CTAB and SDS assisted facile fabrication of SnO2 nanoparticles for effective degradation of carbamazepine from aqueous phase: A systematic and comparative study of their degradation performance

The effects of water, substrate, and intermediate adsorption on the photocatalytic decomposition of air pollutants over nano-TiO2 photocatalysts

The photocatalytic performance of nano-TiO2 photocatalysts in air pollutant degradation greatly depends on the adsorption of water, substrates, and intermediates. Especially under excessive humidity, substrate concentration, and intermediate concentration, the competitive adsorption of water, substrates, and intermediates can seriously inhibit the photocatalytic performance. In the past few years, extensive studies have been performed to investigate the influence of humidity, substrate concentration, and intermediates on the photocatalytic performance of TiO2, and significant advances have been made in the area. However, to the best of our knowledge, there is no review focusing on the effects of water, substrate, and intermediate adsorption to date. A comprehensive understanding of their mechanisms is key to overcoming the limited application of nano-TiO2 photocatalysts in the photocatalytic decomposition of air pollutants. In this review, the progress in experimental and theoretical fields, including a recent combination of photocatalytic experiments and adsorption and photocatalytic simulations by density functional theory (DFT), to explore the impact of adsorption of various reaction components on nano-TiO2 photocatalysts is comprehensively summarized. Additionally, the mechanism and broad perspective of the impact of their adsorption on the photocatalytic activity of TiO2 in air treatment are also critically discussed. Finally, several solutions are proposed to resolve the current problems related to environmental factors. In general, this review contributes a comprehensive perspective of water, substrate, and intermediate adsorption toward boosting the photocatalytic application of TiO2 nanomaterials.

Mechanism analysis of efficient degradation of carbamazepine by chalcopyrite-activated persulfate

In this study, natural chalcopyrite (NCP) was used to activate peroxymonosulfate (PMS) to degrade carbamazepine (CBZ) oxidatively. Before and after the NCP reaction, the physical and chemical properties were characterized by SEM-EDS, XRD, XPS, XRF, and VSM. The effects of the amount of NCP and PMS, the initial pH value, and the reaction temperature on the catalytic performance of NCP were systematically studied. The research results show that the degradation efficiency of the NCP/PMS system for CBZ can reach 82.34% under the optimal reaction conditions, and the degradation process follows a pseudo-second-order kinetic model. The results of the radical quenching experiment and EPR analysis show that the active species in the system are OH·, SO₄^-·, and ¹O², of which SO₄^-· is the main active species. In addition, this study shows that the NCP/PMS system can degrade CBZ with high efficiency of 90.73% only with the assistance of 0.15 g/L Fe⁰. This study determined the optimal reaction conditions for natural chalcopyrite to activate PMS to degrade CBZ and clarified the activation mechanism, which broadened the application of natural ores in the field of water treatment.

Photocatalytic degradation mechanism of phenanthrene over visible light driven plasmonic Ag/Ag3PO4/g-C3N4 heterojunction nanocomposite

Visible light driven plasmonic Ag/Ag₃PO₄/g-C₃N₄ heterojunction nanocomposite with regular morphology was prepared via a modified facile method. The two-dimensional ultrathin g-C₃N₄ nanosheet is uniformly wrapped on the surface of Ag₃PO₄ nanopolyhedron. A charge transfer bridge was built between Ag₃PO₄ nanopolyhedron and g-C₃N₄ nanosheet due to the reduction of Ag nanoparticles. This structure can inhibit the recombination of photogenerated electron-hole pairs and promote the transfer of photogenerated carriers, so as to produce more active species for participating in the photocatalytic reaction. In addition, the surface plasmon resonance (SPR) of appropriate Ag nanoparticles enhanced the absorption and utilization of visible light. Compared with Ag₃PO₄ and Ag/Ag₃PO₄, Ag/Ag₃PO₄/g-C₃N₄ showed higher photocatalytic activity. Under visible light irradiation, the degradation rate of phenanthrene (PHE) was 0.01756 min^-1, which was 3.14 times and 2.38 times that of Ag₃PO₄ and Ag/Ag₃PO₄, respectively. After four cycles of photocatalytic reaction, the Ag/Ag₃PO₄/g-C₃N₄ photocatalyst still maintained high photocatalytic activity. The active sites of PHE were predicted by Gaussian simulation calculation and combined with intermediate products identification of GC-MS, the possible degradation pathway of PHE was speculated. This research has reference significance for the construction of plasmonic heterojunction photocatalyst in the field of environmental pollution remediation.

