Methyl Orange Dye Research Articles

Defect-rich sunlight-responsive SnO2 photocatalyst for methyl orange dye degradation: a step towards wastewater treatment

Defect-rich sunlight-responsive SnO2 photocatalyst for methyl orange dye degradation: a step towards wastewater treatment

Membrane-free Electrolysis Production of Hydrogen Peroxide on Low-Cost Metal-Free Electrocatalysts for Dye Degradation.

The efficient production of hydrogen peroxide (H2O2) solution was achieved by combining cathodic two-electron oxygen reduction (2e- ORR) and anodic two-electron water oxidation (2e- WOR) in two half-reaction cells. h-BN loaded on carbon fibers (h-BN@C) is prepared and employed as an anode material to catalyze 2e- WOR, while sulfonated commercial BP-2000 carbons (BP-2000-SO3H) were prepared as the cathode materials for 2e- ORR. In a 2 M KHCO3 solution, an overall Faradaic efficiency of 97% and a total H2O2 production rate of 1872 mmol g-1 h-1 over metal-free electrodes were accomplished in a membrane-free flow cell. The dilute H2O2 solution could be directly used to degrade cationic Rhodamine B or methyl orange and anionic methylene blue dyes in water. This work proved low-cost production of dilute H2O2 solution in simple membrane-free flow cells with single electrolyte and on-site utilization for efficient dye degradation.

Fabrication and adsorption characteristics of cuprammonium cellulose-based membranes for removing anionic and cationic dyes

A cotton linter-based source was used to form conjugate electrospun membranes composed of cuprammonium cellulose, polyethylene oxide, and polyacrylonitrile for the removal of the anionic and cationic dyes from aqueous media. The highest removal efficiencies of 94 %, 89.9 %, 87.4 % were achieved for the anionic dyes Congo red (CR), Metanil yellow (MY), and Methyl orange (MO), respectively, and less so on the cationic dyes Crystal violet (CV), and Rhodamine B (RB) were 55.8 % and 15.1 %, respectively. The pseudo-second-order model effectively described the adsorption kinetics for both types of dyes. The composite membrane exhibited adsorption behaviors following the Dubinin-Radushkevich (D-R) isothermal model. Thermodynamics study suggests that the adsorption process was spontaneous except for the RB dye. The activation energy values of CR, MY, MO, CV, and RB dyes were 27.65, 21.17, 11.50, 10.47, and 71.12 kJ/mol, respectively, confirming the physisorption phenomenon for CR, MY, MO, and CV dyes, while chemisorption occurs for RB dyes. This study investigates the potential of a conjugate electrospun membranes as a reusable adsorbent for dye removal. The effects of solution pH, temperature, and dye concentration on adsorption performance were systematically evaluated. The conjugate electrospun membrane efficiency declined by only 10 % after undergoing five adsorption/desorption cycles.

Facile electrospinning-electrospray method to fabricate flexible rice straw-derived cellulose acetate/TiO2 nanofibrous membrane with excellent photocatalytic performance

A novel and facile electrospinning-electrospray (EE) method that based on electrospinning technique and simultaneous electrospray was proposed to anchor TiO2 (P25) nanoparticles on the surface of rice straw-derived cellulose acetate (CA) nanofiber, a series of EE-CA/P25 nanofibrous membranes with different P25 dosage were successfully fabricated, which were characterized in terms of SEM, TEM, FI-IR, XRD, DRS, PL, UV–vis and 3D-EMMs, etc. Results confirmed that P25 nanoparticles were anchored on the surface of CA nanofiber. For different organic dyes of Methylene blue (MB), Rhodamine B (RhB) and Methyl orange (MO), EE-CA/P25(0.05) nanofibrous membrane toward MB dye showed the best photocatalytic degradation efficiency of 99.13 % after 30 min of light exposure. For the different antibiotics of Tetracycline (TC), Ciprofloxacin (CIP) and Sulfamethoxazole (SMX), EE-CA/P25(0.05) exhibited the best photocatalytic degradation efficiency of 83.59 % for TC after 30 min of light exposure. Moreover, EE-CA/P25(0.05) exhibited a good antimicrobial efficiency of 98.42 % for E. coli, and maintained 97.49 % after 5 cycles. The reactive radical trapping experiments revealed that h+, •O2−, and •OH participated in the reaction, and h+ and •O2− played a major role in the photocatalytic degradation process. Moreover, EE-CA/P25(0.05) flexible membrane was easy to recycle and transform rice straw waste into treasure.

