Natural Sunlight Driven Photocatalytic Removal of Toxic Textile Dyes in Water Using B-Doped ZnO/TiO2 Nanocomposites

Cellulose Acetate Supported MOF-5/Crystalline Nanocellulose Composite Film as an Adsorbent Material for Methylene Blue Removal from Aqueous Solutions

In this study, a novel, low-cost, and efficient adsorbent film was fabricated by a solvothermal method. The adsorbent film was developed to be hydrolytically stable, not vulnerable to aggregation in aqueous environments, and not prone to secondary contamination. The adsorbent consists of cellulose acetate (CA) as a support embedded with a MOF-5/crystalline nanocellulose (CNC) composite material. The CA-supported MOF-5/CNC film was characterized using a variety of techniques, including X-ray diffraction, thermal gravimetric analysis, scanning electron microscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy, which revealed hydroxyl and carbonyl functional groups on the adsorbent film. The film was evaluated for the adsorptive removal of methylene blue (MB) from an aqueous solution. Adsorption was characterized by a rapid increase in MB adsorption during the first hour with equilibrium achieved within 4-5 h into the adsorption process. The maximum adsorption capacity was determined to be 4.29 mg/g and the maximum dye removal efficiency was 77%. The MB adsorption process best fitted the Freundlich isotherm and pseudo-second-order kinetic models. Thermodynamic studies showed that the adsorption was exothermic and feasible. The adsorbent film showed admirable regeneration ability, demonstrating its cost-effectiveness and its potential as a promising material for wastewater treatment.

Visible Light-Driven SnIn4S8 Photocatalyst Decorated on Polyurethane-Impregnated Microfiber Non-Woven Fabric for Pollutant Degradation

In recent years, polyurethane has drawn great attention because of its many advantages in physical and chemical performance. In this work, firstly, polyurethane was impregnated in a non-woven fabric (NWF). Then, polyurethane-impregnated NWF was coagulated utilizing a wet phase inversion. Finally, after alkali treatment, microfiber non-woven fabrics with a porous polyurethane matrix (PNWF) were fabricated and used as substrates. SnIn4S8 (SIS) prepared by a microwave-assisted method was used as a photocatalyst and a novel SIS/PNWF substrate with multiple uses and highly efficient catalytic degradation ability under visible light was successfully fabricated. The surface morphology, chemical and crystal structures, optical performance, and wettability of SIS/PNWF substrates were observed. Subsequently, the photocatalytic performance of SIS/PNWF substrates was investigated by the decomposition of rhodamine B (RhB) under visible light irradiation. Compared with SIS/PNWF-2% (2%, the weight ratio of SIS and PNWF, same below), SIS/PNWF-5% as well as SIS/PNWF-15%, SIS/PNWF-10% substrates exhibited superior photocatalytic efficiency of 97% in 2 h. This may be due to the superior photocatalytic performance of SIS and the inherent hierarchical porous structure of PNWF substrates. Additionally, the hydrophobicity of SIS/PNWF substrates can enable them to float on the solution and further be applied on an open-water surface. Furthermore, tensile strength and recycle experiments demonstrated that SIS/PNWF substrates possessed superior mechanical strength and excellent recycle stability. This work provides a facile and efficient pathway to prepare SIS/PNWF substrates for the degradation of organic pollutants with enhanced catalytic efficiency.

Photocatalytic Removal of Metronidazole Antibiotics from Water Using Novel Ag-N-SnO2 Nanohybrid Material

