Facile microwave synthesis of pine cone derived C-doped TiO2 for the photodegradation of tetracycline hydrochloride under visible-LED light

Abatement of microbes and organic pollutants using heterostructural nanocomposites of rice straw CQDs with substituted strontium ferrite

Sustainable use of agricultural waste still remains a challenging task. Herein, we used rice straw as a carbon precursor to prepare carbon quantum dots (CQDs) for photocatalytic applications. Nanocomposites of CQDs with Ti4+ and Mg2+ substituted strontium ferrite (Sr0·4Ti0·4Mg0·2Fe2O4.4) nanoparticles (NPs) in varying w:w ratio was synthesized by ultrasonication method. The successful formation of nanocomposites was confirmed by various microscopic and spectroscopic techniques. The photocatalytic and antibacterial activity of NPs, CQDs and nanocomposites was comparatively evaluated using tetracycline hydrochloride, azure B, Staphylococcus aureus and Escherichia coli as model pollutants. The CQDs-Sr0.4Ti0·4Mg0·2Fe2O4.4 nanocomposite with a w:w ratio of 2:1 showed excellent photocatalytic and antibacterial activity, with the degradation and inactivation efficiency ranging from 97.1% to 99.0% in presence of visible light. The increased specific surface area (117.2 m2/g), and reduction in band gap (2.48 eV-2.09 eV) and decreased photoluminescence intensity of nanocomposites all corroborated these results. The impacting experimental parameters such as catalyst dose, pH and contact time were also examined. Quenching experiments confirmed that hydroxyl radicals (HO∙) radicals and holes (h+) played a vital role in the degradation of pollutants. The kinetics of photodegradation was explained by using the Langmuir-Hinshelwood model. Box-Behnken statistical modelling was used to optimize photocatalytic parameters. Results indicated that the nanocomposite of CQDs with Sr0·4Ti0·4Mg0·2Fe2O4.4 can serve as a promising photocatalyst for the removal of pollutants and microbes.

Development of efficient and economic Bi2O3/BN/Co3O4 composite photocatalyst: Degradation mechanism, pathway and toxicity study of norfloxacin

The production of cheap, efficient, and stable photocatalysts for degrading antibiotic contaminants remains challenging. Herein, Bi2O3/boron nitride (BN)/Co3O4 ternary composites were synthesized using the impregnation method. The morphological characteristics, structural features, and photochemical properties of the prepared photocatalysts were investigated via X-ray diffraction, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy, and ultraviolet-visible (Vis) diffuse reflectance spectrum techniques. BN was used as a charge transfer bridge in the ternary composites, which afforded a heterojunction between the two semiconductors. The formation of the heterojunction substantially enhanced the charge separation and improved the photocatalyst performance. The degradation activity of the Bi2O3/BN/Co3O4 ternary composites against norfloxacin (NOR) under Vis light irradiation was investigated. The degradation rate of NOR using 5-wt% Bi2O3/BN/Co3O4 reached 98% in 180 min, indicating excellent photocatalytic performance. The ternary composites also exhibited high photostability with a degradation efficiency of 88.4% after five cycles. Hydroxyl radicals (•OH), superoxide radicals (•O2-), and holes (h+) played a synergistic role in the photocatalytic reaction, where h+ and •O2- were more important than •OH. Consequently, seven intermediates and major photocatalytic degradation pathways were identified. Toxicity experiments showed that the toxicity of the degradation solution to Chlorella pyrenoidosa decreased. Finally, the ecotoxicity of NOR and its intermediates were analyzed using the Toxicity Estimation Software Tool, with most intermediates exhibiting low toxicity.

Recent progress in TiO2-biochar-based photocatalysts for water contaminants treatment: strategies to improve photocatalytic performance

Toxic organic pollutants in wastewater have seriously damaged human health and ecosystems. Photocatalytic degradation is a potential and efficient tactic for wastewater treatment. Among the entire carbon family, biochar has been developed for the adsorption of pollutants due to its large specific surface area, porous skeleton structure, and abundant surface functional groups. Hence, combining adsorption and photocatalytic decomposition, TiO2-biochar photocatalysts have received considerable attention and have been extensively studied. Owing to biochar's adsorption, more active sites and strong interactions between contaminants and photocatalysts can be achieved. The synergistic effect of biochar and TiO2 nanomaterials substantially improves the photocatalytic capacity for pollutant degradation. TiO2-biochar composites have numerous attractive properties and advantages, culminating in infinite applications. This review discusses the characteristics and preparation techniques of biochar, presents in situ and ex situ synthesis approaches of TiO2-biochar nanocomposites, explains the benefits of TiO2-biochar-based compounds for photocatalytic degradation, and emphasizes the strategies for enhancing the photocatalytic efficiency of TiO2-biochar-based photocatalysts. Finally, the main difficulties and future advancements of TiO2-biochar-based photocatalysis are highlighted. The review gives an exhaustive overview of recent progress in TiO2-biochar-based photocatalysts for organic contaminants removal and is expected to encourage the development of robust TiO2-biochar-based photocatalysts for sewage remediation and other environmentally friendly uses.