Preparation of amorphous Nd/Dy-based metal organic framework@MXene for solar driven selective photocatalytic and serving as sensor for fluorescence quenching detection, and biological activity

The development of a new Neodymium/Dysprosium metal–organic framework, referred to as Nd/Dy-BTC MOF, based on benzene-1,2,4-tricarboxylic acid, has been achieved through an in situ growth process on 2D transition metal carbides (MXene) surfaces. This synthesis was conducted via a solvothermal method utilizing a solvent mixture of water, ethanol, and dimethylformamide. The primary objective of this research is to investigate the framework’s efficacy as a photocatalyst for the degradation of anionic dye, as well as its potential for sensing certain explosives. The Nd/Dy-MOF@MXene has been characterized by various analysis techniques. The prepared Nd/Dy-MOF@MXene was utilized as catalyst in selective degradation of methyl orange dye. The study examined the influence of pH and catalyst concentration, revealing that the catalyst achieves peak efficiency of 93.55% when exposed to sunlight in an acidic medium. The reusability of the catalyst shows the highest efficient photocatalyst after four cycles of reusability. The detection of explosives, specifically 2,4,6-trinitrophenol, through photoluminescence techniques has been conducted, utilizing the Stern-Volmer equation to evaluate the quenching efficiency. The findings indicated remarkable efficiency and selectivity of Nd/Dy-MOF@MXene for 2,4,6-trinitrophenol, achieving a quenching efficiency of 91%. Furthermore, the reusability tests demonstrated that Nd/Dy-MOF@MXene exhibits outstanding recyclability, maintaining performance over five cycles. The antibacterial activity of Nd/Dy-MOF@MXene was investigated against Gram-positive and Gram-negative strains due to indication of medicine properties of Nd/Dy-MOF@MXene.

Performance study of the bioreactor for the biodegradation of methyl orange dye by luffa immobilized Stenotrophomonas maltophilia and kinetic studies: A sustainable approach

The biodegradation of methyl orange dye was examined in a biofilm reactor with luffa immobilized Stenotrophomonas maltophilia ((HE963840.1), low-cost packing material. The bacteria were isolated from the sludge collected from a common effluent treatment plant at IOCL refinery Mathura, Uttar Pradesh. The bacteria were characterized using 16rRNA. The reactor performance was studied at 30 ± 5 oC temperatures over a period of thirty days. The reactor was operated with the flow rates of 60 mL/h, 90 mL/h, 240 mL/h, 360 mL/h and 432 mL/h. The pollutant load ranges from 151.6 mg/(L-day) to 1091 mg/(L-day) and the pH of the dye solution was maintained at 7.0 ± 0.4 during the study. The maximum removal efficiency (RE) and elimination capacity (EC) at steady state were determined as 90.2 % and 658.1 mg/(L-day) respectively. The rate of utilization of the methyl orange dye is described by modified stover-kincannon model with kinetic parameters- maximum utilization rate (Umax) and saturation constant (KB) to be 2.70 g/(L-day) and 2.34 g/(L-day) respectively. The toxicity studies confirm the non-toxic nature of the biodegraded products.

Development of a Negatively Charged Polyether Sulfone Membrane Enriched with MIL-101(Cr)-Modified Magnetic Activated Pyrolytic Coke for Enhanced Dye Removal, Permeability, and Antifouling Properties

