Heterogeneous UV-Switchable Au nanoparticles decorated tungstophosphoric acid/TiO2 for efficient photocatalytic degradation process

Unveiling the remarkable simultaneous adsorption-photocatalytic potential of Ag nanoparticles-anchored phosphotungestic acid loaded ZIF-8 for Congo red removal

This research paper presents a direct approach to synthesize AgNPs deposited on polyoxometalate/ZIF-8 on-site (referred to as AgNPS@PW@ZIF-8) to develop a highly efficient photocatalyst in the water treatment. Phosphotungestic acid (PW) serves a multi-purpose in this context: it acts as a bridge layer between AgNPs and Zeolitic Imidazolate Framework-8 (ZIF-8), a local reducing agent, and a catalyst for electron transfer during the photocatalysis process. A comprehensive characterization of the resulting nanostructure was performed utilizing an array of techniques, such as XRD, FTIR, EDX, TEM, BET, Raman, and TGA. The nanostructure that was created exhibited effective removal of Congo red at different pH levels via a combination of simultaneous adsorption and photocatalysis. After 60 min at pH 7, the dye molecules were completely eliminated in the presence of 0.5 g/L AgNPS@PW@ZIF-8 at room temperature. The charge transfer can be facilitated by the PW bridge layer connecting AgNPs and ZIF-8, owing to the photoactive characteristics and strong electron transfer capabilities of PW molecules. Strong electron transferability of PW between Ag nanoparticles and ZIF-8 facilitates charge transfer and significantly improves the photocatalytic performance of ZIF-8. Moreover, the nanostructure demonstrated great structural stability and recyclability, sustaining a high efficiency of removal throughout five consecutive cycles through the implementation of a simple procedure. Widespread applications of the developed nanostructure in aquatic environments for adsorption and photocatalytic reactions are possible.

Catalyzing Artificial Photosynthesis with TiO2 Heterostructures and Hybrids: Emerging Trends in a Classical yet Contemporary Photocatalyst

Titanium dioxide (TiO2) stands out as a versatile transition-metal oxide with applications ranging from energy conversion/storage and environmental remediation to sensors and optoelectronics. While extensively researched for these emerging applications, TiO2 has also achieved commercial success in various fields including paints, inks, pharmaceuticals, food additives, and advanced medicine. Thanks to the tunability of their structural, morphological, optical, and electronic characteristics, TiO2 nanomaterials are among the most researched engineering materials. Besides these inherent advantages, the low cost, low toxicity, and biocompatibility of TiO2 nanomaterials position them as a sustainable choice of functional materials for energy conversion. Although TiO2 is a classical photocatalyst well-known for its structural stability and high surface activity, TiO2-based photocatalysis is still an active area of research particularly in the context of catalyzing artificial photosynthesis. This review provides a comprehensive overview of the latest developments and emerging trends in TiO2 heterostructures and hybrids for artificial photosynthesis. It begins by discussing the common synthesis methods for TiO2 nanomaterials, including hydrothermal synthesis and sol-gel synthesis. It then delves into TiO2 nanomaterials and their photocatalytic mechanisms, highlighting the key advancements that have been made in recent years. The strategies to enhance the photocatalytic efficiency of TiO2, including surface modification, doping modulation, heterojunction construction, and synergy of composite materials, with a specific emphasis on their applications in artificial photosynthesis, are discussed. TiO2-based heterostructures and hybrids present exciting opportunities for catalyzing solar fuel production, organic degradation, and CO2 reduction via artificial photosynthesis. This review offers an overview of the latest trends and advancements, while also highlighting the ongoing challenges and prospects for future developments in this classical yet rapidly evolving field.

Tungsten-based Lindqvist and Keggin type polyoxometalates as efficient photocatalysts for degradation of toxic chemical dyes

Photocatalytic dye degradation employing polyoxometalates (POMs) has been a research focus for several years. We report the facile synthesis of tungsten-based Lindqvist and Keggin-type POMs that degrade toxic chemical dyes, methyl orange (MO) and methylene blue (MB), respectively. The Lindqvist POM, sodium hexatungstate, Na2W6O19, degrades MO under 100 W UV light irradiation within 15 min, whereas the Keggin POM, Ag4PW11VO40, degrades MB under 20 W visible light source within 180 min. The effect of various operating parameters, such as photocatalyst concentration, pH, time, and initial dye concentration, were assessed in the degradation of both dyes. The photoelectrochemical performance of the as-synthesized polyoxometalates shows that the Ag4PW11VO40 shows 2.4 times higher photocurrent density than Na2W6O19 at a potential of 0.9 V vs. Ag/AgCl. Electrochemical impedance analysis reveals that Ag4PW11VO40 exhibits much lower charge transfer resistance as compared to Na2W6O19, which indicates facile charge transfer at the electrode-electrolyte interface. Further Mott-Schottky measurements reveal that both the catalysts possess n-type semiconductivity and the charge carrier concentration of Ag4PW11VO40 (5.89 × 1019 cm-3) is 1.4 times higher as compared to Na2W6O19 (4.25 × 1019 cm-3). This work offers a new paradigm for designing polyoxometalates suitable for efficient photocatalytic degradation of organic dyes.

Carboxymethyl cellulose gels immobilized Ag/AgCl-ZnO nanoparticles for improving sunlight-catalyzed antibacterial performance

Antibacterial sodium carboxymethyl cellulose (CMC) gels were prepared via immobilizing ZnO and/or Ag/AgCl in situ to inhibit the aggregation of nano-photocatalyst. Epichlorohydrin was used as a crosslinking agent to prepare CMC gel, simultaneously introducing chlorine-containing branch chains as Cl reservoir to deposit AgCl. The composite gels presented pH responsive swelling properties, with the minimum swelling ratio at pH 8 and pH 4 for CMC gels containing Ag/AgCl and ZnO, respectively. Zn2+ release from the nanocomposite gels was much greater in acidic than in neutral. Photocatalytic degradation constants of methyl orange by the composite gels under sunlight were greater than UV irradiation. Ag/AgCl loaded gel showed a degradation rate of 71.3 % under sunlight for 1 h, with a rate constant approximately 10.2 times higher than ZnO loaded gel. Extract liquids with the gel content below 0.33 mg/mL were noncytotoxicity. The nanocomposite gels presented good bactericidal rate against E. coli and S. aureus under sunlight for 6 h, comparatively to those in dark for 24 h. Bacteriostatic activity of Ag/AgCl loaded gel under sunlight for 6 h was much greater than that in dark for 24 h. The biocompatible nanocomposite gels with sunlight-catalyzed antibacterial activity would broaden the application of CMC gels.

A biosensor based on graphene oxide nanocomposite for determination of carcinoembryonic antigen in colorectal cancer biomarker

Colorectal cancer is still a major global health concern, and early detection and accurate biomarker analyses are critical to its successful management. This paper describes the design and testing of a new biosensor based on a graphene oxide (GO) nanocomposite for the exact measurement of carcinoembryonic antigen (CEA), a well-known biomarker for colorectal cancer. The current study attempted to create a highly sensitive immunosensor for sensitive measurement of CEA based on a polypropylene-imine-dendrimer (PPI) and GO nanocomposite on GCE (PPI/GO/GCE). The PPI/GO nanocomposite served as an appropriate biocompatible nanostructure with a large surface area for immobilizing carcinoembryonic antigen (anti-CEA) and bovine serum albumin (BSA) molecules (BSA/anti-CEA/PPI/GO/GCE), thereby promoting the selectivity of electrochemical immunosensors, according to structural and electrochemical studies. Results showed that the BSA/anti-CEA/PPI/GO/GCE as a selective, sensitive, and stable immunosensor revealed a wide linear response from 0.001 to 2000 ng/mL, and a limit of detection of 0.3 pg/mL, which indicated comparable or better performance towards the CEA immunosensors in recent reports in the literature. This was due to the synergetic effect of the GO nanosheets and PPI with porous structure and more conductivity. Analytical results showed values of RSD (4.49%-5.04%) and recovery (90.00%-99.98%) are suitable for effective and accurate practical assessments in CEA in clinical samples. The capacity of the BSA/anti-CEA/PPI/GO/GCE to determine CEA in human blood was studied.