Multifunctional Cu:ZnS quantum dots for degradation of Amoxicillin and Dye Sulphon Fast Black-F and efficient determination of urea for assessing environmental aspects

This work is particularly aimed at the preparation of ZnS and Cu doped ZnS (Cu:ZnS) QDs by facile and easy technique, chemical precipitation method for the degradation of water pollutants and a simple scheme was proposed to prepare the urea-sensing system. The morphological and optical properties of the synthesized QDs was studied using high resolution transmission and scanning electron microscopes, X-ray diffraction, energy dispersive X-ray analysis, fluorescence and ultraviolet-visible spectroscopy, differential thermal and thermogravimetric analyses, Brunauer-Emmett-Teller analysis. The photocatalytic performance was systematically assessed by the photodegradation of an important pharmaceutical water pollutant, Amoxicillin (AMX) and a dye Fast Sulphon Black F (SFBF) in aqueous medium under UV light irradiation. Also, a very sensitive system was prepared by depositing the dots over an indium-tin-oxide (ITO) glass substrate for the sensing of biologically active molecule urea as it is an important monitor of public health in water and soil productivity. The results illustrated excellent photocatalytic efficiency (86.46% for AMX and 99.41% for SFBF) with stability up to four cycles of degradation reaction. The optimal photocatalyst dosage for achieving maximum removal of AMX was found to be 70 mg at a pH of 9.5, with a treatment time of 40 min. Similarly, for SFBF, the optimal photocatalyst dosage was determined to be 60 mg at pH 9, with a treatment time of 60 min. Further, the electrochemical analysis was done by fabricating Urease enzyme (UR)/Cu:ZnS QDs/ITO bioelectrode and then the fabricated bioelectrode, was utilized to determine the different concentrations of urea by cyclic voltammetry. Thus, the obtained limit of detection and sensitivity of the fabricated biosensing device for urea detection was obtained to be 0.0092 μM and 12 μA μM-1cm-2, respectively; under the optimized experimental conditions. Hence, it is anticipated that Cu:ZnS QDs can also successfully be applied as a promising material for fabrication of novel bioelectrode for urea determination and the biosensing platform is desirable and viable.

Boosting Tetracycline Degradation with an S-Scheme Heterojunction of N-Doped Carbon Quantum Dots-Decorated TiO2

N-doped carbon quantum dots (N-CQDs) derived from the Rumex crispus L. plant were incorporated into TiO₂ via a facile hydrothermal method. As-prepared materials were characterized and used in the photocatalytic tetracycline (TC) degradation under UVA light irradiation by examining several operational parameters involving the N-CQDs amount, initial TC concentration, pH, and photocatalytic reaction time. XRD analysis revealed the conversion of the rutile phase to the anatase phase after the incorporation of N-CQDs into the TiO₂ structure. The results revealed that the N-CQDs/TiO₂ photocatalysts demonstrated the highest efficiency in TC degradation compared to other processes of adsorption, photolysis (UVA), and photocatalysis with TiO₂ (TiO₂/UVA). Under optimized conditions, 10 mg/L TC at pH 5.15 with 0.2 g/L N-CQDs/TiO₂ catalyst showed 97.7% photocatalytic degradation for 120 min under UVA irradiation. The formation of an S-scheme heterojunction between N-CQDs and TiO₂ provided enhanced charge separation and strong redox capability, causing significant improvement in the photocatalytic performance of N-CQDs/TiO₂. Trapping experiments showed that O₂^•- and h⁺ are the predominant reactive species for the TC elimination in an aqueous solution.

