Construction of a BiOI/ZnO heterojunction on biomass Juncus effusus fiber for photodegradation of organic pollutants

Semiconductor heterojunction engineering and three-dimensional (3D) architecture construction have been considered highly desirable strategies to enhance photocatalytic performance. Herein, a BiOI/ZnO composite photocatalyst with a 3D flower-like architecture was successfully prepared, which was stably immobilized on three-dimensional porous lignocellulosic biomass Juncus effusus (JE) fiber. The outstanding photocatalytic performance of the BiOI/ZnO-JE fiber was confirmed by the degradation of tetracycline hydrochloride (TC, 90%), ciprofloxacin (CIP, 79%), and norfloxacin (NOR, 81%). The enhanced photocatalytic activities were mainly attributed to the synergistic absorption performance of the lignocellulosic JE and the effective transfer and separation of charges. Moreover, the hydroxyl (·OH) and superoxide radicals (·O2-) are the main reactive species in the photocatalytic process according to the analysis. This work may provide a novel perspective for constructing high-performance lignocellulosic-based photocatalytic materials.

Design of double Z-scheme Ag-Ag3O4/CuO-CuFe2O4 magnetic nanophotocatalyst via starch-templated microwave-combustion hybrid precipitation method and modified with corona-plasma: Remediation of dye contaminants

Herein, the novel double Z-scheme Ag-Ag3O4/CuO-CuFe2O4 magnetic nanophotocatalyst with nanosphere-on-nanosheet-like morphology was synthesized via the corona-plasma-assisted starch-templated microwave-combustion-precipitation method to remove the dye pollutants. The CuO-CuFe2O4 meso/macroporous nanophotocatalyst was synthesized using a one-pot-stage combustion-microwave process with/without starch as a hard-template. Subsequently, surface modification was carried out by DC corona-plasma discharge technology at various voltages, namely 500, 1000 and 1500 V. Then, the Ag3O4 photocatalyst was deposited on the CuO-CuFe2O4 fabricated with starch-hard-template and treated with 1000 V corona-plasma (denoted as: Ag-Ag3O4/CuO-CuFe2O4 (Starch) 1000 P). The properties of the synthesized nanophotocatalysts were analyzed using various techniques, including X-ray diffraction (XRD), Diffuse reflectance spectroscopy (DRS), Transmission electron microscopy (TEM), Field emission scanning electron microscopy (FESEM), Brunauer-Emmett-Teller and Barrett-Joyner-Halenda (BET-BJH), Vibrating Sample Manetometer (VSM), and Photoluminescence (PL). The XRD analysis corroborated the presence of CuO, CuFe2O4 and Ag3O4 in the structure of all samples. The BET-BJH analysis indicates that the specific surface area of the Ag-Ag3O4/CuO-CuFe2O4 (Starch) 1000 P nanophotocatalyst as the best sample is 2 m2/g, higher than other samples. Additionally, the DRS analysis revealed that the band gap of the Ag-Ag3O4/CuO-CuFe2O4 (Starch) 1000 P nanophotocatalyst is about 1.68 eV with the surface plasmon resonance. The performance of the ternary heterostructured Ag-Ag3O4/CuO-CuFe2O4 (Starch) 1000 P nanophotocatalyst was 96.2% and 89.1% in the degradation of the crystal violet (10 mg/L) and acid orange 7 (10 mg/L), respectively, proving its outstanding degradation capacity.

Synthesis of a plasmonic AgCl and oxygen-rich Bi24O31Cl10 composite heterogeneous catalyst for enhanced degradation of tetracycline and 2,4-dichlorophenoxy acetic acid

In this study, a AgCl/Bi₂₄O₃₁Cl₁₀ composite heterostructure was constructed. Varying ratios of AgCl nanoparticles were immobilised onto the Bi₂₄O₃₁Cl₁₀ rod-like structure. The physical and optical properties of the synthesised catalysts were characterised using a range of techniques. The photocatalytic activity of the catalysts was investigated by the degradation of 2,4-dichlorophenoxy acetic acid (2,4-D) and tetracycline (TC) under visible light irradiation. The performance of the composite photocatalysts was 18 and 3.4 times better in 2-4,D and TC photodegradation when compared to Bi₂₄O₃₁Cl₁₀ alone. The improved photocatalytic performance was due to the surface plasmon resonance (SPR) effects of the Ag nanoparticles deposited on the surface of the Xwt%AgCl/BOC thereby improving the separation of the electron–hole pair. The effects of the initial contaminant concentration, pH, photocatalyst loading were investigated. Trapping experiments were also carried out to deduce the reactive species responsible for the degradation process and a preliminary mechanism of degradation was proposed. Successful mineralisation of 2,4-D and TC at 65% and 63% efficiency was also measured after 24 h and the potential for reusability of the as-synthesised photocatalyst was established. This work reports a promising heterogeneous photocatalyst for the removal of pollutants such as TC and 2,4-D from wastewater.

