Photocatalyst Concentration Research Articles

Characterization and the Effect of Different Parameters on Photocatalytic Activity of Montmorillonite/TiO2 Nanocomposite under UVC Irradiation

This study aimed to modify montmorillonite (MMT) with titanium dioxide (TiO2) by wet stirring method combined with ultrasonic to form MMT/TiO2 nanocomposite and used as a photocatalyst in the removal of organic dye rhodamine B (RhB). The characteristics of the synthesized samples were analyzed by methods such as energy-dispersive X-ray spectroscopy (EDX), scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and UV-Vis diffuse reflectance spectra (UV-Vis DRS). The degradation of RhB was carried out for 210 min under UVC irradiation, and the decolorization efficiency of RhB was evaluated by UV-vis spectroscopy. The results show that the TiO2 anatase nanoparticles are randomly distributed on the surface or the space between the MMT sheets to form a house-of-card structure. After 210 min of exposure under a UVC light source, the decolorization efficiency reached 91.5% for the solution with pH = 6.8, photocatalyst content 0.1 g/L, initial concentration RhB 10 mg/L, and UVC power 15 W. Liquid chromatography–mass spectrometry (LCMS) identified the degradation intermediates that MMT/TiO2 successfully cleaved the chromophore structure and formed more minor broken-ring by-products. The influence of operating parameters on RhB removal efficiency, including solution pH, photocatalyst content, initial dye concentration, inorganic, and organic scavengers, was studied. In addition, the kinetic modeling study shows that the RhB photodegradation reaction is consistent with the Langmuir-Hinshelwood first-order kinetic model.

Photocatalytic degradation of naphthol blue black dye using undoped and Al-doped cobalt ferrite nanoparticles

The current study aims to evaluate the effectiveness of undoped (CoFe2O4) and aluminium-doped cobalt spinel ferrite (CoFe1.1Al0.9O4) nanoparticles as photocatalysts in the process of photocatalytic degradation of organic naphthol blue black (NBB) dye. In the sol-gel auto combustion method, a combination of metal nitrates, citric acid, sodium hydroxide, and liquid ammonia was utilized as the raw chemical ingredients for synthesizing nanoparticles of CoFe2-xAlxO4 (x = 0.0, 0.3, 0.6, 0.9, 1.2, 1.5) spinel ferrites. The nanoparticles were subjected to various characterization techniques including thermal analysis (TGA/DTA), X-ray diffraction (XRD) analysis, field emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), and UV–visible spectroscopy for comprehensive analysis. The XRD analysis confirmed the presence of a spinel cubic structure in the synthesized spinel ferrite nanoparticles. The interplanar distance (d) and crystalline size (D) were determined using Bragg's equation and Scherrer's relationship, respectively. The morphological characteristics and elemental composition of the spinel ferrites were confirmed through FE-SEM and EDS. Furthermore, the UV spectrum of the synthesized photocatalyst was investigated to compare the energy band gap between undoped and Al-doped cobalt spinel ferrites. The analysis of photoluminescence (PL) spectra was conducted to investigate the dynamics of charge carriers, focusing on their transfer, relocation, and recombination processes. The surface area of the synthesized photocatalyst ranged from 3.525 to 16.113 m2/g. Photocatalytic degradation of naphthol blue black (NBB) dye was carried out under visible light exposure utilizing both cobalt spinel ferrite nanoparticles without doping and those doped with aluminium. Several factors, including pH level, H2O2 concentration, amount of photocatalyst (spinel ferrite) and initial dye concentration, were considered through the photocatalytic degradation of NBB dye. The highest percentage degradation (%) of NBB dye was determined at pH 11. For NBB dye with an initial concentration of 20 ppm, the maximum degradation was achieved using 200 mg of spinel ferrite nanoparticles per 100 mL dye solution under visible light irradiation for 40 min.

