Commercial Photocatalyst Research Articles

Sunlight-Driven Photodegradation of RB49 Dye Using TiO2-P25 and TiO2-UV100: Performance Comparison

By combining measurements of photocatalysis under solar irradiation with measurements of total organic carbon, we have compared the performance of two TiO2-based photocatalysts in the photodegradation of the dye Reactive Blue 49 (RB49). TiO2-P25 and TiO2-UV100 commercial photocatalysts were tested within a concentration ranging from 0.5 to 4 g/L. The dye solution concentration was varied from 10 to 50 mg/L and its pH was increased from 3 to 9. Extensive characterization of the photocatalysts was performed using Fourier-transform infrared spectroscopy, scanning electron microscopy and X-ray diffraction. TiO2-UV100 proved to be more active in adsorbing RB49 dye than TiO2-P25. At low dye concentrations, the adsorption equilibrium is reached in 15 min. This time increases to 1 h at higher concentrations. The photocatalytic degradation of aqueous RB49 under sunlight was monitored by UV-Vis spectrophotometry. The apparent rate constant of dye photodegradation with TiO2-UV100 is twice that of TiO2-P25. The total organic carbon (TOC) analysis showed a removal of around 98% with TiO2-UV100 and only 85% with TiO2-P25 after 3 h of solar irradiation. Over five photocatalytic cycles of 3 h, TiO2-UV100 maintained a more stable and higher efficient photocatalytic performance. All our results converge toward a better photocatalytic performance of TiO2-UV100 for the photodegradation of RB49 dye and indicate that the most decisive factor is its greater capacity to adsorb the pollutant.

Investigation of the influencing factors and optimization study for the removal of levofloxacin in water using commercial TiO2 photocatalyst under UV-LED irradiation

Abstract Photocatalysis holds significant promise for effectively eliminating toxins, hard-to-biodegrade, and persistent organic pollutants in water. In this study, we used commercial TiO2 as a photocatalyst under UVA-LED irradiation to remove levofloxacin from water. In the photocatalytic tests, levofloxacin removal efficiency in water reached 68.21% after 120 minutes at pH 4 with an antibiotic/catalyst concentration ratio of 1:20. ANOVA revealed that the model achieved significance, as indicated by a p-value of 0.009. LEVO degradation under UVA-LED is three times higher than that under natural light. Optimal conditions for LEVO removal include pH 4, LEVO/TiO2 ratio of 1:20, and UVA-LED irradiation. The regression model predicts LEVO removal with high accuracy (R2 = 0.8469). This study highlights the use of photocatalysis with TiO2 as a promising approach for pharmaceutical pollutant removal, emphasizing the need for further research in sustainable water treatment technologies.

NiO/vermiculite composites prepared for photocatalytic degradation of methanol-water solution and hydrogen generation