Efficient Removal of Tetracycline and Bisphenol A from Water with a New Hybrid Clay/TiO2 Composite

New TiO₂ hybrid composites were prepared from kaolin clay, predried and carbonized biomass, and titanium tetraisopropoxide and explored for tetracycline (TET) and bisphenol A (BPA) removal from water. Overall, the removal rate is 84% for TET and 51% for BPA. The maximum adsorption capacities (q_m) are 30 and 23 mg/g for TET and BPA, respectively. These capacities are far greater than those obtained for unmodified TiO₂. Increasing the ionic strength of the solution does not change the adsorption capacity of the adsorbent. pH changes only slightly change BPA adsorption, while a pH > 7 significantly reduces the adsorption of TET on the material. The Brouers-Sotolongo fractal model best describes the kinetic data for both TET and BPA adsorption, predicting that the adsorption process occurs via a complex mechanism involving various forces of attraction. Temkin and Freundlich isotherms, which best fit the equilibrium adsorption data for TET and BPA, respectively, suggest that adsorption sites are heterogeneous in nature. Overall, the composite materials are much more effective for TET removal from aqueous solution than for BPA. This phenomenon is assigned to a difference in the TET/adsorbent interactions vs the BPA/adsorbent interactions: the decisive factor appears to be favorable electrostatic interactions for TET yielding a more effective TET removal.

Zeolite Y-supported carbon-doped TiO2 nanocomposites: Efficient solar photocatalysts for the purification of medicinal wastewater

The existence of antibiotics in aquatic streams destroys water quality and thereby poses serious ecological hitches. Photocatalysis involving nanosemiconductors is an environmentally benign technique for the mineralization of antibiotics. Herein, we prepared a new visible light-sensitive photocatalyst, zeolite Y-supported carbon-doped TiO₂ nanocomposite (zeolite Y-c-TiO₂), for the elimination of cefazolin antibiotic in wastewater systems. The structural and optical properties of the synthesized nanocomposites were investigated by Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller surface area analysis (BET) as well as diffuse reflectance spectroscopy (UV-DRS) and photoluminescence spectroscopy (PL). The UV-Vis absorbance spectrum of zeolite Y-c-TiO₂ exhibited a red shift towards longer wavelength with an increase in visible light absorption as compared to pure TiO₂ nanoparticles and zeolite Y-supported TiO₂ nanocomposites (zeolite Y-TiO₂). Accordingly, the photocatalytic action of the zeolite Y-c-TiO₂ for the degradation of methylene blue was evaluated under solar simulator, and it turned out to be highly efficient (100%) mineralization as compared to TiO₂-nanoparticles (42%) and zeolite Y-TiO₂ (62%) after 70 min irradiation for a 50mg L^-1 methylene blue solution. Radical scavenging experiments revealed the involvement of hydroxyl radicals, superoxide radicals, and photogenerated holes in the degradation process. Consequently, zeolite Y-c-TiO₂ was applied for the photocatalytic degradation of the cefazolin antibiotic in water, and complete degradation of cefazolin (50 mg L^-1) was observed within 6 h of solar light irradiation on zeolite Y-c-TiO₂. The degradation pathway of cefazolin was proposed by considering various intermediates detected via LC-MS analysis. The study points to the significant potential of zeolite Y-c-TiO₂ photocatalyst for the purification of medicinal wastewater under sunlight.

Visible-Light-Driven Photocatalytic Degradation of Tetracycline Using Heterostructured Cu2O-TiO2 Nanotubes, Kinetics, and Toxicity Evaluation of Degraded Products on Cell Lines

This study first reports on the tetracycline photodegradation with the synthesized heterostructured titanium oxide nanotubes coupled with cuprous oxide photocatalyst. The large surface area and more active sites on TiO₂ nanotubes with a reduced band gap (coupling of Cu₂O) provide faster photodegradation of tetracycline under visible light conditions. Cytotoxicity experiments performed on the RAW 264.7 (mouse macrophage) and THP-1 (human monocytes) cell lines of tetracycline and the photodegraded products of tetracycline as well as quenching experiments were also performed. The effects of different parameters like pH, photocatalyst loading concentration, cuprous oxide concentration, and tetracycline load on the photodegradation rate were investigated. With an enhanced surface area of nanotubes and a reduced band gap of 2.58 eV, 1.5 g/L concentration of 10% C-TAC showed the highest efficiency of visible-light-driven photodegradation (∼100% photodegradation rate in 60 min) of tetracycline at pH 5, 7, and 9. The photodegradation efficiency is not depleted up to five consecutive batch cycles. Quenching experiments confirmed that superoxide radicals and hydroxyl radicals are the most involved reactive species in the photodegradation of tetracycline, while valance band electrons are the least involved reactive species. The cytotoxicity percentage of tetracycline and its degraded products on RAW 264.7 (-0.932) as well as THP-1 (-0.931) showed a negative correlation with the degradation percentage with a p-value of 0.01. The toxicity-free effluent of photodegradation suggests the application of the synthesized photocatalyst in wastewater treatment.