Photo-Fenton degradation of carbamazepine and ibuprofen by iron-based metal-organic framework under alkaline condition

Metal-organic frameworks have been widely used as photocatalytic materials. In this paper, a novel photocatalyst HSO₃-MIL-53(Fe) with acidity regulating groups was successfully synthesized by the solvothermal method and applied to remove carbamazepine (CBZ) and ibuprofen (IBP). The photodegradation efficiency of vis/H₂O₂/HSO₃-MIL-53(Fe) can reach 100% when the pH value is 8 or 9. The free radical capture experiment and electron paramagnetic resonance analysis proved that hole (h⁺), hydroxide radical (·OH), singlet oxygen (¹O₂), and superoxide Radical (·O₂^-) are the main active species for pollutants degradation. In the vis/H₂O₂/HSO₃-MIL-53(Fe) system, the high pollutant degradation efficiency under alkaline conditions was attributed to two factors: (1) the acidity adjusting group -HSO₃ adjusts the pH value of the whole system, which is beneficial to the photo-Fenton process. (2) The photogenerated electrons of HSO₃-MIL-53(Fe) can be captured by Fe (III), H₂O₂ and O₂ to accelerate the reduction of Fe (III) and generate ·OH, ¹O₂, and ·O₂^-. Besides, H₂O₂ can also be activated by Fe (II) and Fe (III). The above processes synergistically improved the photocatalytic efficiency. Based on liquid chromatography-mass spectrometry (LC-MS) analysis, the possible degradation pathways of the two pollutants were proposed.

State-of-the-art biosynthesis of tin oxide nanoparticles by chemical precipitation method towards photocatalytic application

Tin oxide (SnO₂) with versatile properties is of substantial standing for practical application, and improved features of the material are demonstrated in the current issue through the integration of nanotechnology with bio-resources leading to what is termed as biosynthesis of SnO₂ nanoparticles (NPs). This review reveals the recent advances in biosynthesis of SnO₂ NPs by chemical precipitation method focused on distinct methodologies, characterization, and reaction mechanism along with a photocatalytic application for dye degradation. According to available literature reviews, numerous bio-based precursors selectively extracted from biological substrates have effectively been applied as capping or reducing agents to achieve the metal oxide NPs. The major precursor obtained from the aqueous extract of root barks of Catunaregam spinosa is found to be 7-hydroxy-6-methoxy-2H-chromen-2-one that has been proposed as a model compound for the reduction of metal ions into nanoparticles due to having highly active functional groups, being abundant in plants (67.475 wt%), easy to extract, and eco benign. In addition, the photocatalytic activity of SnO₂ NPs for the degradation of organic dyes, pharmaceuticals, and agricultural contaminants has been discussed in the context of a promising bio-reduction mechanism of the synthesis. The final properties are supposed to depend exclusively upon a number of factors, e.g., particle size (< 50 nm), bandgap (< 3.6 eV), crystal defects, and catalysts dosage. With this contribution, it has been perceived not only to provide an overview of recent advances in the biosynthesis of SnO₂ NPs but also to indicate the main issues in need aiming to show vision towards innovative outcomes.

