Copper-doped ZrO2 nanoparticles as high-performance catalysts for efficient removal of toxic organic pollutants and stable solar water oxidation

Agro-industrial wastes and their application perspectives in metal decontamination using biocomposites and bacterial biomass: a review

Contamination of water bodies is a significant global issue that results from the deliberate release of pollutants into the environment, especially from mining and metal processing industries. The main pollutants generated by these industries are metallic wastes, particularly metals, which can cause adverse effects on the environment and human health. Therefore, it is crucial to develop effective and sustainable approaches to prevent their discharge into the environment. Biofiltration is a technique used to remediate contaminated fluids using biological processes. Microorganisms and agro-industrial wastes have been used successfully as biosorbents. Hence, this review emphasizes the innovative use of agro-industrial waste reinforced with microbial biomass as bioadsorbents, highlighting their dual capacity for metal removal through various bioremediation mechanisms. The mechanisms at play in these biocomposite materials, which offer enhanced sustainability, are also analyzed. This study contributes to the advancement of knowledge by suggesting new strategies for integrating reinforced materials in biosorption processes, thus providing a novel perspective on the potential of lignocellulosic-based systems to improve decontamination efforts. On the other hand, it shows some studies where the optimization and scaling-up of biosorption processes are reported. Additionally, the implementation of multisystem approaches, leveraging multiple bioremediation techniques simultaneously, can further enhance the efficiency and sustainability of metal removal in contaminated environments.

Zirconium and cerium dioxide fabricated activated carbon-based nanocomposites for enhanced adsorption and photocatalytic removal of methylene blue and tetracycline hydrochloride

Activated carbon (AC) is a porous, amorphous form of carbon known for its strong adsorption capacity, making it highly effective for use in wastewater treatment. In this investigation, AC-based nanocomposites (NCs) loaded with zirconium dioxide and cerium dioxide nanoparticles (ZrO2/CeO2 NPs) were successfully synthesized for the effective elimination of methylene blue (MB) and tetracycline hydrochloride (TCH). The AC-ZrO2/CeO2 NCs have a size of 231.83 nm, a zeta potential of -20.07 mV, and a PDI value of 0.160. The adsorption capacities of AC-ZrO2/CeO2 NCs for MB and TCH were proved in agreement with the Langmuir isotherm and pseudo 1st order kinetic model, respectively. The maximum adsorption capacities were determined to be 75.54 mg/g for MB and 26.75 mg/g for TCH. Notably, AC-ZrO2/CeO2 NCs exhibited superior photocatalytic degradation efficiency for MB and TCH under sunlight irradiation with removal efficiencies reaching up to 97.91% and 82.40% within 90 min, respectively. The t1/2 for the photo-degradation process of MB and TCH were 11.55 min and 44.37 min. Analysis of active species trapping confirmed the involvement of hole (h+), superoxide anion (•O2-), and hydroxyl radical (•OH) in the degradation mechanism. Furthermore, the residual solution post-contaminant removal exhibited minimal toxicity towards Artemia salina and NIH3T3 cells. Importantly, the NCs did not exhibit antibacterial activity against tested pathogens post-absorption/degradation of TCH. Thus, AC-ZrO2/CeO2 NCs could be a promising nanomaterial for wastewater treatment applications.

Mechanisms in the photocatalytic breakdown of persistent pharmaceutical and pesticide molecules over TiO2-based photocatalysts: A review

Titanium dioxide (TiO2) based photocatalysts have been widely used as a photocatalyst for the degradation of various persistent organic compounds in water and air. The degradation mechanism involves the generation of highly reactive oxygen species, such as hydroxyl radicals, which react with organic compounds to break down their chemical bonds and ultimately mineralize them into harmless products. In the case of pharmaceutical and pesticide molecules, TiO2and modified TiO2photocatalysis effectively degrade a wide range of compounds, including antibiotics, pesticides, and herbicides. The main downside is the production of dangerous intermediate products, which are not frequently addressed in the literature that is currently available. The degradation rate of these compounds by TiO2photocatalysis depends on factors such as the chemical structure of the compounds, the concentration of the TiO2catalyst, the intensity, the light source, and the presence of other organic or inorganic species in the solution. The comprehension of the degradation mechanism is explored to gain insights into the intermediates. Additionally, the utilization of response surface methodology is addressed, offering a potential avenue for enhancing the scalability of the reactors. Overall, TiO2photocatalysis is a promising technology for the treatment of pharmaceutical and agrochemical wastewater, but further research is needed to optimize the process conditions and to understand the fate and toxicity of the degradation products.