In this study, we employed a straightforward synthetic approach using the sol-gel method to fabricate a novel photocatalyst, Ag and N co-doped SnO2 (Ag-N-SnO2). The synthesized photocatalysts underwent characterization through various techniques including XRD, FTIR, FESEM-EDS, TEM, UV-vis DRS, BET, and XPS. The UV-vis DRS results confirmed a reduction in the bandgap energy of Ag-N-SnO2, leading to enhanced absorption of visible light. Additionally, TEM data demonstrated a smaller particle size for Ag-N-SnO2, and BET analysis revealed a significant increase in surface area compared to SnO2.The efficiency of the Ag-N-SnO2 photocatalyst in degrading metronidazole (MNZ) under natural sunlight surpassed that of SnO2. Under optimal conditions (Ag-N-SnO2 concentration of 0.4 g/L, MNZ concentration of 10 mg/L, pH 9, and 120 min of operation), the highest MNZ photocatalytic removal reached 97.03%. The reaction kinetics followed pseudo-first-order kinetics with a rate constant of 0.026 min-1. Investigation into the mineralization of MNZ indicated a substantial decrease in total organic carbon (TOC) values, reaching around 56% in 3 h of sunlight exposure. To elucidate the photocatalytic degradation mechanism of MNZ with Ag-N-SnO2, a scavenger test was employed which revealed the dominant role of •O2-. The results demonstrated the reusability of Ag-N-SnO2 for up to four cycles, highlighting its cost-effectiveness and environmental friendliness as a photocatalyst.

Polyol synthesis of one-dimensional Ag nanowires for the photocatalytic degradation of textile dye and effective removal of microbes

Due to the excess release of hazardous pollutants to the environment, the quest for the synthesis of effective nanomaterials for wastewater treatment is never-ending. Present study reports the polyol synthesis of Ag NWs of ~ 85 nm diameter and average length of 4.08 µm using PVP and ethylene glycol. The experimental data on the methylene blue dye degradation substantiated the photocatalytic efficiency of Ag NWs (88% degradation in 120 min). Furthermore, the Ag NWs exhibited microbial load reducing property in air conditioner condensate water (ACW) within a time period of 60 min. Also, the anti-bacterial effect of Ag NWs was estimated using two human pathogenic bacterial strains, namely Staphylococcus aureus and Bacillus cereus. The antibacterial potential of Ag NWs against Staphylococcus aureus and Bacillus cereus was revealed significant with an inhibition zone size of 14 ± 0.1 mm and 9 ± 0.1 mm, respectively. Hence, the present work validates the potential efficiency of Ag NWs in the degradation of textile dyes and reduction of microbial population.

A Fresh Perspective on the Impact of ZnTiO3 Coupling on the Microstructure and Photocatalytic Properties of TiO2 Fabricated at Varied Temperatures

ZnTiO3/TiO2 composite photocatalysts were synthesized via the sol-gel technique, and the impact of varying heat treatment temperatures (470, 570, 670 °C) on their crystalline arrangement, surface morphology, elemental composition, chemical state, specific surface area, optical characteristics, and photocatalytic efficacy was systematically investigated. The outcomes revealed that, as the temperature ascends, pure TiO2 undergoes a transition from anatase to rutile, ultimately forming a hybrid crystal structure at 670 °C. The incorporation of ZnTiO3 engenders a reduction in the TiO2 grain dimensions and retards the anatase-to-rutile phase transition. Consequently, the specimens manifest a composite constitution of anatase and ZnTiO3. In contrast, for pure TiO2, the specimen subjected to 670 °C annealing demonstrates superior photocatalytic performance due to its amalgamated crystal arrangement. The degradation efficacy of methylene blue (MB) aqueous solution attains 91% within a 60-min interval, with a calculated first-order reaction rate constant of 0.039 min-1. Interestingly, the ZnTiO3/TiO2 composite photocatalysts exhibit diminished photocatalytic activity in comparison to pristine TiO2 across all three temperature variations. Elucidation of the photocatalytic mechanism underscores that ZnTiO3 coupling augments the generation of photogenerated charge carriers. Nonetheless, concurrently, it undermines the crystalline integrity of the composite, yielding an excess of amorphous constituents that impede the mobility of photoinduced carriers. This dual effect also fosters escalated recombination of photogenerated charges, culminating in diminished quantum efficiency and reduced photocatalytic performance.

