A designed experiment for CdS-AgBr photocatalyst toward methylene blue

Comparison of Photocatalytic and Adsorption Properties of ZnS@ZnO, CdS@ZnO, and PbS@ZnO Nanocomposites to Select the Best Material for the Bifunctional Removal of Methylene Blue

In this study, photocatalytic- and adsorption-based removal processes were conducted, which are frequently preferred in wastewater treatment due to their ease of control and high removal efficiency. An innovative method aimed at wastewater treatment was developed by combining the advantages of these two distinct approaches within the same material. The study synthesized ZnO, ZnS, CdS, PbS, and their composite structures (ZnS@ZnO, CdS@ZnO, and PbS@ZnO) using a hydrothermal synthesis method. Characterization of the samples was performed through field emission-scanning electron microscopy (FE-SEM), FE-SEM-energy dispersive X-ray (FE-SEM-EDX), X-ray diffraction (XRD), Raman spectroscopy, and Fourier-transform infrared spectroscopy (FTIR) measurement. Additionally, the optical properties of all samples (absorption spectra and band gap) were investigated by using absorbance measurements obtained from ultraviolet (UV)-visible absorption spectroscopy. Although ZnO nanoparticles are among the materials with high photocatalytic properties (exhibiting a photodegradation efficiency of 95.8% in a short duration of 90 min), their adsorption properties are low. Therefore, with the aim of enhancing both the low adsorption values and the photocatalytic properties of pure metal sulfides (ZnS, CdS, PbS), nanocomposites ZnS@ZnO, CdS@ZnO, and PbS@ZnO with different morphologies were synthesized, and their photocatalytic and adsorption-based removal performances on methylene blue (MB) dye were investigated. FE-SEM images indicated that ZnS nanoparticles exhibit a spherical morphology, CdS nanoparticles have a flower-like morphology, and PbS nanoparticles display a dendritic-like structure. The results obtained from experimental studies demonstrated that the highest efficiency in both photocatalytic- and adsorption-based removal was achieved with the ZnS@ZnO nanocomposite. The degradation rates of MB were found to be 95.3, 90.5, and 89.4% for the heterojunction composites ZnS@ZnO, CdS@ZnO, and PbS@ZnO, respectively, over a time range of 0-480 min. The optimal amount of photocatalyst that could effectively degrade MB was determined to be 100 mg, and the reusability studies revealed that the ability of the ZnS@ZnO semiconductor heterojunction photocatalyst to decompose MB into simpler molecules was limited after the fourth cycle. The adsorption-based removal rates were 96.0, 30.5, and 19.4% for the heterojunction composites ZnS@ZnO, CdS@ZnO, and PbS@ZnO, respectively. Finally, parameters influencing the adsorption-based removal of MB, such as pH, mass, and contact time, were examined, indicating that the adsorption capacity of ZnS@ZnO remained unchanged after reaching a value of 40 mg·g-1.

Self-assembly of snowflake-like Cu2S with ultrathin ZnIn2S4 nanosheets to form S-scheme heterojunctions for photocatalytic hydrogen production

Step-scheme (S-scheme) heterojunction has attracted much attention in the design of heterostructures for photocatalysts. In this study, we successfully utilized the principle of electrostatic self-assembly to load ultrathin ZnIn2S4 nanosheets onto snowflake-like Cu2S using a simple grinding method, and synthesized Cu2S/ZnIn2S4 S-scheme heterojunctions according to the different work functions (Φ). At the optimal Cu2S loading ratio (5 wt%), the hydrogen yield of the Cu2S/ZnIn2S4 composites reaches 5.58 mmol·h-1·g-1, which is 5.12 times higher than that of pure ZnIn2S4 (1.09 mmol·h-1·g-1). The apparent quantum efficiency (AQE) of the Cu2S/ZnIn2S4 composites reaches 5.8 % (λ = 370 nm), which is an improvement compared to pure ZnIn2S4 (2.7 %). The AQE of pure ZnIn2S4 is 0.4 %, while the AQE of Cu2S/ZnIn2S4 composites is enhanced to 1.0 % at λ = 456 nm. The heterojunction interface of Cu2S and ZnIn2S4 builds a built-in electric field (IEF), which greatly reduces the recombination rate of photogenerated electrons and holes, retains highly reduced photoelectrons in the conduction band (CB) of ZnIn2S4. The snowflake structure of Cu2S effectively increases the active sites and specific surface area, and improves the light absorption. This work opens a new avenue for designing photocatalysts, synergizing energy development and protecting the environment.