Photocatalytic degradation of tetracycline and 2,4-dichlorophenoxy acetic acid using AgCl/Bi₂₄O₃₁Cl₁₀ photocatalyst in visible light.

Porous hollow Ag/Ag2S/Ag3PO4 nanocomposites as highly efficient heterojunction photocatalysts for the removal of antibiotics under simulated sunlight irradiation

Antibiotic pollutants are a serious and growing threat to human health and the environment that efficient measures must be taken to eliminate them. Here, we report the facile fabrication of porous hollow Ag/Ag₂S/Ag₃PO₄ heterostrucutres for efficient photocatalytic degradation of tetracycline under simulated sunlight irradiation. The morphology manipulation and hetero-nanocomposites construction through a coprecipitation-refluxing approach were applied to enhance the photocatalytic performance of the Ag/Ag₂S/Ag₃PO₄ products. The photodegradation outcomes indicated that the heterojunction Ag/Ag₂S/Ag₃PO₄ photocatalyst with a suitable band gap energy of 2.17 eV, has better degradation performance (∼95%) than individual Ag₂S and Ag₃PO₄ structures after 120 min of simulated sunlight irradiation, even after five recycles. The good photocatalytic activity of Ag/Ag₂S/Ag₃PO₄ nanocomposites could be mainly attributed to the unique hierarchical architectures, promoted visible-light harvesting, reduced a recombination and boosted separation of electron-hole pairs originated from the as-formed heterojunctions. Moreover, we proposed a photocatalytic degradation mechanism based on the radical scavenging results, which disclosed that the ^•O₂^- and ^•OH species perform essential tasks for the photodegradation of antibiotics by Ag/Ag₂S/Ag₃PO₄ nanocomposites.

A critical review on bismuth oxyhalide based photocatalysis for pharmaceutical active compounds degradation: Modifications, reactive sites, and challenges

Pharmaceutical active compounds (PhACs), as a kind of widely used pharmaceutical drugs, has attracted much attention. The bismuth oxyhalides (BiOX)-based photocatalysis can remove PhACs efficiently due to its unique layered structure, optical and electronic properties. Nevertheless, the rapid recombination of photogenerated electron-hole pairs, and the inherent instability of structure have limited its practical application. In order to solve these problems, recent modification studies tend to focus on facet control, elemental doping, bismuth-rich strategies, defect engineering and heterojunction. Therefore, the objective of this review is to summarize the recent developments in multiply modified strategies for PhACs degradation. The synthesis methods, photocatalytic properties and the enhancement mechanism are elaborated. Besides, based on theoretical calculation, the reactive sites of typical PhACs attacked by different reactive oxygen species were also proposed. Subsequently, challenges and opportunities in applications are also featured which include factors, viz., dissolution of halogen ions, instability under visible light, applications of real water/wastewater, intermediates and byproducts toxicity analysis of BiOX-based photocatalysis. Finally, the perspectives of BiOX-based photocatalysis for PhACs photodegradation in actual water applications are highlighted.

Oxygen-rich bismuth oxybromide nanosheets coupled with Ag2O as Z-scheme nano-heterostructured plasmonic photocatalyst: Solar light-activated photodegradation of dye pollutants

In this research to enhance the photocatalytic activity of Bi₂₄O₃₁Br₁₀, precipitation fabrication of the Z-scheme heterojunction with Ag-Ag₂O has been investigated. The characterizations were carried out by XRD, FESEM, TEM, EDX, BET-BJH, DRS and pH_pzc analyzes. The Ag-Ag₂O/Bi₂₄O₃₁Br₁₀ Z-scheme heterojunction nanophotocatalyst with weighted ratio of 3:1 exhibited the wide absorption in the visible light region and displayed the high photocatalytic activity for the photodegradation of acid orange 7 (96.5%, 94.1% and 90% for 10, 20 and 60 mg/L, respectively after 120 min) and eosin yellow (for 10 mg/L: 81.5%) compared to the other composites and pure Bi₂₄O₃₁Br₁₀ and Ag-Ag₂O samples. The highly enhanced photocatalytic activity of Ag-Ag₂O/Bi₂₄O₃₁Br₁₀ (3:1) was assigned to the surface plasmon resonance effect of silver nanoparticles, high solar-light-response and the structure of Z-scheme heterojunction, which effectively reduces the recombination of the photogenerated charge carriers. Moreover Ag-Ag₂O/Bi₂₄O₃₁Br₁₀(3:1) Z-scheme heterojunction nanophotocatalyst exhibited the good photocatalytic activity even after 4 runs.