A novel eco-friendly NiO/Vm clay based photocatalysts were synthesized from two vermiculites (Vm1 and Vm2) and nickel(II) nitrate hexahydrate (Ni(NO3)2·6H2O salt precursor by the chemical precipitation without and with the sodium hydroxide (NaOH) or ammonium hydroxide (NH4OH, 28% NH3 in H2O) as precipitation agents (Synthesis A) in comparison with the solid-state thermal decomposition (Synthesis B) at 600 °C. Structural properties of all specimens were characterized by X-ray fluorescence, scanning electron microscopy, X-ray diffraction, infrared (IR) and Raman spectroscopy. The photocatalytic performance of NiO/Vm composites was evaluated under UV radiation (λ = 254 nm) for decomposition of methanol-water to hydrogen over 4-h and the stable yield of hydrogen over the 24-h periods. The NaOH and NH4OH affected the NiO crystallite size and therefore the photocatalytic activity during 4 h. Different 2:1 layer charge of Vm1 (0.82 e−) and Vm2 (0.40 e−) and the specific surface area of Vm1 (about 43 m2/g) and Vm2 (about 34 m2/g) supported H2 yield of 628.2 μmol/gcat. and 596.8 μmol/gcat., close to 657.0 μmol/gcat. produced in the presence of commercial photocatalyst TiO2 Evonik P25. Crystalline NiO precipitated and anchored in NiO/Vm composites contained smaller crystallites than those in free NiO. Vermiculite silica surface supports coverage of NiO by hydrogen bonding to Si-OH groups influencing the geometry of the NiO crystal structure (disorder NiO(X)). The heterojunction with Si-O-Ni bonding, at which electrons transfer from Vm to NiO cause enriching electron density in NiO and favoring its photocatalytic activity. Photocatalytic hydrogen generation from methanol–water mixture at the presence of all specimens indicated the main product H2 and minimum by-products CH4 and CO. The stable hydrogen production for 24 h was confirmed only in the presence NiO/Vm1–24 while maintaining the NiO(X) in small crystallites. The thermal solid-state procedure provided the gradual dehydration of vermiculites and Ni(NO3)2·6H2O to the same amount and crystallinity of NiO in NiO/Vm1 and NiO/Vm2 composites. The results of this work confirm that vermiculites mixed layer structures with different negative layer charge play a dominant role as semiconductors for anchored NiO. The photocatalytic activity of NiO/vermiculite composites can be harnessed to treat wastewater containing organic contaminants.

Efficient photocatalytic degradation of perfluorooctanoic acid by bismuth nanoparticle modified titanium dioxide

Perfluorooctanoic acid (PFOA) is potentially toxic and exceptionally stable attributed to its robust CF bond, which is hard to be removed by UV/TiO2 systems. In this research, bismuth nanoparticle (Bi NP) modified titanium oxides (Bi/TiO2) were synthesized by a simple photochemical deposition-calcination method and were applied as photocatalysts for the first time to degrade PFOA. The removal rate of 50 mg/L PFOA reached 99.3 % with 58.6 % defluorination rate after 30 min of irradiation via a mercury lamp. Bi/TiO2 exhibited superior performance in PFOA degradation compared to commercial photocatalysts (TiO2, Ga2O3, Bi2O3 and In2O3). In addition, Bi/TiO2 showed high degradation activity under actual sunlight, achieved 100 % removal rate and 59.3 % defluorination rate within 2 h. Bi NPs increase the light trapping ability of Bi/TiO2 and promote the separation of photogenerated electron-hole pairs via local surface plasmon resonance (LSPR) effect, which results in more photogenerated holes (h+) and hydroxyl radicals (OH). Combined with DFT calculations and intermediate detections, the degradation reaction is initiated from the oxidation of the PFOA carboxyl group via h+, followed by the loss of the CF2 unit step by step with the participation of OH. This work presents a novel approach for the practical implementation of TiO2-based photocatalysts to achieve highly efficient photocatalytic degradation of perfluorocarboxylic acids (PFCAs).

Enhanced photocatalytic activity of Er doped ZnO nanospindles and nanorods for degradation of organic pollutants

Rare earth doping in ZnO is an efficient way to improve the photocatalytic performance. In the present work, Er doped ZnO nanospindles and nanorods were prepared through a simple cost effective wet chemical approach and were thoroughly characterized by FESEM, XRD, Raman spectroscopy, UV–vis-DRS, UV–vis absorption and PL spectroscopy. Nanospindle and nanorod-like morphologies of the fabricated samples were revealed by FESEM. XRD analyses revealed hexagonal wurtzite structure of Er doped ZnO nanostructures and confirmed Er doping into ZnO. PL studies showed increased defect concentration in ZnO nanostructures doped with Er ions. The photodegradation ability of nanostructures was investigated using cationic and anionic dyes and photodecomposition rate of 0.042 min−1 was achieved for MB decolorization using 0.5 % Er doped ZnO sample upon 32 min of solar light illumination. The probable photodecomposition mechanism supported by in-situ radical trapping experiments and repeatability test have also been discussed and results suggest that Er doped ZnO photocatalyst exhibit potential for use as commercial solar-active photocatalysts.