Ultrasound-assisted extraction of withanolides from Tubocapsicum anomalum: Process optimization, isolation and identification, and antiproliferative activity

Tubocapsicum anomalum, a Chinese medicinal plant rich in anti-tumor withanolides, requires efficient extraction methods. In this paper, an HPLC method was first established for the detection of withanolides, and gradient elution was carried out using a methanol-water solvent system. It was found that the content of withanolides was the highest in the leaves of T. anomalum, followed by the stems and fruits, and almost none in the roots. During the actual picking process, the quantity of leaves collected was relatively small, while the number of stems was the highest. Therefore, the Box-Behnken response surface method was used to optimize the ultrasonic-assisted extraction process of withanolides from the stems of T. anomalum. The optimal extraction conditions were determined as follows: the liquid-solid ratio was 20:1, the extraction solvent was 70 % ethanol, the ultrasonic power was 250 W, the ultrasonic time was 40 min, and the ultrasonic temperature was 50 °C. Under these conditions, the average yields of tubocapsenolide A (Te-A) and tubocapsanolide A (Ta-A) can reach 2.87 ± 0.12 mg/g and 1.18 ± 0.05 mg/g, respectively. We further compared extraction rates of two withanolides from different parts of T. anomalum using ultrasonic and traditional extraction methods. Ultrasonic extraction significantly increased rates, with the highest yields from leaves, followed by stems and fruits. The results show that ultrasonic optimization can improve extraction rate, reduce time, lower costs, enhance quality, and increase yield. Therefore, the optimized ultrasonic-assisted extraction process was adopted to extract the aerial parts of T. anomalum and separate the components. After optimization, the extract underwent several chromatographic separations to isolate eight previously undescribed withanolides (1-8) and two artificial withanolides (9-10), in addition to fifteen known compounds (11-25). Their structures were established through extensive spectroscopic data analysis. The compounds were evaluated for their antiproliferative effects against multiple cancer cell lines, including human hepatocellular carcinoma cells (HepG2, Hep3B, and MHCC97-H), human lung cancer cells (A549), human fibro-sarcoma cancer cells (HT1080), human chronic myeloid leukemia cells (K562), and human breast cancer cells (MDA-MB-231 and MCF7). Compounds 1-3, 5, 7, 11, 13, 15-16, and 22 displayed significant activity with IC50 values of 5.14-19.87 μM. The above results indicate that ultrasonic-assisted extraction technology can be used to obtain new withanolides more efficiently from T. anomalum, thereby enhancing the utilization rate of T. anomalum resources.

Green synthesized nitrogen-doped nickel hexacyanoferrate incorporated in guar gum-xanthan gel for efficient sunlight-driven degradation of water pollutants

Herein, nitrogen-doped nickel hexacyanoferrate (N@NiHCF) nanoparticles were prepared via co-precipitation and incorporated in guar gum (GG)-Xanthan gum (Xa) based-polymeric-matrix (GGXa@N@NiHCF) for efficient removal of rose bengal (RB) dye and nonyl phenol (NP) pollutants under sunlight. PXRD, FESEM, XPS, and FTIR analysis verified successful integration of N@NiHCF nanoparticles into GGXa matrix. Scherrer and Williamson-Hall equations estimated average-crystallite sizes of GGXa@N@NiHCF nanoparticles to be 16.34 nm. TGA analysis and zeta potential values (-17.7 mV for N@NiHCF and -22.9 mV for GGXa@N@NiHCF nanocomposite) confirmed structural stability. N@NiHCF has band gap of 2.3 eV, demonstrating enhanced photocatalytic efficiency due to improved light absorption and charge separation. Photocatalytic experiments demonstrated high degradation rates of RB (91 %) in 150 min and NP (95 %) in 300 min under optimized conditions highlighting composite's effectiveness. Kinetics of photodegradation process were studied using Hinshelwood formula, yielding rate constant of 0.93 min-1 (t1/2 = 0.74 h) for RB and 0.60 min-1 (t1/2 = 1.14 h) for NP with GGXa@N@NiHCF. LC-MS analysis identified degradation pathways, indicating transformation of pollutants into safer byproducts. Recyclability study showed sustained performance over multiple cycles, emphasizing nanocomposite's durability. This study provides insights into applying GGXa@N@NiHCF, highlighting its promise as a sustainable approach for mitigating water pollution.

Preparation and characterization of cellulose-chitosan/β-FeOOH composite hydrogels for adsorption and photocatalytic degradation of methyl orange

Biopolymer-based hydrogels have received great attention in wastewater treatment due to their excellent properties, e.g., high adsorption capacity, fast kinetics, reusability and ease of operation. In the present work, cellulose-chitosan/β-FeOOH composite hydrogels were prepared via co-dissolution and regeneration process as well as hydrothermal in situ synthesis of β-FeOOH. Effect of β-FeOOH loading on the properties of the composite hydrogels and the removal efficiency of methyl orange (MO) was investigated. Results showed that β-FeOOH was uniformly loaded onto the hydrogel framework, and the nanoporous structure of composite hydrogels could increase not only the effective contact area between β-FeOOH and the pollutants but also the active sites. Moreover, the increased β-FeOOH loading led to the enhanced MO removal rate under light conditions. When the loading time was extended from 6 h to 9 h, the MO removal rate increased by 21%, which can be mainly due to the photocatalytic degradation. In addition, MO removal rate reached 97.75% within 40 min under optimal conditions and attained 80.81% after five repetitions. The trapping experiment and EPR results indicated that the main active species were hydrogel radicals and holes. Consequently, this work provides an effective preparation approach for cellulose-chitosan/β-FeOOH composite hydrogel with high adsorption and photocatalytic degradation, which would hold great promise for wastewater treatment applications.

