Sunlight-driven photodegradation of oxytetracycline antibiotic by BiVO4 photocatalyst

Hydrothermal synthesis of Zingiber/ZnO for enhanced photodegradation of ofloxacin antibiotic and reactive red azo dye (RR141)

The examination of photocatalyst powders for the total removal of pollutants from aqueous solutions is a vital research subject within the realm of environmental preservation. The objective of this study is to develop a photocatalyst heterojunction consisting of Zingiber/ZnO-H for the degradation of both the reactive red dye (RR 141) and ofloxacin antibiotic in wastewater. The current investigation outlines the process of synthesising a composite material by combining Zingiber montanum extract with zinc oxide (ZnO) by a hydrothermal method. The synthesis was conducted at a temperature of 180°C for a period of 4 hours. Consequently. The photocatalyst with a constructed heterojunction shown a notable enhancement in its photocatalytic activity as a result of the improved efficiency in charge separation at the interface. The application of economically viable solar energy facilitated the complete eradication of harmful pollutants through the process of detoxification. The removal of impurities occurs by a process that follows a first-order kinetics. Among the pollutants, RR141 demonstrates the greatest rate constant at 0.02 min-1, while ofloxacin has a rate constant of 0.01 min-1. The assessment of the stability of the produced photocatalyst was conducted after undergoing five cycles. This study additionally investigated the influence of sunshine on degradation, uncovering degradation rates of 97% for RR141 and 99% for ofloxacin when exposed to UV Lamp, and degradation rates of 97% for RR141 and 95% for ofloxacin when exposed to Solar Light.

Facile construction of multifunctional xNiCo2O4/BiVO4 heterojunction with accelerated charge transfer for efficient photocatalytic treatment of Cr (VI), MB and TC under visible light

The release of industrial effluents, comprising of organic dyes, antibiotics, and heavy metals poses substantial environmental and ecological threats. Among the different approaches, the utilization of heterogeneous photocatalysis based on semiconducting metal oxides is of paramount important to removal of organic ( MB dye and TC antibiotic) and inorganic pollutants ( Cr (VI) ) in wastewater. In this work, a new approach for creating type-II heterojunction photocatalysts named xNiCo2O4/BiVO4 or BNC is suggested. The as-prepared samples were thoroughly examined by means of several sophisticated analytical tools to investigate their physicochemical properties. These composites were utilized in the decomposition of MB dye, TC drug and the reduction of Cr (VI) under visible light irradiation. According to the findings, the creation of type-II heterojunction at BiVO4-NiCo2O4 interface greatly improved charge transportation while successfully preventing electron-hole recombination. Among the various composites studied, BNC-2 demonstrated an enhanced photocatalytic activity towards degradation of MB and TC, which were found to be 91 % over a period of 150 min and 95 % within only 60 min, respectively. Moreover, the photocatalytic reduction of Cr (VI) was accomplished 96 % within just 25 min. Additionally, it is discovered that BNC-2 displayed promising photostability and recyclability with a retention of >90 % after five consecutive cycles. The enhanced photocatalytic activity of BNC-2 is evidently attributed to the expedited separation and transfer of charges, as proven by photocurrent measurement, photoluminescence and electrochemical impedance spectroscopy analyses. Hence, the current amalgamation of NiCo2O4 and BiVO4 heterojunction composite has paved novel paths towards photocatalytic removal of organic as well as inorganic contaminants.

Enhanced tetracycline degradation with TiO2/natural pyrite S-scheme photocatalyst

In this study, TiO2 nanoparticles were employed as a photocatalyst for the degradation of tetracycline (TC) under visible light irradiation. The TiO2 nanoparticles were decorated on natural pyrite (TiO2/NP) and characterized using XRD, FTIR, and SEM-EDX methods. This study evaluated the impacts of various operational parameters such as pH, catalyst dosage, initial TC concentration, and light intensity on TC removal. The findings revealed that under optimal conditions (pH 7, catalyst: 2 g/L, TC: 30 mg/L, and light intensity: 60 mW/cm2), 100% of TC and 84% of TOC were removed within 180 min. The kinetics of TC elimination followed a first-order model. The dominant oxidation species involved in the photocatalytic elimination of TC was found to be ·OH radicals in the TiO2/NP system. The reuse experiments showed the high capability of the catalyst after four consecutive cycles. This study confirmed that the TiO2/NP system has high performance in photocatalytic TC removal under optimized experimental conditions.