Te4+ and Er3+ doped ZrO2 nanoparticles with enhanced photocatalytic, antibacterial activity and dielectric properties: A next generation of multifunctional material

Amid rising water contamination from industrial sources, tackling toxic dyes and pathogens is critical. Photocatalysis offers a cost-effective and eco-friendly solution to this pressing challenges. Herein, we synthesized Te4+ and Er3+ doped ZrO2 photocatalysts through hydrothermal method and investigated their efficacy in degrading Congo red (CR) and pathogens under visible light. XRD and Raman Spectroscopy confirm monoclinic and tetragonal mixed-phases without any impurities. Doping-induced defects, reduced crystalline diameter, high surface area, modified bandgap (2.95 eV), photoluminescence quenching, coupled with interfacial polarization, contribute to EZO's excellent dielectric response (1.149 × 106), for achieving remarkable photocatalytic activity, verified by photoelectrochemical measurements, LC-MS and phytotoxicity analysis. Under optimal conditions, EZO achieves 99% CR degradation within 100 min (TOC 79.9%), surpassing ZO (77%) and TZO (84%). Catalyst dosages, dye concentrations, and solution pH effect on EZO's photocatalytic performance are systematically assessed. Scavenging experiment emphasized the pivotal role of · OH in CR degradation with 96.4% efficiency after 4 cycles, affirming its remarkable stability. Moreover, EZO demonstrates ROS-mediated antibacterial activity against E. faecalis and E. coli bacteria under visible light, achieving >97% and >94% inhibition rate with an inhibition zone > 3 mm. Hence, the nanoparticle's dual action offers a practical solution for treating contaminated wastewater, ensuring safe irrigation.

CoFe2O4/PANI/MWCNTs ternary hybrid composites. Synthesis, characterization, the effect of MWCNTs ratio and dye removal capability

We have synthesized cobalt ferrite (CoFe2O4) using the sucrose auto-combustion method and subsequently employed the in situ polymerization technique to fabricate ternary composites comprising CoFe2O4, polyaniline (PANI), and multi-walled carbon nanotubes (MWCNTs). In this novel investigation, we explored the influence of varying MWCNTs ratios on these composites' structural, magnetic, thermal, and electrical properties. The crystal structures of the synthesized composites were analyzed using X-ray diffraction (XRD), while Fourier transform infrared (FT-IR) spectroscopy revealed changes in bonding patterns, including the disappearance of ferrite bonds and the emergence of new ones. Transmission electron microscopy (TEM) images illustrated a complete coating of PANI on both MWCNTs and CoFe2O4 particles, resulting in a substantial reduction in magnetization compared to pure CoFe2O4 ferrite due to PANI's nonmagnetic nature. Vibrating sample magnetometer (VSM) measurements confirmed this reduction, indicating a decrease to 7.3 emu.g-1. Thermal analysis demonstrated an enhancement in thermal stability with increasing MWCNTs content, as evidenced by an increase in the temperature equivalent for half decomposition (T50) from 486 to 522 °C for composites with 40% MWCNTs. Moreover, the electrical conductivity showed a corresponding rise with MWCNTs content, increasing from 3.1 × 10-3 Ω-1.cm-1 to 2.2 × 10-2 Ω-1.cm-1, possibly indicating charge transfer from PANI to MWCNTs. To assess practical applications, we investigated the ability of the composite with 40% MWCNTs to remove phenol red (PR) dye from aqueous solutions. Through a systematic study of adsorption parameters and kinetics, we determined optimal conditions for effective dye removal and elucidated the underlying adsorption mechanism. Our results demonstrated the composite's efficiency in dye removal, with a 6.4 mg·g-1 capacity for PR dye, highlighting its potential for environmental remediation efforts.

Unraveling the effect of Cu doping on the structural and morphological properties and photocatalytic activity of ZrO2

Pristine ZrO2 and doped with different concentrations of Copper (0-7 %) were synthesized using a sol-gel combustion route. Several advanced techniques like XRD, EDX, TEM, XPS, P.L., and UV-vis spectrophotometer have characterized the compositions. The XRD proved that all peaks matched with a tetragonal phase of ZrO2 without any impurities of other phases. An average crystallite size rises from 20 to 55 nm by increasing the concentrations of Copper. The elemental analysis was examined by EDX and confirmed the presence of Cooper, Zirconium, and Oxygen. The red shift was observed due to a decrease in the bandgap (5.5-4.01 eV) with increasing the Cu concentrations. From the analysis of photocatalysis of pure ZrO2 and different concentrations of Cu-doped ZrO2 for M.B., RHB, and mix of them. The increase in doping of Cu led to enhancing the performance of the removing MB from 35 to 80 %, however, the RHB degradation was from 42 to 81 % while the mix of M.B. and RHB reached 85 % with 7 % Cu-doping ZrO2.