Bimetallic Ag/Fe-MOG derived flake-like Ag2O/Fe2O3 p-n heterojunction for efficient photodegradation organic pollutants within a wide pH range

In this paper, we reported a facile and clean strategy to prepare the flake-like Ag2O/Fe2O3 bimetallic p-n heterojunction composites for photodegradation organic pollutants. The surface morphology, crystal structure, chemical composition and optical properties of Ag2O/Fe2O3 were characterized by SEM, high-resolution TEM images with EDX spectra, XRD, XPS, FT-IR and UV-vis DRS spectra respectively. The formation of Ag2O/Fe2O3 p-n heterojunction facilitated the interfacial transfer of electrons as well as the separation of charge carries. Hence, the as-synthesized Ag2O/Fe2O3-3 composites exhibited ultra-high photocatalytic activity. Under the experimental conditions of catalyst dosage of 0.4 mg mL-1 and irradiation time of 60 min, the degradation conversion rate of rhodamine B reached 96.1 %, which was 5.0 and 2.8 times of pure phase Ag2O and Fe2O3, respectively. Meanwhile, the degradation performance of Ag2O/Fe2O3-3 was not limited by pH, and it can achieve high degradation efficiency under 3-11. In addition, Ag2O/Fe2O3-3 also showed superb degradation ability for other common anionic dyes, cationic dyes and antibiotics. XPS and FT-IR spectra showed that Ag2O/Fe2O3-3 retained a carbon skeleton that facilitated electron transport and light absorption conversion. And the analyses of quenching experiment and EPR demonstrated •O2-, •OH and h+ were crucial reactive oxidant species contributing to the rapid organic pollutant degradation. This work provides new insights into obtaining p-n photocatalysts heterojunction with excellent catalytic activity for removing organic pollutants from wastewater.

Facile green synthesis of a novel NiO and its catalytic effect on methylene blue photocatalytic reduction and sodium borohydride hydrolysis

NiO nanoparticles were synthesized from pine cone extract by green synthesis method, which is a simple, cost-effective, environmentally friendly and sustainable method. The particle size of NiO nanoparticles was determined to be in the range of 10-25 nm by X-diffraction differential and transmission electron microscope analysis, and the bandgap energy of NiO nanoparticles was determined to be 2.66 eV. The catalytic effect of NiO nanoparticles in both microwave-assisted sodium borohydride hydrolysis and photocatalytic reduction of methylene blue was examined and it was determined that they had a high catalytic effect in both applications. It was determined that the hydrogen production rate in sodium borohydride hydrolysis was 1135 mL/g/min. The activation energy of sodium borohydride hydrolysis is 29.69 kJ/mol and 29.59 kJ/mol for the nth-order and Langmuir Hinshelwood kinetic models, respectively. In the photocatalytic reduction of methylene blue with NaBH4, it was determined that the reduction did not occur in the absence of a catalyst, but in the presence of the catalyst, the reduction occurred 98% in 3 min. It was determined that NiO nanoparticles were used five times in the photocatalytic reduction of methylene blue and the reduction efficiency for the fifth time was 93%. It was determined that the photocatalytic reduction of methylene blue was pseudo-first order and the rate constant was 1.63 s-1. It was determined that NiO nanoparticles synthesized by the environmentally friendly green synthesis method can be used as catalysts for two different applications.

Heterogeneous photocatalytic degradation of antiviral drug didanosine mediated by rose bengal and TiO2 nanoparticles

There is a great concern among the researcher to remove the problem of the persistent organic pollutants in wastewater. Pharmaceutical agrochemical and personal care products are generally considered Persistent organic pollutants. Therefore, it is a matter of concern to develop new techniques how to remove these pollutants safely at low cost. This study mainly focuses on the commonly used antiviral drug didanosine and one most commonly used dye rose bengal. In this study, an organic dye rose bengal and TiO2 nanoparticles have been used in combination with UV light to achieve the photodegradation of selected pharmaceutical products and the dye was also degraded by using TiO2 Nanoparticles. The formation of three oxidation products was detected by using a very popular separation technique thin layer and column chromatography. The isolated photoproduct was characterized by using advanced characterization techniques like FTIR (Fourier transform infrared spectroscopy), UV Spectroscopy, and Proton and 13C NMR (Nuclear Magnetic Resonance spectroscopy). The role of singlet oxygen as an active species in this reaction was confirmed by using D2O as a reaction medium. The role of singlet oxygen in this photochemical reaction was also established by the addition of sodium azide. The TiO2 nanophotocatalyst efficiently degrade the didanosine and rose bengal in the presence of the UV light. In the TiO2-induced photocatalytic degradation of didanosine and dyes, the hydroxyl and superoxide radical anion play a prominent role. The finding of this manuscript is very useful to develop an efficient low-cost method for the treatment of wastewater contaminated by antiviral drugs, similar pharmaceutical products and dyes. This study was also very helpful to establish a plausible mechanism behind the phototoxicity of the didanosine.