Construction of Ag2O-modified g-C3N4 photocatalyst for rapid visible light degradation of ofloxacin

The design of stable and highly efficient photocatalysts had emerged as an economic and promising way for eliminating harmful pharmaceutical pollutants. In this study, a series of Ag₂O-modified g-C₃N₄ composites with different Ag₂O amounts (denoted as Ag₂O-CN_x) were fabricated via a facile reflux condensation methodology. Ofloxacin (OFL) was chosen as a model pollutant to evaluate the degradation efficiency of the photocatalytic system. The optimal photocatalytic activity was achieved with Ag₂O-CN_1.0, which reached up to 99.1% removal of OFL after 15-min reaction and the pseudo-first-order constant was 0.469 min^-1, approximately 42 times higher than that of g-C₃N₄. Considering the complexity of the actual environment, the important influential factors such as catalyst dosage, initial OFL concentration, solution pH, and natural organic matter on the OFL degradation were systematically investigated. Additionally, Ag₂O-CN_1.0 showed good stability and recyclability in multiple cycle experiments. The feasible photodegradation mechanism of OFL was proposed with radical scavenger experiments, and the degradation products were determined. Furthermore, the enhanced photocatalytic activity could be ascribed to not only the high photogenerated charge separation efficiency and the surface plasmon resonance effect of metallic Ag, but also the p-n heterojunction formed between Ag₂O and g-C₃N₄. Therefore, Ag₂O-CN_1.0 was a treatment material possessing great application prospects for eliminating OFL in wastewater.

β-Cyclodextrin Polymerized in Cross-Flowing Channels of Biomass Sawdust for Rapid and Highly Efficient Pharmaceutical Pollutants Removal from Water

Water pollution arising from pharmaceuticals has raised great concerns about the potential risks for biosphere and human health. However, rapid and efficient removal of pharmaceutical contaminants from water remains challenging. Wood sawdust, a byproduct of the wood-processing industry, is an abundant, cost-effective, and sustainable material with a unique hierarchically porous microstructure. These features make wood sawdust quite interesting as a filtration material. Here, we report a novel cross-flow filtration composite based on β-cyclodextrin-polymer-functionalized wood sawdust (β-CD/WS) in which the pharmaceutical contaminant water flows through the sawn-off vessel channels and the micropores on the surface of the cell walls, generating the turbulence. Such water flow characteristics ensure full contact between pharmaceutical pollutants and β-CD grafted on the cellulose backbone of wood sawdust, thereby enhancing the water treatment efficiency. Consequently, the β-CD/WS filter device shows a high removal efficiency of over 97.5% within 90 s for various pharmaceutical contaminants including propranolol, amitriptyline, chlortetracycline, diclofenac, and levofloxacin, and a high saturation uptake capacity of 170, 156, 257, 159, and 185 mg g^-1, respectively. The high-performance wood-sawdust-based cross-flow filtration opens new avenues for solving the global water pollution issues, especially those caused by pharmaceutical contaminants.

Influence of fuel type and microwave combustion on in-situ fabrication of BimOnBrz mixed-phase nanostructured photocatalyst: Effective sun-light photo-response ability in tetracycline degradation

In this research, Bi_mO_nBr_z nanophotocatalysts were fabricated using various fuels such as ethylene glycol, propylene glycol and glycerol to investigate the effect of fuel types on the photocatalytic activity and structure. Moreover, the influence of conventional and microwave combustion was investigated. Results of XRD, EDX, BET-BJH, FESEM, TEM and DRS techniques illustrated that the simultaneous use of the glycerol and microwave irradiation was leaded to the synthesis of Bi_mO_nBr_z nanophotocatalyst with unique characteristics; which consists of 26 % BiOBr and 74 % Bi₂₄O₃₁Br₁₀. The photocatalytic performance of this sample was investigated in the photo-decomposition of the tetracycline antibiotic under a light source that was simulated as the solar light. The results of reactor test showed the highest photo-degradation efficiency (98.9 %) of tetracycline over this nanophotocatalyst. In addition, in order to appraise the effects of operational variables on the photocatalytic process efficiency the tetracycline concentration, initial pH of polluted solution and dosage of photocatalyst were changed. Moreover, the re-used of the optimum photocatalyst was evaluated. Finally, a mechanism for the photocatalytic decomposition of the antibiotic was suggested.