Green synthesis of CuO/Fe2O3/ZnO ternary composite photocatalyst using grape extract for enhanced photodegradation of environmental organic pollutant

This research delves into fabricating a CuO/Fe2O3/ZnO (CFZ) ternary composite photocatalyst, employing grape extract for its eco-conscious synthesis. The method intricately integrates copper acetate, ferric nitrate, and zinc acetate as precursor compounds, harmonizing them with grape extract serving as a green reducing agent. Meticulous microwave treatment and controlled calcination orchestrate the nuanced formation of the desired composite material. The extensive characterization, involving X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), energy-dispersive X-ray spectroscopy (EDXS), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area analysis, ultraviolet–visible diffuse reflectance spectroscopy (UV-DRS), and photoluminescence (PL) spectroscopy, unveils an array of favorable physical, chemical, and optical attributes conducive to proficient photocatalysis. Notably, CFZ–10mc showcases a narrower bandgap of 1.91 eV, which is pivotal for bolstering electron–hole separation, thereby enhancing its photocatalytic efficacy. Assessment of CFZ's performance in degrading Rhodamine B (RhB) under UV irradiation highlights an impressive 88.8% degradation efficiency within 120 min, accompanied by a kinetic rate constant of 1.81 × 10−2 min−1. Deliberation upon crucial parameters, including photocatalyst dosage, initial RhB pH, and reactor energy consumption, introduces the electrical energy per order (EEO) as a notable efficiency metric. CFZ manifests a substantial reduction in operational costs, estimated to be 18.10 times lower than conventional photolysis, signifying an EEO value of 509.17 kWh m−3 order−1. Optimal operational conditions propose a photocatalyst content of 1.5 g L−1 and an initial RhB pH of 7, fostering the prevalence of the primary active species, •OH. These findings illuminate CFZ's potential in mitigating organic pollutants, underlining its pivotal role in sustainable water remediation. Additionally, practical implementation guidelines for leveraging CFZ's capabilities in real-world applications are presented with care and consideration.

Investigation the changes in the concentration of dye organic pollutant using magnetic titania nanoparticles incorporated on surface of graphene oxide

In this study, in order to prepare magnetic nanocomposite, TiO2 nanoparticles and Fe3O4 nanoparticles are uniformly synthesized on the surface of graphene oxide by hydrolysis and hydrothermal methods, respectively. The efficiency of the synthesized nanocomposite (MGO@ Fe3O4) for the photocatalytic decomposition of methyl orange is investigated and compared with the magnetic hybrid without graphene oxide (Fe3O4@ TiO2). FTIR and VSM analysis are used to characterize the synthesized nanocomposite and hybrid. FTIR analysis confirmed the bond vibrations in TiO2 and Fe3O4 molecules present in both photocatalytic samples. VSM analysis shows the superparamagnetic properties of the synthesized photocatalysts. Investigating the effect of irradiation time and photocatalyst concentration on the ability to remove methyl orange by magnetic photocatalysts showed that both parameters have a positive effect, although based on the results of statistical analysis, irradiation time is more effective than photocatalyst concentration. It is also observed that despite the independent operating parameters having a significant effect on the photocatalytic activity of nanocomposite and hybrid, the mutual interaction between individual factors in nanocomposite and hybrid behaves differently.

Green synthesis of xanthene derivatives through visible light-driven photocatalysis using blackberry dye-sensitized TiO2

Researchers are actively exploring novel approaches to sustainable chemistry, aiming to reduce environmental harm while optimizing efficiency. One promising approach is visible light photocatalysis, which enables organic transformations under mild conditions. This research investigation focuses on the synthesis of xanthene derivatives (12-Aryl/hetroaryl-8,9,10,12-tetrahydrobenzo [a] xanthen-11-oness) via a three-component, one-pot condensation reaction of 2-naphthol, dimedone, and aldehydes using visible light-responsive TiO2 nanoparticles sensitized with blackberry dye. A comparative analysis was conducted between pristine TiO2 nanoparticles and blackberry dye-sensitized TiO2 (BB dye-TiO2) to evaluate their photocatalytic activities. The results unequivocally demonstrated the superior photocatalytic activity of BB dye-TiO2 compared to pristine TiO2 nanoparticles. The study determined the optimal operating conditions for achieving an efficient photocatalytic synthesis of xanthene derivatives and proposed a mechanism for the photocatalytic process. The optimized conditions for photocatalytic synthesis with a yield of 98% included a reaction time of 30 min, a light intensity of 100 mW/cm2, and a photocatalyst concentration of 1 g/L. Moreover, the reusability test revealed that the BB dye-TiO2 maintained its photocatalytic activity for up to four runs, with only a slight decrease observed. This study highlights the immense potential of natural dye sensitization and visible light photocatalysis for sustainable chemical synthesis, effectively bridging the realms of green chemistry and synthetic organic chemistry.

