Ag₂CO₃ Decorating BiOCOOH Microspheres with Enhanced Full-Spectrum Photocatalytic Activity for the Degradation of Toxic Pollutants

Constructing a novel type-Ⅱ ZnO/BiOCOOH heterojunction microspheres for the degradation of tetracycline and bacterial inactivation

A novel ZnO/BiOCOOH microsphere photocatalyst with a type-Ⅱ mechanism was developed for the first time. This strategy was accomplished by immobilizing ZnO onto 3D BiOCOOH microspheres via a single-step hydrothermal synthesis method. The ability to degrade tetracycline (TC) in water under visible light and inactivate bacteria of as-catalyst were analyzed. Among the prepared samples, the ZnO/BiOCOOH composite, with a mass ratio of 40%(Zn/Bi), exhibited the highest photocatalytic activity, which was able to degrade 98.22% of TC in just 90 min and completely eradicated Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) in 48 h, and had potential application in solving water resource environmental pollution. The photoelectric characteristics of the photocatalysts were examined by means of electrochemical impedance spectroscopy (EIS) and photoluminescence (PL) spectroscopy. The findings indicated that the superior photocatalytic performance could be credited to the dissociation of electrons (e-) and holes (h+) in heterojunction composites. Finally, electron paramagnetic resonance (EPR) and capture experiments were conducted to confirm the photocatalytic mechanism of the type-Ⅱ heterojunction. This work provides a new Bi-base photocatalyst for aqueous environmental control.

Ag2CO3-Based Photocatalyst with Enhanced Photocatalytic Activity for Endocrine-Disrupting Chemicals Degradation: A Review

Endocrine-disrupting chemicals (EDCs) in the aquatic environment have garnered a lot of attention during the past few years. Due to their toxic behavior, which interferes with endocrine functions in both humans and aquatic species, these types of compounds have been recognized as major polluting agents in wastewater effluents. Therefore, the development of efficient and sustainable removal methods for these emerging contaminants is essential. Photocatalytic removal of emerging contaminants using silver carbonate (Ag2CO3)-based photocatalyst is a promising process due to the unique characteristics of this catalyst, such as absorption of a larger fraction of the solar spectrum, wide band gap, non-toxicity, and low cost. The photocatalytic performance of Ag2CO3 has recently been improved through the doping of elements and optimization variation of operational parameters resulting in decreasing the rate of electron–hole pair recombination and an increase in the semiconductor’s excitation state efficiency, which enables the degradation of contaminants under UV or visible light exposure. This review summarized some of the relevant investigations related to Ag2CO3-based photocatalytic materials for EDC removal from water. The inclusion of Ag2CO3-based photocatalytic materials in the water recovery procedure suggests that the creation of a cutting-edge protocol is essential for successfully eliminating EDCs from the ecosystem.

Application of visible light active photocatalysis for water contaminants: A review

Organic water pollutants are ubiquitous in the natural environment arising from domestic products as well as current and legacy industrial processes. Many of these organic water pollutants are recalcitrant and only partially degraded using conventional water and wastewater treatment processes. In recent decades, visible light active photocatalyst has gained attention as a non-conventional alternative for the removal of organic pollutants during water treatment, including industrial wastewater and drinking water treatment. This paper reviews the current state of research on the use of visible light active photocatalysts, their modified methods, efficacy, and pilot-scale applications for the degradation of organic pollutants in water supplies and waste streams. Initially, the general mechanism of the visible light active photocatalyst is evaluated, followed by an overview of the major synthesis techniques. Because few of these photocatalysts are commercialized, particular attention was given to summarizing the different types of visible light active photocatalysts developed to the pilot-scale stage for practical application and commercialization. The organic pollutant degradation ability of these visible light active photocatalysts was found to be considerable and in many cases comparable with existing and commercially available advanced oxidation processes. Finally, this review concludes with a summary of current achievements and challenges as well as possible directions for further research. PRACTITIONER POINTS: Visible light active photocatalysis is a promising advanced oxidation process (AOP) for the reduction of organic water pollutants. Various mechanisms of photocatalysis using visible light active materials are identified and discussed. Many recent photocatalysts are synthesized from renewable materials that are more sustainable for applications in the 21st century. Only a small number of pilot-scale applications exist and these are outlined in this review.