The synergistic degradation of pollutants in water by photocatalysis and PMS activation

In recent years, the synergistic degradation of water pollutants through advanced oxidation technology has emerged as a prominent research area due to its integration of various advanced oxidation technologies. The combined utilization of peroxymonosulfate (PMS) activation technology and photocatalysis demonstrates mild and nontoxic characteristics, enabling the degradation of water pollutants across a wide pH range. Moreover, this approach reduces the efficiency of electron hole recombination, broadens the catalyst's light response range, facilitates electron transfer of PMS, and ultimately improves its photocatalytic performance. The paper reviews the current research status of photocatalytic technology and PMS activation technology, respectively, while highlighting the advancements achieved through the integration of photocatalytic synergetic PMS activation technology for water pollutant degradation. Furthermore, this review delves into the mechanisms involving both free radicals and nonradicals in the reaction process and presents a promising prospect for future development in water treatment technology. PRACTITIONER POINTS: Degradation of water pollutants by photocatalysis and PMS synergistic action has emerged. Synergism can enhance the generation of free radicals. This technology can provide theoretical support for actual wastewater treatment.

Synthesis of CeO2/ZrO2/ZnO nano alloy oxide and investigation of photocatalysis of naphthol orange under sunlight

Novel metal-like cerium- and zirconium-doped ZnO photocatalysts were prepared herein with various proportions of molar ratios via a cost-effective co-precipitation method. The effects of novel metal doping on the photocatalytic activity of ZnO were studied. Various techniques were used to investigate the structural, morphological, and elemental composition, particle size, optical properties, and catalytic activity of the synthesized photocatalysts. It was found that the crystallite size and particle size of the nano alloy oxides were 15.12 ± 1 and 5 ± 1 nm, respectively, and the surface morphology of the nanoparticles indicated a satisfactory surface area. Among all synthesized nanocomposites, Ce_xZr_xZn_xO₅ (x = 1) [CZ₁Z₂-A] exhibited satisfactory photo-oxidation activity against naphthol orange (NO) under sunlight with a rate constant of 57.5 × 10^-3 min^-1. The effects of pH, inorganic salts, dye concentrations, and catalytic dosage on NO degradation were studied. A probable mechanistic pathway for the degradation of NO in the presence of CZ₁Z₂-A was proposed, and studies of sacrificial agents indicated that superoxide radical anion (O₂˙^-) was the main accountable active species in NO degradation. In addition, CZ₁Z₂-A exhibited excellent recyclability potential, and XRD studies revealed that there was no change in the crystal structure before or after degradation, which indicated its high stability. The intriguing finding was that Ce- and Zr-doped ZnO did not exhibit satisfactory catalytic performance in the photo-oxidation of NO. However, the composite formula of Ce_xZr_xZn_xO₅ (x = 1) with a 1 : 1 : 1 ratio of metal ions offered excellent catalytic activity.

Biogenic Preparation of ZnO Nanostructures Using Leafy Spinach Extract for High-Performance Photodegradation of Methylene Blue under the Illumination of Natural Sunlight

To cope with environmental pollution caused by toxic emissions into water streams, high-performance photocatalysts based on ZnO semiconductor materials are urgently needed. In this study, ZnO nanostructures are synthesized using leafy spinach extract using a biogenic approach. By using phytochemicals contained in spinach, ZnO nanorods are transformed into large clusters assembled with nanosheets with visible porous structures. Through X-ray diffraction, it has been demonstrated that leafy spinach extract prepared with ZnO is hexagonal in structure. Surface properties of ZnO were altered by using 10 mL, 20 mL, 30 mL, and 40 mL quantities of leafy spinach extract. The size of ZnO crystallites is typically 14 nanometers. In the presence of sunlight, ZnO nanostructures mineralized methylene blue. Studies investigated photocatalyst doses, dye concentrations, pH effects on dye solutions, and scavengers. The ZnO nanostructures prepared with 40 mL of leafy spinach extract outperformed the degradation efficiency of 99.9% for the MB since hydroxyl radicals were primarily responsible for degradation. During degradation, first-order kinetics were observed. Leafy spinach extract could be used to develop novel photocatalysts for the production of solar hydrogen and environmental hydrogen.