Electron confinement promoted the electric double layer effect of BiOI/β-Bi2O3 in photocatalytic water splitting

In the realm of photocatalysis, understanding the interface issues (solid/solid and solid/liquid) inherent in heterojunction at the atomic level is the ultimate for engineering an efficient photocatalyst. Herein, an electrophoretic deposition technique is adopted to synthesize BiOI/β-Bi2O3 heterojunction, exhibiting superior photocatalytic activity and stability in H2 evolution (91.5 μmol g-1 h-1) and H2O2 production (11.3 mg L-1 h-1). Combined with the experimental and computational results, a lower free energy of hydrogen evolution reaction (252.4 meV) has been observed contrast to BiOI and β-Bi2O3 samples. A carrier transfer process of like S-scheme heterojunction is proposed based on density of states (DOS) and carrier distribution calculations. The theoretical calculations illustrate the transition dipole moment, migration and accumulation of carrier in BiOI/β-Bi2O3 heterojunction. Subsequent ab initio molecular dynamics (AIMD) results of solid/liquid interface systems (BiOI/β-Bi2O3/H2O and β-Bi2O3/H2O) unravel the interface H2O (solvent) behaviors. The local aggregation of photo-generated electrons in BiOI/β-Bi2O3/H2O leads to a large potential drop, high proton migration rate and the steady electric double layer (EDL) structure compared to the β-Bi2O3/H2O, which facilitates the occurrence of photocatalytic reactions in solution. In addition to offering new insights into the hydrogen evolution and proton transfer in the EDL model and the association between the heterojunction effect and EDL structure, this work also introduces a novel design strategy for Bi-based heterojunctions.

Photocatalytic evaluation of synthesized MnO2/Fe3O4 NCs by Q. infectoria extract for removal Ni(II) and phenol: Study phytochemical, kinetics, thermodynamics, and antibioactivity

In the present study, the plant extract of the Quercus infectoria galls was used as a reducing, capping, and stabilizer agent for green synthesized MnO2 nanoparticles (NPs) and MnO2/Fe3O4 nanocomposites (NCs) due to its reduction ability from polyphenol and antioxidant content. The green synthesized nanomaterials have been characterized by various techniques such as FTIR, UV-vis, XRD, SEM, EDS, and TEM. The average size of about 7.4 and 6.88 nm was estimated for the NCs crystals of SEM images and XRD analysis by the Scherrer and Williamson-Hall methods. The green synthesized MnO2/Fe3O4 NCs (dosage: 0.1 g) have shown high photocatalytic activity for the removal of Ni(II) in acidic and basic solutions under visible irradiation (220 V lamp). The removal efficiency for the Ni(II) solution (3.6 × 10-3 M) at pH = 3 was increased to pH = 12 from 56 % to 98 %. The oxidase-like activity of MnO2/Fe3O4 NCs at different dosages (0.05, 0.1, and 0.15 g) for the removal and colorimetric of phenol (1 g/40 mL) in the presence 4-AAp (1 g) was seen after only 28, 13, and 5 s, respectively. The kinetic evaluation results showed the pseudo-second-order kinetics model closely matched the adsorption capacity theoretical values qe,cal (578.03, 854.70, 892.85, and 917.43 mg.g-1) and experimental values qe,exp (521.84, 839.74, 887.86, and 913.22 mg.g-1) at different initial pH solution (3-12) for Ni(II) removal. In addition, the investigation of isotherm models revealed that the Langmuir model (R2 = 0.9955) explains a better estimate for a monolayer and favorable removal of Ni(II) ions onto NCs. Also, the low Temkin constant, BT < 0 (0.0200 kJ.mol-1), and positive ∆H° value (0.103 kJ.mol-1.K-1) illustrated that Ni(II) removal is physical sorption and endothermic process. However, the obtained thermodynamic results showed the negative values ΔG° with the increase in temperature (303-318 K) toward a spontaneous removal process of Ni(II). Finally, the plant antioxidant (200 to 3200 μg/mL) and antimicrobial activities (0.001 to 0.1 g/mL) for plant extract, MnO2 NPs, and MnO2/Fe3O4 NCs were evaluated against Gram-positive and Gram-negative bacteria species.