Achieving enhanced sensitivity and accuracy in carcinoembryonic antigen (CEA) detection as an indicator of cancer monitoring using thionine/chitosan/graphene oxide nanocomposite-modified electrochemical immunosensor

The current study has focused on electrochemical immunosensing of carcinoembryonic antigen (CEA) employing an immobilized antibody on a thionine, chitosan, or graphene oxide nanocomposite modified glassy carbon electrode (anti-CEA/THi-CS-GO/GCE) as an indicator of cancer monitoring. THi-CS-GO nanocomposites were made using ultrasonication, and analyses of their morphology and crystal structure using SEM, FTIR, and XRD showed that thionine and chitosan molecules were intercalated with stacking interactions with both the top and bottom of GO nanosheets. Electrochemical experiments revealed anti-CEA, THi-CS-GO/GCE to have exceptional sensitivity and selectivity towards CEA compounds. The detection limit value was established to be 0.8 pg/mL when it was discovered that variations in the decrease peak current were directly proportional to the logarithm concentration of CEA over a wide range from 10-3 to 104 ng/mL. Results of testing the immunosensor's application capability for detecting CEA in a sample of human serum show that ELISA and DPV results are very congruent. The produced immunosensor demonstrated adequate immunosensor precision in determining CEA in prepared genuine samples of human serum and clinical applications.

Hybrid chitosan/molecularly imprinted polymer hydrogel beads doped with iron for selective ibuprofen adsorption

Pharmaceutical pollutants are a group of emerging contaminants frequently found in water streams. In this study, the composite chitosan beads with incorporated molecularly imprinted polymers (monoliths or microparticles) and iron(III) hydroxide were fabricated to remove ibuprofen from aqueous solutions. The adsorptive properties were investigated in different conditions to evaluate the influence of solution pH, adsorbent dose, ibuprofen initial concentration, adsorption time, and temperature. The highest adsorption capacity (79.41 mg g-1), about twice as large as that for the chitosan beads without polymers (39.42 mg g-1), was obtained for the ones containing monoliths imprinted with ibuprofen. The theoretical maximum adsorption capacity of 103.93 mg g-1 was obtained based on the experiments in optimal pH 5. The adsorption of ibuprofen on the hybrid hydrogel beads followed the Freundlich isotherm and pseudo-second-order kinetic models. The process was found as endothermic and thermodynamically spontaneous. The adsorbent with a molecularly imprinted polymer retained its selectivity in the presence of other molecules. The imprinted cavities, chitosan functional groups, and iron hydroxide were presumably responsible for interactions with ibuprofen molecules. Additionally, the effectiveness of the adsorbent did not change significantly in real water samples and remained at a satisfactory level for up to four desorption-adsorption cycles.

Multifunctional Cu:ZnS quantum dots for degradation of Amoxicillin and Dye Sulphon Fast Black-F and efficient determination of urea for assessing environmental aspects

This work is particularly aimed at the preparation of ZnS and Cu doped ZnS (Cu:ZnS) QDs by facile and easy technique, chemical precipitation method for the degradation of water pollutants and a simple scheme was proposed to prepare the urea-sensing system. The morphological and optical properties of the synthesized QDs was studied using high resolution transmission and scanning electron microscopes, X-ray diffraction, energy dispersive X-ray analysis, fluorescence and ultraviolet-visible spectroscopy, differential thermal and thermogravimetric analyses, Brunauer-Emmett-Teller analysis. The photocatalytic performance was systematically assessed by the photodegradation of an important pharmaceutical water pollutant, Amoxicillin (AMX) and a dye Fast Sulphon Black F (SFBF) in aqueous medium under UV light irradiation. Also, a very sensitive system was prepared by depositing the dots over an indium-tin-oxide (ITO) glass substrate for the sensing of biologically active molecule urea as it is an important monitor of public health in water and soil productivity. The results illustrated excellent photocatalytic efficiency (86.46% for AMX and 99.41% for SFBF) with stability up to four cycles of degradation reaction. The optimal photocatalyst dosage for achieving maximum removal of AMX was found to be 70 mg at a pH of 9.5, with a treatment time of 40 min. Similarly, for SFBF, the optimal photocatalyst dosage was determined to be 60 mg at pH 9, with a treatment time of 60 min. Further, the electrochemical analysis was done by fabricating Urease enzyme (UR)/Cu:ZnS QDs/ITO bioelectrode and then the fabricated bioelectrode, was utilized to determine the different concentrations of urea by cyclic voltammetry. Thus, the obtained limit of detection and sensitivity of the fabricated biosensing device for urea detection was obtained to be 0.0092 μM and 12 μA μM-1cm-2, respectively; under the optimized experimental conditions. Hence, it is anticipated that Cu:ZnS QDs can also successfully be applied as a promising material for fabrication of novel bioelectrode for urea determination and the biosensing platform is desirable and viable.

Self-polarized schorl optimizing TiO2 for photocatalytic persulfate activation and organic pollutants degradation

Photocatalytic activation of persulfate has exhibited tremendous potential in water purification because of its green and environmentally friendly process. However, this process often exhibits low activation efficiencies and difficult recovery of the photocatalyst. Herein, schorl-supported nano-TiO2 composite photocatalysts (S/TiO2) were prepared by a mechanical grinding method for efficient activation of potassium monopersulfate (PMS). The anatase TiO2 nanoparticles with particle size of approximately 30 nm was uniformly loaded on the surface of schorl via forming Si-O-Ti bonds. The S/TiO2 assisted with PMS (S/TiO2-PMS) exhibited remarkable degradation performance and stability. In this system (S/TiO2-PMS), the C/C0 value of phenol solution (10 ppm) were decreased to 0.070 and 0 after 30 min and 90 min of irradiation, where the degradation extent were 93.0% and 100% respectively. The rate of phenol degradation with S/TiO2-PMS was 12.6 times that seen with TiO2-PMS. The oxidation active species were holes and SO4•- in S/TiO2-PMS system subjected to simulated sunlight. It was demonstrated that the polarization electric field of the schorl enhanced the separation efficiency of the photoinduced electrons and holes for improving the performance of the S/TiO2-PMS. On the other hand, the transformations of Fe3+ and Fe2+ on the schorl surface further promotes the activation of PMS. This work provides a new choice for designing TiO2-based photocatalytic persulfate activation system targeting the field of advanced oxidation water treatment.

Preparation of SnO2-Sb/attapulgite (AP) clay particulate electrode for efficient phenol electrochemical oxidation

A novel SnO2-Sb/AP (attapulgite) particle electrode was prepared for three-dimensional electrocatalytic oxidation (3D/EO) of organic pollutants using a co-sintering method. The electrochemical properties and micromorphology were determined using polarization, cyclic voltammetry (CV), and field emission scanning electron microscope (FE-SEM), and compared with activated carbon (AC), AP, and TiO2/AP particle electrodes. Besides, their potential application in the electrochemical degradation of phenol was investigated. The SnO2-Sb/AP particle electrode exhibited higher electrochemical activity than other particle electrodes due to its large number of active sites, low transfer coefficient (α, 0.12), and high-volt ampere charge (q*, 1.18 C·cm-2). The electrochemical CODCr degradation efficiency (100%) of phenol on SnO2-Sb/AP particle electrodes is much higher than for other particle electrodes. Moreover, an excellent stability of the SnO2-Sb/AP particle electrode is also verified by repeated experiments. These results indicate that the SnO2-Sb/AP particle electrodes broaden the application area of clays and are expected to be a promising method for 3D/EO.

Vanadia as an electron-hole recombination inhibitor on fibrous silica-titania for selective hole oxidation of ciprofloxacin and Congo red photodegradation

Vanadia (V2O5)-incorporated fibrous silica-titania (V/FST) catalysts, which were successfully synthesized using a hydrothermal method followed by the impregnation of V2O5. The catalysts were then characterized using numerous techniques, including X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, nitrogen adsorption-desorption analyses, ultraviolet-visible diffuse reflectance spectroscopy, Fourier-transform infrared, X-ray photoelectron spectroscopy, and photoluminescence (PL) analyses. The study found that varying the amount of V2O5 (1-10 wt%) had a significant impact on the physicochemical properties of the FST, which in turn improved the photodegradation efficiency of two organic compounds, ciprofloxacin (CIP) and congo red (CR). 5V/FST demonstrated the best performance in degrading 10 mg L-1 of CIP (83%) and CR (100%) at pH 3 using 0.375 g L-1 catalyst under visible light irradiation within 180 min. The highest photoactivity of 5V/FST is mainly due to higher crystallinity and the highest number of V2O5-FST interactions. Furthermore, as demonstrated by PL analysis, the 5V/FST catalyst has the most significant impact on interfacial charge transfer and reduces electron-hole recombination. The photodegradation of both contaminants follows the Langmuir-Hinshelwood pseudo-first-order model, according to the kinetic study. The scavenger investigation demonstrated that hydroxyl radicals and holes dominated species in the system, indicating that the catalyst effectively generated reactive species for pollutant degradation. A possible mechanism was also identified for FST and 5V/FST. Interestingly, V2O5 acts as an electron-hole recombination inhibitor on FST for selective hole oxidation of ciprofloxacin and congo red photodegradation. Finally, the degradation efficiency of the catalyst remained relatively stable even after five cyclic experiments, indicating its potential for long-term use in environmental remediation.