The Synthesis of carbon dots//zincoxide (CDs/ZnO-H400) by using hydrothermal methods for degradation of ofloxacin antibiotics and reactive red azo dye (RR141)

The development of photocatalytic powders to remove contaminants from air solutions is an important field of research in the field of environmental conservation. CD/ZnO-H400, a heterogeneous photocatalytic production, is utilized to degrade the reactive red dye and the antibiotic ofloxacin found in wastewater. This study explains the synthesis of carbon dots (CDs) derived from coconut air and zinc oxide (ZnO) using a hydrothermal method at a temperature of 180 °C with a duration of 4 h and subsequently calcinated at a 400 °C temperature for 4 h. This shows a significant improvement in photocatalytic performance due to improved delivery efficiency at the interface. The cost-efficient use of solar energy allows the comprehensive elimination of harmful pollutants through detoxification. The removal of the contaminant takes place through the first-order reaction, with RR141 showing the highest constant rate at 0.03 min-1, while ofloxacin has a constant speed at 0.01 min-1. The photocatalytic stability is measured after five cycles. The study also tested the impact of sunlight on degradation, showing a degrading rate of 98% for RR141 and 96% for ofloxacin. This study displays a new catalyst powder synthesized from carbon dots derived from the air, coconut and ZnO, showing remarkable photoactivity to completely remove harmful dyes and antibiotics from the surrounding environment.

Nanotechnology-assisted treatment of pharmaceuticals contaminated water

The presence of pharmaceutical compounds in wastewater due to an increase in industrialization and urbanization is a serious health concern. The demand for diverse types of pharmaceutical compounds is expected to grow as there is continuous improvement in the global human health standards. Discharge of domestic pharmaceutical personal care products and hospital waste has aggravated the burden on wastewater management. Further, the pharmaceutical water is toxic not only to the aquatic organism but also to terrestrial animals coming in contact directly or indirectly. The pharmaceutical wastes can be removed by adsorption and/or degradation approach. Nanoparticles (NPs), such as 2D layers materials, metal-organic frameworks (MOFs), and carbonaceous nanomaterials are proven to be more efficient for adsorption and/or degradation of pharmaceutical waste. In addition, inclusion of NPs to form various composites leads to improvement in the waste treatment efficacy to a greater extent. Overall, carbonaceous nanocomposites have advantage in the form of being produced from renewable resources and the nanocomposite material is biodegradable either completely or to a great extent. A comprehensive literature survey on the recent advancement of pharmaceutical wastewater is the focus of the present article.

Effective Reinforcement of Visible Light Photocatalytic and Gas Sensing Characteristics of Nanocrystalline TiO2: Gd-Based Nb and Mo Dopants

Efficient compositions for the selective detection of ethanol gas and the removal of organic contaminants were realized by codoping of (Gd, Nb) and (Gd, Mo) ions into TiO2. TiO2, Ti0.96Gd0.01Nb0.03O2, and Ti0.96Gd0.01Mo0.03O2 samples were prepared by a coprecipitation method. For all compositions, a crystalline anatase phase of TiO2 was detected. Compared to pure TiO2, the absorption edges of Ti0.96Gd0.01Nb0.03O2 and Ti0.96Gd0.01Mo0.03O2 samples were red-shifted, further broadening towards visible light. The morphological studies demonstrate that the grains of TiO2 were more refined after (Gd, Nb) and (Gd, Mo) codoping. The photocatalytic efficiency of the Ti0.96Gd0.01Mo0.03O2 catalyst for degrading 20 mg/L reactive yellow 145, brilliant green, and amoxicillin was 98, 95, and 93% in 90 min, respectively. The reusability experiments indicate that the Ti0.96Gd0.01Mo0.03O2 catalyst had high stability during reuse. The high photocatalytic activity of the Ti0.96Gd0.01Mo0.03O2 catalyst was correlated to the broad visible-light absorption and effective separation of electron-hole pairs by Gd3+ and Mo6+ cations. The gas sensing characteristic is reflected by the high sensitivity of the Ti0.96Gd0.01Nb0.03O2 sensor to ethanol gas in the presence of different gases at 275 °C. The obtained results indicated that the (Gd, Mo) mixture could more effectively induce the photocatalytic properties of TiO2 while (Gd, Nb) dopants were the best for reinforcing its sensing characteristics.

