An intriguing Z-scheme titania loaded on fibrous silica ceria for accelerated visible-light-driven photocatalytic degradation of ciprofloxacin

Modification of Sugar Cane Bagasse with CTAB and ZnO for Methyl Orange and Methylene Blue Removal

Sugar cane bagasse (SB) was modified with cetyltrimethylammonium bromide (CTAB), followed by impregnation with zinc oxide (ZnO) to create a synergistic adsorption and photocatalytic system for methyl orange (MO) and methylene blue (MB) removal. The presence of CTAB and ZnO was confirmed by X-ray diffraction, Fourier transform infrared, and energy dispersive X-ray (for Zn and O). Modification of SB with CTAB (CSB) generated more positive sites on the surface of SB, which enhanced MO removal compared with that of pristine SB. ZnO impregnation induces a decrease in MO removal due to the ZnO presence on the CSB surface, which might reduce the positive sites on the CSB. In addition, the positive sites on CSB can interact with Zn2+ and O2- to form ZnO and lead to a decrease in MO removal. In contrast, the presence of ZnO facilitated good removal of MB compared to CSB, indicating that the photocatalytic process plays a greater role in removing MB. However, the addition of H2O2 can improve MO and MB removal under irradiation due to the formation of external •OH. The photocatalytic performance of MO and MB was also observed to be favored under acidic and alkaline conditions, respectively.

Nickel-doped red mud-based Prussian blue analogues heterogeneous activation of H2O2 for ciprofloxacin degradation: waste control by waste

Red mud (RM) is a typical bulk solid waste with Fe/Al/Si/Ca-rich characteristics that has been used to prepare various heterogeneous catalysts such as iron-based catalysts and supported catalysts. Prussian blue analogues (PBA) is a low-cost, environmentally friendly, and active site rich iron-based metal organic framework, but its catalytic properties are adversely affected by their easy aggregation. In this study, nickel-doped RM-based PBA (RM-Ni PBA) was synthesized by acid dissolution-coprecipitation method for the degradation of ciprofloxacin (CIP). The characterization showed that RM-Ni PBA was a material with excellent dispersibility, large specific surface area, and abundant active sites. The degradation results showed that the removal efficiency of CIP in the RM-Ni PBA/H2O2 system was 16.63, 1.78, and 1.81 times that of RM, RM-PB, and Ni PBA, respectively. It was found that 1O2 was the main reactive oxygen species (ROS) dominated the degradation process, and its formation was accompanied by the mutual conversion of Ni(II)/Fe(II) and Ni(III)/Fe(III). Notably, the degradation process maintained a satisfactory efficiency over a wide pH range (3-9) and exhibited strong anti-interference ability against impurities such as Cl-, SO42-, and NO3-. The components and contents of RM-Ni PBA remained relatively stable during the degradation process. In addition, the degradation intermediates of CIP were identified, and possible degradation pathways were proposed. This study is expected to provide theoretical basis and technical guidance for the application of RM-based heterogeneous catalyst in the treatment of antibiotic wastewater.

Degradation of norfloxacin by red mud-based prussian blue activating H2O2: A strategy for treating waste with waste

The massive accumulation of red mud (RM) and the abuse of antibiotics pose a threat to environment safety and human health. In this study, we synthesized RM-based Prussian blue (RM-PB) by acid solution-coprecipitation method to activate H2O2 to degrade norfloxacin, which reached about 90% degradation efficiency at pH 5 within 60 min and maintained excellent catalytic performance over a wide pH range (3-11). Due to better dispersion and unique pore properties, RM-PB exposed more active sites, thus the RM-PB/H2O2 system produced more reactive oxygen species. As a result, the removal rate of norfloxacin by RM-PB/H2O2 system was 8.58 times and 2.62 times of that by RM/H2O2 system and PB/H2O2 system, respectively. The reactive oxygen species (ROS) produced in the degradation process included ·OH, ·O2- and 1O2, with 1O2 playing a dominant role. The formation and transformation of these ROS was accompanied by the Fe(III)/Fe(II) cycle, which was conducive for the sustained production of ROS. The RM-PB/H2O2 system maintained a higher degradation efficiency after five cycles, and the material exhibited strong stability, with a low iron leaching concentration. Further research showed the degradation process was less affected by Cl-, SO42-, NO3-, and humic acids, but was inhibited by HCO3- and HPO42-. In addition, we also proposed the possible degradation pathway of norfloxacin. This work is expected to improve the resource utilization rate of RM and achieve treating waste with waste.