Integrating K and P co-doped g-C3N4 with ZnFe2O4 and graphene oxide for S-scheme-based enhanced absorption coupled photocatalytic real wastewater treatment

Recently, there has been a significant increase in the interest of using photocatalysis for environmental clean-up applications. In this research, potassium, and phosphorus co-doped graphitic carbon nitride (KPCN) photocatalyst modified with graphene oxide (GO) and heterostructured with ZnFe₂O₄ was synthesized via the hydrothermal method (KPCN/GO/ZnFe₂O₄). The photoactivity of KPCN/GO/ZnFe₂O₄ photocatalyst was examined for the photocatalytic degradation of target pollutants such as methylene blue (MB) dye, rhodamine B (RhB) dye, and tetracycline (TC) antibiotic. Furthermore, the chemical oxygen demand (COD) removal efficiency for real wastewater was determined to explore the practical application of KPCN/GO/ZnFe₂O₄ photocatalyst. The degradation efficiencies of bare graphitic carbon nitride, KPCN, KPCN/GO, and KPCN/GO/ZnFe₂O₄ photocatalysts for tetracycline antibiotics were 30%, 42%, 57%, and 87% within 60 min, respectively. Moreover, KPCN/GO/ZnFe₂O₄ photocatalyst showed 71% COD removal efficiency within 240 min. The ^•OH and ^•O₂^- were the major reactive species in the photocatalytic process. Results showed that the degradation efficiencies of graphitic carbon nitride were greatly enhanced upon doping and further improved with the addition of GO and ZnFe₂O₄. Doping improved light harvesting, GO enhanced the adsorption ability and heterojunction with ZnFe₂O₄ enhanced the charge separation as well as the reusability of synthesized KPCN/GO/ZnFe₂O₄ photocatalyst.

Photocatalytic degradation of organic pollutants and inactivation of pathogens under visible light via SnO2/rGO composites

The domains of environmental cleanup and pathogen inactivation are particularly interesting in nanocomposites (NCs) due to their exceptional physicochemical properties. Tin oxide/reduced graphene oxide nanocomposites (SnO₂/rGO NCs) have potential uses in the biological and environmental fields, but little is known about them. This study aimed to investigate the photocatalytic activity and antibacterial efficiency of the nanocomposites. The co-precipitation technique was used to prepare all the samples. XRD, SEM, EDS, TEM, and XPS analyses were employed to characterize the physicochemical properties of SnO₂/rGO NCs for structural analysis. The rGO loading sample resulted in a decrease in the crystallite size of SnO₂ nanoparticles. TEM and SEM images demonstrate the firm adherence of SnO₂ nanoparticles to the rGO sheets. The chemical state and elemental composition of the nanocomposites were validated by the XPS and EDS data. Additionally, the visible-light active photocatalytic and antibacterial capabilities of the synthesized nanocomposites were assessed for the degradation of Orange II and methylene blue, as well as the suppression of the growth of S. aureus and E. coli. As a result, the synthesized SnO₂/rGO NCs are improved photocatalysts and antibacterial agents, expanding their potential in the fields of environmental remediation and water disinfection.

Comparison of photocatalysis and photolysis of 2,2,4,4-tetrabromodiphenyl ether (BDE-47): Operational parameters, kinetic studies, and data validation using three modern machine learning models

Polybrominated diphenyl ethers (PBDEs) are halogenated organic compounds that are among the major pollutants of water, and there is an urgent need for their removal. This work compared the application of two techniques, i.e., photocatalytic reaction (PCR) and photolysis (PL), for 2,2,4,4- tetrabromodiphenyl ether (BDE-47) degradation. Although a limited degradation of BDE-47 was observed by photolysis (LED/N₂), photocatalytic oxidation by using TiO₂/LED/N₂ proved to be effective in the degradation of BDE-47. The use of a photocatalyst enhanced the extent of BDE-47 degradation by around 10% at optimum conditions in anaerobic systems. Experimental results were systematically validated through modeling with three new and powerful Machine Learning (ML) approaches, including Gradient Boosted Decision Tree (GBDT), Artificial Neural Network (ANN), and Symbolic Regression (SBR). Four statistical criteria (Coefficient of Determination (R²), Root Mean Square Error (RMSE), Average Relative Error (ARER), and Absolute Error (ABER)) were calculated for model validation. Among the applied models, the developed GBDT was the desirable model for predicting the remaining concentration (Ce) of BDE-47 for both processes. Total Organic Carbon (TOC) and Chemical Oxygen Demand (COD) results confirmed that BDE-47 mineralization required additional time than its degradation in both PCR and PL systems. The kinetic study demonstrated that BDE-47 degradation for both processes followed the pseudo-first-order form of the Langmuir-Hinshelwood (L-H) model. More importantly, the calculated electrical energy consumption of photolysis was shown to be ten percent higher than that for photocatalysis, possibly due to the higher irradiation time required in direct photolysis, which in turn increases electricity consumption. This study is useful in proposing a feasible and promising treatment process for the degradation of BDE-47.

CaTiO3/g-C3N4 heterojunction-based composite photocatalyst: Part I: Experimental design, kinetics, and scavenging agents' effects in photocatalytic degradation of gemifloxacin

A critical, challenging environmental issue is explored pollution of water supplies by discharging industrial/pharmaceutical/hospital/urban wastewaters into the aquatic environment. These needs introducing/developing novel photocatalysts/adsorbents/procedures for removing or mineralizing various pollutants in wastewater before discharging them into marine environments. Further, optimizing conditions to achieve the highest removal efficiency is an important issue. In this study, CaTiO₃/g-C₃N₄ (CTCN) heterostructure was synthesized and characterized by some identification techniques. The simultaneous interaction effects of the experimental variables on the boosted photocatalytic activity of CTCN in the degradation of gemifloxcacin (GMF) were studied in RSM design. The optimal values for four parameters were: catalyst dosage: 0.63 g L^-1, pH: 6.7, C_GMF: 1 mg L^-1, and irradiation time: 27.5 min, with approximately 78.2% of degradation efficiency. The quenching effects of the scavenging agents were studied to show the reactive species' relative importance in GMF photodegradation. The results illustrate that the reactive ^•OH plays a significant role, and the electron plays a minor role in the degradation process. The direct Z-scheme mechanism better described the photodegradation mechanism due to the great oxidative and reductive abilities of prepared composite photocatalysts. This mechanism is an approach to efficiently separating photogenerated charge carriers and improving the CaTiO₃/g-C₃N₄ composite photocatalyst activity. The COD has been performed to study the details of the mineralization of GMF. The pseudo-first-order rat (from the Hinshelwood model) constants of 0.046 min^-1 (t_1/2 = 15.1 min) and 0.048 min^-1 (t_1/2 = 14.4 min) were respectively obtained from the GMF photodegradation data and COD results. The prepared photocatalyst retained its activity after five reusing runs.

Novel g-C3N4/BiVO4 heterostructured nanohybrids for high efficiency photocatalytic degradation of toxic chemical pollutants

Novel heterostructured hybrid catalysts are essential for the efficient photocatalytic removal of organic pollutants from wastewater generated by the pharmaceutical and textile industries. In this study, novel g-C₃N₄/BiVO₄ nanohybrid catalysts were prepared using a solvothermal technique, and examined their structural and optical properties using different characterizations. The X-ray diffraction analysis confirmed the monoclinic crystal phase of BiVO₄. Field emission scanning electron microscopy (FESEM) images revealed that g-C₃N₄ sheets anchored on the surface of BiVO₄ nanospheres. X-ray photoelectron spectroscopy (XPS) analysis confirmed the oxidation states of g-C₃N₄/BiVO₄ composite sample. UV-Vis DRS spectroscopy analysis revealed that the composite (2.08 eV) sample had a reduced bandgap compared to other samples. The photocatalytic properties of the prepared samples were tested in the presence of organic methylene blue (MB) and antibiotic tetracycline (TC) pollutants under visible light illumination. The hybrid composite catalyst exhibited enhanced photocatalytic degradation efficiency of MB (88%) and TC (89%) pollutants at elevated rate constants of 0.0128 and 0.01174 min^-1, respectively. The improved catalytic performance of the composite catalyst is due to the heterojunctions between g-C₃N₄ and BiVO₄ that successfully reduced the rate of charge carrier recombination in the catalyst system. Scavenger experiments revealed that O₂^●- and h⁺ radicals played a main role in the degradation of the chemical pollutants. The developed g-C₃N₄/BiVO₄ heterostructured catalyst is a suitable candidate for removing contaminants from industrial wastewater because of its facile fabrication and exceptional photocatalytic activity under visible light irradiation.