A photo-enzyme coupled system for carbon dioxide conversion to solar fuel: The rate-matching and compatibility between photocatalysis and enzyme catalysis

Using reduced nicotinamide adenine dinucleotide (NADH) as cofactor, formate dehydrogenase (FDH) can reversely catalyze CO2 reduction to formic acid. However, the industrialized application of FDH is fairly limited due to its high cost and stoichiometric cofactor consumption. Enzyme immobilization and cofactor regeneration are vital solutions to these problems. Ascribed to the benefits of utilizing a cheap, environmentally friendly, and renewable energy source, photocatalytic NADH regeneration is naturally sustainable and promising. Nonetheless, the rate-matching and compatibility between photocatalysis and enzyme catalysis have not been well revealed. In this study, polyethyleneimine (PEI) modified hollow fiber membrane (HFM) as the enzyme support was in-situ integrated with a visible-light-driven NADH regeneration system using thiophene-modified macroporous graphitic carbon nitride (ATCN-CN) as the catalyst. First, NADH regeneration conditions were regulated to accommodate enzyme catalysis. Then, the photo-enzyme coupled system (PECS) for the sustainable synthesis of formic acid with triethanolamine (TEOA) or H2O as electron donor was constructed, and the influencing factors were investigated. At last, the PECS was compared with other methods as well as a system that used FDH immobilized on silica nanoparticles. The results show that the reaction pH, electron donor, and catalyst concentration have a significant impact on NADH regeneration. For the PECS with TEOA as electron donor, the optimal pH value and photocatalyst concentration for formic acid synthesis are 7.0 and 1.2 mg mL−1, respectively. With the initial addition of 1 mmol L−1 NAD+, a formic acid yield of 35.3% was obtained after 5 h, standing out among the reported values. H2O as a green and low-cost electron donor meets the desire for low-cost photocatalysis. Although the production of formic acid after 5 h was lower in the PECS with H2O as electron donor than in the TEOA system, it was still 14.6 times that of the immobilized enzyme system without cofactor regeneration, and the yield of formic acid could reach 14.8% and 98.3% with 1 or 0.1 mmol L−1 NAD+, validating that current PECS is feasible to a sustainable and green synthesis of solar fuel from CO2.

One-Pot Facile Synthesis of ZrO2-CdWO4: A Novel Nanocomposite for Hydrogen Production via Photocatalytic Water Splitting

ZrO2-based nanocomposites are highly versatile materials with huge potential for photocatalysis. In this study, ZrO2-CdWO4 nanocomposites (NC) were prepared via the green route using aqueous Brassica rapa leaf extract, and its photocatalytic water-splitting application was evaluated. Brassica rapa leaf extract acts as a reducing agent and abundant phytochemicals are adsorbed onto the nanoparticle surfaces, improving the properties of ZrO2-CdWO4 nanocomposites. As-prepared samples were characterized by using various spectroscopic and microscopic techniques. The energy of the direct band gap (Eg) of ZrO2-CdWO4 was determined as 2.66 eV. FTIR analysis revealed the various functional groups present in the prepared material. XRD analysis showed that the average crystallite size of ZrO2 and CdWO4 in ZrO2-CdWO4 was approximately 8 nm and 26 nm, respectively. SEM and TEM images suggested ZrO2 deposition over CdWO4 nanorods, which increases the roughness of the surface. The prepared sample was also suggested to be porous. BET surface area, pore volume, and half pore width of ZrO2-CdWO4 were estimated to be 19.6 m2/g. 0.0254 cc/g, and 9.457 Å, respectively. PL analysis suggested the conjugation between the ZrO2 and CdWO4 by lowering the PL graph on ZrO2 deposition over CdWO4. The valence and conduction band edge positions were also determined for ZrO2-CdWO4. These band positions suggested the formation of a type I heterojunction between ZrO2 and CdWO4. ZrO2-CdWO4 was used as a photocatalyst for hydrogen production via water splitting. Water-splitting results confirmed the ability of the ZrO2-CdWO4 system for enhanced hydrogen production. The effect of various parameters such as photocatalyst amount, reaction time, temperature, water pH, and concentration of sacrificial agent was also optimized. The results suggested that 250 mg of ZrO2-CdWO4 could produce 1574 µmol/g after 5 h at 27 °C, pH 7, using 30 vol. % of methanol. ZrO2-CdWO4 was reused for up to seven cycles with a high hydrogen production efficiency. This may prove to be useful research on the use of heterojunction materials for photocatalytic hydrogen production.

