A synergistic consequence of catalyst dosage, pH solution and reactive species of Fe-doped CdAl2O4 nanoparticles on the degradation of toxic environmental pollutants

Synergistic Mechanism of Hydroxyl Regulation and a Polyvinylpyrrolidone Surfactant in Enhancing the Catalytic Oxidation Abilities of BiOBr

The rational design of BiOBr photocatalysts with optimized surface properties and enhanced photooxidative capacities is crucial. This study proposes a synergistic strategy combining hydroxyl-rich solvents with polyvinylpyrrolidone (PVP) surfactants to modulate the structural and electronic properties of BiOBr through a solvothermal approach. The resulting self-assembled microspheres demonstrated exceptional efficiency in degrading ciprofloxacin (CIP), methyl orange (MO), and rhodamine B (RhB). Among the synthesized variants, BiOBr-EG-PVP (fabricated with ethylene glycol and PVP) exhibited the highest photocatalytic activity, achieving near-complete removal of 20 mg/L CIP and RhB within 10 min under visible light irradiation, with degradation rates 60.12-101.73 times higher than pristine BiOBr. The structural characterization revealed that ethylene glycol (EG) not only induced the formation of self-assembled microspheres but also introduced abundant surface hydroxyl groups, which simultaneously enhanced the hole-mediated oxidation capabilities. The incorporation of PVP further promoted the development of hierarchical honeycomb-like microspheres and synergistically enhanced both the hydroxyl group density and photooxidative potential through interfacial engineering. Density functional theory (DFT) calculations confirmed that the enhanced photooxidative performance originated from an increased surface oxygen content. This work elucidates the synergistic effects of hydroxyl-rich solvents and surfactant modification in the fabrication of advanced BiOBr-based photocatalysts, providing new insights for high-performance photocatalysis for environmental remediation.

In Situ Pyrolysis of ZIF-67 to Construct Co2N0.67@ZIF-67 for Photocatalytic CO2 Cycloaddition Reaction

The development of heterogeneous catalysts with abundant active sites is pivotal for enhancing the efficiency of photothermal CO2 conversion. Herein, we report the construction of Co2N0.67@ZIF-67 through the in situ pyrolysis of ZIF-67 under low-temperature pyrolysis conditions. During the pyrolysis process, the crystal structure of ZIF-67 is predominantly preserved concurrently with the formation of Co2N0.67 nanoparticles (NPs) within the ZIF-67 pores. The optimal catalyst Co2N0.67@ZIF-67(450,2) not only possesses high photothermal efficiency but also can efficiently activate CO2. Benefiting from these characteristics, Co2N0.67@ZIF-67(450,2) exhibited significant catalytic activity in the photocatalytic cycloaddition of CO2 and epichlorohydrin. The yield of (chloromethyl)ethylene carbonate reached 95%, which is more than 4 times higher than that of ZIF-67 under visible light irradiation (300 W·m2 Xe lamp, 3 h). This study could offer an alternative approach to enhance the photocatalytic activity of MOFs through low-temperature pyrolysis.

Rational Design and Synthesis of Fe-Doped Co-Based Coordination Polymer Composite Photocatalysts for the Degradation of Norfloxacin and Ciprofloxacin

The solar light-responsive Fe-doped Co-based coordination polymer (Fe@Co-CP) photocatalyst was synthesized under mild conditions. [Co(4-padpe)(1,3-BDC)]n (Co-CP) was first constructed using mixed ligands through the hydrothermal method. Then, Fe was introduced into the Co-CP framework to achieve the enhanced photocatalytic activity. The optimal Fe@Co-CP-2 exhibited excellent catalytic degradation performance for norfloxacin and ciprofloxacin under sunlight irradiation without auxiliary oxidants, and the degradation rates were 91.25 and 92.66% in 120 min. These excellent photocatalytic properties were ascribed to the generation of the Fe-O bond, which not only enhanced the light absorption intensity but also accelerated the separation efficiency of electrons and holes, and hence significantly improved the photocatalytic property of the composites. Meanwhile, Fe@Co-CP-2 displayed excellent stability and reusability. In addition, the degradation pathways and intermediates of antibiotic molecules were effectively analyzed. The free radical scavenging experiment and ESR results confirmed that •OH, •O2-, and h+ active species were involved in the catalytic degradation reaction; the corresponding mechanisms were deeply investigated. This study provides a fresh approach for constructing Fe-doped Co-CP-based composite materials as photocatalysts for degradation of antibiotic contaminants.

Synergistic effect of Fe doping and oxygen vacancy in AgIO3 for effectively degrading organic pollutants under natural sunlight