A Z-scheme CdS/Ag3PO4 catalyst: Characterization, experimental design and mechanism consideration for methylene blue

Due to the explosive use of Azo dyes in various industries such as textiles, discharging these industrial effluents into the environment critically polluted water supplies. Accordingly, constructing/developing novel binary catalysts to diminish the pollution extent of such effluents before discharging into environment is an excellent issue in environmental chemistry. Here, a binary CdS/ Ag₃PO₄ was constructed, and its boosted photocatalytic activity was proven against methylene blue (MB), as a model dye pollutant. The Wurtzite CdS and Ag₃PO₄ cubic crystal nanoparticles were synthesized and coupled mechanically. The binary sample's lowest photoluminescence (PL) results confirm a higher e/h separation. DRS results confirmed a decreased energy gap for the coupled system. The semiconductors' VB and CV potentials were calculated and used for constructing of Z-scheme mechanism. The photocatalytic activity was followed via an experimental design approach. The model F-value of 89.75 > F_0.05,14,13 = 2.42 and LOF F-value of 6.57 < F_{0.05,10, 3} = 8.79 reveal that the model well processed data. The optimal run conditions were CMB: 5 ppm, Catalyst dose: 1 g/L, pH: 3.25, and irradiation time: 139 min, at which 85% of MB molecules were degraded. Based on the trend of ascorbic acid > isopropanol > formic acid ≈ nitrate obtained for the scavengers' importance in decreasing the photocatalyst activity, superoxide radicals had the highest effect in MB degradation and then ^•OH. The results showed the direct Z-scheme has the main effect on MB degradation by the binary sample.

Modification of multi-walled carbon nanotubes with platinum-osmium to develop stable catalysts for direct methanol fuel cells

In the study, a new bimetallic catalyst was synthesized for methanol oxidation using multi-walled carbon nanotube (MWCNT)-supported platinum-osmium (PtOs) nanoparticles (PtOs@MWCNT NPs). The morphological structures of the prepared NPs were examined using different techniques, such as scanning electron microscopy (SEM) and X-ray diffraction (XRD). The electrochemical characterization of the synthesized PtOs@MWCNT catalysts, such as chronoamperometry (CA), cyclic voltammetry (CV), scan rate (SR) analysis, cyclic catalytic test, and electrochemical surface area (ECSA) evaluation, were performed in an alkaline medium. From the results obtained, the size of the NPs was found to be 3.12 nm according to the Debye-Schrrer equation, and the MWCNTs were clearly observed by SEM imaging. After the characterization of the prepared nanomaterials, the PtOs@MWCNT catalysts were employed in the methanol oxidation reaction, and a high oxidation current value of 220.86 mA cm^-2 was observed. Besides, according to the CA results, the catalyst exhibited high stability for 4000 s, and it was seen that Os metal improved the catalytic activity of the main catalyst. These results show that the PtOs@MWCNT catalyst is highly stable and reusable, and provides high electrocatalytic activity in the methanol oxidation reaction. Moreover, the obtained catalyst gave ideal results in terms of CO tolerance and activity. These data show that the obtained catalyst will provide significant improvement and superior efficiency in fuel-cell applications.

Photocatalytic investigation of textile dyes and E. coli bacteria from wastewater using Fe3O4@MnO2 heterojunction and investigation for hydrogen generation on NaBH4 hydrolysis

Various impurities found nowadays in water can be detrimental to human health. This work focused on utilizing Fe₃O₄@MnO₂ nanocomposite for cleaning organic contaminants from water, including rhodamine B (RhB) and Escherichia coli (E. coli). Analysis methods such as XRD, UV-vis, TEM, and FTIR were used to describe the nanocomposite. The results showed that the developed nanocomposite has good photocatalytic activity against pollutants in wastewater. The E. coli was destroyed after 90 min, and the RhB photodegradation rate was 75%. Moreover, the Fe₃O₄@MnO₂ efficiency as a catalyst for producing hydrogen as an alternative energy source was tested. According to the calculations, the nanomaterial's turnover frequency, activation energy, enthalpy, and entropy are 1061.3 h^-1, 28.93 kJ/mol, 26.38 kJ/mol, and -128.41 J/mol.K, respectively. Four reusability tests were completed, and the average reusability was 78%. The obtained data indicated the excellent potential for the developed Fe₃O₄@MnO₂ nanomaterial to act as an adsorbent, thus representing an alternative to the classical depollution methods. This study showed that nanoparticles have a photocatalytic effect against pathogenic bacteria and RhB azo dye in polluted waters and offer an effective catalytic activity to produce hydrogen as an alternative energy source.

Photo-Fenton assisted AgCl and P-doped g-C3N4 Z-scheme photocatalyst coupled with Fe3O4/H2O2 system for 2, 4-dimethylphenol degradation

In this study graphitic carbon nitride (g-C₃N₄ or GCN) and phosphorus doped graphitic carbon nitride (p-g-C₃N₄ or PCN) were prepared using facile thermal polycondensation method. Phosphorus doping was employed to preserve the non-metallic nature of GCN. The AgCl/PCN/Fe₃O₄ heterojunction was synthesized using a simple in-situ route. The photocatalytic performance of the GCN, PCN, Fe₃O₄ and AgCl/PCN/Fe₃O₄ was tested towards 2, 4-dimethylphenol (DMP) pollutant. The work explored improvement in physiochemical properties and reduction of band gap of GCN after P doping (through Tauc's plot method). Coupling with AgCl (silver halide) also enhanced photoinduced charge carriers' separation and migration ability due to apt band alignment among both AgCl and PCN photocatalysts which resulted in formation of direct Z-scheme charge transfer mechanism. Similarly, the incorporation of ferrimagnetic material i.e. Fe₃O₄ enhanced the generation of hydroxyl (^•OH) radicals via photo-Fenton process and facilitated photocatalysts easy separation from the aqueous medium. Through PL and EIS analysis the enhanced charge separation and migration ability in AgCl/PCN/Fe₃O₄ nanocomposite was validated. The attained DMP degradation efficiency of photo-Fenton assisted AgCl/PCN/Fe₃O₄/H₂O₂ Z-scheme nanocomposite was much higher i.e. 99% compared to other photocatalysts within 60 min of visible light irradiation following pseudo-first-order kinetics. Electron paramagnetic resonance (EPR) and scavenging tests confirmed the substantial role of ^•OH and ^•O₂^- radicals in the photo-Fenton reaction. Furthermore, liquid chromatography-mass spectrometry (LC-MS) analysis detected the generated oxidative products and mineralization pathways associated with DMP degradation. The proposed direct Z-scheme charge transfer route presented efficient charge separation and migration ability in AgCl/PCN/Fe₃O₄ nanocomposite. Recycle ability of the fabricated AgCl/PCN/Fe₃O₄ photocatalyst was tested up to 5 cycles with 90% removal efficacy, confirming the excellent reusability and stability of AgCl/PCN/Fe₃O₄ photocatalyst.

Two dimensional (2D) materials and biomaterials for water desalination; structure, properties, and recent advances

BACKGROUND

An efficient solution to the global freshwater dilemma is desalination. MXene, Molybdenum Disulfide (MoS₂), Graphene Oxide, Hexagonal Boron Nitride, and Phosphorene are just a few examples of two-dimensional (2D) materials that have shown considerable promise in the development of 2D materials for water desalination. However, other promising materials for desalinating water are biomaterials. The benefits of bio-materials are their wide distribution, lack of toxicity, and superior capacity for water desalination.

METHODS

For the rational use of water and the advancement of sustainable development, it is of the utmost importance to research 2D-dimensional materials and biomaterials that are effective for water desalination. The scientific community has concentrated on wastewater remediation using bio-derived materials, such as nanocellulose, chitosan, bio-char, bark, and activated charcoal generated from plant sources, among the various endeavors to enhance access to clean water. Moreover, the 2D-materials and biomaterials may have ushered in a new age in the production of desalination materials and created a promising future.

RESULTS

The present review article focuses on and reviews the progress of 2D materials and biomaterials for water desalination. Their properties, surface, and structure, combined with water desalination applications, are highlighted. Further, the practicability and potential future directions of 2D materials and biomaterials are proposed. Thus, the current work provides information and discernments for developing novel 2D materials and biomaterials for wastewater desalination. Moreover, it aims to promote the contribution and advancement of materials for water desalination, fabrication, and industrial production.