Developing high-performance nanofiltration membranes for effectively treating wastewater contaminated with organic pollutants has become increasingly important. Given the hazardous nature of these contaminants, proper treatment of wastewater is crucial before it is released into natural water bodies. This study synthesized a novel composite membrane by incorporating Fe3O4@APC@MIL-101(Cr) nanocomposites into a polyether sulfone (PES) matrix using a phase inversion technique. The inclusion of 0.5wt.% Fe3O4@APC@MIL-101(Cr) significantly enhanced the membrane's hydrophilicity, porosity, and surface characteristics. The optimized membrane achieved an impressive pure water flux (PWF) of 90.24L/m²h, reflecting a 400% improvement over pristine PES membranes. Moreover, it exhibited excellent rejection rates of 97.21% for crystal violet (CV) and 99.43% for methylene blue (MB), alongside a rejection efficiency of 57.73% for the anionic dye methyl orange (MO). The antifouling performance was notably improved, as evidenced by an increase in the flux recovery ratio (FRR) from 46% for bare PES membranes to 81.11% for hybrid membranes. Additionally, the effects of various salt types on the membrane's separation performance were investigated. The Fe3O4@APC@MIL-101(Cr) modified PES membranes demonstrate significant potential as effective candidates for treating wastewater contaminated with dye pollutants.

Synthesis and characterization of ZnO nanorods via hydrothermal route for wastewater recycling

In this work, highly efficient ZnO nanorods (NRs) were prepared using an easy and costeffective hydrothermal process. The Synthesized ZnO NR have been analyzed for their structure, morphology, and optical characteristics using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier Transform Infrared (FTIR), and ultraviolet-visible (UV-visible) spectroscopy, respectively. Additionally, a test is conducted on the ZnO nanorod's photocatalytic efficiency towards the degradation of certain dyes, Methylene Blue (MB) and Methyl Orange (MO). The FESEM investigation revealed that the ZnO nanostructures show nanorods with varying diameters (needle-like shape) with an estimated size of (10 to 20) µm. According to the XRD examination, the NRs had a hexagonal-shaped wurtzite pattern, exhibiting an average crystallite diameter of about 50 nm. FTIR spectra confirmed that functional groups from the substance being extracted were present in the ZnO NRs. The band-gap value of 3.37 eV was determined through the TAUC plot model from the ultraviolet-visible spectrum data. In the presence of as-synthesized ZnO NRs, the MO dye degraded by 100 percent in 46 minutes, but the MB dye significantly degraded by approximately 100 % in 20 minutes with high degradation rate constants kMO = 0.086 min-1 and kMB = 0.180 min-1, respectively.

Insights into mixed dye pollutant degradation by oxygen and air plasma bubbling array

Abstract Synthetic organic dye pollutants pose a serious threat to the aquatic ecological environment due to their difficulty in complete degradation. This study employed a plasma bubble array reactor to degrade individual and mixed dye pollutant solutions of Sunset Yellow (SY), Methyl Orange (MO), and Methyl Violet (MV). The degradation efficiencies and mechanisms of the plasma were investigated under different working gas atmospheres. It was found that oxygen plasma degraded the target dyes and their mixtures more significantly than air plasma. Specifically, compared with air plasma, the removal of single dyes SY, MO and MV by oxygen plasma was increased by 76.6%, 13.8% and 3%, respectively, after 20 min of treatment. As for mixed dyes, after 25 min treatment, oxygen plasma removed 99.1%, which was 31.6% higher than air plasma. However, the degradation kinetic order in oxygen plasma was SY > MO > MV, while that in air plasma was MV > MO > SY. Combined with the detection of reactive oxygen-nitrogen species (RONS), the results showed that the reactive oxygen species (ROS) played an important role in the degradation of SY, and it was also important for the degradation of MO, whereas both the ROS and reactive nitrogen species (RNS) were important for the degradation of MV. Scavenger experiments revealed that hydroxyl (·OH) and superoxide anion (·O2-) played the most important roles in the degradation process. The three dyes were basically completely degraded within 14-20 minutes of treatment, with corresponding yields of 1.94-2.79 g/kWh. Possible degradation pathways for each dye were deduced based on LC-MS and the toxicities of solutions were evaluated by phytotoxicity tests and ion chromatography. The results showed that the biotoxicity of the intermediates was significantly reduced. This study may provide a feasible option for effective application of plasma technology in organic dye wastewater treatment.