Recent advances of modification effect in Co3O4-based catalyst towards highly efficient photocatalysis

Tricobalt tetroxide (Co3O4) has been developed as a promising photocatalyst material for various applications. Several reports have been published on the self-modification of Co3O4 to achieve optimal photocatalytic performance. The pristine Co3O4 alone is inadequate for photocatalysis due to the rapid recombination process of photogenerated (PG) charge carriers. The modification of Co3O4 can be extended through the introduction of doping elements, incorporation of supporting materials, surface functionalization, metal loading, and combination with other photocatalysts. The addition of doping elements and support materials may enhance the photocatalysis process, although these modifications have a slight effect on decreasing the recombination process of PG charge carriers. On the other hand, combining Co3O4 with other semiconductors results in a different PG charge carrier mechanism, leading to a decrease in the recombination process and an increase in photocatalytic activity. Therefore, this work discusses recent modifications of Co3O4 and their effects on its photocatalytic performance. Additionally, the modification effects, such as enhanced surface area, generation of oxygen vacancies, tuning the band gap, and formation of heterojunctions, are reviewed to demonstrate the feasibility of separating PG charge carriers. Finally, the formation and mechanism of these modification effects are also reviewed based on theoretical and experimental approaches to validate their formation and the transfer process of charge carriers.

Vanadia as an electron-hole recombination inhibitor on fibrous silica-titania for selective hole oxidation of ciprofloxacin and Congo red photodegradation

Vanadia (V2O5)-incorporated fibrous silica-titania (V/FST) catalysts, which were successfully synthesized using a hydrothermal method followed by the impregnation of V2O5. The catalysts were then characterized using numerous techniques, including X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, nitrogen adsorption-desorption analyses, ultraviolet-visible diffuse reflectance spectroscopy, Fourier-transform infrared, X-ray photoelectron spectroscopy, and photoluminescence (PL) analyses. The study found that varying the amount of V2O5 (1-10 wt%) had a significant impact on the physicochemical properties of the FST, which in turn improved the photodegradation efficiency of two organic compounds, ciprofloxacin (CIP) and congo red (CR). 5V/FST demonstrated the best performance in degrading 10 mg L-1 of CIP (83%) and CR (100%) at pH 3 using 0.375 g L-1 catalyst under visible light irradiation within 180 min. The highest photoactivity of 5V/FST is mainly due to higher crystallinity and the highest number of V2O5-FST interactions. Furthermore, as demonstrated by PL analysis, the 5V/FST catalyst has the most significant impact on interfacial charge transfer and reduces electron-hole recombination. The photodegradation of both contaminants follows the Langmuir-Hinshelwood pseudo-first-order model, according to the kinetic study. The scavenger investigation demonstrated that hydroxyl radicals and holes dominated species in the system, indicating that the catalyst effectively generated reactive species for pollutant degradation. A possible mechanism was also identified for FST and 5V/FST. Interestingly, V2O5 acts as an electron-hole recombination inhibitor on FST for selective hole oxidation of ciprofloxacin and congo red photodegradation. Finally, the degradation efficiency of the catalyst remained relatively stable even after five cyclic experiments, indicating its potential for long-term use in environmental remediation.

CuO improved energy band of AgO/fibrous SiO2-ZrO2 for optimized simultaneous photocatalytic redox of chromium (VI) and p-cresol using response surface methodology