Catalytic activation of hydrogen peroxide by Cr2AlC MAX phase under ultrasound waves for a treatment of water contaminated with organic pollutants

This study aims to investigate the sonocatalytic activation of hydrogen peroxide (H₂O₂) using Cr₂AlC MAX phase prepared by the reactive sintering process. The hexagonal structure of the crystalline MAX phase was confirmed by X-ray diffraction. Moreover, the compacted layered structure of the MAX phase was observed via scanning electron microscopy and high-resolution transmission electron microscopy. Under the desired operating conditions, Cr₂AlC MAX phase (0.75 g/L) showed suitable potential to activate H₂O₂ (1 mmol/L) under sonication, thereby allowing a considerable removal efficiency for various organic pollutants, including dimethyl phthalate (69.1%), rifampin (94.5%), hydroxychloroquine (100%), and acid blue 7 (91.5%) with initial concentration of 15 mg/L within 120 min of treatment. Kinetic analysis proved that the degradation reaction followed pseudo-first-order kinetics. Scavenging tests demonstrated that hydroxyl radicals and singlet oxygen were effective species during degradation. Furthermore, a probable mechanism for dimethyl phthalate degradation was suggested according to gas chromatography-mass spectroscopy and nuclear magnetic resonance analyses. The obtained results confirmed the capability of the triple Cr₂AlC/H₂O₂/US process as a promising method for treating contaminated water.

The effect of Fe-Zn mole ratio (2:1) bimetallic nanoparticles supported by hydroxyethyl cellulose/graphene oxide for high-efficiency removal of doxycycline

In this research, Hydroxyethyl cellulose - graphene oxide HEC-GO and HEC-GO/Fe-Zn mole ratio (2:1) nanocomposite as adsorbents were fabricated by crosslinking ethylene glycol dimethacrylate (EGDMA) to study the thermodynamic, kinetic and isotherm of doxycycline antibiotic adsorption. The morphology and structure of the adsorbents were analyzed by Fourier transform infrared spectroscopy (FT-IR), Field Emission Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy (FE-SEM- EDX), and Transmission electron microscopy (TEM). The adsorption behavior of doxycycline (DOX) was studied with different parameters including doxycycline concentration, pH, the dose of adsorbent (HEC-GO and HEC-GO/Fe-Zn, mole ratio (2:1)), contact time, and temperature. The optimal conditions for the removal of DOX are pH = 3.0, contact time 100 min, and 20 min for HEC-GO and HEC-GO/Fe-Zn mole ratio (2:1). The removal percentage for HEC-GO and HEC-GO/Fe-Zn mole ratio (2:1) was 97% and 95.5%, respectively. Equilibrium adsorption isotherms such as the Langmuir, Freundlich, and Temkin models were analyzed according to the experimental data. Also, four adsorption kinetics were investigated for removing DOX. The Langmuir isotherm and pseudo-second-order kinetic models provided the best fit for experimental data for HEC-GO and HEC-GO/Fe-Zn mole ratio (2:1). Thermodynamic data showed that negative values of Gibbs free energy (ΔG°) and the negative value of enthalpy (ΔH°) of the adsorption process for adsorbents. It means that DOX removal was a spontaneous and exothermic reaction.

Hybrid TiO2:Au nanostars based polymeric membranes for photocatalytic degradation of ciprofloxacin in water samples

Antibiotics represent one increasingly harmful type of contaminant of emerging concern in treated and non-treated water. They cause the generation of antibiotic-multiresistant organisms, one of the major challenges in current medicine. Plasmonic-photocatalysis using solar energy represents a promising solution for their removal with low energy consumption. Its successful application requires the improvement of photocatalysts' efficiency under sunlight and the development of robust, durable, and efficient substrates for photocatalysts immobilisation. In this work, hybrid TiO₂:Au nanostars were initially synthesised. Then, two porous membranes were prepared to support this nanocatalyst based on poly (vinylidenefluoride-co-hexafluoropropylene) polymer. Doctor blade and salt leaching casting methods, combined with temperature-induced phase separation, were used to generate membranes with high porosity, 80-90%, which was maintained after nanoparticle incorporation (3, 8 and 10 wt%). The photocatalytic activity of the nanocomposite membranes was tested through the degradation of the antibiotic ciprofloxacin under UV and visible radiation. Salt-leaching membranes containing 10 wt% nanoparticles presented the highest degradation efficiencies, 45% under UV and 35% under visible radiation. In contrast, doctor blade membranes showed 36% and 32% degradation efficiencies, respectively. The reusability of the membranes was assessed in repeated cycles, presenting an average efficiency loss of only 2% after three uses. Finally, the reusability of these membranes was also tested in treated effluent water matrixes, presenting similar, or even better, degradation efficiencies, and a minimum reusability efficiency lost 0-1%. The results demonstrate that these membranes are a promising alternative for the degradation of a wide variety of contaminants under sunlight radiation.

One-step synthesized biogenic nanoparticles using Linum usitatissimum: Application of sun-light photocatalytic, biological activity and electrochemical H2O2 sensor

This study aimed to synthesize Ag NPs as a green catalyst for photocatalytic activity and to examine their biological activities. It was determined that they have high activity in catalytic and biological activities. The green synthesis which is an environmentally friendly and inexpensive method was used to synthesize Ag-NPs using Linum usitatissimum as a reducing agent. Transmission electron microscopy (TEM), infrared to Fourier transform infrared (FTIR) spectroscopy, UV-Visible (UV-Vis) spectroscopy, and X-ray diffraction (XRD) were used to characterize the Ag NPs. In UV-Vis examination, Ag-NPs had intense peaks in the 435 nm region. The antibacterial activity of Ag NPs was investigated, and Ag NPs showed a high lethal effect against S. aureus, E. coli, B. subtilis, and MRSA. In addition, Ag NPs were tested for anticancer activity against the HT-29 colon cancer cell line, MDA-MB-231 breast cancer cell line, healthy cell line L929-Murine Fibroblast cell Lines, and MIA PaCa-2 human pancreatic cancer cell line at various concentrations (1-160 μg/mL) and showed a high anticancerogenic properties against MDA-MB-231 cells. Ag NPs showed the ability of DNA cleavage activity. Also, the antioxidant activity of Ag NPs against DPPH was found to be 80% approximately. Furthermore, the photocatalytic activity of Ag NPs against methylene blue (MB) was determined to be 67.13% at the 180^th min. In addition, it was observed that biogenic Ag NPs have high electrocatalytic activity for hydrogen peroxide (H₂O₂) detection. In the sensor based on Ag NPs, linearity from 1 μM to 5 μM was observed with a detection limit (LOD) of 1.323 μM for H₂O_2. According to these results, we conclude that the biogenic Ag NPs synthesized using Linum usitatissimum extract can be developed as an efficient biological agent as an antibacterial and anticancer also can be used as a photocatalyst for industrial wastewater treatment to prevent wastewater pollution.

Recent Advances in Hybrid Materials of Metal Nanoparticles and Polyoxometalates

Polyoxometalates (POMs), anionic metal-oxygen nanoclusters that possess various composition-dependent properties, are widely used to modify the existing properties of metal nanoparticles and to endow them with new ones. Herein, we present an overview of recent advances in hybrid materials that consist of metal nanoparticles and POMs. Following a brief introduction on the inception of this area and its development, representative properties and applications of these materials in various fields such as electrochemistry, photochemistry, and catalysis are introduced. We discuss how the combination of two classic inorganic materials facilitates cooperative and synergistic behavior, and we also give personal perspectives on the future development of this field.

Facile bio-fabrication of ZnO@AC nanoparticles from chitosan: Characterization, hydrogen generation, and photocatalytic properties

In this work, activated carbon-supported zinc oxide nanoparticles (ZnO@AC NPs) were studied using the thermal synthesis method. The activated carbon-supported zinc oxide catalyst was characterized by UV-Vis spectrometry techniques, Fourier Transform Infrared Spectrophotometer (FTIR), Transmissive electron microscopy (TEM), and X-ray diffraction (XRD) methods. XRD characterization measurements showed that the average size of the crystal NPs was 6.89 nm. According to the TEM analysis results, the nanoparticles' average size was 11.411 nm, and the particles had a spherical structure. The catalytic properties of the synthesized material were determined using the sodium borohydride methanolysis reaction. A kinetic study was performed regarding the effects of temperature, catalyst, and substrate concentration on the methanolysis reaction. Reusability experiments showed that the catalyst had excellent catalytic activity (85%), stability, and selectivity. As a result of the kinetic study, activation energy, enthalpy (ΔH), entropy (ΔS), and hydrogen production rate activation parameters were found to be 42.52 kJ/mol, 39.98 kJ/mol, -181.42 J/mol.K, 1257.69 mL/min. g, respectively. Also, the photocatalytic activity of ZnO@AC NPs was analyzed against Rhodamine B (RhB) dye, and the maximum degradation percentage was observed to be 76% at 120 min. This study aimed to develop the ZnO@AC NPs into an efficient photocatalyst to prevent industrial wastewater pollution and as a catalyst for hydrogen synthesis as an alternative energy source.