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

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

Dimensionality effects of g-C3N4 from wettability to solar light assisted self-cleaning and electrocatalytic oxygen evolution reaction

Unique interfacial properties of 2D materials make them more functional than their bulk counterparts in a catalytic application. In the present study, bulk and 2D graphitic carbon nitride nanosheet (bulk g-C₃N₄ and 2D-g-C₃N₄ NS) coated cotton fabrics and nickel foam electrode interfaces have been applied for solar light-driven self-cleaning of methyl orange (MO) dye and electrocatalytic oxygen evolution reaction (OER), respectively. Compared to bulk, 2D-g-C₃N₄ coated interfaces show higher surface roughness (1.094 > 0.803) and enhanced hydrophilicity (θ ∼ 32° < 62° for cotton fabric and θ ∼ 25° < 54° for Ni foam substrate) due to oxygen defect induction as confirmed from morphological (HR-TEM and AFM) and interfacial (XPS) characterizations. The self-remediation efficiencies for blank and bulk/2D-g-C₃N₄ coated cotton fabrics are estimated through colorimetric absorbance and average intensity changes. The self-cleaning efficiency for 2D-g-C₃N₄ NS coated cotton fabric is 87%, whereas the blank and bulk-coated fabric show 31% and 52% efficiency. Liquid Chromatography-Mass Spectrometry (LC-MS) analysis determines the reaction intermediates for MO cleaning. 2D-g-C₃N₄ shows lower overpotential (108 mV) and onset potential (1.30 V) vs. RHE for 10 mA cm^-2 OER current density in 0.1 M KOH. Also, the decreased charge transfer resistance (R_CT = 12 Ω) and lower Tafel's slope (24 mV dec^-1) of 2D-g-C₃N₄ make it the most efficient OER catalyst over bulk-g-C₃N₄ and state-of-the-art material RuO₂. The pseudocapacitance behavior of OER governs the kinetics of electrode-electrolyte interaction through the electrical double layer (EDL) mechanism. The 2D electrocatalyst demonstrates long-term stability (retention ∼94%) and efficacy compared to commercial electrocatalysts.

The enhance mechanism of DOM on tetracyclines degradation by electrochemical technology: A improvement of treatment processes

Tetracyclines (TC) is a typical broad-spectrum antimicrobial agent, and excessive use of TC can lead to a large accumulation of residual tetracycline in water. DOM is organic substances that can pass through the 0.45 μm filter. While dissolved organic matter (DOM) is one of the most significant substances in water, which has an important effect on water treatment. In this study, ultraviolet and visible spectrophotometry (UV-Vis) is applied to explore DOM to the effect of the electrochemical degradation. Three-dimension excitation emission matrix fluorescence spectroscopy (3D-EEM) is used to identify the component variation of DOM after the electrochemical oxidation (EO). Liquid chromatograph mass spectrometer (LC-MS) is used to confirm the degradation pathway of TC whether spontaneous or electrochemical oxidation. High performance liquid chromatography (HPLC) suggests the ROS production by DOM in the electrochemical oxidation under different conditions. Results show that DOM can promote the degradation of TC in the electrochemical oxidation. Tailwater DOM containssubstances can produce persistent free radicals, which can promote the degradation under light and dark conditions, natural source DOM can produce more free radicals under light. Therefore, TC wastewater should be added tailwater to promote the degradation of TC before the further water treatment. Otherwise, TC can be degraded to differentpathways (light, electricity, and degrade spontaneously). This study provides a significant idea for practical water treatment of tetracyclines, and promotes the practical application of electrochemical technology.

Enhanced pollutant photodegradation over nanoporous titanium-vanadium oxides with improved interfacial interactions

This study addressed the separation problem of colloidal catalytic powder from its solution and pore blockage of traditional metallic oxides by fabricating nanoporous composites of titanium (Ti)-vanadium (V) oxide via magnetron sputtering, electrochemical anodization, and annealing processes. The effect of V-deposited loading on the composite semiconductors was investigated by varying V sputtering power (20-250 W) to correlate their physicochemical properties to the photodegradation performance of methylene blue. The obtained semiconductors revealed circular and elliptical pores (14-23 nm) and formed different metallic and metallic oxide crystalline phases. Within the nanoporous composite layer, V ions substituted Ti⁴⁺, leading to Ti³⁺ formation accompanied by decreased band gap values and higher visible-light absorption. Thus, the band gap of TiO₂ was 3.15 eV, while that of Ti-V oxide with the maximum V content (at 250 W) was 2.47 eV. The interfacial separators between clusters in the mentioned composite created traps disrupting the charge carrier movements between crystallites, thereby decreasing the photoactivity. In contrast, the composite prepared with the minimum V content showed approximately 90% degradation efficiency under solar-simulated irradiation resulting from the homogeneous V dispersion and the lower recombination possibility, owing to its p-n heterojunction constituent. The nanoporous photocatalyst layers with their novel synthesis approach and outstanding performance can be applied in other environmental remediation applications.