Optimization of the Photodegradation of Metoclopramide Drug using Super Nanoparticles in Aqueous Solutions

In the present research carry out to remove pharmaceutical pollutants as a model metoclopramide (MCP) drug from an aqueous medium utilizing a photocatalytic degradation method with super nanoparticles called TiO2 nanoparticles (NP). synthesis of TiO2 nanoparticles by utilizing the hydrothermal processes. The physical characterizations of materials by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), thermogravimetric analysis (TGA), and transmission electron microscope (TEM). The results showed that the efficiency of the TiO2 nanoparticle increased by 88.88%. It also showed that the photocatalytic degradation rate increased with decreasing concentration of MCP drug increasing the intensity of the light led to an increase in the rate of photocatalytic degradation. Study effect of several factors, concentration on the drug, mass of nanoparticle, light intensity that the best conditions for the photocatalytic degradation of 0.3 g of the nanocomposite, MCP drug concentration of 50 m/L, pH solution 8, and light intensity 1.7 mW/Cm2, Thus, the photocatalytic degradation increased with decreasing the concentration of MCP drug. The obtained TiO2 nanoparticle exhibits best photocatalytic degradation than the commercial photo-catalysts TiO2 NPs. Finally, it is essential to evaluate the recycled photocatalytic degradation efficiency, which is one of the utmost significant factors towards photodegradation.

Augmentation of photocatalytic degradation of methylene blue dye using lanthanum and iodine Co-doped TiO2 nanoparticles, their regeneration and reuse; and preliminary phytotoxicity studies for potential use of treated water

The photocatalytic degradation of methylene blue (MB) dye using Lanthanum (La) and Iodine (I) co-doped TiO2 (Ti1−x-yLaxIyO2, where x = 0.00 – 0.05, y = 0.00 – 0.005) nanoparticles prepared through the solution combustion method has been investigated in the current study. The photocatalysts' characterization was done using various techniques, including FTIR for identifying functional groups, XRD for determining crystallinity and crystallite size, DRS for estimating the band gap, and XPS for identifying elements and their oxidation states. The co-doping of La and I in TiO2 causes narrowing the band gap and suppresses the recombination of e–/h+ pairs, which surges its photocatalytic activity. The La and I co-doped TiO2 nanoparticles exhibited a photodegradation efficiency of 98% for MB within 40 min, significantly outperforming undoped TiO2 and commercial TiO2 photocatalyst Aeroxide P-25. Moreover, regeneration experiments demonstrated excellent reusability of the nanoparticles. To find potential use of photocatalytically treated water in irrigation, the phytotoxicity study was done with "Vigna radiata" germination. The evaluation of phytotoxicity demonstrates that the treated water may be used for irrigation purposes.

Effect of oxygen vacancy modification of ZnO on photocatalytic degradation of methyl orange: A kinetic study

This study investigated a novel kinetic model of the adsorption and photocatalytic degradation of methyl orange, an anionic dye, using a commercial ZnO and reduced commercial ZnO photocatalysts. The results were compared and discussed with our previous study on methylene blue, a cationic dye, providing new insights into the interaction of the catalyst with molecules with different charges. The kinetic model was applied to describe adsorption in the dark, followed by photocatalytic degradation under simulated sunlight. In addition, the predicted pKa values of methyl orange were estimated using the kinetic model, which were found to be 4.40 and 9.34. The effect of ZnO oxygen vacancies (created through hydrogen reduction at 500 °C) on the adsorption and photocatalytic degradation of methyl orange was investigated. The existence and effects of oxygen vacancies on ZnO were analyzed using TPR, PL, XPS, XRD, FE-SEM, EDS, BET, Tauc plot, Mott-Schottky, and cyclic Voltammetry. The appearance of oxygen vacancies was clearly observed by the characterization results, while the morphology of the nanoparticles was found to be unchanged. Additionally, the band gap of ZnO was decreased from 3.22 to 3.07 eV, and the maximum valence band of the catalyst was increased from 2.43 to 2.67 eV due to the reduction pretreatment. The findings suggest that the photocatalytic degradation rate of the reduced ZnO substantially increased. However, the adsorption removal of the anionic dye declined, which could be attributed to the more negative zeta potential of ZnO after hydrogen reduction. Finally, the quantum yield of photocatalytic process was calculated and compared with the results of methylene blue.