Synthesis and characterization of Ce0.5Bi0.5VO4/rGO nanocomposite by sonochemical method for photocatalytic desulfurization of petroleum derivatives

In order to improve the desulfurization efficiency of petroleum derivatives, Ce0.5Bi0.5VO4/rGO nanocomposite was synthesized by sonochemical method. The prepared nanocomposites were characterized by XRD, FESEM, EDS, FT-IR, BET, and DRS analyses. XRD analysis shows that the synthesized nanocomposite is amorphous. FESEM images showed that nanostructures with a smaller particle size distribution were synthesized under optimal conditions, i.e. controlling the synthesis temperature between 0 and 5 °C. The results of desulfurization showed that nanocomposites containing reduced graphene oxide (rGO) have higher photocatalytic efficiency than pure samples, the main reason of which can be better charge separation in the samples through the π electron in the rGO structure. The highest amount of desulfurization of CeVO4/rGO, BiVO4/rGO, and Ce0.5Bi0.5VO4/rGO nanocomposites was 95.62, 91.25, and 96.38%, respectively, after exposure to UV light for 40 min. The enhancement of photocatalytic activity of Ce0.5Bi0.5VO4/rGO composite could be attributed to the efficient separation of electron-hole pairs and the inhibition of recombination. Desulfurization in the presence of hydrochloric acid and hydrogen peroxide increased the efficiency by 12%, which is a significant amount.

Photoelectrocatalytic peroxymonosulfate activation over CoFe2O4-BiVO4 photoanode for environmental purification: Unveiling of multi-active sites, interfacial engineering and degradation pathways

This work reported on the development of CoFe₂O₄-BiVO₄ photoanode based photoelectrocatalytic system collaborating with peroxymonosulfate activation for organic contaminants removal. CoFe₂O₄ layer not only provided active sites for direct peroxymonosulfate activation but also accelerated charge separation process for the enhancement of photocurrent density and photoelectrocatalytic performance. Junction of CoFe₂O₄ layer on BiVO₄ photoanode led to the improvement of photocurrent density to 4.43 mA/cm² at 1.23 V_RHE, which was approximately 4.06 times higher than that of pure BiVO₄. Subsequently, the corresponding optimal degradation efficiency toward the tetracycline model contaminant achieved to be 89.1% with total organic carbon removal value of about 43.7% within 60 min. Moreover, the degradation rate constant of CoFe₂O₄-BiVO₄ photoanode in photoelectrocatalytic system was 0.037 min^-1, which was about 1.23, 2.64 and 3.70 times higher than the values in photocatalysis, electrocatalysis and PMS only based systems, respectively. In addition, radical scavenging experiments and electron spin resonance spectra indicated a synergy of radical and nonradical coupling process where •OH and ¹O₂ played vital roles during tetracycline degradation. Plausible photoelectrocatalytic mechanism and degradation pathway were proposed. This work provided an effective strategy to construct peroxymonosulfate assisted photoelectrocatalytic system toward green environmental applications.