Carbamazepine degradation by visible-light-driven photocatalyst Ag3PO4/GO: Mechanism and pathway

Carbamazepine (CBZ), as one of the most frequently detected pharmaceuticals, is of great concern due to its potential impact on the ecosystem and human health. This study provides an effective approach to remove CBZ by using photocatalyst silver phosphate combined with graphene oxide (Ag₃PO₄/GO) under visible irradiation. The morphology, composition, and optical properties of Ag₃PO₄/GO were characterized employing SEM, XRD, and DRS. Graphene oxide could improve the visible-light utilization and promote electron's charge to enhance the photocatalytic performance of Ag₃PO₄/GO. With the optimal reaction condition of 5.86 mW/cm² light intensity, 15-25 °C temperature, 5-7 pH, and 0.5 mg/L catalytic dosages, 5 mg/L CBZ could be completely degraded in 30 min, and the apparent rate constant could reach 0.12 min^-1. Additionally, the radical trapping experiments indicated •OH and O₂-• were the main reactive oxygen species employed to eliminate CBZ. The decay pathways of CBZ had been proposed accordingly, and the main product was the low-molecular products.

CQDs/biochar from reed straw modified Z-scheme MgIn2S4/BiOCl with enhanced visible-light photocatalytic performance for carbamazepine degradation in water

The application of environmental-friendly and sustainable green materials in constructing photocatalysts to degrade pharmaceuticals and personal care products (PPCPs) attracts more attention. Herein, biochar (BC) or biomass carbon quantum dots (CQDs) were used to modify MgIn₂S₄/BiOCl (MB) heterojunction photocatalyst with Z-scheme structure, and improved the photocatalytic degradation performance for carbamazepine (CBZ) in the aqueous solution. Both BC and CQDs could form electron transfer interface with MB heterojunction, resulting in the photodegradation rate of MgIn₂S₄/BiOCl/CQDs (MBC, 96.43%) and MgIn₂S₄/BiOCl/BC (MBB, 88.09%) to CBZ within 120 min visible-light irradiation, which were significantly higher than that of MB (65.84%). Moreover, photoelectrochemical and photoluminescence tests verified that CQDs could act as a bridge for storing and transferring electrons in the entire Z-scheme system. Thence, compared with MBB, MBC could produce more •OH and •O₂^- under the visible light, which was indicated by the results of radical quenching experiments and electron paramagnetic resonance. Interestingly, under the natural sunlight, the photocatalytic performance of MBC to CBZ was even better than under laboratory conditions. In addition, the TOC removal efficiencies of MBB and MBC could reach 85.09% and 93.79% respectively, and ECOSAR program was utilized to further evaluate the eco-toxicity of CBZ and the intermediates towards fish, daphnid, and green algae, indicating that the photocatalytic process involving MBB and MBC showed outstanding toxicity reduction performance. Finally, compared with other composites, MBB and MBC showed higher photocatalytic performance and lower energy consumption, which would provide a green strategy for biochar materials in the photocatalytic treatment of PPCPs in water.

Au-SnO2-CdS ternary nanoheterojunction composite for enhanced visible light-induced photodegradation of imidacloprid

Herein, we have developed a novel synthetic strategy for the fabrication of Au-SnO₂-CdS ternary nano-heterojunction catalyst and its utility towards LED light derived photocatalytic degradation of imidacloprid has been evaluated. The synthesized ternary nanocomposite was characterized using sophisticated analytical techniques to evaluate the catalyst's morphological, structural and surface chemical properties. The photocatalytic activity of the ternary catalyst towards the degradation of imidacloprid was evaluated under LED irradiation. Approximately 95% of the degradation efficiency was achieved with a pseudo-first-order reaction rate of 15.6 × 10^-3 min^-1. The degradation efficiency of Au-SnO₂-CdS nano-catalyst was found to be ~1.2, 1.4 and 2.1 times to that of the pristine Au, CdS and SnO₂ nanomaterials under similar experimental conditions. The effect of variation of parameters like contact time, initial pollutant concentration and pH on degradation efficiency has also been investigated. Moreover, the identification of various degradation products and reactive intermediates were made with high-performance liquid chromatography and electron spin resonance techniques.