Continuous removal of pharmaceutical drug chloroquine and Safranin-O dye from water using agar-graphene oxide hydrogel: Selective adsorption in batch and fixed-bed experiments

In this work, Chloroquine diphosphate, and the cationic dye Safranin-O were selectively removed from water using the agar-graphene oxide (A-GO) hydrogel, produced via simple one-step jellification process. The morphology of the A-GO biocomposite was characterized and batch experiments were performed, with adsorption isotherms satisfactorily fitting (R² > 0.98) Sips (Safranin-O) and Freundlich (Chloroquine) isotherms. Driving force models and Fick's diffusion equation were applied to the modeling of kinetic data, and a satisfactory fit was obtained. Selective adsorption carried out in batch indicated that competitive adsorption occurs when both components are mixed in water solution - the adsorptive capacities dropped ∼10 mg g^-1 for each component, remaining 41 mg g^-1 for safranin-O and 31 mg g^-1 for chloroquine. Fixed-bed breakthrough curves obtained in an adsorption column showed adsorption capacities over 63 mg g^-1 and 100 mg g^-1 for chloroquine and safranin-O, respectively, also exhibiting outstanding regenerative potentials. Overall, the biocomposite produced using graphene oxide proved to be a viable and eco-friendly alternative to continuously remove both contaminants from water.

Customization of surface wettability of nano-SiO2 by coating Trimethoxy(vinyl)silane modifier for oil-water separation: Fabrication of metal-based functional superwetting nanomaterial, characterizations and performance evaluation

The wettability of nano-SiO₂ surface was transformed from the inherent hydrophilicity to functional superhyderophobicity by coating Trimethoxy (vinyl)silane modifier, and the resultant surface showed contrasting wettability for water and oil (Superhydrophobic and Superoleophilic), which is a desired characteristic for the membranes used in oil-water separation. Initially Trimethoxy (vinyl)silane coated SiO₂ nanoparticles (TMVS@SiO₂) were synthesized by hydrolysis and poly-condensation reactions, and this nano dispersion was spray coated on the annealed stainless-steel mesh surface, whose resulting hierarchical surface texture brought about the desired wettability, with the water-surface-air (θ_WA) and oil-surface-air (θ_OA) interfacial contact angles of 150° and 0° respectively. In addition to the wettability studies (contact angles), FTIR, morphological, and elemental characterizations of the TMVS@SiO₂ coated surfaces were carried out to understand the alterations that have taken place on the TMVS@SiO₂ surface that in turn rendered superhydrophobicity and superoleophilicity to the surface. The FTIR absorption peaks indicate that after modifying SiO₂ with TMVS, the -OH groups on SiO₂ surface are clearly replaced by -CH₃. The morphological studies indicated that modification of SiO₂ leads to better cross-linking between coating composition and nanoparticles and EDS spectra and elemental mapping of the modified surface showed the presence of Si, O and C elements. Finally, this surface was tested for its efficiency and stability as a membrane in the process of separating oil and water from the oily water using gravity driven method. The oil-water separation efficiency was estimated to be 99% for this membrane and also it was found to be quite stable as the surface effectively retained this oil-water separation efficiency even after 10 cycles of separation process.

A censorious review on the role of natural lignocellulosic fiber waste as a low-cost adsorbent for removal of diverse textile industrial pollutants

BACKGROUND

Textile industries produce fabricated colored products using toxic dyes and other harsh chemicals. It is the responsibility of the textile industries to treat and eliminate these hazardous pollutants. However, due to the growing population demand, the treatment of these hazardous effluents is ineffective and imposes the treatment cost over the end users. The release of partially treated effluents in the environment may cause a severe threat to the ecology and its biota. The critical objective is to treat textile effluents efficiently using agricultural natural fiber waste. Generation of agricultural lignocellulosic fibrous waste increases every year due to growing population demand. Its use in the modern world is limited due to synthetic products. An alternative has enumerated to avoid wastage of fibrous resources and its clean disposal.

OBJECTIVE

The main objective of this review paper discussed the feasibility of lignocellulosic fibers and other lignocellulosic materials as natural low-cost adsorbent.

METHODS

The literature study was performed using Web of Science and Scopus indexed journals. The main factors considered to increase the adsorption ability, including the types of lignocellulosic surface modification techniques were searched with utmost importance for quality results. Intending to summarize the literature survey and provide persuasive content, systematic review process was considered for this novel article.

RESULTS

Out of 230 valuable publications, 159 published articles were considered for the present study until March 2022. The articles surplus with factors affecting adsorption (pH, adsorption dosage, surface area, temperature, initial concentration, contact time, physical and chemical properties of pollutants) and surface modification techniques (physical, chemical, and biological) were considered for this manuscript.

CONCLUSION

Overall, the physical and chemical modification methods are widely used instead of biological methods due to various factors as discussed briefly. Furthermore, the finding of this article supports the fact that the fibrous by-product resources are wasted in various occasions due to the modern lifestyle. Even though there is evidential possibility to implement the low-cost adsorbents, the industries limit their application prospects due to existing technology and financial compromises.

Heterogeneous Cu2O-Au nanocatalyst anchored on wood and its insight for synergistic photodegradation of organic pollutants

In this study, a Cu₂O-Au nanoparticles (NPs) heterojunction catalyst anchored on wood was developed by in situ reduction and hydrothermal treatment, and the properties of the catalyst were systematically characterized. The catalyst exhibited prominent photocatalysis of methyl orange (MO, 0.169 min^{- 1}), and tetracycline (TC, 0.122 min^-1) which were degraded completely within 20 min. Even after four recyclings, the efficiency of MO degradation by the catalyst remained at 80%. The natural wood with three-dimensional porous structures acted as a reducing agent and a stabilizer for Au NPs and Cu₂O, which helped to maintain high performance and reusability. The presence of Au NPs mediated the light-induced electron transfer and enhanced the absorption of visible light for promoting photocatalytic activity. The intermediates of contaminants within the degradation process were characterized by liquid chromatography-mass spectrometry. Additionally, the photogenerated superoxide radicals and holes were identified by electron spin resonance. Thus, the potential degradation mechanism catalyzed by the Cu₂O-Au NPs-wood was proposed. This findings of this study valorizes biomass as a photocatalyst for wastewater remediation.

Electrospun composite nanofibers as novel high-performance and visible-light photocatalysts for removal of environmental pollutants: A review

Environmental pollution caused by industries and human manipulations is coming a serious global challenge. On the other hand, the world is facing an energy crisis caused by population growth. Designing solar-driven photocatalysts which are inspired by the photosynthesis of plant leaves is a fantastic solution to use solar energy as green, available, and unlimited energy containing ∼50% visible light for the removal of environmental pollutants. The polymeric and non-polymeric-based electrospun composite nanofibers (NFs) are as innovative photocatalytic candidates which increase photocatalytic activity and transition from UV light to visible light and overcome the aggregation, photocorrosion, toxicity, and hard recycling and separation of the nanosized powder form of photocatalysts. The composite NFs are fabricated easily by either embedding the photocatalytic agents into the NFs during electrospinning or via their decorating on the surface of NFs post-electrospinning. Polyacrylonitrile-based, tungsten trioxide-based, zinc oxide-based, and titanium dioxide-based composite NFs were revealed as the most reported composite NFs. All the lately investigated electrospun composite NFs indicated long-term stability, high photocatalytic efficiency (∼> 80%) within a short time of light radiation (10-430 min), and high stability after several cycles of use. They were applied in various applications including degradation of dyes/antibiotics, water splitting, wastewater treatment, antibacterial usage, etc. The photogenerated species especially holes, O₂^∙-, and ^.OH were mostly responsible for the photocatalytic mechanism and pathway. The electrospun composite NFs have the potential to use in large-scale productions in condition that their thickness and recycling conditions are optimized, and their toxicity and detaching are resolved.