Photocatalyst of manganese ferrite and reduced graphene oxide supported on activated carbon from cow bone for wastewater treatment.

The present research aimed to evaluate the photocatalytic activity of manganese ferrite (M) and reduced graphene oxide (G) supported on pulverized activated carbon from cow bone waste (PAC-MG). PAC-MG was characterized by different instrumental techniques. The efficiency of PAC-MG was evaluated using solar irradiation under different conditions of photocatalyst concentration, H2O2 concentration, and pH ranges for the discoloration of methylene blue dye (MB). The synergy between the nanomaterials potentiated the photocatalytic activity, reaching 85.5% of MB discoloration when using 0.25 g L-1 of catalyst at neutral pH with no oxidant needed. Furthermore, PAC-MG demonstrated excellent stability in 6 consecutive cycles. Finally, it is expected that the present study can add value to industrial waste and contribute to the development of novel water and wastewater treatment methods, ensuring water quality for human consumption and the environment.

Kinetic simulation of hydrogen production reaction parameters based on TiO2 photocatalyst

Hydrogen is a clean, efficient, and renewable energy source with significant potential to reduce greenhouse gases. Solar photocatalytic water splitting is a promising and sustainable route to produce hydrogen. Currently, the strategies to improve the efficiency of photocatalytic hydrogen production are mainly focused on the development of sustainable photocatalysts. However, the extent to which multiple working conditions affect photocatalytic hydrogen production efficiency is not yet clear. This paper established a TiO2-based photocatalytic phenomenological kinetic model and then validated it using experimental data to clarify the impact of the combined effects of various reaction conditions on the efficiency of photocatalytic hydrogen production. The effects of photocatalyst dosage, reaction temperature, sacrificial agent concentration, and other decisive parameters on TiO2-based photocatalytic hydrogen evolution performance were analyzed under light intensity of 365 nm. The optimization results revealed that the maximum STH efficiency of 5.30 % was observed, at the reaction temperature of 348.15 K and 0.25 g/L photocatalyst concentration. The model provides insights into the combined effects of different factors on photocatalytic efficiency. The identified optimal reaction conditions relationships are helpful to provide guidance for efficient designing of solar photocatalytic hydrogen evolution systems.

Photocatalytic Simulation of Phenol Waste Degradation Using Titanium Dioxide (TiO2) P25-Based Photocatalysts

Phenol waste treatment is vital in industries such as polymer production, coal gasification, refinery, and coke production. Photocatalytic technology using semiconductor materials offers an effective and ecofriendly approach to degrade phenol. TiO2 P25 is a widely used photocatalyst, known for its cost-effectiveness, favorable optical and electronic properties, high photoactivity, and photostability. The PHOTOREAC application, a recently developed MATLAB-based software, simulates the degradation of phenol using visible light. A study that combines existing literature and research revealed that pH significantly influences photocatalytic activity, with an optimum pH of 7 for TiO2 P25-mediated phenol degradation. The recommended photocatalyst concentration ranged from 0 to 10 g/L for reactor volumes between 25 and 60 mL, and from 0 to 5 g/L for 100-mL reactors. Phenol wastewater volume and light intensity also impact degradation efficiency. Adequate oxygen supply, achieved through bubbling and mixing, is essential for the formation of radical compounds. The Ballari kinetic model proved to be the most suitable for phenol degradation with TiO2 P25. Thus, by combining PHOTOREAC simulations with experimental data, the treatment process could be optimized to achieve higher degradation efficiency and estimate the treatment time for specific waste degradation levels. This study contributes to the advancement of phenol waste treatment and the development of improved photocatalytic wastewater treatment technologies.

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.

Binary metal doped spinel ferrite nanoparticles and their Nano hybrid with MXene matrix to enhance catalytic properties