Synergistic effect of sonication on photocatalytic oxidation of pharmaceutical drug carbamazepine

Photocatalytic, sono-photocatalytic oxidation of pharmaceutical drug of carbamazepine was successfully carried out using Ag/AgCl supported BiVO4 catalyst. For this purpose, firstly, photocatalytic oxidation was optimized by central composite design methodology and then synergistic effect of sonication was investigated. Low frequency (20 kHz) probe type and high frequency (850 kHz) plate type sonication at pulse and continuous mode were studied to degrade the carbamazepine (CBZ) containing wastewater. Pulse duties of 1:5 and 5:1 (on : off) were tested using the high frequency sonication system in the sono-photocatalytic oxidation of CBZ. The effects of frequency, power density measured from calorimetry by changing amplitudes were discussed in the sono-photocatalytic oxidation of CBZ. Complete carbamazepine removal was achieved at the optimum conditions of 5 ppm CBZ initial concentration with 1.5 g/L of catalysts loading and at an alkaline pH of 10 at the end of 4 h of photocatalytic reaction under visible LED light irradiation. Both low frequency and high frequency sonication systems caused an increase in photocatalytic efficiency in a shorter treatment time of 60 min. CBZ removal increased from 44% to 65.42% in low frequency sonication of 20 kHz at the amplitude of 20% (0.15 W/mL power density). In the case of high frequency ultrasonic system (850 kHz), CBZ removal increased significantly from 44% to 89.5 % at 75% amplitude (0.12 W/mL power density) within 60 min of reaction. Continuous mode sonication was observed to be more effective than that of pulse mode sonication not only for degradation efficiency and also for electrical energy consumption needed to degrade CBZ. Sono-catalytic oxidation was also conducted with simulated wastewater that contains SO42-, CO32-, NO3-, Cl- anions and natural organic component of fulvic acid. The CBZ degradation was inhibited slightly in the presence of NO3- and Cl-, and fulvic acid, however, the existence of SO42- and CO32- increased the degradation degree of CBZ. Toxicity tests were performed to determine the toxicity of untreated CBZ, and treated CBZ by photocatalytic, and sono-photocatalytic oxidations.

Fabrication of Bi4O5Br2 photocatalyst for carbamazepine degradation under visible-light irradiation

Bi₄O₅Br₂ with irregular flake shape was synthesized by a facile and energy-saving hydrolysis method. Its band gap energy (E_g) was 2.1 eV. The formation mechanism was proposed. The Bi₄O₅Br₂ exhibited superb visible-light-induced photocatalytic activity (>90%) toward the oxidation of carbamazepine. The kinetics rate constant (k) attained 0.0196 min^-1. The effect of Bi₄O₅Br₂ dosage, initial solution pH value, and inorganic anions on carbamazepine degradation was investigated. During the oxidation process, photogenerated holes (h⁺) and superoxide radical anions (•O₂^-) were the main active species. Based on the reaction intermediates results determined through a combined system of liquid chromatography and mass spectrometry, a possible reaction mechanism was speculated. The degree of contamination of carbamazepine solution after treatment was evaluated through the teratogenic effect experiment. After 120 min of visible light exposure, the carbamazepine solution is free of pollution. Also, the as-synthesized Bi₄O₅Br₂ maintains good chemical stability and could be reused in the photodegradation process, indicating its potential in practical applications.