Effect of Calcination Temperature of SiO2/TiO2 Photocatalysts on UV-VIS and VIS Removal Efficiency of Color Contaminants

This paper presents the effect of fumed silica modification and calcination temperature on the physicochemical properties of photocatalysts and their activity under the UV-VIS and VIS light range. The materials were obtained by hydrolysis of titanium tetraisopropoxide (TTIP) combined with a calcination step. The obtained nanomaterials were characterized using analytical methods such as X-ray diffraction XRD, FT-IR/DRS infrared spectroscopy, UV-Vis/DRS spectroscopy and SEM scanning electron microscopy. BET specific surface area and zeta potential were also measured. It was observed that SiO2 modification inhibited the transformation phase of anatase to rutile and the increase in crystallite size during calcination. The calcination process contributed to a change in the surface character of photocatalysts under study from positively to negatively charged. The photocatalytic activity of samples was identified by determining the methylene blue decomposition under UV-VIS and VIS light. Experimental results showed that the addition of SiO2 and the calcination process increased the photoactivity. The obtained materials showed higher activity compared to the reference samples. It was found that the degree of dye removal increased along with increased calcination temperature. The highest activity was observed for photocatalyst SiO2(11.1%)/TiO2_600.

Visible LED photocatalysis combined with ultrafiltration driven by metal-free oxygen-doped graphitic carbon nitride for sulfamethazine degradation

A novel visible light emitting diode (LED) photocatalysis combined ultrafiltration (UF) system driven by metal-free O-doped C₃N₄ was established for sulfamethazine (SMZ) removal in environmental remediation. Among different O-doping ratios, 8%O-C₃N₄ exhibited the optimal SMZ degradation efficiency (89.36%) and the flux of 8%O-C₃N₄/LED/UF system could reach up to 38.92 L/m²/h. Benefitting from the O-doping, the synergetic effect of the expansion of visible-light absorption, enhancement of electron redox capacity, and improvement of e^--h⁺ separation efficiency could produce the intensified photoactivity. Superoxide radical (O₂^•-) and single oxygen (¹O₂) were proved to be the primary active species by EPR and quenching tests. Moreover, the influence of several parameters such as photocatalyst dosage, SMZ concentration, raw turbidity and humic acid concentration in 8%O-C₃N₄/LED/UF system on SMZ removal were systematically studied. Under simulated surface water matrix, 8%O-C₃N₄/LED/UF system could also remove 96.88% SMZ and stable membrane flux stabilized as high as 33.36 L/m²/h. This study makes a demonstration for applying highly-effective powdery photocatalysts in the actual wastewater treatment and designing future photocatalytic reactors.

Photocatalysis process to treat polluted water by azo dye Cibacron Brilliant Yellow 3G-P

The main objective of this study was to investigate the photodegradation of azo dye Cibacron Brilliant Yellow 3G-P using Anatase, Degussa-P25 and ZnO. These semi-conductors were characterized using XRD, BET and TEM-EDX. The variation of the amount of semi-conductors significantly affect the rate of color removal. The decolorization rate increased as the catalyst dosage was increased. Other parameters were also studied, such as stirring speed, pH, and initial dye concentration. It was found that the rate of decolorization increases with the increase of stirring speed. Decolorization of about 30, 60 and 80% was respectively achieved in the case of Anatase, Degussa-P25 and ZnO at low stirring speed (50rpm). At pH = 3, the degradation rate was found to be higher than the alkaline pH, about 95.58 and 85.71% of color has been decolorized with Anatase and Degussa-P25 respectively. While using ZnO, the color removal reached maximum in acidic and alkaline solutions, more than 95% of dye was decolorized. The concentrations dye solutions less than 80ppm led to the removal rate of about 95% in the case of ZnO, while it was only about 8-15% in the case of TiO₂ with the concentration more than 20 ppm.