Sustainable Activated Carbon from Agricultural Waste: A Study on Adsorption Efficiency for Humic Acid and Methyl Orange Dyes

In this study, porous activated carbon was produced from coffee waste and used as an effective adsorbent for the removal of humic acid (HA) from seawater and methyl orange (MO) dye from aqueous solutions. Phosphoric acid H3PO4 was used as an activating agent for the chemical activation of these agricultural wastes. The characterization of the activated carbon obtained using a scanning electron microscope (SEM), Fourier-transform infrared (FTIR) spectroscopy analysis, X-ray diffraction (XRD) and the Brunauer–Emmett–Teller (BET) method revealed that the activated carbon products exhibited high porosity and the formation of various functional groups. The effects of different parameters were examined using batch adsorption experiments, such as the adsorbent masses, pH, initial pollutant concentration and contact time. The results show that the performance increased with an increased adsorbent mass (up to 0.25 g/L) and decreased initial concentration of the adsorbent tested. On the other hand, this study clearly showed that the adsorption efficiency of the MO on the raw spent coffee grounds (SCGs) waste was around 43%, while no removal was observed for the humic acid. The experiments demonstrated that the activated carbon synthesized from the used coffee grounds (the efficiency was compared with commercial activated carbon (CAC) with a difference of 13%) was a promising alternative to commercially available adsorbents for the removal of humic acid from seawater. To understand and elucidate the adsorption mechanism, various isothermal and kinetic models were studied. The adsorption capacity was analyzed by fitting experimental data to these models. The experimental data for methyl orange dyes were analyzed using Langmuir and Freundlich isothermal models. The Freundlich isotherm model provided a superior fit to the equilibrium data, as indicated by a higher correlation coefficient (R2) than that of the Langmuir model. The maximum adsorption was observed at pH 3. The Freundlich adsorption capacity was found to be 333 mg/g adsorbent. The PAC showed a high adsorption capacity for the MO and HA. The PAC showed the highest adsorption capacities for the HA and MO compared with the other adsorbents used (SCGs and CAC) and would be a good material to increase the adsorption efficiency for humic acid removal in the seawater pretreatment process. In addition, the prepared AC BET surface area was 520.40 m2/g, suggesting a high adsorption capacity. This makes the material potentially suitable for various applications that require a high surface area. These results indicate that high-quality sustainable activated carbon can be efficiently produced from coffee waste, making it suitable for a wide range of adsorbent applications targeting various pollutants.

Physical and enhanced photocatalytic MO dye degradation behaviour of Zn doped β-Ga2O3 microrods

This work explored the effects of Zn doping on the structural, micrographic, optical and photocatalytic behaviour of gallium oxide (β-Ga2O3) microrods. The X-ray diffractogram (XRD) and Raman spectral analyses confirmed the monoclinic structure of β-Ga2O3, with a shift to lower angles in the XRD pattern indicating Zn incorporation into the Ga2O3 lattice. The Scanning electron microscopy (SEM) images revealed a rod-like shape, with the diameter decreasing from 604 nm to 573 nm with Zn doping. Further analysis using TEM, HR-TEM, SAED, EDX, and elemental mapping confirmed the shape, crystallinity, crystal structure, and elemental distribution. The interplanar spacings were measured as 0.4 and 0.2 nm, corresponding to the (002) and (−311) planes of β-Ga2O3. UV–Vis diffuse reflectance spectroscopy (UV–Vis DRS) showed a slight shift in the absorption edge, while photoluminescence (PL) analysis demonstrated strong UV and weak visible light emission. Photocatalytic results revealed a high efficiency of dye degradation,(i.e) 98 % (20 ppm) and 89 % (30 ppm) against methyl orange (MO) dye aqueous solution over 150 min, with a rate constant of 0.02/min and 0.01/min, respectively for 1.5 wt% Zn doping. This suggests that the Zn-doped material holds promise as a photocatalyst for wastewater treatment applications.