Ultrasound-Assisted Synthesis of a ZnO/BiVO4 S-Scheme Heterojunction Photocatalyst for Degradation of the Reactive Red 141 Dye and Oxytetracycline Antibiotic

The preparation of novel sunlight active photocatalysts for complete removal of pollutants from aqueous solutions is a vital research topic in environmental protection. The present work reports the synthesis of a ZnO/BiVO₄ S-scheme heterojunction photocatalyst for degradation of the reactive red dye and oxytetracycline antibiotic in wastewater. ZnO and BiVO₄ were first fabricated by a hydrothermal technique, and then, the ZnO/BiVO₄ heterostructure was synthesized using an ultrasonic route. An increase of the surface area, compared to that of ZnO, was found in ZnO/BiVO₄. The enhancement of charge separation efficiency at the interface was obtained so that a remarkable enhancement of the photocatalytic performance was detected in the prepared heterojunction photocatalyst. Complete detoxification of harmful pollutants was achieved by using the economical solar energy. The removal of the pollutants follows the first-order reaction with the highest rate constant of 0.107 min^-1. The stability of the prepared photocatalyst was detected after five cycles of use. The ZnO/BiVO₄ S-scheme heterostructure photocatalyst still provides high photoactivity even after five times of use. Hydroxyl radicals play an important role in the removal of the pollutant. This work demonstrates a new route to create the step-scheme heterojunction with high photoactivity for complete removal of the toxic dye and antibiotic in the environment.

Ag-Modified ZnO for Degradation of Oxytetracycline Antibiotic and Reactive Red Azo Dye

It is known that low electron-hole separation efficiency is the major disadvantage influencing low photoactivity of the UV-active ZnO photocatalyst. To solve this drawback, the excellent fabrication technique has been used to disperse silver metal on ZnO surface. In this study, an addition of silver content up to 15 wt% was carried out. The 5Ag-ZnO sample, comprising 5 wt% of silver metal, displayed a hexagonal wurtzite structure, and a band gap of 3.00 eV, with high sunlight-active photocatalytic performance of 99-100% and low photo-corrosion problem. The complete degradation of oxytetracycline (OTC) antibiotic and reactive red dye 141 (RR141) dye under natural sunlight was achieved. The highest rate constant of 0.061 min-1 was detected. The enhancement of the performance is mainly due to lowering of the electron-hole recombination rate. Dispersion of silver on ZnO causes the generation of the Schottky barrier at the interface between Ag and ZnO, so that improvement of quantum efficiency and enhancement of the resultant photoactivity could be expected. Furthermore, good distribution of metallic silver also causes a red shift in absorption of light toward the visible spectrum. This is strongly attributed to the surface plasmon resonance effect, which occurred after successful decoration of the noble metal on ZnO. The photocatalyst, with great structural stability, still maintains high photocatalytic efficiency even after five times of use, implying its excellent cycling ability. The present finding offers a new road to generate a silver decorated ZnO photocatalyst for the complete removal of dye and antibiotics contaminated in the environment.

A review on bismuth-based materials for the removal of organic and inorganic pollutants

Modernized lifestyle and increased industrialization threaten living organisms because of the pollutants released from industries and household wastes. The presence of even small amounts of pollutants (organic pollutants (OPs) and inorganic pollutants-heavy metals (HMs)) shows significant effects. Thus wastewater treatment is urgently needed before being subjected to use. Many methods and materials have been developed and reported for the removal of pollutants from wastewater. This review focused on the removal of both OPs and HMs using bismuth-based (Bi-based) materials because of their low toxicity and excellent properties compared to other metals. Bi-based materials as a photocatalyst for photodegradation of OPs are discussed in detail with synthesis methods. Further, since few reviews are available on the Bi-based material for the removal and sensing of HMs, this topic was intentionally summarized. About 200 published articles and reviews have been reviewed here. Additionally, the key point that needs to be focused on the development of Bi-based photocatalysts for the removal of OPs and for upgrading the Bi-based materials as adsorbents for HMs are conferred in the outlook. This will help many researchers in their upcoming work.