The Preparation of {001}TiO2/TiOF2 via a One-Step Hydrothermal Method and Its Degradation Mechanism of Ammonia Nitrogen

{001}TiO₂/TiOF₂ photocatalytic composites with a high activity {001} crystal plane were prepared by one-step hydrothermal methods using butyl titanate as a titanium source and hydrofluoric acid as a fluorine source. X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), raman spectroscopy, N₂ adsorption-desorption curve (BET), UV-Vis diffuse absorption spectroscopy (UV-Vis DRS), X-ray photoelectron spectroscopy (XPS), and fluorescence spectroscopy (PL) were used to evaluate the structure, morphology, specific surface area, optical properties, and photocarrier separation ability of {001}TiO₂/TiOF₂. Ammonia nitrogen was taken as the target pollutant, and the degradation performance of the catalyst was investigated. The results show that hydrofluoric acid improves the content of {001} crystal plane of TiO₂ with high activity; it also improves the specific surface area and dispersion of the composite material and adjusts the ratio of {001}TiO₂ to TiOF₂ in the composite material to enhance the absorption capacity of the composite material and reduce the band gap width of the composite material. The degradation rate of ammonia nitrogen by 100 mg F15 is 93.19% when the initial concentration of ammonia nitrogen is 100 mg/L and pH is 10. Throughout the reaction process, the {001}TiO₂/TiOF₂ composite produces superoxide anion radical (·O₂^-) and hydroxyl radical (·OH) to oxidize NH₃·H₂O and generate N₂ accompanied by a small amount of NO₃^- and NO₂^-.

Structure, light absorption properties and photocatalytic activity of carbon-containing titania nanocomposites synthesized via a facile sol-gel method

Facile and green sol–gel method was used to synthesize carbon-containing titania nanopowder, and diethanolamine (DEA) was used as the in situ carbon source. The titania gel was heat treated at temperatures ranging from 300 to 700 °C. X-ray diffraction (XRD), thermal analysis, and Raman spectroscopy reported no crystalline phase at <325 °C. Crystallization of the anatase phase with traces of brookite phases was observed at T > 325 °C, followed by a transformation to anatase/rutile in the range of 400 °C < T ≤ 650 °C. Finally, the complete phase transformation to the rutile phase occurs at temperatures of T > 650 °C. High-resolution electron microscopy (HREM) micrographs confirm the coexistence of anatase and rutile nanocrystals and amorphous carbon clusters in the composite samples. Chemical element analysis via X-ray photoelectron spectroscopy (XPS) indicated nonstoichiometry in the O/Ti ratio, the presence of (Ti³⁺) oxidation state, and elemental carbon. Thermogravimetric (TG) measurements are the most accurate method to measure the carbon content in samples. UV-vis spectroscopy demonstrated considerable enhancement in the optical absorption properties and electronic structure of prepared samples compared to the pure anatase and rutile. This enhancement is strongly correlated with the structure and composition of prepared samples and consequently depends on the preparation method as well as conditions. Innovative features such as self-cleaning action was demonstrated in carbon containing titanate nanocomposite.

High-performance photocatalytic membranes for water purification in relation to environmental and operational parameters

Growing technologies, increasing population and environmental pollution lead to severe contamination of water and require advanced water treatment technologies. These aspects lead to the need to purify water with advanced smart materials. This paper reviews the recent advances (during the last 5 years) in photocatalytic composite membranes used for water treatment. For this purpose, the authors have reviewed the main materials used in the development of (photocatalytic membranes) PMs, environmental and operational factors affecting the performance of photocatalytic membranes, and the latest developments and applications of PMs in water purifications. The composite photocatalytic membranes show good performance in the removal and degradation of pollutants from water.