Enriched photocatalytic degradation of methylene orange dye using carbon quantum dots surface-decorated TiO2 nanocomposites

Complex molecules in methylene orange (MO) dye-contaminated water are carcinogenic and mutagenic risks to human health. Carbon quantum dot surface-decorated titanium dioxide nanocomposites (CQD-TiO2 NCs) were synthesized via a sustainable hydrothermal method at concentrations of 1.5–3 mL. These NCs exhibits superior electron transfer, light harvesting capabilities, high stability, easy modification, optical characteristics, and photocatalytic properties. The surface morphology, porosity, physiochemical, and optical features of these CQD-TiO2 NCs were characterized using TEM, UV–Vis, PL, BET, BJH micromeritics, pHzpc, and photoelectrochemical measurements. The prepared NCs were evaluated against the photocatalytic degradation of MO dye molecules using a solar simulator system. The TEM revealed ultra-sensitive and tiny CQD materials with graphite phases ranging from 5 to 10 nm and attached to the octahedron surface of TiO2 NCs. The PL analysis observed three distinct emission peaks in the visible region, attributed to the near band edge, interstitial (Tii), and oxygen vacancy (V0). The BET and BJH analyses were conducted to determine the N2 adsorption-desorption surface area and mesoporous structure with pore sizes ranging from 2 to 50 nm. These NCs showed excellent photocatalytic performance, effectively degrading MO up to 99.00 % in a 3 mL variation, indicating that they could be a great candidate for photocatalytic purification of wastewater containing MO dyes.

Performance optimisation of new basket-shaped TiO2 photoelectrodes in a photocatalytic fuel cell utilising the response surface method: dye elimination and energy generation

ABSTRACT Response Surface Methodology (RSM) simplifies fuel cell design and offers possibilities for process improvement, operating condition optimisation, and performance improvements. By identify the best design parameters, RSM helps create fuel cell systems that are dependable, economical, and efficient. Although RSM is widely applied in many domains, more studies are still needed evaluating photocatalytic fuel cell performance in dye removal and optimising the conditions of reactions. Using RSM (central composite design), the system's ability to remove Methyl Orange (MO) and produce energy was enhanced in this study. TiO2/Ti and CuO/Cu are employed in this system as the photoelectrodes. Effective optimised parameters on contaminant removal and energy production, including dye concentration, electrolyte concentration, and pH, were achieved as 23.31 mg/L, 0.1 M, and pH = 3, respectively. 71.26% MO dye was removed, and 0.63 V, 0.19 mA/cm2, and 0.037 mW/cm2 values were recorded for the open-circuit voltage (VOC), short-circuit current (JSC), and maximum power density (PMAX), respectively, under optimal conditions, which was very close to the experimental values. The analysis of variances for dye removal and VOC, JSC, PMAX, correlation coefficient, and adjusted correlation coefficient for the four mentioned responses indicated a strong correlation between the predicted and experimental data, confirming the model's accuracy.

Rhombohedral phase high-entropy alloy of AlMnCuZnBi as a photo-Fenton catalyst for methyl orange degradation

The formation of solid solutions with five or more elements having nearly equiatomic contributions termed as high entropy alloys (HEA), is recent strategy for the development of new materials. Such alloys have displayed superior properties than the conventional ones. The prepared alloys are generally face- or body-centered cubic structures with a few exceptions for orthorhombic and hexagonal close packed structure. In this, we report the synthesis of HEA of AlMnCuZnBi having rhombohedral crystal structure. The material was prepared by vacuum arc melting route. Both the diffractions (X-ray and electron) confirm its structure. The calculated thermodynamic empirical parameters e.g. ΔSmix, ΔHmix, δ, VEC and Ω even validate the feasibility of this single phase solid solution. The HEA had shown feeble ferromagnetic behaviour. The rhombohedral structured HEA may open up new possibilities for various emerging applications. The proposed HEA acted as a catalyst for photo-Fenton like reaction and could degraded methyl orange dye completely in 170 minutes.

Boosting Reactive Oxygen Species Generation via Contact‐Electro‐Catalysis with FeIII‐Initiated Self‐cycled Fenton System