Photocatalytic activity of visible-light-driven L-Proline-TiO2/BiOBr nanostructured materials for dyes degradation: The role of generated reactive species

L-Proline (2%)-TiO₂/BiOBr (30%) nanocomposite was synthesized to obtain high photocatalytic performance in the visible light region and infrared radiation(IR) for methylene blue (MB) and congo red (CR) removal from the contaminated wastewater. L-Proline (2%)-TiO₂/BiOBr (30%) photocatalyst with strong absorption near IR wavelength and high charge separation ability was fabricated for the first time. X-ray diffraction (XRD), Fourier transform infrared (FTIR), field-emission scanning electron microscope (FESEM)/Energy Dispersive X-ray (EDX), UV-Vis diffuse reflectance spectrum (DRS), photoluminescence (PL) and Brunauer-Emmett-Teller (BET) characterization techniques show that the visible driven nanocomposite was successfully synthesized. According to the UV-DRS analysis, the estimated band gaps for the L-proline (2%)-TiO₂ and L-Proline (2%)-TiO₂/BiOBr (30%) nanostructures were respectively 2.3 eV and 2.1 eV.The nanoparticles exhibited enhanced photocatalytic activity (93-100%) and high mineralization efficiency (71-89% TOC removal) for both the dyes. The best photocatalytic activity was achieved by adding 2 wt% of L-Proline and 30 wt% of BiOBr into TiO₂ sol. Response surface methodology (RSM) was employed to find significant parameters and their optimum values for maximum degradation, which show pH, dye concentration, irradiation time, and catalyst dosage for both the dyes are significant. The best photocatalytic degradation efficiency was achieved at the optimum conditions of pH = 7.7, catalyst dosage = 0.71 g/L, irradiation time = 142 and dye concentration = 11 mg/L for MB. Scavenger study showed that •OH radicals are responsible for the degradation process.

Sulfite activation by cobaltosic oxide nanohydrangeas for tetracycline degradation: Performance, degradation pathways and mechanism

Sulfite has been used as a classic reductant for the dehalogenation and reduction of organic compounds for a long time, it is recently deemed as a promising alternative (for persulfate) to generate sulfate radical for wastewater treatment due to its low price and eco-toxicity. In contrast with the enormous work developed in the field of tetracycline (TC) degradation via PMS activization, sulfite activization could play a important role in TC degradation but there is only very few available reports in this area. Herein, the novel and efficient CoNHs nanocatalyst is designed and developed, via immobilization of hydrangea-shaped Co₃O₄ nanoparticles onto graphitic carbon nanosheet (GCN), for the degradation of tetracycline via sulfite activation. The detailed characterizations have confirmed that CoNHs possesses a nanohydrangea-shaped structure with high microporosity. The comparison with other supports (such as CeO₂ and MoS₂), CoNHs provides the highest degradation efficiency in TC degradation, due to the synergistic effect between Co₃O₄ and GCN. Free radical quenching experiments and EPR analysis confirm that SO₄•^- and O₂•^- are major reactive oxygen species in the CoNHs/sulfite system. This work could provide a simple, economical and durable cobalt-based catalyst for organic wastewater treatment via sulfite activation.

Leveraging the potential of silver nanoparticles-based materials towards sustainable water treatment

Increasing demand of pure and accessible water and improper disposal of waste into the existing water resources are the major challenges for sustainable development. Nanoscale technology is an effective approach that is increasingly being applied to water remediation. Compared to conventional water treatment processes, silver nanotechnology has been demonstrated to have advantages due to its anti-microbial and oligodynamic (biocidal) properties. This review is focused on environmentally friendly green syntheses of silver nanoparticles (AgNPs) and their applications for the disinfection and microbial control of wastewater. A bibliometric keyword analysis is conducted to unveil important keywords and topics in the utilisation of AgNPs for water treatment applications. The effectiveness of AgNPs, as both free nanoparticles (NPs) or as supported NPs (nanocomposites), to deal with noxious pollutants like complex dyes, heavy metals as well as emerging pollutants of concern is also discussed. This knowledge dataset will be helpful for researchers to identify and utilise the distinctive features of AgNPs and will hopefully stimulate the development of novel solutions to improve wastewater treatment. This review will also help researchers to prepare effective water management strategies using nano silver-based systems manufactured using green chemistry.

Covalent and Non-covalent Functionalized Nanomaterials for Environmental Restoration

Nanotechnology has emerged as an extraordinary and rapidly developing discipline of science. It has remolded the fate of the whole world by providing diverse horizons in different fields. Nanomaterials are appealing because of their incredibly small size and large surface area. Apart from the naturally occurring nanomaterials, synthetic nanomaterials are being prepared on large scales with different sizes and properties. Such nanomaterials are being utilized as an innovative and green approach in multiple fields. To expand the applications and enhance the properties of the nanomaterials, their functionalization and engineering are being performed on a massive scale. The functionalization helps to add to the existing useful properties of the nanomaterials, hence broadening the scope of their utilization. A large class of covalent and non-covalent functionalized nanomaterials (FNMs) including carbons, metal oxides, quantum dots, and composites of these materials with other organic or inorganic materials are being synthesized and used for environmental remediation applications including wastewater treatment. This review summarizes recent advances in the synthesis, reporting techniques, and applications of FNMs in adsorptive and photocatalytic removal of pollutants from wastewater. Future prospects are also examined, along with suggestions for attaining massive benefits in the areas of FNMs.