The development of biomass-derived carbon-based photocatalysts for the visible-light-driven photodegradation of pollutants: a comprehensive review

Biomass-derived carbonaceous materials have recently attracted extensive interest on account of their exceptional physicochemical properties which make them promising candidates for various critical applications. Several achieved advances have been reported in the recent literature, mainly focusing on the areas of energy storage and conversion. There is no review dedicated specifically to the potential applications of biomass-derived carbon-based photocatalytic materials for environmental remediation using the visible spectral region. The excellent characteristics of carbon materials, such as good electronic conductivity, unique nanocrystal structures, inherent hydrophobicity, and the tunable surface characteristics, are fully compatible with diverse catalytic reactions including organic transformations and photocatalysis processes. Importantly, biomass-carbon-based materials are considered to be green and viable alternative photocatalysts due to their environmentally friendly and naturally abundant nature. This work aims to provide a comprehensive review of recent advances relating to the synthesis of biomass-derived carbon-based photocatalysts, focusing on their potential for the photodegradation of various pollutants. First, potential natural biomass sources, various synthetic routes, and the properties of carbon materials are systematically discussed. Recent advances in the production of biomass-carbon-based photocatalysts (including material design, mechanisms, and photocatalytic performance) are highlighted. Regarding ideas for the development of new biomass-derived photocatalysts, we outline research gaps that are worthy of further research in the future.

High mesoporosity phosphorus-containing biochar fabricated from Camellia oleifera shells: Impressive tetracycline adsorption performance and promotion of pyrophosphate-like surface functional groups (C-O-P bond)

In China, more than 3.5 million tons of Camellia oleifera discarded shells are produced every year. This work first prepared phosphorus-containing biochar (PBC) from C. oleifera shells and was successfully applied to the efficient removal of tetracycline (TC) from solutions. The prepared PBC exhibits superior TC adsorption capacity of 451.5 mg/g, and TC uptake rapidly reached 315.5 mg/g at the first 5 min (C₀ = 50 mg/L). Furthermore, PBC also shows excellent applicability to the broad range pH value (1-9) and superior selective removal in the presence of various high concentration coexisting ions (1 mM). Mechanisms underlying TC adsorption were also put forward, and analysis suggested that pyrophosphate-like surface functional groups (C-O-P bond) played a critical role in this process. Notably, treating pharmaceutical wastewater with PBC can efficiently reduce chemical oxygen demand (COD) and total organic carbon (TOC) concentration below the discharge standard of China (GB21904-2008).

Structure, Photoluminescence Emissions, and Photocatalytic Activity of Ag2SeO3: A Joint Experimental and Theoretical Investigation

In this paper, we report the synthesis of silver selenite (Ag₂SeO₃) by different methods [sonochemistry, ultrasonic probe, coprecipitation, and microwave-assisted hydrothermal methods]. These microcrystals presented a structural long-range order as confirmed by X-ray diffraction (XRD) and Rietveld refinements and a structural short-range order as confirmed by Fourier transform infrared (FTIR) and Raman spectroscopies. X-ray photoelectron spectroscopy (XPS) provided information about the surface of the samples indicating that they were pure. The microcrystals presented different morphologies and sizes due to the synthesis method as observed by field emission scanning electron microscopy (FE-SEM). The optical properties of these microcrystals were evaluated by ultraviolet-visible (UV-vis) spectroscopy and photoluminescence (PL) measurements. Thermal analysis confirmed the temperature stability of the as-synthetized samples. Further trapping experiments prove that the holes and hydroxyl radicals, to a minor extent, are responsible for the photocatalytic reactions. The experimental results are sustained by first-principles calculations, at the density functional theory (DFT) level, to decipher the structural parameters, electronic properties of the bulk, and surfaces of Ag₂SeO₃. By matching the experimental FE-SEM images and theoretical morphologies, we are capable of finding a correlation between the morphology and photocatalytic activity, along with photodegradation of the Rhodamine B dye under UV light, based on the different numbers of unsaturated superficial Ag and Se cations (local coordination, i.e., clusters) of each surface.

Metal-organic frameworks derived C/TiO2 for visible light photocatalysis: Simple synthesis and contribution of carbon species

A series of in-situ carbon-doped TiO₂ (C_x/TiO₂) composites with a porous and crystalline structure were successfully synthesized via one-step and low-temperature calcination of titanium metal-organic framework (MOF), MIL-125(Ti). The resultant materials were comprehensively investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), N₂ adsorption-desorption measurements, UV-vis diffuse reflectance spectrum (DRS), photoluminescence (PL) spectra and photoelectrochemical measurements, and their photocatalytic activities for bisphenol A (BPA) degradation were assessed. Compared with the benchmark TiO₂ photocatalyst (P25), the C_x/TiO₂ composite material with high specific surface, lower band gap, and reduced photogenerated electron hole ratio exhibited outstanding photodegradation activity and durability for BPA, which could be attributed to the combined effect of co-doping of multiple carbon species (substituent carbon and carbonate) and porous structure. During BPA degradation, the holes and superoxide radicals were the primary role oxidative species in the reaction process. Therefore, this new efficient photocatalyst is promising candidate for photodegradation of organic pollutants.