Morphological guided sphere to dendrite BiVO4 for highly efficient organic pollutant removal and photoelectrochemical performance under solar light

Monoclinic BiVO₄ (m-BiVO₄) has been reported as promising phase for solar light driven photocatalysis. However, in the case of morphology guided BiVO₄ with different synthetic conditions maintaining the m-BiVO₄ phase remains a substantial challenge for achieving an efficient photocatalyst driven by solar light. Herein, a simple hydrothermal approach was used to produce well-defined template free m-BiVO₄ dendrites with distinct branches for photo catalytically removal of organic pollutant and photocurrent generation. The development of monoclinic dendrite BiVO₄ was confirmed after comprehensive structural, morphological, and optical examinations. FE-SEM images of m-BiVO₄ revealed transformation of spherical to dendritic morphology with distinct branches by simply changing the HNO₃ to NaOH ratios from 2:1 to 2:2, which are named as BVO 2-1 and BVO 2-2, respectively. The BVO 2-2 dendrites exhibited improved activity of 98% towards methylene blue (MB) photodegradation upon simulated solar light irradiation. The BVO 2-2 dendrites photoelectrode showed an outstanding photocurrent density of 1.4245 mAcm^-2 than that of the BVO 2-1 spherical photoelectrode (0.7367 mAcm^-2). Enhanced photocatalytic and photoelectrochemical action, could be ascribed to the unique morphological changes provides photoactive sites, harvest more light utilization together with higher separation of e^-/h⁺ pairs. Furthermore, photocatalytic mechanism is investigated based on scavenger trapping agent, valence band XPS, UV Visible DRS and PL study. Our findings could pave the way for the development of dendritic nanostructure photocatalysts with improved photocatalytic activity.

Solar-light driven photodegradation of antimicrobials, their transformation by-products and antibiotic resistance determinants in treated wastewater

This study aimed to assess the possibility of using solar light-driven photolysis and TiO₂-based photocatalysis to remove (1) antibiotic residues, (2) their transformation products (TPs), (3) antibiotic resistance determinants, and (4) genes identifying the indicator bacteria in a treated wastewater (secondary effluent). 16 antimicrobials belonging to the different classes and 45 their transformation by-products were selected for the study. The most susceptible to photochemical decomposition was tetracycline, which was completely removed in the photocatalysis process and in more than 80% in the solar light-driven photolysis. 83.8% removal (on average) was observed using photolysis and 89.9% using photocatalysis in the case of the tested genes, among which the genes sul1, uidA, and intI1 showed the highest degree of removal by both methods. The study revealed that applied methods promisingly remove the tested antibiotics, their TPs and genes even in such a complex matrix including treated wastewater and photocatalysis process had a higher removal efficiency of antibiotics, TPs and genes tested. Moreover, the high percentage removal of the intI1 gene (>93%) indicates the possibilities of use of the solar light-driven photolysis and TiO₂-based photocatalysis in minimizing the antibiotic resistance genes transfer by mobile genetic elements.

Effect of water-oil ratio on the photocatalytic performance of visible light-active BiVO4 nanoparticles prepared by inverse microemulsion-calcination method

Nowadays, nano-photocatalysts (NPs) have become the research focus in the field of photocatalysis due to their excellent photocatalytic activity, and microemulsion is an effective method to prepare high-efficiency nano-photocatalysts. Here, BiVO₄ NPs with high efficiency under visible light were prepared by a combination of reverse microemulsion method and calcination method. XRD, SEM, TEM, XPS, DRS, PL, BET and other characterization tests were used to comprehensively explore the influence of water-oil ratio on the physicochemical properties of the catalysts. The results show that BiVO₄ NPs of monoclinic scheelite with high crystallization degree can be obtained by this method. The microscopic morphology, specific surface area and total pore volume of BiVO₄ NPs are significantly affected by the water-oil ratio. It is difficult to obtain BiVO₄ NPs with small particle size and uniform dispersion under the condition of too low or too high water-oil ratio. Meanwhile, the photogenerated carrier recombination efficiency of the catalyst is significantly improved, thus reducing the photocatalytic activity of the catalyst. Strikingly, the BiVO₄ NPs obtained under the condition of water-oil ratio is 20 exhibited well-dispersed nanospheres with diameters ranging from 80 to 100 nm. It has the highest photocatalytic activity due to its high crystallinity, large specific surface area and total pore volume and relatively low photogenerated carrier recombination efficiency. Under visible light irradiation, the degradation efficiency of RhB can reach 97.69% in 100 min, and the rate constant is 0.03253 min^-1.