Fabrication of different adsorbents based on zirconium oxide, graphene oxide, and dextrin for removal of green malachite dye from aqueous solutions

In this study, graphene oxide and amine graphene were studied by binding to dextrin and zirconium oxide nanoparticles as adsorbent nanocomposites to the removal of dye. Identification and characterization of the synthesized materials were examined using FTIR, XRD, SEM, and BET analyses. Adsorption tests between adsorbents and green malachite (MG) dye solution for the synthesized nanocomposites were performed by considering parameters such as contact time, solution pH, and adsorbent dosage. The data indicated that dye removal increased with increasing the amount of adsorbent dosage. Increased dye removal by increasing the adsorbent dosage can be attributed to the increase of availability of the number of active sites. The active adsorption sites are saturated during the adsorption process, by the molecules of the adsorbate and filled over time. The results showed that the synthesized bio-composite had malachite green removal ability from aqueous media.

Separation of organic contaminant (dye) using the modified porous metal-organic framework (MIL)

Herein, the porous metal-organic framework (MIL-88B: Materials Institute Lavoisier) was synthesized and identified by FT-IR (Fourier transform infrared), SEM (Scanning Electron Microscopy), EDS (Energy Dispersive X-Ray Spectroscopy), and XRD (X-ray powder diffraction) analyses. Then MIL-88B was modified using 3-aminopropyl trimethoxy silane and presented as NH₂-MIL-88B. The synthesized materials were used to separate direct red dye 23 (DR23) as an organic contaminant from water. The effect of various important factors such as the amount of adsorbent, initial concentration of contaminants, and pH was investigated. The results showed that the modified adsorbent (NH₂-MIL-88B) had a higher adsorption capacity than the row adsorbent (MIL-88B). The amount of dye adsorption is high at lower pH values. The percentage of DR23 dye removal was complete under optimal conditions. Increasing the amount of adsorbent (0.001-0.003 g) and decreasing the pH (2.1-8.1) increases the percentage of dye removal and increasing the concentration of contaminant (50-125 mg/L) reduces the dye removal in the process. Isotherm data showed that the adsorption process followed the Langmuir model. Also, pseudo-first-order, pseudo-second-order, and intraparticle diffusion kinetic models were used to investigate the adsorption kinetics. Dye adsorption followed pseudo-second-order kinetics with correlation coefficient (0.99 <). The results showed that the modified adsorbent could be used as a suitable adsorbent with a high adsorption capacity for dye removal from water.

Engineering microbes for enhancing the degradation of environmental pollutants: A detailed review on synthetic biology

Anthropogenic activities resulted in the deposition of huge quantities of contaminants such as heavy metals, dyes, hydrocarbons, etc into an ecosystem. The serious ill effects caused by these pollutants to all living organisms forced in advancement of technology for degrading or removing these pollutants. This degrading activity is mostly depending on microorganisms owing to their ability to survive in harsh adverse conditions. Though native strains possess the capability to degrade these pollutants the development of genetic engineering and molecular biology resulted in engineering approaches that enhanced the efficiency of microbes in degrading pollutants at faster rate. Many bioinformatics tools have been developed for altering/modifying genetic content in microbes to increase their degrading potency. This review provides a detailed note on engineered microbes - their significant importance in degrading environmental contaminants and the approaches utilized for modifying microbes. The genes responsible for degrading the pollutants have been identified and modified fir increasing the potential for quick degradation. The methods for increasing the tolerance in engineered microbes have also been discussed. Thus engineered microbes prove to be effective alternate compared to native strains for degrading pollutants.

Polyol-assisted hydrothermal synthesis of Mn-doped α - Fe2O3(MFO) nanostructures: Spin disorder-induced magnetism and photocatalytic properties

Hierarchical nanostructures play an important role in environmental clean-up and sustainability applications. The magnetic and photocatalytic characteristics of flower-like Mn-doped α-Fe₂O₃ nanostructures were prepared by using a polyol-assisted hydrothermal method. Crystallite sizes are in the range of 35-42 nm, and the existence of 3D hierarchical nanostructures was observed in FESEM pictures. The optical band gap energy varies between 2.08 and 2.16 eV, while XPS examination exposes the ions' charge states and validates Mn³⁺ inclusion in the Fe³⁺ lattice. At room temperature, the addition of Mn to α-Fe₂O₃ results in a spin disorder ferromagnetism and coercivity of about 600 Oe was achieved. Methylene blue (MB) dye solution degraded by 92% when 2.5% Mn doped with α-Fe₂O₃ under visible conditions for 120 min irradiation time.

Synthesis and study of CuNiTiO3 as an ORR electrocatalyst to enhance microbial fuel cell efficiency

Microbial fuel cells (MFCs) have the capability of simultaneous sewage treatment and electricity generation. Modifying the cathode electrode enhances their efficiency. In this study, NiTiO₃ and CuNiTiO₃ were synthesized for practical application as cathode catalysts in a dual-chamber MFC and the performance of the modified cathodes was evaluated against a bare graphite electrode. SEM images showed that the particle sizes were mostly in the range of 40-120 and 20-80 nm for NiTiO₃ and CuNiTiO₃, respectively. According to AFM results, CuNiTiO₃ presented a higher surface roughness than NiTiO₃. MFC using CuNiTiO₃/G electrode with a reduction potential value of -0.27 V (vs. SCE) and a power density of 62.18 mW m^-2 showed better oxygen reduction reaction (ORR) activity compared with NiTiO₃/G and the bare graphite. MFC using CuNiTiO₃ cathode also showed the highest values in terms of chemical oxygen demand (COD) removal (75%) and the calculated coulombic efficiency (CE, 10%). The results obtained in this study, introduce CuNiTiO₃ as a promising electrocatalyst for further improvement of the cathodic reactions in MFC applications.

Existence of Ti3+ and dislocation on nanoporous CdO-TiO2 heterostructure applicable for degrading chlorophenol pollutant

This study addresses the significance of wastewater recuperation by a simple and facile treatment process known as photocatalyst technology using visible light. Titanium di-oxide (TiO₂) is the most promising photocatalyst ever since longing decades, has good activity under UV light, owing to its small band gap. Hence, TiO₂ has been modified with metal oxides for the positive response against visible light. Since this is an efficient process, the novelty has been made on nanometal oxide CdO (cadmium oxide) combined with TiO₂ to acquire the best efficiency of degrading organic chlorophenol contaminant. Initially, the composites were synthesized by sol-gel and thermal decomposition methods and investigated for their various outstanding properties. The characterized outcomes have exhibited heterostructures with reduced crystallite size from the X-ray diffraction studies. Then, the determination of nanoporous feature was recognized through HR-TEM analysis which was also detected with some dislocations. The EDX spectrum was identified the perfect elemental composition. The nitrogen adsorption-desorption equilibrium was attained that offers many pores measured with high surface area. The XPS result convinced that Ti³⁺ was accessible along with TIO₂/CdO composite. Further the absorption towards higher wavelength was obtained from UV-vis spectra. Finally, for the photocatalytic application of chlorophenol, the composite shows higher percentage of degrading efficiencies than the pristine TiO₂. The photocatalytic mechanism was discussed in detail.

Visible-light-driven photodegradation of organic pollutants by simply exfoliated kaolinite nanolayers with enhanced activity and recyclability

The need for abundant photocatalyst in wastewater treatment is currently a must. A simple intercalation process was utilized to exfoliate Kaolinite clay mineral structure Al₂Si₂O₅(OH)₄ into two-dimensional nanostructured separated layers operated in visible light range. The intercalating agents were hydrazine hydrate and urea. Detailed characterization confirmed the nanolayered structures of kaolinite hexagonal nanosheets (NK). In addition, Bandgap energy was reduced based on intercalating agents from 3.45 to 2.48 eV as revealed by light absorption spectra. The quenching of PL spectra for the nK has also been ascribed to the suppression of charge carrier recombination. The exfoliated nK was utilized to photodegrade Rhodamine B dye (RhB) and P-nitrophenol (PNP) as industrial pollutants in wastewater. The results showed 92.3% and 99.7% photodegradation of RhB and PNP within 180 min of visible-light irradiation utilizing the exfoliated NK by urea. We denote the boosted photocatalytic performance of this NK to the uncovered, low bandgap metal oxide inclusions on the exterior of NK besides the nitrogen doping due to exfoliation with urea. This simple exfoliation has modified abundant and stable clay nanolayers that are a promising alternative for the eminent nanostructured oxide photocatalysts to overcome the organic pollutants in wastewater at a high scale.