Plasma Treatment as a Promising Environmentally Benign Approach for Synthesis of Valuable Multi-gas Doped Nano-TiO2 -P25: An Efficient Way to Boost the Photocatalytic Performance under Visible Light Illumination

An ingenious prospect has been established to synthesize a wide range of non-metal-doped TiO₂ -P25 by plasma technique. Different atmospheres (Air, O₂ , N₂ , Ar and CO₂ ) have been embedded on the surface of TiO₂ -P25 by plasma treating as an effective alternative to wet chemical pretreatment processes. This approach is clean beyond recognition by employing pure gases as well as no need to poison precursors or organic solvents without producing waste stream, which surprisingly can meet green chemistry purposes. More specifically, plasma has been a contributing factor in the narrowing band gap energies of doped photocatalysts in comparison with pure TiO₂ -P25. Synthesized photocatalysts gained enormous benefit from the plasma treatment in the selective oxidation of benzyl alcohols to associating aldehydes under blue LED illumination with excellent yields, which dramatically decreased the time reaction to many folds. Additionally, benzaldehyde formation under influence of various wavelengths of visible light, including blue photons (λ_max = 460 nm), green photons (λ_max = 510 nm) and red photons (λ_max = 630 nm) was compared to assess the effect of plasma treating on photoactivity of nano-TiO₂ -P25. Furthermore, as-prepared photocatalysts were investigated by diverse characterization techniques.

Sonochemical synthesis of graphitic carbon nitride-manganese oxide interfaces for enhanced photocatalytic degradation of tetracycline hydrochloride

The present study focuses on the sonochemical synthesis of graphitic carbon nitride-manganese oxide (GCN/MnO₂) nanocomposite for photocatalytic degradation of an environmentally hazardous pharmaceutical compound, tetracycline hydrochloride (TcH). The sonochemical synthesis aided in tailoring the morphology of GCN/MnO₂. The characterization results of SEM/FESEM, XRD, FTIR, UV-Vis spectra, EIS, CV, etc., revealed on the morphology, composition, crystallinity, and other photo-electro-intrinsic properties of the materials. The synergy of GCN and MnO₂ results in rapid electron transfer, efficient visible-light absorption, and slower electron-hole pair recombination through its photo-responsive traits against TcH. It was noted that ~ 93% TcH (20 mg L^-1) degradation was achieved for 30-mg catalyst dose under light-emitting diode (LED) irradiation (9 W, 220 V) in 135-min duration. The TcH mineralization results were well fit to pseudo-first-order kinetics with a rate constant of 0.02 min^-1 (R² = 0.994). In addition, the composite possessed fair reusability for consequent cycles. Hence, the as-synthesized composite applied for photocatalysis and photoelectrocatalysis fosters a fit-for-purpose and reliable system in the decontamination of TcH in environmental samples. Graphical Abstract.

Conventional and emerging technologies for removal of antibiotics from wastewater

Antibiotics and pharmaceuticals related products are used to enhance public health and quality of life. The wastewater that is produced from pharmaceutical industries still contains noticeable amount of antibiotics, and this has remained one of the major environmental problems facing public health. The conventional wastewater remediation approach employed by the pharmaceutical industries for the antibiotics wastewater removal is unable to remove the antibiotics completely. Besides, municipal and livestock wastewater also contain unmetabolized antibiotics released by human and animal, respectively. The antibiotic found in wastewater leads to antibiotic resistance challenges, also emergence of superbugs. Currently, numerous technological approaches have been developed to remove antibiotics from the wastewater. Therefore, it was imperative to critically review the weakness and strength of these current advanced technological approaches in use. Besides, the conventional methods for removal of antibiotics such as Klavaroti et al., Homem and Santos also discussed. Although, membrane treatment is discovered as the ultimate choice of approach, to completely remove the antibiotics, while the filtered antibiotics are still retained on the membrane. This study found, hybrid processes to be the best solution antibiotics removal from wastewater. Nevertheless, real-time monitoring system is also recommended to ascertain that, wastewater is cleared of antibiotics.