Novel g-C3N4/Cu-doped ZrO2 hybrid heterostructures for efficient photocatalytic Cr(VI) photoreduction and electrochemical energy storage applications

Pure ZrO₂, graphitic carbon nitride, Cu-doped ZrO₂ nanoparticles (Cu-Zr), and doped Cu-Zr nanoparticles decorated on the g-C₃N₄ surface (g-CuZr nanohybrids) were successfully prepared by a hydrothermal technique. Synthesized catalysts were examined by XRD, FE-SEM, TEM, UV-Vis spectroscopy, photoluminescence (PL), and BET surface measurements, respectively. The photocatalytic reduction of Cr(VI) photoreduction as well as energy storage supercapacitor applications were thoroughly investigated. The g-CuZr hybrid photocatalyst outperformed other pristine photocatalysts in terms of light absorption and catalytic Cr(VI) reduction performance under stimulated solar light irradiation. Furthermore, methylene blue (MB) was used as a photosensitizer to further improve the Cr(VI) photoreduction performance. In precise, the heterostructured hybrid catalyst exhibited improved photocatalytic Cr(VI) photoreduction activity (∼88.1%) in 5 mg/L MB solution over other catalysts. Moreover, the decoration of Cu-Zr on the surface of g-C₃N₄ enhanced the absorption ability of light and catalytic Cr(VI) photoreduction performance. The PL, EIS, and transient photocurrent analysis demonstrated that the efficiency of the charge carrier's separation in the nanohybrid catalyst was superior over other catalysts. Furthermore, heterostructured g-CuZr nanohybrid electrode exhibited superior specific capacitance (297.2 F/g) over other electrodes, which are 5.5 folds (54.01 F/g), ∼2 folds (144.01 F/g) better than pure ZrO₂ and g-C₃N₄ electrodes. Likewise, the nanohybrid electrode retained about 90% of the capacitive value after 2500 cycles over its initial capacitance.

Nanobioremediation: A sustainable approach for the removal of toxic pollutants from the environment

In recent years, the proportion of organic and inorganic contaminants has increased rapidly due to growing human interference and represents a threat to ecosystems. The removal of these toxic pollutants from the environment is a difficult task. Physical, chemical and biological methods are implemented for the degradation of toxic pollutants from the environment. Among existing technologies, bioremediation in combination with nanotechnology is the most promising and cost-effective method for the removal of pollutants. Numerous studies have shown that exceptional characteristics of nanomaterials such as improved catalysis and adsorption properties as well as high reactivity have been subjects of great interest. There is an emerging trend of employing bacterial, fungal and algal cultures and their components, extracts or biomolecules as catalysts for the sustainable production of nanomaterials. They can serve as facilitators in the bioremediation of toxic compounds by immobilizing or inducing the synthesis of remediating microbial enzymes. Understanding the association between microorganisms, contaminants and nanoparticles (NPs) is of crucial importance. In this review, we focus on the removal of toxic pollutants using the cumulative effects of nanoparticles with microbial technology and their applications in different domains. Besides, we discuss how this novel nanobioremediation technique is significant and contributes towards sustainability.

Novel Z-scheme binary zinc tungsten oxide/nickel ferrite nanohybrids for photocatalytic reduction of chromium (Cr (VI)), photoelectrochemical water splitting and degradation of toxic organic pollutants

A simple hydrothermal approach was demonstrated for synthesizing a coupled NiFe₂O₄-ZnWO₄ nanocomposite, wherein one-dimensional ZnWO₄ nanorods were inserted into two-dimensional NiFe₂O₄ nanoplates. Herein, we evaluated the photocatalytic removal of Cr(VI), and degradation of tetracycline (TC) and methylene blue (MB) by the nanocomposite, as well as its ability to split water. The ZnWO₄ nanorods enriched the synergistic interactions, upgraded the solar light fascination proficiency, and demonstrated outstanding detachment and migration of the photogenerated charges, as confirmed by a transient photocurrent study and electrochemical impedance spectroscopy measurements. Compared to pristine NiFe₂O₄ and ZnWO_4, the NiFe₂O₄-ZnWO₄ nanocomposite exhibited a higher Cr(VI) reduction (93.5%) and removal of TC (97.9%) and MB (99.6%). Radical trapping results suggested that hydroxyl and superoxide species are dominant reactive species, thereby facilitating the Z-scheme mechanism. Furthermore, a probable photocatalytic mechanism was projected based on the experimental results. The photoelectrochemical analysis confirmed that NiFe₂O₄-ZnWO₄ exhibited minor charge-transfer resistance and large photocurrents. We propose a novel and efficient approach for designing a coupled heterostructured nanocomposites with a significant solar light ability for ecological conservation and water splitting.

