A novel quadripartite Cu2O-CdS-BiVO4-WO3 visible-light driven photocatalyst: Brief characterization and study the kinetic of the photodegradation and mineralization of sulfasalazine

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.

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

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

A facile two-step hydrothermal preparation of 2D/2D heterostructure of Bi2WO6/WS2 for the efficient photodegradation of methylene blue under sunlight

A facile two-step hydrothermal method was successfully used to prepare a photocatalyst Bi2WO6/WS2 heterojunction for methyl blue (MB) photodegradation. Fabricated photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive X-ray analysis (EDX), and X-ray photoelectron spectroscopy (XPS). Band gap measurements were carried out by diffuse reflectance spectroscopy (DRS). Results indicated that the prepared heterostructure photocatalyst has increased visible light absorption. Photocatalytic performance was evaluated under sunlight irradiation for methylene blue (MB) degradation as a model dye. Variations in pH (4-10), amount of catalyst (0.025-0.1 g/L), and initial MB concentrations (5-20 ppm) were carried out, whereas all prepared catalysts were used to conduct the tests with a visible spectrophotometer. Degradation activity improved with the pH increase; the optimum pH was approximately 8. Catalyst concentration is directly related to degradation efficiency and reached 93.56% with 0.075 g of the catalyst. Among tested catalysts, 0.01 Bi2WO6/WS2 has exhibited the highest activity and a degradation efficiency of 99.0% in 40 min (min) for MB. MB photodegradation follows pseudo-first-order kinetics, and obtained values of kapp were 0.0482 min-1, 0.0337 min-1, 0.0205 min-1, and 0.0087 min-1 for initial concentrations of 5 ppm, 10 ppm, 15 ppm, and 20 ppm, respectively. The catalyst was reused for six cycles with a negligible decrease in the degradation activity. Heterostructure 0.01 Bi2WO6/WS2 has exhibited a photocurrent density of 16 μA cm-2, significantly higher than 2.0 and 4.5 μA cm-2 for the pristine WS2 and Bi2WO6, respectively. The findings from these investigations may serve as a crucial stepping stone towards the remediation of polluted water facilitated by implementing such highly efficient photocatalysts.

Pd nanoparticles decorated BiVO4 pine architectures for photocatalytic degradation of sulfamethoxazole

Sulfamethoxazole (SMX) has been extensively detected in wastewater treatment plant effluents and surface water. Because of its potential risks to ecology and health, treatment for eliminating SMX is urgently required. In this study, we report the application of Pd nanoparticles decorated on BiVO₄ pine architecture for the photocatalytic degradation of SMX. The results showed that the barer BiVO₄ and Pd-BiVO₄ eliminated SMX under visible-light irradiation. After 210 min of irradiation, 98.8% of SMX was substantially eliminated by Pd-BiVO₄, whereas bare BiVO₄ can degraded approximately 36.3% of SMX. Pd-BiVO₄ also exhibited a high mineralization rate (84% of total organic carbon (TOC) removal) compared to bare BiVO₄ (51% of TOC removal). Through three-dimensional excitation-emission matrix fluorescence spectra, SMX with high fluorescence intensity can be degraded to non-fluorescence intermediate products, further confirming the high mineralization of SMX over Pd-BiVO₄ catalyst. Well-dispersed Pd nanoparticles on the {040} facet of BiVO₄ pine architecture can support the recombination of photogenerated charge carriers because of the formation of the Schottky junction at the Pd-BiVO₄ interface. Besides, the active species trapping tests indicated that ^•O₂^- and h⁺ radicals dominate SMX photodegradation over Pd-BiVO₄. The main degradation intermediates of SMX in the reaction solution was also identified through ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry analysis. This investigation can provide insight into designing metallic/semiconductor junctions for antibiotic elimination in water media.

High interfacial charge separation in visible-light active Z- scheme g-C3N4/MoS2 heterojunction: Mechanism and degradation of sulfasalazine

Examination of highly proficient photoactive materials for the degradation of antibiotics from the aqueous solution is the need of the hour. In the present study, a 2D/2D binary junction GCM, formed between graphitic-carbon nitride (g-C3N4) and molybdenum disulphide (MoS2), was synthesized using facile hydrothermal method and its photo-efficacy was tested for the degradation of sulfasalazine (SUL) from aqueous solution under visible-light irradiation. Morphological analysis indicated the nanosheets arrangement of MoS2 and g-C3N4. The visible-light driven experiments indicated that 97% antibiotic was degraded by GCM-30% within 90 min which was found to be quite high than pristine g-C3N4 and MoS2 at solution pH of 6, GCM-30% dose of 20 mg, and SUL concentration of 20 mgL-1. The degradation performance of GCM-30% was selectively improved due to enhanced visible-light absorption, high charge carrier separation, and high redox ability of the photogenerated charges which was induced by the effective Z-scheme 2D/2D heterojunction formed between g-C3N4 and MoS2. The reactive radicals as determined by the scavenging study were •O2-, and h+. A detailed degradation mechanism of SUL by GCM-30% was also predicted based on the detailed examination of the band gaps of g-C3N4 and MoS2.