Fabrication of Ternary MoS2/CdS/Bi2S3-Based Nano Composites for Photocatalytic Dye Degradation

The synthesis and design of low-cost visible-light-active catalysts for the photodegradation of organic dyes have been regarded as an efficient way to use solar energy in addressing environmental issues. We report the fabrication of MoS2/CdS nanoparticles functionalized with Bi2S3 nanoflakes. The ternary composites of “MoS2/CdS/Bi2S3” were synthesized in situ by a hydrothermal method at different temperatures. The changes in structural, optical, and morphological properties of the synthesized CdS/MoS2/Bi2S3 were explored. The effects of Bi2S3 on CdS/MoS2 were thoroughly studied by performing an X-ray diffractometer (XRD), a scanning electron microscope (SEM), an ultra-violet–visible spectrometer (Uv–vis), and Fourier transform infrared spectroscopic (FT-IR) studies of the nanoparticles. XRD confirms the cubical crystal structure of the nanoparticles. SEM studies possess the modulation in the surface morphology with the tenability in volume ratios of “MoS2/CdS/Bi2S3” composites. It was observed that the bandgaps calculated using absorption measurements could be manipulated from 2.40 eV to 0.97 eV with varying Bi2S3 in the MoS2/CdS nanostructures. FT-IR confirmed the synthesis of “MoS2/CdS/Bi2S3” nanoparticles. On allowing the visible light to fall for 120 min, it was observed that “MoS2/CdS/Bi2S3” degrades the methylene blue up to 90%. The calculated results of “MoS2/CdS/Bi2S3” suggest that the synthesized material could be a strong candidate for photodegradation applications. This research work explains the synthesis of MoS2/CdS/Bi2S3-based nanocomposites for the degradation of dye using a photocatalytic process. The final results show that this catalyst effectively degrades the dye.

A Z-scheme CdS/Ag3PO4 catalyst: Characterization, experimental design and mechanism consideration for methylene blue

Due to the explosive use of Azo dyes in various industries such as textiles, discharging these industrial effluents into the environment critically polluted water supplies. Accordingly, constructing/developing novel binary catalysts to diminish the pollution extent of such effluents before discharging into environment is an excellent issue in environmental chemistry. Here, a binary CdS/ Ag₃PO₄ was constructed, and its boosted photocatalytic activity was proven against methylene blue (MB), as a model dye pollutant. The Wurtzite CdS and Ag₃PO₄ cubic crystal nanoparticles were synthesized and coupled mechanically. The binary sample's lowest photoluminescence (PL) results confirm a higher e/h separation. DRS results confirmed a decreased energy gap for the coupled system. The semiconductors' VB and CV potentials were calculated and used for constructing of Z-scheme mechanism. The photocatalytic activity was followed via an experimental design approach. The model F-value of 89.75 > F_0.05,14,13 = 2.42 and LOF F-value of 6.57 < F_{0.05,10, 3} = 8.79 reveal that the model well processed data. The optimal run conditions were CMB: 5 ppm, Catalyst dose: 1 g/L, pH: 3.25, and irradiation time: 139 min, at which 85% of MB molecules were degraded. Based on the trend of ascorbic acid > isopropanol > formic acid ≈ nitrate obtained for the scavengers' importance in decreasing the photocatalyst activity, superoxide radicals had the highest effect in MB degradation and then ^•OH. The results showed the direct Z-scheme has the main effect on MB degradation by the binary sample.

Cefotaxime degradation by the coupled binary CdS-PbS: characterization and the photocatalytic process kinetics

Increased water pollution due to discharging industrial/urban/hospital wastewater has been adopted to introduce/develop novel removal techniques/catalyst/adsorbent. The hexagonal (wurtzite) CdS and the cubic PbS nanoparticles (NPs) were synthesized, coupled, and supported onto clinoptilolite NPs (CNP). Then, the sample was characterized by X-ray powder diffraction (XRD), diffuse reflectance spectroscopy (DRS), Fourier transform infrared (FTIR), and a scanning electron microscope equipped with an energy dispersive X-ray analyzer (SEM-EDX) techniques. The average crystallite size for CdS NPs, PbS NPs, CNP, and CdS-PbS/CNP samples was obtained at about 24, 36, 27, and 14 nm using the Scherrer formula value of nanometer, by the W-H formula, 31, 17, 39, and 51, respectively. Only a detectable slope can be observed from the DRS spectra for CdS NPs at 591 nm corresponding to an Eg value of 2.1 eV. PbS NPs have a broad abruption peak that begins from the visible region and extends to the IR region of the light. A boosted photocatalytic activity of the supported binary catalysts towards cefotaxime (CT) was reached. An apparent first kinetic model was reached with a k-value of 0.021 min^-1 corresponding to the t_1/2 value of 33 min. A decreased COD trend for the photodegraded CT solutions was reached, and the chemical oxygen demand (COD) results in the Hinshelwood model showed a k-value of 0.016 min^-1, corresponding to a t_1/2 value of 43 min.