Facile fabrication of hierarchical p-Ag2O/n-Nb2O5 heterojunction microspheres with enhanced visible-light photocatalytic activity

Constructing p–n heterojunction is an efficient strategy to improve the photocatalytic efficiency. Here, we report a hierarchical Ag₂O/Nb₂O₅ heterojunction composite as a novel and efficient visible-light driven photocatalyst. Hierarchical Nb₂O₅ microspheres were prepared by a hydrothermal method, and then the in situ growth of Ag₂O nanoparticles on their surfaces was realized by a simple deposition method. Structural and textural features of the Ag₂O/Nb₂O₅ composites were investigated, revealing that Ag₂O nanoparticles were well distributed on the surface of Nb₂O₅ microspheres. Photocatalytic degradation of rhodamine B (RhB) was significantly enhanced by Ag₂O/Nb₂O₅ photocatalysts under visible light. The optimal Ag/Nb molar ratio was determined to be 0.15 : 1, which yielded a 21.8 times faster degradation rate constant than plain Nb₂O₅ microspheres and had excellent stability for at least 4 catalytic cycles. The superior photocatalytic performance of Ag₂O/Nb₂O₅ photocatalyst can be ascribed to the hierarchical superstructure as well as the heterojunction between Ag₂O and Nb₂O₅, which facilitated the separation of photogenerated charge carriers. This work has potential application in the future for solving environmental pollution.

Constructing p–n heterojunction is an efficient strategy to improve the photocatalytic efficiency.

BiOCOOH Microflowers Decorated with Ag/Ag2CrO4 Nanoparticles as Highly Efficient Photocatalyst for the Treatment of Toxic Wastewater

A novel flower-like Ag/Ag2CrO4/BiOCOOH heterojunction photocatalyst was synthesized by a facile in-situ precipitation strategy combined with photoreduction treatment. Morphological studies revealed that numerous Ag/Ag2CrO4 nanoparticles were evenly anchored on BiOCOOH microflowers, producing a novel heterojunction with the compactly interfacial contact. Optical absorption characterization demonstrated that Ag/Ag2CrO4/BiOCOOH possessed much better sunlight harvesting ability than Ag2CrO4/BiOCOOH and BiOCOOH. Photocatalytic experiments verified that compared with BiOCOOH, Ag2CrO4, Ag/Ag2CrO4, and Ag2CrO4/BiOCOOH, Ag/Ag2CrO4/BiOCOOH achieved remarkable efficiency by eliminating 100% of rhodamine B (RhB), 82.6% of methyl orange (MO) or 69.4% of ciprofloxacin (CIP) within 50 min at a catalyst dosage of 0.4 g/L. The high photocatalytic performance is likely owing to the improved sunlight response and the distinctly suppressed recombination of charge carriers arising from the formation of the novel 3D hierarchical heterostructure. The quenching test signified that h+, and •O2− were detected as the prevailing active species in wastewater treatment. This study may provide a viable strategy for enhancing the photocatalytic performance of wide band-gap semiconductors.

Facile Fabrication of Flower-Like BiOI/BiOCOOH p-n Heterojunctions for Highly Efficient Visible-Light-Driven Photocatalytic Removal of Harmful Antibiotics

Novel heterojunction photocatalysts with remarkable photocatalytic capabilities and durability for degrading recalcitrant contaminants are extremely desired; however, their development still remains quite challenging. In this study, a series of flower-like BiOI/BiOCOOH p–n heterojunctions were fabricated via a controlled in situ anion-exchange process. During the process, BiOI formation and even deposition on BiOCOOH microspheres with tight interfacial contact were realized. As expected, BiOI/BiOCOOH heterojunctions revealed remarkable enhancements in photocatalytic antibiotic degradation capacities under visible light irradiation compared with pristine BiOI and BiOCOOH. The best-performing BiOI/BiOCOOH heterojunction (i.e., IBOCH-2) showed much improved photocatalytic CIP degradation efficiency of approximately 81- and 3.9-fold greater than those of bare BiOI and BiOCOOH, respectively. The eminent photocatalytic performances were due not only to the enhanced capability in harvesting photon energies in visible light regions, but also the accelerated separation of electrons and holes boosted by the p–n heterojunction. Active species trapping tests demonstrated that superoxide free radicals (•O₂⁻) and photo-generated holes (h⁺) were major active species for CIP degradation. Recycling experiments verified the good durability of BIBO-2 over four runs. The facile in situ synthesis route and excellent performance endow flower-like BiOI/BiOCOOH heterojunctions with a promising potential for actual environmental remediation.