Assessing the Photocatalytic Degradation of Fluoroquinolone Norfloxacin by Mn:ZnS Quantum Dots: Kinetic Study, Degradation Pathway and Influencing Factors

Norfloxacin (NOFX), a broadly used fluoroquinolone antibiotic, has been a subject of great concern in the past few years due to its undesirable effect on human beings and aquatic ecosystems. In this study, novel Mn doped ZnS (Mn:ZnS) quantum dots (QDs) were prepared through a facile chemical precipitation method and used as photocatalysts for NOFX degradation. Prior to photodegradation experiments, morphological and optical parameters of the QDs were examined through transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray analysis, Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, fluorescence spectroscopy, Brunauer-Emmett-Teller analysis, and differential thermal and thermogravimetric analyses. Mn:ZnS QDs exhibited excellent properties of photodegradation, not only under UV irradiation but also in sunlight, which induced NOFX to photodegrade. The utmost photodegradation efficiency was obtained under optimal conditions (25 mL of NOFX, 15 mg/L, pH 10, 60 min UV irradiation, 60 mgs QDs), adopting first order kinetics. In addition, hydroxyl radicals produced by the conduction band electrons were found to be the primary reason dominating the transformation of NOFX in basic conditions, while holes, oxygen atoms, as well as the doped metal (Mn) enhanced the degradation. The QDs showed excellent reusability and stability in four repeated cycles. Finally, four different pathways were predicted, derived from the identified intermediates, with piperazinyl ring transformation being the primary one. It is expected that the synthesized Mn:ZnS QDs could be utilized as efficient photocatalytic materials for energy conversion and ecological remediation.

Comparative study of the photocatalytic degradation of 2-chlorophenol under UV irradiation using pristine and Ag-doped species of TiO2, ZnO and ZnS photocatalysts

A comparative photocatalytic degradation of 2-chlorophenol (2CP) in aqueous solution was investigated using pristine and Ag-doped semiconductor photocatalysts obtained from TiO₂, ZnO and ZnS. Varying percentages (1, 3 and 5%) of Ag nanoparticles were doped on the semiconductor photocatalysts via the sol-gel method. The pristine and Ag-doped photocatalysts were characterized using UV-Vis diffuse reflectance spectroscopy, photo-luminescence spectroscopy, X-Ray diffractometry, Fourier transform infrared spectroscopy and transmission electron microscopy; and these techniques confirmed the successful syntheses of the pristine and Ag-doped species. The photocatalytic activities of all species for the degradation of 2CP were carried in photo-reactor using UV irradiation intensity of 1.4 mW/cm² for 150 min; and the effects of various operating parameters (such as catalyst loading, pH and 2CP initial concentrations) were studied. The results showed enhanced 2CP degradation in the Ag-doped species in comparison to the pristine species while alkaline pH region was most suitable for 2CP degradation especially at low concentration. Lower loadings of the photocatalysts were usually more effective for the 2CP degradation and the degradation trend in the TiO₂ and ZnS species was 5% Ag-doped >3% Ag-doped >1% Ag-doped > Pristine, while it was 1% Ag-doped >3% Ag-doped >5% Ag-doped > Pristine in the ZnO. Thus, although the Ag doping enhanced 2CP by all semiconductor photocatalysts, the Ag-doped TiO₂ was more effective than the ZnO and ZnS species.

Transformation of novel TiOF2 nanoparticles to cluster TiO2-{001/101} and its degradation of tetracycline hydrochloride under simulated sunlight

The anatase type cluster TiO₂-{001/101} was rapidly generated by a one-step hydrothermal method. The transformation process of coral-like TiOF₂ nanoparticles to cluster TiO₂-{001/101} was investigated for the first time, and the sensitization between cluster TiO₂-{001/101} and tetracycline hydrochloride (TCH) was also discussed. The degradation rate of TCH by cluster TiO₂-{001/101} under simulated sunlight was 92.3%, and the total removal rate was 1.76 times that of P25. Besides, cluster TiO₂-{001/101} settles more easily than P25 in deionized water. The study showed that cluster TiO₂-{001/101} derived from coral-like TiOF₂ nanoparticles had a strong adsorption effect on TCH, which was attributed to the oxygen vacancy (O_v) and {001} facets of cluster TiO₂-{001/101}. The strong adsorption effect promoted the sensitization between cluster TiO₂-{001/101} and TCH, and widened the visible light absorption range of cluster TiO₂-{001/101}. In addition, the fluorescence emission spectrum showed that cluster TiO₂-{001/101} had a lower luminous intensity, which was attributed to the heterojunction formed by {001} facets and {101} facets that reduces the recombination rate of carriers. It should be noted that cluster TiO₂-{001/101} still has good degradation performance for TCH after five cycles of degradation. This study provides a new idea for the synthesis of cluster TiO₂-{001/101} with high photocatalytic performance for the treatment of TCH wastewater.