Cerium oxide: synthesis, brief characterization, and optimization of the photocatalytic activity against phenazopyridine in an aqueous solution

Water pollution by antibiotics is a global crisis, and its risk is critically more severe due to the explosive use of these drug compounds. A critical effective removal method to diminish this risk is heterogeneous photocatalysis and optimizing the conditions to reach higher mineralization efficiency. CeO₂ anoparticles (NPs) were synthesized and characterized by X-ray diffraction (XRD), UV-Vis diffuse reflection spectroscopy (DRS), and Fourier transform infrared spectroscopy (FTIR) techniques. A cubic structural crystallite phase was detected that had crystallite sizes of 17.9 and 16.7 nm estimated by the Scherrer and Williamson-Hall models. A typical FTIR absorption band for the Ce-O stretching absorption has appeared at 554 cm^-1. Based on DRS data and the Kubelka-Munk and Tauc models, Eg values of 2.80, 3.06, 3.12, and 3.13 eV were obtained for n-values of 1/2, 2, 3/2, and 3, respectively. pHpzc of CeO₂ NPs was about 5.7. The direct photolysis and surface adsorption processes have no critical role in phenazopyridine (PP) removal by appearing with 2.7 and 6.7% removal efficiencies, respectively. Due to the highest photocatalytic activity of CeO₂ NPs toward PP, the effects of the critical operating variable on the activity were evaluated, and the optimal conditions were as catalyst dose, 0.7 g/L; pH, 6; irradiation time, 90 min; and C_PP, 20 ppm. The Hinshelwood kinetics equation plot was y =  - 6.6442 - 0.4677x (r² = 0.9296), in which its slope as the rate constant of the photodegradation process was 0.4677 min^-1 (corresponding to a t_1/2 value of 1.48 min).

Novel La3+/Sm3+ co-doped Bi5O7I with efficient visible-light photocatalytic activity for advanced treatment of wastewater: Internal mechanism, TC degradation pathway, and toxicity analysis

Controlling semiconductor photocatalysts by doping rare-earth ions is an effective strategy to improve photocatalytic performance. Simple solvothermal and calcination methods were used to prepare La³⁺ and Sm³⁺ modified Bi₅O₇I nanomaterials. Some characterizations such as XRD, XPS, SEM, TEM, UV-vis, etc. were carried out to explore its structural composition and photoelectrochemical properties. The photocatalytic activity was investigated by simulating the degradation of TC and RhB under visible-light irradiation. The degradation results showed that the photocatalytic efficiency of 4S4L-Bi₅O₇I was the best among the samples with the 100% degradation rate of TC (Tetracycline hydrochloride) and 93% of RhB (Rhodamine B). The capture experiment and ESR test proved that the active substances that play a role in the photocatalytic degradation of pollutants were ·O₂^-, ¹O₂ and h⁺, and on this basis, the possible degradation mechanism was proposed. The final results showed that La/Sm co-doping expanded the light absorption range of Bi₅O₇I and improved the charge separation efficiency and the specific surface area. Besides, the surface defects were formed on the surface of Bi₅O₇I due to ion-doping, which could catch e^- to promote the separation and transfer of carriers and improve the photocatalytic activity. LC-MS was used to analyze the possible degradation pathways of TC. And the toxicity of TC was also analyzed via T.E.S.T and Toxtree. The results showed comprehensive toxicity of TC was decreased by 4S4L-Bi₅O₇I so that the overall water pollution was reduced. This work can provide a reference for the subsequent development of bismuth-based photocatalysts.

Preparation of new hydrogels by visible light cross-linking of dextran methacrylate and poly(ethylene glycol)-maleic acid copolymer

In this work, a series of new biodegradable and biocompatible hydrogels were synthesized by photopolymerization of dextran-methacrylate (DXM) with poly(ethylene glycol)-maleic acid copolymer (poly(PEG-co-MA, PEGMA)) using (-)-riboflavin as a visible light photoinitiator and L-arginine as a co-photoinitiator. DXM was prepared by acylation of dextran (DX) with methacryloyl chloride (MAC), and PEGMA was synthesized by polycondensation of poly(ethylene glycol) (PEG) and maleic acid (MA). The DXM and PEGMA were characterized by FT-IR and ¹HNMR spectroscopy. Different types of hydrogels from various ratios of DXM and PEGMA were prepared and characterized by SEM. The results showed that the prepared hydrogel by photo-cross-linking of DXM (DPHG0) was transparent and flexible, and its physical shape was excellent, but it was sticky. The stickiness was reduced by increasing the PEGMA contents, and different types of DXM/PEGMA hydrogels (DPHG1-4) with various properties were prepared. For example, DPHG2 (PEGMA content was 0.25 g) was transparent and flexible, its physical shape was excellent, and it was not sticky. The prepared hydrogels showed excellent cytocompatibility, and their tensile and compressive strength were also evaluated. Additionally, the in vitro degradation and swelling ratios of the prepared hydrogels were studied in buffer solution at different pHs.