A separation-free and pizza-structure PAM/GCN/PAA composite hydrogel (PCH) in wastewater treatment at visible light or solar light

During wastewater treatment, the separation of powder nano-photocatalyst from treated water is a limiting factor for the commercial application of the powder photocatalysts. In this study, a photocatalyst, i.e. graphitic carbon nitride (GCN) was immobilized in network of polyacrylic acid (PAA) hydrogel to solve this issue. To further immobilizing GCN and strengthening hydrogel, polyacrylamide (PAM) was introduced to form interpenetrating network with PAA. In this structure, PAM acted the role of cheese in a pizza, tightly covering and immobilizing GCN into the interpenetrating network. During the cyclic tests, PCH with 20 mg (PCH₂₀) can be successively reused 5 times compared 3 times of GCN/PAA with the RhB photodegradation efficiency over 95% each time. Meanwhile, GCN retention rates of GCN/PAA and PCH₂₀ are 71.2 ± 5.2% and 97.2 ± 1.9% respectively. Besides, GCN played initiator role in the polymerization of PAM. PCH₂₀ was more stable comparing with GCN/PAA hydrogel at both mechanical and thermal characterization. Furthermore, PCH₂₀ showed excellent photocatalysis capability to RhB dyed wastewater at both visible and solar light. During 5 time's continuously cyclic tests, the photodegradation efficiency of PCH₂₀ over RhB solution (10 mgL^-1) was over 95% within 2 h under visible light (100 mWcm^-2) each time. By changing pH values of solution from 3 to 9, the degree of swelling ratio (D_sw) of PCH₂₀ could achieve from 307 ± 39% to 2361 ± 135%. PCH₂₀ was feasible to obtain large surface area through swelling and it was beneficial for GCN to harvest the light. Hence, the photodegradation performance of PCH₂₀ in RhB solution of pH 7, 9 was better than its in the original (pH 5.7) or the pH 3 RhB solution. The preparation of PCH₂₀ was environmental friendly and cost-efficient without using any photoinitiators and crosslinking agents except GCN.

Hollow core/shell β-Bi2O3@WS2 p–n heterojunction for efficient photocatalytic degradation of fluoroquinolones: a theoretical and experimental study

An efficient visible-light-driven β-Bi₂O₃@WS₂ p–n core–shell heterostructure was rationally designed using theoretical calculations and then fabricated via a facile self-assembly method.

Plasmon-assisted demolition of antibiotic using sono-photoreduction decoration of Ag on 2D C3N4 nanophotocatalyst enhanced with acid-treated clinoptilolite

In this study, the plasmon silver/bulk graphitic carbon nitride-clinoptilolite (denoted as: Ag/BCN-CLT) nanophotocatalysts synthesized using sono-photoreduction dispersion of Ag over C₃N₄ nanophotocatalyst with various contents of acid-treated clinoptilolite (10, 20, 40 wt%) that was employed in the tetracycline degradation, as the model antibiotic pollutant, using simulated solar-light radiation. X-ray diffraction, field emission scanning electron microscopy, Energy-dispersive X-ray spectroscopy-Dot mapping, Brunauer-Emmett-Teller and Barrett-Joyner-Halenda, particle size distribution, and Ultraviolet-Visible diffuse reflectance spectroscopy analyses results showed a high quality of synthesis of nanophotocatalysts and good dispersion of particles on the surface of nanophotocatalyst. Using photodegradation results, the Ag/BCN-CLT(10) sample with 10 wt% of clinoptilolite showed a better tetracycline degradation efficiency (87.23%), which is a result of a high surface area of nanophotocatalyst due to the exerting sonication in synthesis procedure. Also, using Ag nanoparticles as a noble metal and creation of surface plasmon resonance effect, the edge of light absorption was shifted to the visible light region, which was proven by UV-Vis DRS results. Furthermore, the using of both Ag and acid-treated clinoptilolite had an efficient influence on decreasing band gap energy position. At last, the effect of different operational parameters and the reusable property of the photocatalyst have experimented. Finally, the suggested mechanisms of the tetracycline degradation reactions were drawn and were analyzed accurately.