A highly efficient supported TiO2 photocatalyst for wastewater remediation in continuous flow

Although TiO2 materials have been extensively studied as photocatalysts, there is not any commercial TiO2-supported photocatalyst used for wastewater remediation. This fact set the goal to synthesize a new supported titanium dioxide photocatalyst which, besides being robust, also has a high reaction surface and a very efficient TiO2 shell thickness. Hence, we present a novel TiO2-supported photocatalyst composed of titania-covered glass wool (GW) fibers decorated with SiO2@TiO2 core-shell spheres. For optimizing the photocatalytic activity of this material, the surface of SiO2 microspheres, as well as, the highly mechanically resistant GW fibers, were covered by a robust titania layer of ca. 20–30 nm of thickness. This layer contains nanometric crystals, ca. 12 nm in size, linked to each other and to the surfaces of both SiO2 microspheres and GW. An exhaustive characterization of the physicochemical properties of this new SiO2-TiO2 composite was performed to confirm the SiOTi linkage and the anatase crystal phase. The photocatalytic activity was initially evaluated in batch through the photodegradation of Methylene Blue as a standard dye. Afterward, the addition of the new photocatalyst in a solid phase stationary (SPS) photoreactor coupled to a TOC detector allowed studying in situ the mineralization of the recalcitrant pollutant phenol under a continuous flow regime. Results revealed that the optimized TiO2 surface of the SiO2-TiO2 composite produced the complete mineralization of phenol in less than three minutes. Even more, it was demonstrated that this photocatalyst is suitable for the industrial scale-up of wastewater treatment because it does not leach titania, its reuse does not require filtration procedures, and it can be easily implemented in SPS photoreactors at plant scale. In this context, the new material could be a good starting point to prepare other supported photocatalysts for wastewater remediation.

Reduction of COD concentration and complete removal of phenol in industrial wastewater utilizing mesoporous TiO2 nanoparticles under UVA illumination

Toxic organic pollutants with low biodegradability are observed and detected in industrial wastewater with high contents. Phenol is one of the toxic organic compounds, and discharging it into the water can be extremely harmful to the environment and the organism's health. In this contribution, the photodegradation of phenol and minimizing COD concentration in industrial wastewater collected from the pharmaceutical industry utilizing mesoporous TiO2 nanoparticles (NPs) contrasted with commercial TiO2 photocatalysts have been conducted under UVA illumination. The results indicated that 100% phenol removal and 60.4% of the total COD were achieved at pH = 6, 1 g/L of catalyst loading, and 10.5 mg/L phenol content, 2476 mg/L of COD content within 140 min of UVA illumination. The phenol photodegradation and COD removal over the mesoporous TiO2, UV-100, and P-25 obeyed a pseudo-first-order model, and their rate constants (k) were determined about 0.0175, 0.0091 and 0.0127 min−1. The k value of mesoporous TiO2 NPs was enhanced 2 and 1.4 folds greater than that of the photocatalysts of UV-100 and P-25. The photodegradation of phenol using mesoporous TiO2 NPs for being recycled five times without losing was acquired, which indicated the obtained mesoporous TiO2 NPs are very stable for long illumination time. The active species' role during photocatalytic degradation phenol and COD removal over mesoporous TiO2 photocatalyst under illumination are the critical oxidative species of •OH and O2•− radicals. Consequently, the COD reduction and complete phenol removal in real industrial wastewater have been verified.