A core/shell TiO2 magnetized molecularly imprinted photocatalyst (MMIP@TiO2): synthesis and its photodegradation activity towards sulfasalazine

Although the selectivity of TiO₂ for the degradation of target molecules is not enough, it is a broadly employed photocatalyst for the degradation of many pollutants. Molecularly imprinted compounds owing to their extreme recognition specificity have become increasingly popular for preparing selective photocatalysts. In this work, based on molecularly imprinted magnetized TiO₂ (MMIP@TiO₂), a selective photocatalyst was prepared. Via the co-precipitation method, Fe₃O₄ particles were prepared and coated respectively by SiO₂, vinyl end groups, and molecularly imprinted polymers (MIP). The synthesized photocatalyst was characterized by the X-ray diffraction method (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy-dispersive x-ray spectrometry (EDX), vibrating sample magnetometry (VSM), high-performance liquid chromatography (HPLC), and photoluminescence analysis (PL). The photocatalyst was then used to degrade the sulfasalazine pharmaceutical pollutant under UV irradiation. An average crystallite size of 9 nm was obtained for the MMIP@TiO₂ sample from the Scherrer formula and 34.5 nm by the Williamson-Hall formula. The results revealed that compared to the non-imprinted counterpart, the molecularly imprinted photocatalyst had significantly higher efficiency and selectivity for the degradation of target molecules. The process was forwarded with 90% efficiency within 10 min. Optimal conditions were 10.0 min irradiation when 25 mL SSZ solution (50 mg/L), 0.07 g/L catalyst dose, and pH 6.0 were applied. The maximum removal efficiency was calculated to be 92%. The external magnetic field quickly removed the photocatalyst from the solution and regenerated it. It was revealed that after each regeneration cycle, the efficiency dropped. Nevertheless, 63% of the preliminary effectiveness remained after four regeneration steps.

A Z-scheme CdS/BiVO4 photocatalysis towards Eriochrome black T: An experimental design and mechanism study

The synergistic photocatalytic activity was obtained when CdS and BiVO₄ nanoparticles (NPs) were coupled. The samples were characterized by XRD, FTIR, SEM-EDX, and UV-DRS techniques, and their pHpzc was also estimated. The crystallite size of the coupled sample was estimated at 37.3 and 12.5 nm by the Scherrer and Williamson-Hall equations, respectively. The band gaps and the potential positions of VB and CB levels of the semiconductors used were determined. The highest boosted photocatalytic activity was obtained when the CdS: BiVO₄ mole ratio was 1:1. RSM studied the simultaneous interactions between the selected variables, and the model F-value of 110.61> F_{0.05, 14, 13} = 2.4 accompanied by the LOF F-value of 5.20 < F_{0.05, 10, 3} = 8.79 confirm the model significance. The correlation coefficients of R² = 0.9861, the adjusted R² = 0.9710, and the predicted R² = 0.9417, also establish a satisfactory model for processing the experimental data. In the scavenging agent study, photodegradation mechanisms were suggested; among them, the direct Z-scheme mechanism is more favorable for illustrating the EBT-photodegradation by the binary CdS-BiVO₄ photocatalyst. The proposed system, especially the direct Z-scheme mechanism, is suitable as a potential hydrogen production system.

Fabrication of binary g-C3N4/UU-200 composites with enhanced visible-light-driven photocatalytic performance toward organic pollutant eliminations

In this study, g-C₃N₄/UU-200 heterojunction photocatalysts displaying superior photocatalytic activity for organic pollutant elimination under white LED light irradiation were fabricated via an in situ solvothermal method. The successful construction of a heterojunction between g-C₃N₄ and UU-200 was evidenced by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The improved photocatalytic degradation of rhodamine B (RhB) and tetracycline hydrochloride (TCH) over g-C₃N₄/UU-200 compared with that over the individual components can be attributed to the anchoring of the g-C₃N₄ layered structure on the UU-200 surface promoting the decrease of the bandgap of UU-200, as confirmed by ultraviolet–visible diffuse reflectance spectroscopy, and to the light-induced charge separation efficiency stemming from a suitable heterojunction structure, which was revealed by photoluminescence spectroscopy and electrochemical analyses. Specifically, the 40% g-C₃N₄/UU-200 composite showed the highest photocatalytic activity toward the degradation of RhB (97.5%) within 90 min and TCH (72.6%) within 180 min. Furthermore, this catalyst can be recycled four runs, which demonstrates the potential of the g-C₃N₄/UU-200 composite as an alternative visible-light-sensitive catalyst for organic pollutant elimination.

The binary g-C₃N₄/UU–200 heterojunction photocatalysts displaying superior photocatalytic activity for organic pollutant elimination under white LED light irradiation were fabricated via an in situ solvothermal method.