AbstractContact Electro‐Catalysis (CEC) using commercial dielectric materials in contact‐separation cycles with water can trigger interfacial electron transfer and induce the generation of reactive oxygen species (ROS). However, the inherent hydrophobicity of commercial dielectric materials limits the effective reaction sites, and the generated ROS inevitably undergo self‐combination to form hydrogen peroxide (H2O2). In typical CEC systems, H2O2 does not further decompose into ROS, leading to suboptimal reaction rates. Addressing the generation and activation of H2O2 is therefore crucial for advancing CEC. Here, we synthesized a catalyst by loading the dielectric material polytetrafluoroethylene (PTFE) onto ZSM‐5 (PTFE/ZSM‐5, PZ for short), achieving uniform dispersion of the catalyst in water for the first time. The introduction of an FeIII‐initiated self‐cycling Fenton system (SF‐CEC), with the synergistic effects of O2 activation and FeIII‐activated H2O2, further enhanced ROS generation. In the FeIII‐initiated SF‐CEC system, the synergistic effects of ROS and protonated azo dyes enabled nearly 99 % degradation of azo dyes within 10 minutes, a sixfold improvement compared to the CEC system. This represents the fastest degradation rate of methyl orange dye induced by ultrasound to date. Without extra oxidants, this system enabled stable dissolution of precious metals in weakly acidic solutions at room temperature, achieving 80 % gold dissolution within 2 hours, 2.5 times faster than similar CEC systems. This study also corrects the unfavorable perception of CEC applications under acidic conditions, providing new insights for the fields of dye degradation and precious metal recovery.

Adsorption of methyl orange and methylene blue from aqueous solutions on pure bentonite: statistical physical modeling provides an analytical interpretation.

This study investigates the adsorption of methylene blue (MB) and methyl orange (MO) dyes from aqueous solutions using purified Moroccan bentonite, being mainly composed of silica and alumina, in the form of quartz and cristobalite. The temperature controls the adsorption capacity for the kinetics, increasing 5.08% (from 295.1 to 310.1 mg/g) for the MB and 55.47% (from 86.8 to 134.9 mg/g) for the MO. It was discovered that the pseudo-second-order model, with a low Bayesian criterion indicator of 12.72 and R2adj > 0.996, was the best suitable for explaining both systems. The adsorption isotherm, experimental data indicate that both systems follow the Langmuir isotherm. At lower temperatures, 298.15 K 1.22 molecules are adsorbed per site. However, at a higher temperature of 328.15 K, the number of molecules is less than a unit of 0.68. As for MO, the number of molecules remains above 1.4 per site for all the temperatures studied. The endothermic nature of the system is indicated by the observation that the adsorption energy tends to grow for both systems: for the MB, it increases from 18.85 to 21.26 kJ/mol, and for the MO, it increases from 14.83 to 19.01 kJ/mol. Last, thermodynamic functions indicate that maximum entropy is reached around the half-concentration saturation at 25 and 124 mg/L, which is the maximum energetic concentration of the system. The same results were obtained for Gibbs free energy, where the maximum energy found was - 5.39 × 10-18 kJ/mol for the MB and - 1.99 × 10-18 kJ/mol for the MO at 328.15 K.

Synergistic Effect of NiAl-Layered Double Hydroxide and Cu-MOF for the Enhanced Photocatalytic Degradation of Methyl Orange and Antibacterial Properties

This study synthesized NiAl-layered double hydroxide (LDH)/Cu-MOF photocatalyst using a simple impregnation method involving NiAl-LDH and Cu-MOF. The successful synthesis was confirmed through Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), zeta potential measurements, thermogravimetric analysis (TGA), ultraviolet diffuse reflectance spectroscopy (UV-DRS), N2 adsorption at −196 °C, and electrochemical impedance spectroscopy (EIS). Photocatalysts based on NiAl-LDH, Cu-MOF, and NiAl-LDH/Cu-MOF were used to remove methyl orange (MO) dye from contaminated water. The impact of various factors, including pH, dye concentration, and photocatalyst amount, on MO degradation efficiency was assessed. FTIR analysis was conducted both before and after dye degradation. The optimal degradation conditions were a photocatalyst dose of 25 mg and a pH of 3. Kinetic studies indicated that the degradation of MO dye onto NiAl-LDH/Cu-MOF followed a pseudo-first-order and an L–H or Langmuir–Hinshelwood model. The value of R2 = 0.94 confirms the validity of pseudo-first-order and Langmuir–Hinshelwood (L–H) kinetic models for the photocatalytic degradation of MO dye. This study highlights the importance of developing novel photocatalysts with improved degradation efficiency to protect the water environment. Antibacterial activity was also performed with antibacterial sensibility testing by disk diffusion to determine minimal inhibitory and bactericidal concentrations. In short, NiAl-LDH/Cu-MOF can be helpful for various biomedical and industrial applications.