TiO2-loaded nanotubular kaolin group minerals: The effect of mineral support on photodegradation of dyes as model pollutants

One prevailing trend in order to design efficient photocatalysts is to support TiO2 on kaolin-based mineral carriers. This prevents TiO2 aggregation, improves textural parameters and adsorption properties as well as lowers costs. This research is a comprehensive comparison of photocatalysts based on different TiO2-loaded kaolin group minerals, including platy kaolinite, halloysite, halloysite-containing sample, and raw and calcined synthetic kaolinite nanotubes. The impregnation of the platy kaolinite sample led to the formation of star-like TiO2 aggregates, which were unevenly attached to the platelets surface. In contrast, the TiO2 formed nanocrystallites that homogenously covered the external surface of synthetic calcined kaolinite nanotubes. These differences had a significant impact on the textural properties of the resulting photocatalysts. The sample based on calcined nanotubes achieved a specific surface area of 257.1 m2/g, which was ∼4.5 times higher than the photocatalyst based on raw kaolinite. These distinctions influenced the photocatalytic performance of the materials in the decomposition of dyes. The comparison of the results to the commercial photocatalyst P25 highlighted the high potential of selected materials in the photodegradation of methylene blue and safranin O. The practical applicability and sustainability of the investigated materials was also attested via successful experiments on their regeneration and reuse.

Functionalized Regulation of Metal Defects in ln2S3 of p-n Homojunctions.

The introduction of metal vacancies into n-type semiconductors could efficiently construct intimate contact interface p-n homojunctions to accelerate the separation of photogenerated carriers. In this work, a cationic surfactant occupancy method was developed to synthesize an indium-vacancy (VIn)-enriched p-n amorphous/crystal homojunction of indium sulfide (A/C-IS) for sodium lignosulfonate (SL) degradation. The amount of VIn in the A/C-IS could be regulated by varying the content of added cetyltrimethylammonium bromide (CTAB). Meanwhile, the steric hindrance of CTAB produced mesopores and macropores, providing transfer channels for SL. The degradation rates of A/C-IS to SL were 8.3 and 20.9 times higher than those of crystalline In2S3 and commercial photocatalyst (P25), respectively. The presence of unsaturated dangling bonds formed by VIn reduced the formation energy of superoxide radicals (•O2-). In addition, the inner electric field between the intimate contact interface p-n A/C-IS promoted the migration of electron-hole pairs. A reasonable degradation pathway of SL by A/C-IS was proposed based on the above mechanism. Moreover, the proposed method could also be applicable for the preparation of p-n homojunctions with metal vacancies from other sulfides.

Photocatalytic Removal of Thiamethoxam and Flonicamid Pesticides Present in Agro-Industrial Water Effluents

Pesticide residues, when present in agricultural wastewater, constitute a potential risk for the environment and human health. Hence, focused actions for their abatement are of high priority for both the industrial sectors and national authorities. This work evaluates the effectiveness of the photocatalytic process to decompose two frequently detected pesticides in the water effluents of the fruit industry: thiamethoxam-a neonicotinoid compound and flonicamid-a pyridine derivative. Their photocatalytic degradation and mineralization were evaluated in a lab-scale photocatalytic batch reactor under UV-A illumination with the commercial photocatalyst Evonik P25 TiO2 by employing different experimental conditions. The complete degradation of thiamethoxam was achieved after 90 min, when the medium was adjusted to natural or alkaline pH. Flonicamid was proven to be a more recalcitrant substance and the removal efficiency reached ~50% at the same conditions, although the degradation overpassed 75% in the acidic pH medium. Overall, the pesticides’ degradation follows the photocatalytic reduction pathways, where positive charged holes and hydroxyl radicals dominate as reactive species, with complete mineralization taking place after 4 h, regardless of the pH medium. Moreover, it was deduced that the pesticides’ degradation kinetics followed the Langmuir-Hinshelwood (L-H) model, and the apparent rate constant, the initial degradation rate, as well as the L-H model parameters, were determined for both pesticides.