In this work, a series of hydrogenated Fe-doped AgIO3 (FAI-x) catalysts are synthesized for photodegrading diverse azo dyes and antibiotics. Under the irradiation of natural sunlight with a light intensity of ∼60 mW/cm2, the optimum FAI-10 exhibits a considerable rate constant for decomposing methyl orange (MO) of 0.067 min-1, about 7.4 times higher than that of AgIO3 (0.009 min-1), and 24.6% and 83.8% of MO can be decomposed over AgIO3 and FAI-10 after irradiation for 40 min. In the amplification photodegradation experiments with using 0.5 g catalyst and 400 mL MO dye solution (10 mg/L), FAI-10 possesses greatly higher photoreactivity to common semiconductors (ZnO, TiO2, In2O3 and Bi2MoO6), and the photodegradation rates over FAI-10 are 92%. Particularly, the FAI-10 shows superior stability, the activity of which remains unaltered after 8 continuous cycles. Foreign ions and water bodies have slight effect on the activity of FAI-10, but the MO degradation rates are decreased by adjusting pH values, especially when pH = 11 because of the strong electrostatic repulsion between MO and FAI-10. FAI-10 can also effectively decompose another azo dye (rhodamine B (RhB)) and diverse antibiotics (sulflsoxazole (SOX), chlortetracycline hydrochloride (CTC), tetracycline hydrochloride (TC) and ofloxacin (OFX)). The activity enhancement mechanism of FAI-10 has been systemically investigated and is ascribed to the promoted photo-absorption, charge separation and transfer efficiency, and affinity of organic pollutants, owing to the synergistic effect of Fe doping and oxygen vacancy (Ov). The photocatalytic mechanisms and process for decomposing MO are verified and proposed based on radical trapping experiments and liquid chromatography-mass spectrometry (LC-MS). This work opens an avenue for the fabrication of effective photocatalysts toward water purification.

An efficient electrochemical degradation of toxic pollutants in wastewater using BiOBr/BiVO4 hierarchical structured electrode material

The electrochemical degradation of alizarin red dye was studied using bismuth oxyhalide attached to bismuth vanadate nanocomposite synthesized via a simple solvothermal method. The electrochemical degradation of alizarin red dye was treated at current densities of 3 and 5 mA cm-1 for 30 min under different supporting electrolyte mediums (NaCl and KCl). Also, the electrochemical degradation of BiOBr/BiVO4 electrode shows higher degradation percentages of 97 and 99 for NaCl and KCl electrolyte solutions, which are higher degradation percentages than pure BiVO4 electrode (88 and 91 for NaCl and KCl). Also, the BiOBr/BiVO4 electrode shows 100% COD reduction during the 30th min of alizarin red dye using both NaCl and KCl electrolyte solutions. This may indicate that the prepared BiOBr/BiVO4 electrode shows an efficient electrode material for the degradation of textile dyes.

Electrospun Fe doped TiO2 fiber photocatalyst for efficient wastewater treatment

Water pollution caused by industrial wastewater is the most critical environmental problem in the world. Synthetic dyes are commonly used in various industries such as paper, plastic, printing, leather and textile for their ability to impact color. Complex composition, high toxicity and low biodegradability of dyes make them difficult to degrade which causes a substantial negative impact on overall ecosystems. To address this issue we synthesized TiO₂ fibers photocatalyst using the combination of sol-gel and electrospinning techniques to be used in the degradation of dyes which causes water pollution. We doped Fe in TiO₂ fibers to enhance the absorption in the visible region of the solar spectrum which will also help to increase the degradation efficiency. As synthesized pristine TiO₂ fibers and Fe doped TiO₂ fibers were analyzed using different characterization techniques such as X-ray diffraction, Scanning electron microscopy, Transmission electron microscopy, UV-Visible spectroscopy, X-ray photoelectron spectroscopy. 5% Fe doped TiO₂ fibers show excellent photocatalytic degradation activity for rhodamine B (99% degradation in 120 min). It can be utilized for degradation of other dye pollutants such as methylene blue, Congo red and methyl orange. It shows good photocatalytic activity (97%) even after 5 cycles of reuse. The radical trapping experiments reveals that holes, ^•O₂^- and ^•OH has a significant contribution in the photocatalytic degradation. Due to the robust fibrous nature of 5FeTOF the process of collection of photocatalysts was simple and without loss as compared to powder photocatalysts. This justifies our selection of electrospinning method of synthesis of 5FeTOF which is also useful for large scale production.

Two-step fabrication of cellulose embedded Fe3O4/Fe3+ composite beads as catalyst in degradation of sulfamethoxazole in floating bed reactor

In this study, magnetite particles were successfully embedded in sodium carboxymethyl cellulose as beads using FeCl₃ as the cross-linker in two step-method and it was used as a Fenton-like catalyst to degrade sulfamethoxazole in aqueous solution. The surface morphology and functional groups influence of the Na-CMC magnetic beads was studied using FTIR and SEM analysis. The nature of synthesized iron oxide particles was confirmed as magnetite using XRD diffraction. The structural arrangement of Fe³⁺ and iron oxide particles with CMC polymer was discussed. The influential factors for SMX degradation efficiency were investigated including the pH of the reaction medium (4.0), catalyst dosage (0.2 g L^-1) and initial SMX concentration (30 mg L^-1). The results showed that under optimal conditions 81.89% SMX degraded in 40 min using H₂O₂. The reduction in COD was estimated to be 81.2%. SMX degradation was initiated neither by the cleaving of C-S nor C-N followed by some chemical reactions. Complete mineralization of SMX was not achieved which could be due to an insufficient amount of Fe particles in CMC matrix that are responsible for the generation of *OH radicals. It was explored that degradation followed pseudo-first order kinetics. Fabricated beads were successfully applied in a floating bed column in which the beads were allowed to float in sewage water spiked with SMX for 40 min. A total reduction of 79% of COD was achieved in treating sewage water. The beads could be used 2-3 times with significant reduction in catalytic activity. It was found that the degradation efficiency was attributed to a stable structure, textural property, active sites and *OH radicals.