Selective detection of sulfasalazine antibiotic and its controllable photodegradation into 5-aminosalicylic acid by visible-light-responsive metal-organic framework

The extensive use of sulfasalazine (SSZ) antibiotics has brought potential threats to aquatic ecosystems and human health. Thus, necessary measures for the removal of SSZ must be taken to prevent arbitrary antibiotic exposure to the aquatic environment. However, not all the recent photocatalysts that have been used for the degradation of SSZ could not achieve the controlled release of SSZ and hence are losing their medicinal values. Herein, by utilizing an Eosin Y moiety as an efficient light-harvesting and emission site, an Eosin Y-based visible-light-responsive metal-organic framework has been synthesized and characterized, which exhibits high selectivity for detecting the antibiotic SSZ in water and simulated physiological conditions, with a detection limit of below 1 μM (0.4 μg mL^-1). It also represents the first example of a MOF-based photocatalyst for the controllable degradation of SSZ into 5-aminosalicylic acid with excellent catalytic activity and recyclability.

The physical and optical investigations of the tannic acid functionalised Cu-based oxide nanostructures

The need for a mild, low-cost, green environment that is able to produce exotic properties of output nanostructures is appealing nowadays. Employing these requirements, the copper (Cu)-based oxide nanostructures have been successfully synthesised via one-pot reaction using biocompatible natural polyphenol, tannic acid (TA) as both the reducing agent and stabiliser at 60, 70 and 80 °C. The structural and optical studies disclosed the effect of TA on the surface morphology, phase purity, elemental composition, optical microstrain and optical intrinsic energy of this mixed Cu₂O and CuO nanostructures. The optically based method describes the comparative details of the multi-band gap in the presence of more than one element with overlapping spectra from the first-derivative absorbance curve [Formula: see text] and the exponential absorbance of Urbach tail energy [Formula: see text] towards the conventional Tauc bandgap. The [Formula: see text] demonstrates that the pronounced effect of TA that Cu₂O and CuO nanostructures creates much sensitive first-derivative bandgap output compared to the Tauc bandgap. The results also show that the [Formula: see text] reduced as the temperature reaches 70 °C and then experienced sudden increase at 80 °C. The change in the pattern is parallel to the trend observed in the Williamson-Hall microstrain and is evident from the variations of the mean crystallite size [Formula: see text] which is also a cause response to the change in temperature or pH. Therefore, the current work has elucidated that the structural and optical correlations on the as-synthesised Cu₂O and CuO nanostructures in the presence of TA were the combined reaction of pH change and the ligand complexation reactions. The acquired results suggest a more comprehensive range of studies to further understand the extent relationship between the physical and optical properties of TA functionalised Cu-based oxide nanostructures.

BiVO4 prepared by the sol-gel doped on graphite felt cathode for ciprofloxacin degradation and mechanism in solar-photo-electro-Fenton

In this research, bismuth vanadate-doped graphite felt (GF-BiVO₄) was successfully prepared by sol-gel method, in which BiVO₄ owned superior electro-Fenton (EF) and solar-photo-electro-Fenton (SPEF) performance. Combined with the analysis by X-ray diffractometer (XRD), field emission transmission electron microscopy (FE-TEM), nitrogen adsorption-desorption isotherms and cyclic voltammetry (CV), the changes of electrodes were reflected in structure and physicochemical properties. The doping of monoclinic BiVO₄ endued GF with a higher surface area and more electro-active sites and better electrode activity in comparison to Raw-GF. Then, the GFs were used as cathodes to detect •OH concentration with coumarin (COU) as probe molecule and to evaluate photoelectric performance with ciprofloxacin (CIP) in photocatalysis, EF and SPEF processes. The results demonstrated that the concentration of •OH followed an order of SPEF> EF> photocatalysis, which was consistent with the removal rate of CIP (99.8%, 99.4% and 21.2%, respectively) on GF-BiVO₄ at 5 min. Further, five degradation pathways of CIP in SPEF system were proposed including the attack on piperazine ring, oxidation on cyclopropyl group, decarboxylation and hydroxyl radical addition, oxidation on benzene group and defluorination. The study provides insights into the enhancement of EF and SPEF performance and the degradation pathway of CIP in SPEF.

Differentiation Between Metronidazole Residues Disposal by Using Adsorption and Photodegradation Processes Onto MgO Nanoparticles

Background

Metronidazole (MNZ) is an antibiotic form that is considered as a dangerous environmental pollutant due to its widespread use as growth promoters in livestock and aquaculture operations along with its therapeutic application for humans.

Purpose

The objective of this work was to conduct a comparative study between the efficiency of the adsorption and photocatalytic degradation of MNZ in an aqueous solution by using magnesium oxide nanoparticles (MgO NP) under different effects, as well as evaluate the performance, reusability and cost study.

Materials and Methods

Several instruments such as XRD, EDX, SEM, and TEM were used to characterize the chemical composition and morphological properties of the synthesized MgO NP, while the GC-MS analysis was used to monitor the degradation pathway of MNZ particles within 180 min. The simple photo-batch reactor was used to investigate the degradation of MNZ under the effect of UV radiation, initial concentration of MNZ, pH, catalyst loading, inorganic salts addition, time, and temperature.

Results

The degradation efficiency is mainly divided into two steps: 35.7% for maximum adsorption and 57.5% for photodegradation. Adsorption isotherm models confirmed that the process nature is chemisorption and appropriate Langmuir model, as well as to be a nonspontaneous and endothermic reaction according to the thermodynamic study. Adsorption constant during dark condition is smaller than typical adsorption equilibrium constant derived from the Langmuir-Hinshelwood kinetic model through photodegradation of MNZ that follows pseudo-first-order kinetics. Toxicity rates were reduced considerably after the photodegradation process to 88.21%, 79.84%, and 67.32% and 57.45%, 51.98%, and 43.87% by heamolytic and brine shrimp assays, respectively, for initial MNZ concentrations (20, 60, and 100 mg/L).

Conclusion

We significantly recommend using MgO NP as a promising catalyst in the photodegradation applications for other organic pollutants in visible light.