Production and utilization of pyrolysis oil from solidplastic wastes: A review on pyrolysis process and influence of reactors design

This paper reviews the new progress, challenges and barriers on production of pyrolysis oil from the plastic waste. Among the different processes thermal and catalytic are the potential methods to produce oil. Since the global plastic production increased over years the accumulation of plastic waste increases. Thus, converting the waste plastics into useful energy is very essential to avoid the environmental concerns. Initially the thermal pyrolysis process and its advantage on production of pyrolysis oil were discussed. During the thermal decomposition the waste plastic had been converted into the products such as gas, crude oil and solid residues. Secondly, the catalytic process and its recent trends were discussed. In addition, the factors affecting the catalytic pyrolysis process had been evaluated. Furthermore, the optimized concentration of catalyst subjected to the higher yield of fuel with low hydrocarbon content was found. The pyrolysis oil produced from the catalytic process has higher heating values, lower density and lower viscosity compared to thermal process. In addition, the application of pyrolysis oil on the diesel engines had been discussed. The effects of pyrolysis oil on combustion and emission characteristics were observed. This review summarizes the potential advantages and barriers of both thermal and catalytic process. Further, the optimized solutions and applications of pyrolysis oil are suggested for sustainability of the process. Besides the introduction of the pyrolysis oil were viable without making major modification to the existing engine design.

Recent advances in photocatalytic remediation of emerging organic pollutants using semiconducting metal oxides: an overview

Many untreated and partly treated wastewater from the home and commercial resources is being discharged into the aquatic environment these days, which contains numerous unknown and complex natural and inorganic compounds. These compounds tend to persist, initiating severe environmental problems, which affect human health. Conventionally, physicochemical treatment methods were adopted to remove such complex organic chemicals, but they suffer from critical limitations. Over time, photocatalysis, an advanced oxidation process, has gained its position for its efficient and fair performance against emerging organic pollutant decontamination. Typically, photocatalysis is a green technology to decompose organics under UV/visible light at ambient conditions. Semiconducting nanometal oxides have emerged as pioneering photocatalysts because of large active surface sites, flexible oxidation states, various morphologies, and easy preparation. The current review presents an overview of emerging organic pollutants and their effects, advanced oxidation processes, photocatalytic mechanism, types of photocatalysts, photocatalyst support materials, and methods for improving photodegradation efficiency on the degradation of complex emerging organic pollutants. In addition, the recent reports of metal-oxide-driven photocatalytic remediation of emerging organic pollutants are presented in brief. This review is anticipated to reach a broader scientific community to understand the first principles of photocatalysis and review the recent advancements in this field.

Intracellular Exposure Dose-Associated Susceptibility of Steatotic Hepatocytes to Metallic Nanoparticles

Non-alcoholic fatty liver disease (NAFLD), mainly characterized by the accumulation of excess fat in hepatocytes, is the most prevalent liver disorder afflicting ~25% of adults worldwide. In vivo studies have shown that adult rodents with NAFLD were more sensitive to metallic nanoparticles (MNPs) than healthy MNPs. However, due to the complex interactions between various cell types in a fatty liver, it has become a major challenge to reveal the toxic effects of MNPs to specific types of liver cells such as steatotic hepatocytes. In this study, we reported the susceptibility of steatotic hepatocytes in cytotoxicity and the induction of oxidative stress to direct exposures to MNPs with different components (silver, ZrO₂, and TiO₂ NPs) and sizes (20-30 nm and 125 nm) in an oleic acid (OA) -induced steatotic HepG2 (sHepG2) cell model. Furthermore, the inhibitory potential of MNPs against the process of fatty acid oxidation (FAO) were obvious in sHepG2 cells, even at extremely low doses of 2 or 4 μg/mL, which was not observed in non-steatotic HepG2 (nHepG2) cells. Further experiments on the differential cell uptake of MNPs in nHepG2 and sHepG2 cells demonstrated that the susceptibility of steatotic hepatocytes to MNP exposures was in association with the higher cellular accumulation of MNPs. Overall, our study demonstrated that it is necessary and urgent to take the intracellular exposure dose into consideration when assessing the potential toxicity of environmentally exposed MNPs.

CuZrO3: If it exists it should be a sandwich

CuZrO₃ has been hypothesized to be a catalytic material with potential applications for CO₂ reduction. Unfortunately, this material has received limited attention in the literature, and to the best of our knowledge the exact crystal structure is still unknown. To address this challenge, we utilize several different structural prediction techniques in concert, including the Universal Structure Predictor: Evolutionary Xtallography (USPEX), the Materials Project Structure Predictor, and the Open Quantum Materials Database (OQMD). Leveraging these structural prediction techniques in conjunction with Density-Functional Theory (DFT) calculations, we determine a possible structure for CuZrO₃, which resembles a "sandwich" morphology. Our calculations reveal that this new structure is significantly lower in energy than a previously hypothesized perovskite structure, albeit it still has a thermodynamic preference to decompose into CuO and ZrO₂. In addition, we experimentally tried to synthesize CuZrO₃ based on literature reports and compared computational to experimental X-ray Diffraction (XRD) patterns confirming that the final product is a mixture of CuO and ZrO₂. Finally, we conducted a computational surface energetics and CO₂ adsorption study on our discovered sandwich morphology, demonstrating that CO₂ can adsorb and activate on the material. However, these CO₂ adsorption results deviate from previously reported results further confirming that the CuZrO₃ is a metastable form and may not be experimentally accessible as a well-mixed oxide, since phase segregation to CuO and ZrO₂ is preferred. Taken together, our combined computational and experimental study provides evidence that the synthesis of CuZrO₃ is extremely difficult and if this oxide exists, it should have a sandwich-like morphology.