Synthesis and design strategies of codoped titanium dioxide with band alignment and multiple reflections of incident light for efficient visible light activity

To increase the visible-light photocatalytic performance of Titania, it was codoped with specific elements and was effectively synthesized. The goal of enhancing visible-light photocatalytic performance was achieved by broadening its absorption spectrum in the visible light range and enhancing the quantum efficiency of the photocatalytic reaction toward the degradation of the hazardous dye methyl orange. Mixed phase photocatalyst with different percentage hierarchical secondary nanostructure has been synthesized by the combination of chemical bath deposition methods and hydrothermal. The density of the sprout-like branches changes from the concentration levels of titanium butoxide in the precursor solution. Based on the experimental analysis, a mechanism was proposed to interpret the evolution of the secondary growth. The band edge difference between anatase and TiO2(B) phases induces transfer of charge at the interface. The result revealed that in the TiO2 crystal some O-sites were substituted by N and S anions resulting in band mixing and incorporation of extra energy states in between the valence band maxima and conduction band minimum, which caused a shift towards longer wavelengths in the absorption edge. Compared with pure TiO2 nanobelt, the surface modified doped samples exhibited good visible light activity. The combined effect of fast charge transfer in the atomic level contact between two phases and localized N 2p and S 3p band above valence-band edge in the same material makes titanium dioxide suitable for use in the presence of visible light.

Phyto-mediated synthesis of ZnO nanoparticles and their sunlight-driven photocatalytic degradation of cationic and anionic dyes

Abstract In this study, zinc oxide-based nanocatalysts were biosynthesized using Ocimum basilicum (OB) and Olea africana (OA) leaf aqueous extracts, termed OB-ZnO and OA-ZnO, as a simple, affordable, and environmentally friendly approach. Their characteristics and efficacy in photodegrading cationic dyes (crystal violet and methylene blue) and anionic dyes (methyl orange and naphthol blue black) were investigated. The catalyst’s properties were analyzed using various techniques, including Fourier transform infrared, X-ray diffraction, photoluminescence, thermogravimetric analysis, UV-Vis, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and Brunauer–Emmett–Teller. Analysis revealed pure products having a hexagonal wurtzite structure, crystallite sizes of 15.04 and 21.46 nm, surface areas of 23.65 and 7.97 m2/g, particle sizes of 35 and 170 nm with spherical (uniform) and oval-like (non-uniform) shapes, and optical bandgaps of 3.15 and 3.05 eV, respectively. Photocatalytic applications under sunlight indicated excellent activity of both catalysts against targeted cationic and anionic dyes. Most notably, even though OA-ZnO has a lower surface area than OB-ZnO, it demonstrated greater efficiency. The variation in effectiveness is explained by the lower bandgap value of OA-ZnO and its ability to reduce electron–hole recombination due to its larger crystal size, which accelerates the degradation process. Additionally, both catalysts exhibited high stability after being used four times.

Magnetically separable Bi2O2CO3/MIL-101(Fe)/CoFe2O4 nanostructured catalysts for heterogeneous reductive remediation of nitrophenols and organic dyes

A new magnetically separable nanocomposite, Bi2O2CO3/MIL-101(Fe)/CoFe2O4, was successfully synthesized through a hydrothermal method. The composite was characterized through various analytical techniques. The nanocomposite demonstrated good catalytic efficiency in reducing nitroaromatic compounds and organic dyes by using NaBH4 reducing agent in aqueous solutions at room temperature. The apparent rate constant (kapp) values for 4-nitrophenol, 2-nitrophenol, 2-nitroaniline, and 4-nitroaniline were recorded at 0.457, 0.253, 1.52, and 0.564 min⁻¹, respectively, achieving complete conversion in just 2 to 9 min. Under similar conditions, methylene blue, methyl orange, rhodamine B, congo red, and crystal violet organic dyes were reduced to 98–100 % within 4 to 20 min, with kapp values ranging from 0.157 to 0.885 min⁻¹. Furthermore, the influence of catalyst dosage, NaBH4 concentration, and substrate concentration on the reduction process was examined. Importantly, the nanocomposite can be recovered using an external magnet and reused over four consecutive cycles without a significant reduction in catalytic efficiency.