Enhanced Photocatalytic Degradation of Tetracycline and Oxytetracycline Antibiotics by BiVO4 Photocatalyst under Visible Light and Solar Light Irradiation

The efficient degradation of a toxic antibiotic from an aqueous solution is essential for environmental protection. Our research aimed to fabricate a bismuth vanadate (BiVO4) catalyst via a facile hydrothermal method. The prepared catalyst exhibited a monoclinic phase with a band gap energy of 2.33 eV, indicating the excellent visible-light-active properties of a semiconductor. The photocatalytic performance of the synthesized BiVO4 catalyst was studied by determining the removal of tetracycline (TC) and oxytetracycline (OTC) antibiotics. After 240 min, under sunlight conditions, a high performance of 72% and 83% degradation of TC and OTC, respectively, was achieved. The photocatalytic degradation of the antibiotics correlates well with a first-order reaction, with a high rate constant of 0.0102 min−1. Photogenerated electrons and holes played an important role in the removal of the pollutant. After photocatalytic study, the structural stability of the prepared bismuth vanadate photocatalyst was confirmed. The photocatalyst provided a promising performance even after five successive runs. The result indicates the excellent cycling ability of the sample. The present work demonstrates a promising route for the preparation of a BiVO4 catalyst for the complete removal of toxic antibiotics in aqueous solutions.

Recent advances in degradation of organic pollutant in aqueous solutions using bismuth based photocatalysts: A review

Today, a major concern associated with the environment is the water pollution occurred due to the introduction of variety of persistent organic pollutants and residual dyes from different sources (e.g., dye and dye intermediates industries, paper and pulp industries, textile industries, tannery and craft bleaching industries, pharmaceutical industries, etc.) into our natural water resources. Recently, advanced oxidation processes (AOPs) by photocatalyst have garnered great attention as a new frontier promising eco-friendly and sustainable wastewater treatment technology. Utilization of the photocatalytic technology efficiently is significant for cleaner environment. Bismuth based photocatalyst have aroused widespread attention as a visible light responsive photocatalyst for waste water treatment due to their non-toxicity, low cost, modifiable morphology, and outstanding optical and chemical properties. In this review, we have dealt with the research progress on bismuth-based photocatalysts for waste water treatment. However, it seems to give limitation over pristine photocatalysts such as slow migration of charge carriers, charge carrier recombination, low visible light absorption, etc., Various bismuth based photocatalyst and its modifications via doping, heterojunction, Z-scheme etc., are discussed in detail. Further, the strategies adopted to improve the photocatalytic activity of bismuth based photocatalyst to improve the waste water treatment (mostly drugs and dyes) are critically reviewed. Also, we have discussed the bacterial inactivation by bismuth based photocatalyst. Finally, the challenges and future aspects against bismuth based photocatalyst are explored for further research.

Facilitating space charge directional separation for enhancing photocatalytic CO2 reduction over tetragonal BiVO4

Spatially separated Ag/MnOx cocatalysts are selectively loaded on BiVO4 by a photo-deposition method. The synergistic effect of the dual cocatalysts enables the optimal photocatalytic activity of the sample to be 3.1 times higher than that of pristine BiVO4.

Direct complexation of citric acid to synthesize high-efficiency bismuth vanadate through molten polymerization route for the degradation of tetracycline hydrochloride under visible light irradiation

Tetracycline hydrochloride can be efficiently degraded over BiVO4 prepared through direct citric acid complexation.