Investigation of electrochemical performance of an efficient Ti2O3-CeO2 nanocomposite for enhanced pollution-free energy conversion applications

The development of an economical, abundant, stable, and greatly active electrocatalyst for water oxidation is extremely important for future energy conversion system. Electrochemical water splitting is a new move toward H₂ and O₂ gas production. It can be used in sustainable and pollution-free energy conversion applications. In this work, Ti₂O₃-CeO₂ nanocomposites were successfully synthesized with different molar ratios by facile hydrothermal method for electrochemical water oxidation. Mixed phase structure of Ti₂O₃-CeO₂ nanocomposites was confirmed by X-ray diffraction spectra and well identified by highest peak of Ti₂O₃ in 2θ values of 33.0 and CeO₂ in 2θ values of 28.5. The characteristic peaks from Raman and photoluminescence spectroscopy further confirmed Ti₂O₃-CeO₂ nanocomposite formation. Existence of multidimensional nanostructures such as nanoparticles and small nanocubes of Ti₂O₃-CeO₂ nanocomposites were investigated by scanning electron microscope images. Mesoporous nature of Ti₂O₃-CeO₂ nanocomposites was further analyzed by Brunauer-Emmett-Teller analysis. The high surface area could benefit the Ti₂O₃-CeO₂ nanocomposites with greatly improved oxygen evolution reaction (OER) performance. In three molar ratios, 1:3 M ratios of Ti₂O₃-CeO₂ nanocomposites showed high catalytic action at overpotential of 244 mV. The best OER electrocatalyst was obtained by 1:3 M ratios of Ti₂O₃-CeO₂ nanocomposites, which exhibited high current density and high specific capacitance values of 238 mA/g and 517 F/g, respectively. Therefore, Ti/Ce molar ratio played a crucial role in enhancing the OER performance.

Electrochemical investigations for COVID-19 detection-A comparison with other viral detection methods

Virus-induced infection such as SARS-CoV-2 is a serious threat to human health and the economic setback of the world. Continued advances in the development of technologies are required before the viruses undergo mutation. The low concentration of viruses in environmental samples makes the detection extremely challenging; simple, accurate and rapid detection methods are in urgent need. Of all the analytical techniques, electrochemical methods have the established capabilities to address the issues. Particularly, the integration of nanotechnology would allow miniature devices to be made available at the point-of-care. This review outlines the capabilities of electrochemical methods in conjunction with nanotechnology for the detection of SARS-CoV-2. Future directions and challenges of the electrochemical biosensors for pathogen detection are covered including wearable and conformal biosensors, detection of plant pathogens, multiplexed detection, and reusable biosensors for on-site monitoring, thereby providing low-cost and disposable biosensors.

Metal-facilitated Photocatalytic Nanohybrids: Rational Design and Promising Environmental Applications

As a promising technique to potentially address the energy crisis and environmental issues, photocatalysis has been reported widely to exhibit various outstanding behaviors in production of new fuels/chemicals and treatment of contaminants. The photocatalytic performance is extremely dependent on the used photocatalysts, so that the design and preparation of efficient photocatalysts are critically important for significantly improving the photocatalytic activity. Among various strategies, the hybridization of metal with semiconductors has recently been attracting more and more research interest owing to their expended spectral absorption, promoted transferring rate of charge carriers and Plasmon-enhanced effect. In this minireview, the metal-facilitated hybrid photocatalysts are overviewed comprehensively to first reveal unique functions of metals in improvement of photoactivity and summarize the emerging metal-involved hybrid systems. Subsequently, the synthetic methods towards hybrid photocatalysts are introduced and their practical applications are emphasized in environmental remediation including degradation of organic pollutants, conversion of harmful gases, treatment of heavy metal ions and sterilization of bacteria. At the end, the challenges for industrializing these hybrid photocatalysts are discussed carefully and future development is suggested rationally.

A Facile Fabrication of ZnFe2O4/Sepiolite Composite with Excellent Photocatalytic Performance on the Removal of Tetracycline Hydrochloride

The excellent photo-response of ZnFe2O4 in the visible light region makes it a promising catalyst, whereas some defects like serious particle agglomeration and easy recombination of photo-generated electron-hole pairs hinder its application. In this work, the ZnFe2O4/sepiolite (ZF-Sep) composites were synthesized using a co-precipitation method. The obtained ZF-Sep composites were characterized by XRD, SEM, TEM, FT-IR, XPS, BET, VSM and DRS. Moreover, the photocatalytic performance was evaluated by the tetracycline hydrochloride removal efficiency under simulated visible light illumination. The results displayed that the ZnFe2O4 with average sizes about 20 nm were highly dispersed on sepiolite nanofibers. All the composites exhibited better photocatalytic performance than pure ZnFe2O4 due to the synergistic effect of the improvement on the agglomeration phenomenon of ZnFe2O4 and the reduction on the recombination rate of photo-generated electrons and holes. The optimum removal efficiency was that of the ZF-Sep-11 composite, which reached 93.6% within 3 h. Besides, the composite exhibited an excellent stability and reusability. Therefore, ZF-Sep composite is a promising catalyst for the treatment of wastewater contained antibiotics.