Interlocked cobalt-substituted magnesium zinc ferrite nanoparticles and their composites with MXene (Ti3C2Tx) were synthesized by the micro-emulsion technique. The as-synthesized Nano hybrid material Mg0.6Zn0.2Co0.2Fe2O4/MXene shows the best photocatalytic performance as compared to the pristine Mg0.6Zn0.2Co0.2Fe2O4 and MXene. The incorporation of Mg0.6Zn0.2Co0.2Fe2O4 nanoparticles (Nps) into MXene sheets not only avoids the restacking of MXene flakes but also provides a larger surface area to enhance its photocatalytic performance. The prepared samples were investigated through the X-ray powder diffractometer (XRD), Scanning electron microscopy (SEM), Fourier transforms-infrared (FT-IR) analysis, and UV–vis spectrum analysis. By the wavelength vs. absorbance spectra, the observed band-gap values of the fabricated Mg0.6Zn0.4Fe2O4 and Mg0.6Zn0.2Co0.2Fe2O4 were 1.96 eV and 1.94 eV respectively. The calculated crystalline size of the fabricated samples Mg0.6Zn0.4Fe2O4, Mg0.6Zn0.2Co0.2Fe2O4, and Mg0.6Zn0.2Co0.2Fe2O4/MXene was 10.7 nm, 9.3 nm, and 8.37 nm respectively. The catalytic efficiency of the synthesized samples was checked through the photodegradation of Congo red (CR) and benzoic acid (BA) pollutants. The observed photodegradation proficiency of Mg0.6Zn0.2 Co0.2Fe2O4/MXene material is 78.23% for 50 ppm Congo-red (CR) and 53.7% for 10 ppm. Furthermore, the efficiency of the photocatalyst was also checked by using different concentrations of CR dye and photocatalyst. In addition to this, the recyclability test was also evaluated to check the stability of the prepared photocatalyst for four cycles which showed a minimal decline in the activity of the photocatalyst from 78.23 to 70 % after four runs. The enhanced photocatalytic activity of Mg0.6Zn0.2 Co0.2Fe2O4/MXene is attributed to the presence of MXene which provides larger surface active sites for the better catalytic reaction.

Unleashing the power of solar light: WO3 nanorods decorated onto BiVO4 dendrites for tetracycline detoxification and water splitting.

The coupling of different oxide materials in a nanohybrid enables the customization of their optical and charge transport properties, leading to improved interfacial charge segregation and migration. In this study, BiVO4/WO3 (BVW), a sunlight-driven photocatalyst with distinct mole ratios was synthesized via a facile hydrothermal approach. The resultant catalyst exhibits a nanorods shape morphology decorated onto dendrite-like matrix and is studied for photocatalytic elimination of tetracycline (TC) and photoelectrocatalytic (PEC) H2 production. The effect of illumination time, solution pH, photocatalyst concentration, and mole ratios of BiVO4 to WO3 on the photocatalytic abatement of TC were tested sequentially as effective operating factors. Under optimal condition, 3:1 BiVO4:WO3 (31BVW) nanohybrid demonstrated a maximum degradation efficacy of 96.2% (rate constant ~0.0241 min-1), which is much better than its individual components and commercial TiO2-P25 (50.9%). The resultant by-products of TC decomposition were analyzed using GC-MS to explain the degradation mechanism. Moreover, as a photoanode, 31BVW showed a high photocurrent density of 0.64 mA/cm2 at 1.23 V vs RHE and a steady photocurrent for ~6 h under chronoamperometry study at1.23 V vs RHE. However, bare BiVO4 and WO3 exhibited the photocurrent density of 0.001 mA/cm2, and 0.015 mA/cm2, respectively at 1.23 V vs RHE. The Mott-Schottky analysis of 31BVW confirms their n-type behavior, with a calculated flat band potential of -0.067 V. The hydrogen production rate was theoretically calculated as 4.56 mmolcm-2 s-1 from chronoamperometric measurements. The photocatalyst's efficacy in TC degradation was further established via its reusability upto 7 cycles. Post degradation characterization of catalyst confirms its stability in lieu of practical usage. Comparative studies with existing literature revealed the superiority of reported photocatalysts in both applications. Overall, the binary BVW photocatalyst shows great potential for removing detrimental contaminants as well as H2 production via PEC water splitting due to efficient charge separation, reduced recombination, high surface area, and widen absorption window of the nanohybrid.