Avoiding Hemolytic Anemia by Understanding the Effect of the Molecular Architecture of Gemini Surfactants on Hemolysis

Hemolytic behavior of a series of different categories of Gemini surfactants was determined in their low concentration range. Cationic Gemini surfactants of different molecular architectures prove to be highly cytotoxic even at 0.1 mM. Anionic and amino acid-based Gemini surfactants were minimally cytotoxic, although their toxicity was concentration-dependent. With respect to monomeric surfactants of comparable hydrocarbon chain lengths, cationic Gemini surfactants were much more toxic than anionic Gemini surfactants. Incubation temperature was another important parameter that significantly drove the hemolysis irrespective of the molecular structure of the surfactant. Results indicated that the surface activity or liquid-blood cell membrane adsorption tendency of a surfactant molecule determined the degree of hemolytic anemia. Greater surface activity induced greater cytotoxicity, especially when the surfactant possessed a stronger ability to interact with the membrane proteins through hydrophilic interactions. That provided cationic Gemini surfactants a higher ability for hemolytic anemia because they were able to interact with an electronegative cell membrane with favorable interactions in comparison to anionic or amino acid-based Gemini surfactants. These findings are expected to help in designing surface-active drugs with a suitable molecular architecture that can avoid hemolytic anemia.

Synthesis and characterization of SnO2 crystalline nanoparticles: A new approach for enhancing the catalytic ozonation of acetaminophen

A novel sol-gel method was employed in this study to efficiently synthesize SnO₂ nanoparticles to catalyze the ozonation of acetaminophen (ACT) from aqueous solutions. The influence of various parameters including Sn source, type of capping and alkaline agents, and calcination temperature on the catalytic activity of the SnO₂ preparations was investigated. The SnO₂ nanoparticles prepared by tin tetrachloride as Sn source, NaOH as gelatin agent, CTAB as capping agent and at calcination temperature of 550 °C (SnNaC-550) exhibited the maximum performance in the catalysis of ACT. The optimized catalyst (SnNaC-550) had spherical-homogeneous and cubic-shaped nanocrystalline particles with 5.5 nm mean particle size and a BET surface area of 81 m²/g, which resulted in 98% degradation and 84% mineralization of 50 mg/L ACT at 20 and 30 min reaction time, respectively when combined with ozonation (COP). Based on the radical scavenger experiments, ^•OH was the major oxidizing agent involved in the removal of ACT. LC/MS analysis showed that short-chain carboxylic acids were the main intermediates. Furthermore, the SnNaC-550 catalytic activity was preserved after four successive cycles. Collectively, the new method has the potential to efficiently synthesize stable and reusable SnO₂ nanoparticles to catalyze the ozonation of ACT from aquatic environments.

Organoarsenic conversion to As(III) in subcritical hydrothermal reaction of livestock manure

Liquid phase produced by the subcritical hydrothermal liquefaction (HTL) of livestock manure is extensively used in agronomic and environmental applications, but the potential risks caused by inherent pollutants (e.g., roxarsone, ROX) of the livestock manure have not been considered. This study shows that less toxic ROX is completely converted into highly toxic As(III) and As(V) in the HTL reaction with temperature more than 240 °C. Moreover, more than 81.5% of As is distributed in the liquid phase generated by the livestock manure HTL reaction. Notably, the hydrothermal products of livestock manure facilitate the conversion of As(V) to As(III). The resulting hydrochar and aldehydes act as electron donors for As(V) reduction, thus resulting in the formation of As(III). Furthermore, the dissociated As promotes the depolymerization and deoxygenation of the macromolecular compounds to produce more small oxygen-containing compounds such as aldehydes, further boosting the As(V) reduction to As(III). These results indicate that the liquid phase of the livestock manure has potential risks in applications as a fertilizer. Such findings have substantial implications in biomass utilization and redox reactions of envirotechnical and biogeochemical relevance.