A novel bio-electro-Fenton system with dual application for the catalytic degradation of tetracycline antibiotic in wastewater and bioelectricity generation

In this new insight, the potential application of the eco-friendly Bio-Electro-Fenton (BEF) system was surveyed with the aim of simultaneous degradation of tetracycline and in situ generation of renewable bioenergy without the need for an external electricity source. To shed light on this issue, catalytic degradation of tetracycline was directly accrued via in situ generated hydroxyl free radicals from Fenton's reaction in the cathode chamber. Simultaneously, the in situ electricity generation as renewable bioenergy was carried out through microbial activities. The effects of operating parameters, such as electrical circuit conditions (in the absence and presence of external resistor load), substrate concentration (1000, 2000, 5000, and 10 000 mg L⁻¹), catholyte pH (3, 5, and 7), and FeSO₄ concentration (2, 5, and 10 mg L⁻¹) were investigated in detail. The obtained results indicated that the tetracycline degradation was up to 99.04 ± 0.91% after 24 h under the optimal conditions (short-circuit, pH 3, FeSO₄ concentration of 5 mg L⁻¹, and substrate concentration of 2000 mg L⁻¹). Also, the maximum removal efficiency of anodic COD (85.71 ± 1.81%) was achieved by increasing the substrate concentration up to 2000 mg L⁻¹. However, the removal efficiencies decreased to 78.29 ± 2.68% with increasing substrate concentration up to 10 000 mg L⁻¹. Meanwhile, the obtained maximum voltage, current density, and power density were 322 mV, 1195 mA m⁻², and 141.60 mW m⁻², respectively, at the substrate concentration of 10 000 mg L⁻¹. Present results suggested that the BEF system could be employed as an energy-saving and promising technology for antibiotic-containing wastewater treatment and simultaneous sustainable bioelectricity generation.

In this new insight, the potential application of the Bio-Electro-Fenton system was surveyed with the aim of simultaneous degradation of tetracycline and in situ generation of renewable bioenergy without the need for an external electricity source.

Microplastics in the environment: Occurrence, perils, and eradication

Microplastics (MPs) with sizes < 5 mm are found in various compositions, shapes, morphologies, and textures that are the major sources of environmental pollution. The fraction of MPs in total weight of plastic accumulation around the world is predicted to be 13.2% by 2060. These micron-sized MPs are hazardous to marine species, birds, animals, soil creatures and humans due to their occurrence in air, water, soil, indoor dust and food items. The present review covers discussions on the damaging effects of MPs on the environment and their removal techniques including biodegradation, adsorption, catalytic, photocatalytic degradation, coagulation, filtration and electro-coagulation. The main techniques used to analyze the structural and surface changes such as cracks, holes and erosion post the degradation processes are FTIR and SEM analysis. In addition, reduction in plastic molecular weight by the microbes implies disintegration of MPs. Adsorptive removal by the magnetic adsorbent promises complete elimination while the biodegradable catalysts could remove 70-100% of MPs. Catalytic degradation via advanced oxidation assisted by S O 4 • - or O H • radicals generated by peroxymonosulfate or sodium sulfate are also adequately covered in addition to photocatalysis. The chemical methods such as sol-gel, agglomeration, and coagulation in conjunction with other physical methods are discussed concerning the drinking water/wastewater/sludge treatments. The efficacy, merits and demerits of the currently used removal approaches are reviewed that will be helpful in developing more sophisticated technologies for the complete mitigation of MPs from the environment.

Construction of an electrochemical sensor with graphene aerogel doped with ZrO2 nanoparticles and chitosan for the selective detection of luteolin

A simple, fast and sensitive method for the detection of luteolin is proposed based on the chitosan/reduced graphene oxide aerogel with dispersed ZrO₂ nanoparticles modified glassy carbon electrode (ZrO₂/CS/rGOA-GCE) as an electrochemical sensor. The ZrO₂/CS/rGOA composite was prepared by one pot synthesis from a mixture of GO, CS and zirconyl chloride octahydrate, and subsequently be freeze-dried. Scanning electron microscope images showed a typical thin, wrinkled and fluctuant morphology of graphene nanosheets and the polymerized CS and ZrO₂ nanoparticles deposited on the surface of rGOA. Cyclic voltammetry and differential pulse voltammetry were used to measure the electrochemical response of ZrO₂/CS/rGOA composite-based biosensor towards luteolin at the working potential window (-0.8-0.8 V). The improved performance of this biosensor was attributed to efficient electron transfer and large surface area of 3D rGOA, and high specific activity of Zr towards adjacent hydroxyl groups. Under optimized conditions, the analytical performance of this method towards luteolin was investigated with a detection limit of 1 nM and a linear range from 5 nM to 1000 nM.. Finally, the ZrO₂/CS/rGOA-GCE electrochemical method coupled with solid phase extraction was used for the detection of luteolin in real samples. Recoveries of  spiked samples with different concentrations were in the range 78.6-103.3% with a relative RSD lower than 12.0%. Graphical abstract Schematic representation of the preparation of the ZrO₂ nanoparticles and chitosan doped graphene aerogel modified electrode. The electrode was employed for the detection of luteolin coupled with the solid-phase extraction technique.