A Novel Flower-Like Ag/AgCl/BiOCOOH Ternary Heterojunction Photocatalyst: Facile Construction and Its Superior Photocatalytic Performance for the Removal of Toxic Pollutants

Novel 3D flower-like Ag/AgCl/BiOCOOH ternary heterojunction photocatalysts were fabricated by the solvothermal and in-situ precipitation methods, followed by light reduction treatment. The Ag/AgCl nanoparticles were homogeneously distributed on 3D BiOCOOH microspheres. These obtained catalysts were characterized by XRD, SEM, TEM, diffuse reflectance spectra (DRS), and photoluminescence (PL). As expected, they exhibited extraordinary photocatalytic capabilities for the elimination of rhodamine B (RhB) and ciprofloxacin (CIP) under simulated sunlight, the results revealed that the Ag/AgCl/BiOCH-3 with 20 wt.% of Ag/AgCl possessed the maximum activity, and the rate constant for the RhB degradation reached up to 0.1353 min⁻¹, which was about 16.5 or 12.2 times that of bare BiOCOOH or Ag/AgCl. The PL characterization further verified that Ag/AgCl/BiOCOOH heterojunctions were endowed with the effective separation of photogenerated carriers. The excellent photocatalytic ability of Ag/AgCl/BiOCOOH could be credited to the synergistic interactions between Ag/AgCl and BiOCOOH, which not only substantially widened the light absorption, but also evidently hindered the charge recombination. The trapping experiments revealed that the dominant reactive species in RhB removal were h⁺, •OH, and •O₂⁻ species. In addition, Ag/AgCl/BiOCOOH was quite stable and easily recyclable after multiple cycles. The above results imply that the 3D flower-like Ag/AgCl/BiOCOOH ternary heterojunction photocatalyst holds promising prospects in treating industrial wastewater.

Composite Magnetic Photocatalyst Bi₅O₇I/MnxZn1-xFe₂O₄: Hydrothermal-Roasting Preparation and Excellent Photocatalytic Activity

A new composite magnetic photocatalyst, Bi₅O₇I/Mn_xZn_1-xFe₂O₄, prepared by a hydrothermal-roasting method was studied. The photocatalytic properties of Bi₅O₇I/Mn_xZn_1-xFe₂O₄ were evaluated by degradation of Rhodamine B (RhB) under simulated sunlight irradiation, and the structures and properties were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet-visible light (UV-Vis) diffuse reflectance spectra (DRS), and a vibrating sample magnetometer (VSM). The results indicated that Bi₅O₇I/Mn_xZn_1-xFe₂O₄ was an orthorhombic crystal, which was similar to that observed for Bi₅O₇I. Bi₅O₇I/Mn_xZn_1-xFe₂O₄ consisted of irregularly shaped nanosheets that were 40⁻60 nm thick. The most probable pore size was 24.1 nm and the specific surface area was 7.07 m²/g. Bi₅O₇I/Mn_xZn_1-xFe₂O₄ could absorb both ultraviolet and visible light, and the energy gap value was 3.22 eV. The saturation magnetization, coercivity and residual magnetization of Bi₅O₇I/Mn_xZn_1-xFe₂O₄ were 3.9 emu/g, 126.6 Oe, and 0.7 emu/g respectively, which could help Bi₅O₇I/Mn_xZn_1-xFe₂O₄ be separated and recycled from wastewater under the action of an external magnetic field. The recycling experiments revealed that the average recovery rate of the photocatalyst was 90.1%, and the photocatalytic activity was still more than 81.1% after five cycles.