Environmentally safe ZVI/ZnS-based polymer composite for lindane degradation in water: Assessment of photocatalytic activity and eco-toxicity

Monolithic composite aerogel based on a photocatalytic system, constituted by Fe0 (ZVI) coupled with ZnS (FZ), embedded into syndiotactic polystyrene (sPS) matrix was used, for the first time, in the lindane degradation under UV light. The content of FZ photocatalyst inside the monolithic composite aerogel (FZsPS) composite was 3 wt%. FESEM images of FZsPS indicate that the FZ photocatalyst is well dispersed in the polymer matrix. EDS analyses and temperature-programmed reduction (TPR-H2) measurements revealed an interpenetrated structure of the ZVI and ZnS phases as well the presence of some iron in an oxidized form. Photocatalytic activity data showed that in presence FZsPS aerogel, the almost complete lindane degradation was achieved after only 30 min of UV irradiation time. FZsPS was also effective in the lindane mineralization since a TOC removal of about 94 % was detected after 180 min of treatment time. Remarkably, based on the toxicity evaluation on Artemia franciscana, while the bare FZ photocatalyst showed significant toxicity per se, no toxicity or genotoxicity was found in the water treated with the FZsPS composite system where FZ is immobilized into the sPS aerogel matrix. Therefore the proposed composite photocatalyst can be considered as a model for a strategy to eliminate the environmental impact of catalysts that would otherwise be harmful to water.

Construction of polynary systems by coupling Cd/CdS with magnetic recyclable CuO/Fe2O3/CuFe2O4 nanocomposite for enhancing photo-Fenton degradation of antibiotics

The exploitation of magnetic recyclable and effective degradation photocatalysts with wide-pH-range response was essential to the practical application in the photo-Fenton process. In this study, Cd/CdS coupling with CuO/Fe2O3/CuFe2O4(CF) was employed to prepare an efficient and recyclable photocatalyst Cd/CdS-CuO/Fe2O3/CuFe2O4(CCCF). The obtained CCCF was utilized to activate H2O2 for the photo-Fenton degradation of tetracycline after verifying optical properties and energy band structures. The photo-Fenton degradation performance of CCCF on tetracycline was researched in the effects of photocatalyst concentration, initial pH and H2O2 volume. The photo-Fenton removal efficiency of CCCF+H2O2 was capable of achieving 82.43 % under the optimal reaction condition, which was apparently higher than that of Cd/CdS and CF. The enhanced degradation efficiency could be owned to the effective carriers separation thanks to the p-n heterojunction. The development of such photocatalysts offers a new approach to degrading organic pollutants from industrial wastewater, making it a valuable tool for contaminants degradation.

Regime Switch in the Dual-Catalyzed Coupling of Alkyl Silicates with Aryl Bromides.

Metallaphotoredox catalyzed cross-coupling of an arylbromide (Ar-Br) with an alkyl bis-catecholato silicate (R-Si⊖) has been analyzed in depth using a continuum of analytical techniques (EPR, fluorine NMR, electrochemistry, photophysics) and modeling (micro-kinetics and DFT calculations). These studies converged on the impact of four control parameters consisting in the initial concentrations of the iridium photocatalyst ([Ir]0), nickel precatalyst ([Ni]0) and silicate ([R-Si⊖]0) as well as light intensity I0 for an efficient reaction between Ar-Br and R-Si⊖. More precisely, two regimes were found to be possibly at play. The first one relies on an equimolar consumption of Ar-Br with R-Si⊖ smoothly leading to Ar-R, with no side-product from R-Si⊖ and a second one in which R-Si⊖ is simultaneously coupled to Ar-Br and degraded to R-H. This integrative approach could serve as a case study for the investigation of other metallaphotoredox catalysis manifolds of synthetic significance.

Photocatalytic Degradation of Eriochrome Black-T Dye by Immobilized Dowex-1x8

Eriochrome Black-T (EBT) is a commonly used textile dye. It is a harmful organic molecule and is also present in textile effluent. The photocatalytic degradation has been studied using MBIR Dowex-1×8 as the photocatalyst. Some parameters such as pH, light intensity, the amount of photocatalyst and initial dye concentration were also studied. At room temperature at pH 7.5, the optimal degradation of Eriochrome Black-T dye (30 mg/L) was observed in about 210 minutes and the photo catalyst load was 2.0 gm. The kinetic study related to the photocatalytic degradation of EBT followed first order kinetics where the rate constant is 2.11x10-2 min-1. This catalyst can degrade dye molecules and can recover transparent water from coloured textile effluent in few hours of treatment.

Effective photocatalytic degradation of amphotericin B and naproxen from aqueous solutions using carbon quantum dots combined in MIL-88B(Fe) under visible light.