Degradation of tetracycline hydrochloride by cluster TiO₂-{001/101} under simulated sunlight.

Highly efficient visible-light photoactivity of Z-scheme MoS2/Ag2CO3 photocatalysts for organic pollutants degradation and bacterial inactivation

Here, a novel Z-scheme MoS₂/Ag₂CO₃ heterojunction photocatalyst was assembled from two-dimensional MoS₂ nanosheets and Ag₂CO₃ nanoparticles through facile hydrothermal and in-situ precipitation method. The MoS₂/Ag₂CO₃ heterojunction exhibited much enhanced visible-light photocatalytic performance in probe experiment for organic pollutants degradation and Escherichia coli (E. coli) inactivation compared to pristine Ag₂CO₃ and MoS₂. The degradation rates of Lanasol Red 5B, rhodamine B, ciprofloxacin, and metronidazole reached 95%, 90%, 80%, and 72%, respectively. On the other hand, E. coli was completely inactivated in 80 min in the presence of 5%-MoS₂/Ag₂CO₃. The improved photocatalytic performance was ascribed to the enhanced photogenerated charge separation efficiency and increased lifetime of the charge carriers, proved by photoluminescence spectra, time-resolved fluorescence emission decay spectra, and electrochemical measures. In addition, the active species trapping and ESR experiments all indicated that holes (h⁺) exhibited a significant contribution and superoxide radicals (O₂^-) acted as assistants. Based on experiment results, the photocatalytic enhancement mechanism for organic pollutants degradation and E. coli inactivation was discussed. The effect of representative environmental factors on the degradation of Lanasol Red 5B was investigated. The experiment results indicated that the degradation efficiency was partially influenced in the presence of inorganic salt. Furthermore, the appearance of a small amount of Ag nanoparticles not only enhanced the charge transfer, but also improved the stability of photocatalyst. Overall, MoS₂/Ag₂CO₃ heterojunction has a great application potential for future water purification.

Sonochemical Synthesis of Ce-doped TiO2 Nanostructure: A Visible-Light-Driven Photocatalyst for Degradation of Toluene and O-Xylene

Ce-doped TiO2 nanostructures (CeT) with different amounts of Ce (0.5, 0.75, 1.0, 1.5, and 2.0 wt.%) were synthesized using a sonochemical processing method. The physicochemical properties of the prepared samples were explored using UV-visible diffuse reflectance spectroscopy (UV-vis DRS), field-emission TEM (FE-TEM), XRD, X-ray photoelectron spectroscopy (XPS), photoluminescence spectroscopy (PL), and surface area and pore size analyzers. The photocatalytic performance of the prepared CeT was assessed by monitoring their degradation efficiencies for gaseous toluene and o-xylene-widely known as significant indoor air pollutants-under daylight irradiation. The prepared CeT exhibited significantly improved photocatalytic performance towards the degradation of toluene and o-xylene, which was much higher than that observed for pure TiO2 and commercial P25 TiO2. Particularly, photocatalytic degradation efficiencies by the prepared CeT catalysts increased remarkably in the case of o-xylene (up to 99.4%) compared to toluene (up to 49.1%). The degradation efficiency by the CeT was greatest for the CeT-0.75 sample, followed by, in order, CeT-1.0, CeT-0.5, CeT-1.5, and CeT-2.0 samples in agreement with the order of the surface area and the particle size of the catalysts. According to the change of light source, the average decomposition efficiencies for toluene and o-xylene by CeT-0.75 were shown in the order of conventional daylight lamp > violet light emitting diodes (LEDs) > white LEDs. The decomposition efficiencies normalized to supplied electric power, however, were estimated to be in the following order of violet LEDs > white LEDs > conventional daylight lamp, indicating that the LEDs could be a much more energy efficient light source for the photodecomposition of target toluene and o-xylene using the CeT-0.75 photocatalyst.