Enhancing the photocatalytic removal of toluene by modified porous TiO2 with internal hydrophobic interface

The efficiency and stability of photocatalytic oxidation techniques in the treatment of volatile organic compounds (VOCs) in the air are affected by the adsorption performance at the reaction interface and the photogenerated electron–hole separation efficiency. Carbon-loaded porous TiO2 with an internal hydrophobic interface was prepared by finely controlling the calcination time and temperature of a titanium-based metal–organic framework (MIL-125). The carbon load in the porous TiO2 presents a gradient from the pore surface to the interior. The formed hydrophobic interface in the channel avoids competitive adsorption between gas-phase toluene and H2O and effectively improves photogenerated electron transfer. Experiments and comprehensive analysis by using techniques such as thermogravimetric analysis, Raman spectroscopy, and ultraviolet diffuse-reflectance spectroscopy clarified the mechanism of gradient carbon formation in the porous TiO2, in which the organic ligands in MIL-125 are carbonized during calcination because of the low oxygen content of the pores. The sample prepared by pyrolyzing MIL-125 at 400 ​°C for 1 ​h showed the best activity in the photocatalytic degradation of toluene; the activity was twice that achieved with the commercial photocatalyst P25. Surface photovoltage spectroscopy and photoelectrochemical measurements proved that the gradient carbon load enhances photogenerated electron transfer in the porous TiO2. In-situ diffuse-reflectance infrared Fourier-transform spectroscopy was used to investigate the processes of photocatalytic degradation of toluene, in which the generation of C–H-containing intermediates is a crucial step. This research provides a novel concept for the future design and modification of photocatalyst structures for the effective photocatalytic degradation of VOCs.

Ecotoxicity of TiO2, cerium and zirconium doped TiO2 photocatalysts prepared by different preparation methods and using different titanium precursors

Ecotoxicological effects of manufactured TiO2, cerium doped TiO2 and zirconium doped TiO2 prepared by different chemical methods and using different chemical precursors were evaluated, since these nanomaterials are keenly investigated semiconductor photocatalysts for waste and drinking water and waste gas purification in last three decades. Acute biological toxicity of manufactured photocatalysts was evaluated based on Sinapis alba seeds germination and Lemna minor fronds growth tests, and was compared to commercial photocatalyst TiO2 Degussa P25. Toxicity tests exhibited good sensitivity for monitoring of the toxicity of investigated nanomaterials. TiO2 toxicity results demonstrate that TiO2 prepared using titanyl sulphate as a Ti precursor are toxic to both plant species contrary to TiO2 prepared using titanium (IV) isopropoxide. Cerium doped TiO2 with Ce amount <5.5 wt.% proved to be non-toxic to both plant species and zirconium doped TiO2 even stimulates both plant species growth. Small crystallite-size and high surface area are not the toxicity-determining factors. In case of TiO2 prepared by using titanyl sulphate (TiO2-TH-C, TiO2-TH-PW), the chemical issues, i.e. the huge release of Ti4+ ions to nutrient aqueous solutions from TiO2 photocatalysts and the presence of SO42− onto TiO2 photocatalyst surfaces were identified. The presence of SO42− was identified as the chemical cause of TiO2 toxicity to both Lemna minor fronds and Sinapis alba seeds. High toxicity of Ce0.05Ti0.95On photocatalyst to Sinapis alba seeds was attributed to high content of cerium (∼9 wt.%) in TiO2 which led to formation of CeO2 of nuclei-size.