Photoelectrocatalytic reactor improvement towards oil-in-water emulsion degradation

Oil-in-water (O/W) emulsion is critical wastewater that is challenging to eliminate and requires a long treatment process, and it is necessary to develop highly effective removal methods before releasing it into natural water sources. This research has selected the photoelectrocatalytic (PEC) technique to solve this problem by developing a PEC reactor for high efficiency in O/W degradation and understanding the essential factors related to the PEC reactor's efficiency improvement. The PEC reactor has been designed on a large scale with suitable positioning of an electrode that is, designing a light source near the anode electrode to enhance light irradiation efficiency and including a circulating pump to provide continuous flow to the solution through the electrode surface. We studied the main factors of supporting the electrolyte, electrode characteristics, and catalytic process. We investigated the O/W-degradation efficiency using a UV/Vis spectrophotometer, chemical oxygen demand (COD) measurement, and GC-MS analysis. We optimized the PEC reactor using the developed BiVO₄ photoanodes and placed them parallel with the zinc plates. Then, we controlled the applied potential at 1.0 V in 0.1 M Na₂SO₄ supporting an electrolyte under visible light irradiation. The developed PEC reactor can be degraded in the O/W emulsion up to 76% and decreased the COD value up to 78% for 7h. This PEC cell can be completely decomposed of many functional groups, such as carbonyl, ester, nitrile, amine, phosphate, chloro group, and nitro group, that were contained in the O/W substance. The highlight of this research is the designed light source and circulating pump inside of the PEC reactor to enhance the light irradiation, refresh the anode electrode, and understand the critical factor for the improvement of O/W-degradation efficiency. This PEC reactor presents a high-efficiency O/W degradation with practical use and a fast process suitable for further application in high turbidity of wastewater treatment from the oil industry.

Removal of nickel(II) from wastewater using a zeolite-packed anaerobic bioreactor: Bacterial diversity and community structure shifts

In recent years, overexploited industrialization and urbanization activities have led to significant amounts of heavy metals released into the environment. Metal ion contamination of water, especially with toxic metals such as nickel(II) [Ni(II)], which is extensively applied in the electroplating industry, has been a serious problem. The aim of the present study was to evaluate the Ni(II) removal from real industrial wastewater using a 2 L, lab-scale, up-flow, anaerobic, zeolite-packed bioreactor inoculated with a heterotrophic consortium as the bioadsorbent. High-throughput sequencing of 16S rRNA genes revealed significant shifts in their bacterial diversity and structural composition along the bioreactor treatment location, where the bacterial genus was dominated by Kosmotogae followed by Firmicutes as Ruminococcus and Clostridium. However, Fervidobacterium and the Geobacter genus were absent at the end of the bioreactor treatment, suggesting that they play a key role in the beginning of Ni(II) removal anaerobic treatment. The physico-chemical results revealed that the Ni(II) removal rate was 99% for 250-500 ppm metal tested, with an efficient alkalinity rate and high production of biogas, which confirmed that anaerobic digestion of microorganisms was successfully performed through the process. Finally, this anaerobic bioreactor configuration offers an accessible and ecofriendly high-rate metal removal strategy from mining and electroplating effluents.

Simultaneous catalytic reduction of p-nitrophenol and hydrogen production on MIL-101(Fe)-based composites

MIL-101(Fe)-based composite materials and their application for the generation of H₂ by the catalytic reduction of nitro organics are reported in this study.

One-step synthesis of high photocatalytic graphitic carbon nitride porous nanosheets

As a metal-free photocatalyst, graphitic carbon nitride (g-C₃N₄) has attracted tremendous attention. Preparation of porous few-layer g-C₃N₄ nanosheets has been proven to be an effective strategy to obtain high photocatalytic performance. At present, most methods are expensive, time-consuming or complicated. Here, a low-cost, facile and environment-friendly one-step synthesis method of porous few-layer g-C₃N₄ nanosheets is designed by introducing water in the precursor. Straightforward calcination of the precursor, which decomposes to form ammonia, can produce g-C₃N₄ nanosheets with the assistance of water. Under the visible light (>400 nm), the photocatalytic H₂ evolution performance of the so-obtained nanosheets is 3214 μmol · g^-1 · h^-1, which is 17.3 times of the original bulk g-C₃N₄. The apparent quantum yield is 27% under the 380 nm monochromatic light irradiation.