An innovative microbial electrochemical ultraviolet photolysis cell (MEUC) for efficient degradation of carbamazepine

Discharge of recalcitrant pharmaceuticals into aquatic environments can lead to serious negative environmental effects. While traditional wastewater treatment plants (WWTPs) are efficient for a wide range of non-toxic pollutants (i.e. ammonia), some wastewater streams contain recalcitrant toxic trace micropollutants such as pharmaceuticals that cannot be removed by the treatment processes that are typically employed in common WWTPs. Herein, an innovative 20 L microbial electrochemical ultraviolet photolysis cell (MEUC) was developed for the first time by the integration of a UV irradiation and a bioelectrochemical system, which exhibited efficient treatment of carbamazepine-a model pharmaceutical compound. Notably, neither the UV irradiation nor the bioelectrochemical system alone could effectively eliminate carbamazepine. The effect of operational parameters including applied voltage, cathodic aeration rate, UV intensity, and hydraulic retention time were evaluated. The obtained results elucidated that the degradation of carbamazepine was consistent with pseudo-first-order reaction kinetics, and required a lower energy input than traditional advanced oxidation processes. Five main transformation products were identified, and probable transformation pathways were established. Furthermore, the eco-toxicity as tested by Vibrio fischeri showed no significant bioluminescence inhibition by the treated carbamazepine effluent. Finally, the MEUC system was further tested with a real wastewater matrix, which again exhibited effective removal of carbamazepine. This paper provides a proof-of-concept verification of the novel MEUC system, which contributes insight for the subsequent vigorous development of the application of such efficient and cost-effective technologies for the treatment of trace pharmaceuticals wastewater.

Environmentally benign fabrication of SnO2-CNT nanohybrids and their multifunctional efficiency as an adsorbent, catalyst and antimicrobial agent for water decontamination

Herein, we described a biogenic, additive fee, eco-friendly synthesized SnO₂-CNT nanohybrid as an efficient, re-collectable and reusable material for onsite water remediation. We demonstrated that the SnO₂-CNTs can provide a one stop solution for water remediation as it effectively accomplished the major treatment tasks like adsorption, catalytic transformation/degradation and disinfection. The structural, morphological, surface chemical compositions of the nanocomposite and the adsorption, catalytic and antimicrobial properties were investigated using common characterization and instrumental techniques. The results revealed the brilliant efficiency of SnO₂-CNT nanoadsorbent towards As (III) and a maximum Langmuir adsorption capacity of 106.95 mg/g was observed at high arsenite concentration (C₀ = 1 mg/L). The nanoadsorbent was also found to be equally efficient in low arsenite concentration ranges (C₀ = 100 μg/L) as it could bring down the arsenic concentration below maximum permissible limit. Moreover, using model pollutants like p-nitrophenol, Alizarin red S, Metronidazole, bacterial strains (Bacillus subtilis, Escherichia coli, Streptococcus pneumonia etc.), and fungal strains (Aspergillus niger and Candida albicans), the multifunctional capability of SnO₂-CNT towards water decontamination has been established. Our results suggested the promising potential of hierarchical nano-heterojunctions for engineering efficient water treatment processes.

Fabrication of Surfactant-Enhanced Metal Oxides Catalyst for Catalytic Ozonation Ammonia in Water

The new surfactant-enhanced metal oxides composite catalysts have been prepared using solid state method and characterized by the N₂-adsorption-desorption, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscope (TEM), and X-ray diffraction (XRD) techniques. Catalytic activity of the synthesized powders has been investigated in the liquid-phase catalytic ozonation ammonia nitrogen (NH₄⁺) (50 mg/L). Especially, the effect of parameters such as optimum molar ratio for metal salt, NaOH and surfactants, temperature, and time of calcinations was also considered. Leveraging both high catalytic activity in NH₄⁺ degradation and more harmless selectivity for gaseous nitrogen, the CTAB/NiO catalyst is the best among 24 tested catalysts, which was generated by calcining NiCl₂·6H₂O, NaOH, and CTAB under the molar ratio 1:2.1:0.155 at 300 °C for 2 h. With CTAB/NiO, NH₄⁺ removal rate was 95.93% and gaseous nitrogen selectivity was 80.98%, under the conditions of a pH of 9, ozone flow of 12 mg/min, dosage of catalyst 1.0 g/L, reaction time 120 min, and magnetic stirring speed 600 r/min in room temperature.