Green Synthesis of Silver-Doped Titanium Dioxide Nanostructures for Acetaminophen Degradation Under Solar Radiation

Objective: In this paper, the photocatalytic degradation of acetaminophen was evaluated using silver-doped titanium dioxide nanoparticles in a cylindrical-parabolic composed photoreactor. Materials and methods: Titanium dioxide was synthesized via green synthesis using Cymbopogon citratus leaf extract and doped by silver photodeposition. Results and discussion: Morphological information shows that large agglomerates of approximately 49 nm can be attributed to the strong interaction between nanoparticles and their polycrystalline nature. The photodeposition of metallic silver reduces the surface effects, allowing a decrease in the electrostatic interaction and diameter size of the titanium dioxide, as well as the optical properties due to surface poising during the reduction of silver ions to metallic silver. The photocatalytic activity was performed to degrade acetaminophen as the drug model under visible-light radiation. The results are promising, with superior photodegradation of acetaminophen of approximately 37% and 11% for unmodified titanium dioxide and silver-doped titanium dioxide (0.75 at%) nanostructures compared to the commercial photocatalyst, respectively. Conclusions: Accordingly, the potential photocatalytic application of silver-doped titanium dioxide nanostructures is highlighted and represents a promising alternative for the photodegradation of organic compounds from wastewater eluents.

Construction of BiOIO3/AgIO3 Z-Scheme Photocatalysts for the Efficient Removal of Persistent Organic Pollutants under Natural Sunlight Illumination.

The efficient removal of persistent organic pollutants (POPs) in natural waters is vital for human survival and sustainable development. Photocatalytic degradation is a feasible and cost-effective strategy to completely disintegrate POPs at room temperature. Herein, we develop a series of direct Z-scheme BiOIO3/AgIO3 hybrid photocatalysts via a facile deposition-precipitation method. Under natural sunlight irradiation, the light intensity of which is ∼40 mW/cm2, a considerable rate constant of 0.185 min-1 for photodecomposing 40 mg/L MO is obtained over 0.5 g/L Bi@Ag-5 composite photocatalyst powder, about 92.5 and 5.3 times higher than those of pristine AgIO3 and BiOIO3. The photoactivity of Bi@Ag-5 for photodecomposing MO under natural sunlight illumination surpasses most of the reported photocatalysts under Xe lamp illumination. After natural sunlight irradiation for 20 min, 95% of MO, 82% of phenol, 78% of 2,4-DCP, 54% of ofloxacin, and 88% of tetracycline hydrochloride can be photodecomposed over Bi@Ag-5. Relative to the commercial photocatalyst TiO2 (P25), Bi@Ag-5 exhibits greatly higher photoactivity for the treatment of MO-phenol-tetracycline hydrochloride mixture pollutants in the scale-up experiment of 500 mL of solution, decreasing COD, TOC, and chromaticity value by 52, 19, and 76%, respectively, after natural sunlight irradiation for 40 min. The photodegradation process and mechanism of MO have been systematically investigated and proposed. This work provides an archetype for designing efficient photocatalysts to remove POPs.

Photocatalytic Degradation of Dye Acid Orange Seven on Titanium Dioxide Photocatalysts Immobilized on Stainless Steel Coated Layers: Role of Catalyst Loading and Ultrasonic Treatment

