suggested the potential of the innovative GP/CTS/AA-co-AM hydrogel as a practical and feasible approach for eliminating heavy metals and dyes from water solutions.

Photodegradation of oxytetracycline hydrochloride by Z-scheme g-C3N4 @MIL-101(Fe) heterojunction: Experimental optimization, mechanism evaluation and practical application

The residues of oxytetracycline hydrochloride (OTC) in water have potential adverse effects on human health and ecological environment. Photocatalytic degradation has been widely studied in the treatment of antibiotic pollution due to its environmentally friendly and efficient characteristics. However, the band gap of traditional photocatalysts is too wide, and the recombination of photogenerated electrons and holes is serious, which has negative effects on photocatalysis. Therefore, the Z-scheme heterojunction g-C3N4@MIL-101(Fe) composite photocatalyst was synthesized by high temperature calcination combined with solvothermal method. g-C3N4@MIL-101(Fe) was characterized by XRD, FTIR, SEM, TEM and other tests. All the results showed that the compound was successful A series of photoelectric tests showed that g-C3N4@MIL-101(Fe) has a narrower band gap, stronger light absorption ability, and improved the separation rate of photogenerated electrons and holes. Under visible light irradiation, g-C3N4@MIL-101(Fe) could remove 87.68% of OTC in 300 min. g-C3N4 @MIL-101(Fe) showed good potential for practical application in five real water samples and stability after six cycles. Finally, superoxide radicals and hole radicals were identified as the main reactive species in the photodegradation process. The mechanism and pathway of the photocatalytic degradation of OTC by g-C3N4@MIL-101(Fe) are proposed. This work expands the construction and application of Fe-MOF based Z-scheme heterostructure and provides a new idea for water pollution remediation.

Comparative study of visible-light active BiOI and N,Pd-TiO2 photocatalysts: Catalytic ozonation for dye degradation

The increasing demand for clean water requires the development of simple, cheap, and efficient catalysts systems for water pollution remediation. To develop cheap yet efficient hybrid advanced oxidation processes for degradation of organic pollutants in water requires their systematic comparison under similar conditions to make informed decisions of economically feasible and sustainable systems. Visible light active single BiOI and N, Pd co-doped TiO2 were investigated for photocatalytic ozonation (PCO) for methylene blue (MB) degradation. Metal and non-metal co-doping improved morphology, band structure and active sites on the surface of TiO2 to shift its light absorption into the visible region. The degradation of MB with BiOI PCO and N,Pd-TiO2 PCO was practically similar but showed improvement of the ozonation mineralization efficiency. However, mineralization of MB on BiOI PCO surpassed that of N,Pd-TiO2 PCO due to band structure that influenced generated free radicals during the PCO processes. BiOI PCO system progressed through the existence and involvement of strongly oxidizing and non-selective hydroxyl radicals towards enhanced mineralization of dye and intermediates while N,Pd-TiO2 PCO was steered by the superoxide radical that is selective and had lower mineralization efficiency of formed intermediates despite its high initial degradation efficacy. The work demonstrated cheap and efficient visible light active semiconductors like BiOI as potential candidates for application in photocatalytic ozonation for real applications with matching activities to that of co-doped UV active semiconductors like TiO2. This work advances the use of visible light active semiconductors towards PCO based processes for environmental pollution remediation.

Water pollution remediation: Synthesis and characterization of poly(o‐methylaniline)/ZnO/rGO composite for photocatalytic degradation of dyes

AbstractWater pollution is growing at an alarming rate, particularly due to the colored wastewater released by the various industries into aquifers and fresh water sources, and in some extreme cases, they have reached the water table. Faisalabad, a city in Pakistan where there is an industrial cluster of textiles dyeing and manufacturers, water table has become undrinkable. The presence of hazardous dyes and chemicals imposes serious health issues on humans, animals, and plants. The treatment of such toxic dye effluents is crucial and could be done by efficient degradation methods such as photocatalysis. The current study presents synthesis of poly(o‐methylaniline)/zinc oxide/reduced graphene oxide nanocomposite (POMA/ZnO/rGO NC) using a chemical oxidative polymerization process and explores its properties as a photocatalyst by demonstrating degradation of three dyes. The composite was characterized using X‐ray diffraction (XRD), Fourier‐transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), photoluminescence emission spectroscopy (PL), Brunauer Emmett–Teller analysis (BET), and UV–visible spectroscopy (UV–visible). Further, the photocatalytic activity of POMA/ZnO/rGO NC was evaluated and compared by degrading the direct yellow 12 (DY 12), congo red (CR), and malachite green (MG) dyes in aqueous media under UV irradiation. The results indicated that after 110 min, POMA/ZnO/rGO composite degraded the dyes by 92% (DY 12), 86.1% (CR), and 82.1% (MG), respectively. Moreover, kinetic studies of the photocatalyst were also performed along with reusability test, total organic carbon, chemical oxygen demand, and degradation mechanism.