A photocatalytic adsorbent composed of carbon dots (CD) embedded in a metal-organic framework (MOF) of MIL-88 B(Fe) was prepared by solvothermal technique. The synthesized CD@MIL-88 B(Fe) was characterized by different X-ray-based microscopic and spectroscopic methods, as well as electrochemical impedance spectroscopy, UV–Vis, FT-IR, DRS, TGA, and photoluminescence (PL) analysis. The prepared adsorbent showed a remarkable photocatalytic activity for eliminating amphotericin B (AmB) and naproxen (Nap) from aqueous solutions under visible light, reaching up to 92% and 90% removal, respectively, with an RSD value of around 5%. The parameters affecting the degradation process of pharmaceuticals were investigated. The optimal conditions for the degradation process were determined, including pH values (3 and 4 for AmB and Nap), photocatalyst concentration (0.2 g L−1), and H2O2 concentration (40–50 mM). Reactive oxidative species were also identified (·OH, ·O2) by examination of different scavengers. The adsorption isotherm and kinetic studies reveal that the synthesized photocatalyst exhibits dual functionality as an effective adsorbent (with maximum adsorption capacities of 42.5 and 121.5 mg g−1 for AmB and Nap) and a photocatalytic agent for removal purposes.

Bismuth ferrite (BiFeO3) 2D-nanoflakes for the photocatalytic degradation of chromogenic dyes under solar irradiation

Two-dimensional (2D) nanostructures show interesting properties compared to other low-dimensional nanostructures due to their pronounced anisotropic features governing the physicochemical properties of materials. In this context, multiferroic bismuth ferrite (BiFeO3/BFO) nanostructures are developed via a facile hydrothermal process by varying the surfactants leading to 3D nanoparticulate and 2D nanoflaky structures with dimensions in the range of 50–100 nm. The developed materials are characterized for their structural, morphological, optical and surface properties using XRD, Rietveld refinements, XPS, FTIR, UV–Vis, PL and BET techniques. The optimization studies by varying the concentration of dye (5, 10, 15, 20 ppm) and photocatalyst (25, 50, 75 and 100 mg) suggest that 10 ppm of dye and 50 mg of photocatalyst concentration is optimal, which showed around 98% and 96% degradation of chromogenic methyl orange and crystal violet dye molecules, respectively within 120 min. The insights from UV–Vis, PL, Mott-Schottky analysis, photocurrent and electrochemical impedance suggested that the opto-electronic properties of BFO are meaningly improved due to its 2D-flaky anisotropic features compared to 3D isotropic particulate structure. The radical detection experiment revealed that the dye degradation is mediated by advanced oxidation process via high energetic hydroxyl radicals driven by the improved ferroelectricity-mediated band-bending and internal electrical fields in BFO flakes compared to particles. Magnetic studies by VSM showed that the BFO flakes manifest enhanced ferromagnetic properties compared to particles contribute to both catalytic activity as well as its easy catalyst-recovery with minimal loss. The recycle experiments confirmed that the BFO-flakes are photochemically stable for prolonged use for industrial application.

Performance evaluation of a solar nano-photocatalytic reactor for wastewater treatment applications: Reaction kinetics, CFD, and scale-up perspectives

The solar-driven photocatalytic process, as a clean and efficient advanced oxidation process (AOP), is widely operated in wastewater treatment applications. In the present work, a solar nano photocatalytic reactor is designed, manufactured, and tested under different operating conditions. The irradiation-dependence reaction kinetics is studied in a batch operation process. A comprehensive computational fluid dynamics (CFD) model taking into account realistic solar flux distribution is developed and validated using experimental data. Finally, the reactor scaling-up analysis for higher treatment capacities is performed with the aim of the design of industrial-scale solar photocatalytic reactors. The research results indicate that when the initial dye concentration is increased from 5 to 175 mg/L, the period required to achieve 95% pollutant removal in 20 L solution and 10 mg/L photocatalyst concentration boosts up to 2.2 times. When the photocatalyst concentration in the solution is increased from 5 to 20 mg/L, the time required to achieve 95% total removal is reduced to 35.7%. For the photocatalyst concentration of 75 mg/L compared to 20 mg/L, the time required for 95% degradation increases up to 16.7%. To treat 90% of the total pollutant in a 50 mg/L dye solution with an initial volume of 5 m3 and using 20 mg/L photocatalyst concentration under 11 h operation with an average solar irradiation intensity of 750.46 W/m2, a solar reactor with a surface area of 50.45 m2 is required, while for 10 m3 wastewater sample and the same conditions and 95% pollutant removal, the collector area is obtained to be 121.36 m2. A horizontal solar reactor compared to its optimal tilt angle can reduce the treatment capacity up to 55%.