Supported titanium dioxide (TiO2) was investigated for potential application in photocatalytic degradation of dye acid Orange 7 in textile wastewater. Two commercial powder photocatalysts, Degussa (P25) and Precheza (AV01), were immobilized on stainless steel plates of dimensions (75 mm × 25 mm) through Electrophoretic Deposition Process (EPD) from aqueous colloidal suspensions of n-TiO2, c=10 g.L-1 produced in methanol. Two sets of coated layers were prepared - using ultrasonically treated TiO2 colloidal suspensions and without ultrasonic treatment. The prepared coated layers were fitted onto a four-hole photocatalytic reactor operating under batch-mode conditions. As a source of UV light, Sylvania LynxS, 11W UV lamps emitting light of wavelength between 320-400 nm with maximum wavelength at λ=355 nm was used. The current study aimed to evaluate the effect of ultrasonic treatment on the catalyst’s colloidal suspension and electrophoretic deposition loading (mg/cm2) on its surface area on the resultant photocatalytic degradation of dye Acid Orange 7. The photocatalytic degradation of the dye was monitored by changes in dye absorbance for 120 minutes at an interval of 30 minutes. Changes in dye concentration were determined by ultraviolet spectrophotometry at λ = 485 nm. The initial concentration of dye Acid Orange 7 used in the experiments was c=1×10-4 mol. L-1. The findings show that 61.1 % of dye mineralization was achieved after 120 minutes of photocatalytic degradation. The optimum catalytic loading for maximum photocatalytic degradation was determined at 0.75 mg/cm2 for the two commercial powder catalysts - TiO2 (P25/AV01) in ultrasonically treated TiO2 (P25) and non-ultrasonically treated TiO2 (AV01). Ultrasonic treatment of TiO2 (P25) colloidal suspensions before immobilisation positively influenced its photocatalytic activity, whereas ultrasonic treatment negatively affected the photoactivity of TiO2 (AV01). Overall, TiO2 (AV01) proved to be more efficient by 28.6%, compared to TiO2 (P25). The results show the potential application of UV-TiO2 treatment model in the remediation of coloured dye Acid Orange textile wastewater.

Photocatalytic activity of Co3O4@C enhanced by induction of amorphous cobalt-based MOF

A series of Co3O4@C-N (N = 1, 2, 3) composite photocatalysts were prepared by simple agitation and pyrolysis for degradation of organic dyes. The hollow macroscopic spherical structure of Co3O4@C-2 was constructed by adjusting the pyrolysis time. Compared with pure Co3O4, the carbon composite Co3O4@C-2 significantly enhanced light absorption in the UV and visible range, improved the electron transport efficiency and prevented the necessary photoexcited electron-hole pair recombination. Hence, the photocatalytic degradation rate of methylene blue (MB, 20 mg/L) reached 100% in 120 min under UV–vis light irradiation. Under the coupling of Co3O4 and graphitized carbon, Co3O4@C-2 obtained high structural stability, good reusability and low biotoxicity. Scavenging experiments and ESR test showed that •O2- radical was the active species for MB removal. After six cycles of tests, the photocatalytic efficiency of Co3O4@C-2 remained at 90.42%. The macroscopic spherical structure Co3O4@C-2 effectively avoids the problem of dispersion and recovery of powder catalyst, which also paves a path for the designing of candidate commercial photocatalyst with high efficiency and low consumption.

In-situ upcycling of cadmium from wastewater into core–shell ZnS@Zn0.58Cd0.42S heterojunction photocatalyst for environmental purification and H2 evolution

Uncontrolled exploitation of heavy metals has caused environmental pollution and mineral resource depletion crises. The first-choice approach for addressing these issues is heavy metal upcycling. However, efficient retrieval and conversion of heavy metals from contaminated environments into high-value-added products remains challenging. Here, we developed a strategy to simultaneously achieve efficient accumulation (256 mg/g), magnetic separation (∼1 min), and directly in-site conversion of Cd2+ from wastewater into core–shell ZnS@Zn0.58Cd0.42S heterojunction photocatalysts (ZSC). Microalgae-derived yolk-shell microspheres containing multicomponent nanocores (Fe3O4 and ZnS) were developed to serve as adsorbent, magnetic carrier, and photocatalyst assembly platform to achieve Cd2+ upcycling into ZSC. In particularly, ZSC shows much higher photocatalytic activity for H2 generation and organic pollutant degradation than do commercial photocatalysts (P25-TiO2 and CdS) due to its greater utilization of solar energy and heterostructure. Altogether, we provide an appealing strategy for upcycling cadmium into high-performance heterojunction photocatalysts for environmental purification and clean energy generation.