Coimmobilized enzymes as versatile biocatalytic tools for biomass valorization and remediation of environmental contaminants - A review

Due to stringent regulatory norms, waste processing faces confrontations and challenges in adapting technology for effective management through a convenient and economical system. At the global level, attempts are underway to achieve a green and sustainable treatment for the valorization of lignocellulosic biomass as well as organic contaminants in wastewater. Enzymatic treatment in the environmental aspect thrived on being the promising rapid strategy that appeased the aforementioned predicament. On that account, coimmobilization of various enzymes on single support enhances the catalytic activity ensuing operational stability with industrial applications. This review pivoted towards the coimmobilization of enzymes on diverse supports and their applications in biomass conversion to industrial value-added products and removal of contaminants in wastewater. The limelight of this study chronicles the unique breakthroughs in biotechnology for the production of reusable biocatalysts, which inculcating various enzymes towards the scope of environment application.

Evaluation of promoted Ni-based nanocatalysts in wall-coated microchannel reactor on the dry reforming of methane and effect of ultrasound waves on physiochemical properties of synthesized nanocatalysts

The deactivation of nickel catalysts in the dry reforming of methane (DRM) process has been one of the issues of interest to researchers. In this research, the effect of active phase and support promoter uses and synthesis method on synthesized Ni–Co/Al2O3–MgO nanocatalysts efficiency in wall coated microreactor on dry reforming of methane process studied. To determine the characteristics of the synthesized samples, XRD, BET, FESEM, and Ft-IR analyses have been performed. Analyses show that the use of ultrasound waves in the synthesis of catalysts improves the catalyst surface morphology so that about 82% of the particles of the synthesized sample are smaller than 100 nm and , increases the specific surface area to an average of 10%, and makes its structure smaller. Also, the total pore volume on the surface of the samples also shows a 10% increase. The use of promoters increases the catalyst activity and makes it more stable up to 18 h on stream. The use of a wall-coated microreactor improves heat transfer, easier access of reactants to active sites, no pressure drop, and higher activity than a conventional U-type fixed bed reactor. Nanocatalysts with Ni/Co = 5 and Al/Mg = 5 has shown the highest and most stable activity throughout the temperature range in the DRM process.

Study of synergistic effect of cobalt and carbon codoped with TiO2 photocatalyst for visible light induced degradation of phenol

In this work, we reported synthesis of cobalt and carbon codoped TiO₂ (Co-C-TiO₂) nanoparticles were prepared using co-precipitation technique. The synthesized catalysts are analyzed by various methods. The powder XRD pattern confirmed that all the samples were polycrystalline of anatase phase and particle size of resultant nanoparticle was reduced correlated with bare TiO₂ sample. FTIR measurements exhibit the identification of functional groups present at the surface of TiO₂. FESEM micrograph showed that the shape of codoped TiO₂ nanoparticles are approximately sphere. The attained energy gap of Co doped and C codoping of TiO₂ modifies to a level below the energy gap of TiO₂ anatase specifying a high capability to absorb visible light. The recombination rate of photo-induced electrons and holes for Co-C codoped TiO₂ nanoparticles is significantly reduced. The synthesized samples are assessed in degradation of phenol by the illumination of visible light. The results confirmed that photocatalytic activity enhanced due to doping and codoping of Co and C. As a result, Co-C codoped TiO₂ nanoparticles exhibited a higher visible-light photocatalytic activity in compared with Co-TiO₂ and bare TiO₂ with the maximum degradation efficiency of 98, 75 and 15%, respectively. And also, the reusability of the catalyst was proved when 95% degradation could be achieved after consecutive batches. It is predictable that this work will provide new insights to increase the visible light active photocatalysts for environmental problems.

Lignosulfonate valorization into a Cu-containing magnetically recyclable photocatalyst for treating wastewater pollutants in aqueous media

This study presents an eco-friendly and economical process for preparing a magnetic copper complex conjugated to modified calcium lignosulfonate (LS) through a diamine (Fe₃O₄@LS@naphthalene-1,5-diamine@copper complex; FLN-Cu) as a green and novel catalyst. The prepared catalyst was characterized by Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), Brunauer-Emmett-Teller (BET), energy-dispersive X-ray spectroscopy (EDS), elemental mapping, inductively coupled plasma-optical emission spectrometry (ICP-OES) and field emission scanning electron microscopy (FESEM) techniques. The photocatalytic performance of the synthesized FLN-Cu catalyst was investigated by the degradation of aqueous solutions of dyes such as Rhodamine B (RhB), methylene blue (MB), and Congo red (CR) under UV irradiation. The dye degradation was followed by UV-Vis (ultraviolet-visible) spectrophotometry by measuring the changes in absorbance. The effects of different factors such as pH, contact time, photocatalyst dosage, and initial concentration of dye on the adsorption percentage were also investigated. Moreover, the catalyst showed high stability and could be readily separated from the reaction media using a magnet and reused five times without a remarkable loss of catalytic ability.

Recent advances in electrochemical sensor developments for detecting emerging pollutant in water environment

In the latest times, considerable studies have been performed closer to detecting emerging pollutant such as paracetamol in wastewater. Electrochemical sensor developments have recently started to determine in fewer concentrations effectively. The detection of paracetamol using standard protocols corresponding to electroanalytical techniques has a greater impact noticed in directing the detecting process toward biosensors. Non-enzymatic sensors are the peak of all electro analysis approaches. Functionalized materials, such as metal oxide nanoparticles, conducting polymers, and carbon-based materials for electrode surface functionalization have been used to create a fortification for distributing passive enzyme-free biosensors. Synergic effects are possible by enhancing loading capacity and mass transfer of reactants for attaining high analytical sensitivity using a variety of nanomaterials with large surface areas. The main focus of this study is to address the prevailing issues in the identification of paracetamol with the tasks in the non-enzymatic sensors field, followed by the useful methods of electro analysis studies.

Efficient green photocatalyst of silver-based palladium nanoparticles for methyle orange photodegradation, investigation of lipid peroxidation inhibition, antimicrobial, and antioxidant activity

Nanotechnology is an interdisciplinary study that has been developing worldwide in recent years and has a serious impact on human life. The fact that the nanoparticles of plant origin are clean, non-toxic, and biocompatible has enabled new fields of study. The Hibiscus sabdariffa (H. sabdariffa) plant has been attracted by scientists because of its impact on health and many other areas. The lipid peroxidation inhibiting activity, antioxidant properties, and antimicrobial properties of H. sabdariffa plant with Ag-Pd metal was ditermined. For the total phenolic component, gallic acid was used as the standard and quarcetin was used for the total flavonoid. The lipid peroxidation inhibition activity of Ag-Pd NPs in ethanol extract was found to be very well compared to the positive control (BHA). The lowest and highest concentrations of DPPH radical scavenging activity were 82.178-97.357%, whereas for BHA these values were found to be 84.142-94.142%. The highest concentration of Ag-Pd NPs at 200 μg/mL the DPPH radical quenching activity was higher than BHA. Ag-Pd NPs showed a good antimicrobial activity against certain pathogenic microorganisms such as Bacillus subtilis, Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa, Candida albicans, which are the causative agents of various diseases in humans. The photodegradation activity of Ag-Pd NPs also investigated against Methyl orange dye (MO) under sunlight irradiation for 120 min and was found to be as 67.88.

Nano-architectural design of TiO2 for high performance photocatalytic degradation of organic pollutant: A review

In the past several decades, significant efforts have been paid toward photocatalytic degradation of organic pollutants in environmental research. During the past years, titanium dioxide nano-architectures (TiO₂ NAs) have been widely used in water purification applications with photocatalytic degradation processes under Uv/Vis light illumination. Photocatalysis process with nano-architectural design of TiO₂ is viewed as an efficient procedure for directly channeling solar energy into water treatment reactions. The considerable band-gap values and the subsequent short life time of photo-generated charge carriers are showed among the limitations of this approach. One of these effective efforts is the using of oxidation processes with advance semiconductor photocatalyst NAs for degradation the organic pollutants under UV/Vis irradiation. Among them, nano-architectural design of TiO₂ photocatalyst (such as Janus, yolk-shell (Y@S), hollow microspheres (HMSs) and nano-belt) is an effective way to improve oxidation processes for increasing photocatalytic activity in water treatment applications. In the light of the above issues, this study tends to provide a critical overview of the used strategies for preparing TiO₂ photocatalysts with desirable physicochemical properties like enhanced absorption of light, low density, high surface area, photo-stability, and charge-carrier behavior. Among the various nanoarchitectural design of TiO₂, the Y@S and HMSs have created a great appeal given their considerable large surface area, low density, homogeneous catalytic environment, favorable light harvesting properties, and enhanced molecular diffusion kinetics of the particles. In this review was summarized the developments that have been made for nano-architectural design of TiO2 photocatalyst. Additional focus is placed on the realization of interfacial charge and the possibility of achieving charge carriers separation for these NAs as electron migration is the extremely important factor for increasing the photocatalytic activity.