Ternary CuO/AgO/FSZr photocatalysts were fabricated via the hydrothermal and electrochemical methods with three different CuO loading (1, 3 and 5 wt%), indicated as 1CuO/AgO/FSZr, 3CuO/AgO/FSZr and 5CuO/AgO/FSZr. The photocatalytic reaction was tested towards simultaneous chromium (VI) photoreduction and p-cresol photooxidation and the performance in order as follow: 3CuO/AgO/FSZr > 5CuO/AgO/FSZr > 1CuO/AgO/FSZr > AgO/FSZr > FSZr. CuO/AgO/FSZr photocatalysts showed an improvement in photocatalytic activity compared to AgO/FSZr and FSZr due to the reduction potential of chromium (VI) aligned closer to the conduction band of CuO and provided abundant free active electrons (e^-) and holes (h⁺) with efficient transportation and migration. Interestingly, the 3CuO/AgO/FSZr was established as the best photocatalyst with 98% reduction of chromium (VI) and 83% oxidation of p-cresol simultaneously, owing to its strong corporation between the metal oxides and support and higher total pore volume. The Langmuir-Hinshelwood model were employed for kinetics which followed the pseudo-first-order kinetics model well. Based on the simultaneous photocatalytic mechanism, chromium (VI) and p-cresol were directly reduced and oxidized by e^- and h⁺, respectively. The response surface methodology (RSM) discovered that the quadratic term initial concentration of chromium (VI) is the main significant factor in photocatalytic performance. The optimum parameters for simultaneous photoredox of chromium (VI) and p-cresol predicted from RSM are 9.6 mg L^-1 of chromium (VI) concentration, 9.8 mg L^-1 of p-cresol concentration and 0.32 g L^-1 of catalyst dosage. Under these conditions the error between the predicted and experimental values is only 3.7%. The 3CuO/AgO/FSZr sustained the photocatalytic performance after reused for five cycles and could oxidized various organic pollutants as well as reduced chromium (VI) simultaneously.

Visible-light driven excellent photocatalytic degradation of ofloxacin antibiotic using BiFeO3 nanoparticles

The extensive exploration of multiferroic materials for degradation of contaminants and environmental remediation is promptly strengthened because of their distinct applications. BiFeO₃, a prominent class of multiferroics, have received immense attention in recent times. Present study reports the synthesis of a highly crystalline BiFeO₃ via facile combustion method. The prepared catalyst was characterized using different techniques like XRD, FTIR, FESEM, EDS, XPS, DRS and PL. From DRS results, the energy band gap of BiFeO₃ was computed as 2.1 eV which was suitable enough for its exploration as a visible light photocatalyst. Therefore, BiFeO₃ was efficiently utilized for the degradation of ofloxacin drug under the exposure of visible light. The obtained results depicted 80% ofloxacin degradation under optimized conditions (pH 8, 0.5 g/L catalyst dose and 10 mg/L drug concentration) in 180 min. Pseudo first order kinetics was followed with rate constant 0.0097 min^-1, as inferred from the kinetic studies. Furthermore, 64% TOC reduction was attained by utilizing the prepared catalyst under optimum conditions. Additionally, the photocatalytic experiments showed excellent degradation efficiency even after five cycles which demonstrated good stability of the fabricated catalyst.

Interfacial engineering of novel inorganic-organic β-Ga2O3/COF heterojunction for accelerated charge transfer towards artificial photosynthesis

Semiconductor-based solar-driven CO₂ to fuels has been widely reckoned as an ingenious approach to tackle energy crisis and climate change simultaneously. However, the high carrier recombination rate of the photocatalyst severely dampens their photocatalytic uses. Herein, an inorganic-organic heterojunction was constructed by in-situ growing a dioxin-linked covalent organic framework (COF) on the surface of rod-shaped β-Ga₂O₃ for solar-driven CO₂ to fuel. This novel heterojunction is featured with an ultra-narrow bandgap COF-318 (absorption edge = 760 nm), which is beneficial for fully utilizing the visible light spectrum, and a wide bandgap β-Ga₂O₃ (absorption edge = 280 nm) to directional conduct electrons from COF to reduce CO₂ without electron-hole recombination occurred. Results showed that the solar to fuels performance over β-Ga₂O₃/COF was much superb than that of COF. The optimized Ga₂O₃/COF achieved an outstanding CO evolution rate of 85.8 μmol h^-1·g^-1 without the need of any sacrificial agent or cocatalyst, which was 15.6 times more efficient than COF. Moreover, the analyses of photoluminescence electrochemical characterizations and density functional theory (DFT) calculations revealed that the fascinate construction of β-Ga₂O₃/COF heterojunction significantly favored charge separation and the directional transfer of photogenerated electrons from COF to β-Ga₂O₃ followed by CO₂. This study paves the way for developing effective COF-based semiconductor photocatalysts for solar-to-fuel conversion.

Removal of ciprofloxacin antibiotic pollutants from wastewater using nano-composite adsorptive membranes

The emergence of antibiotics in water has been globally recognized as a critical pollution issue. Antibiotics (such as Ciprofloxacin (CPFX) pose a serious threat to humans and to the ecosystem due to its accumulation in water sources which can lead to chronic health problems and endanger aquatic life. It is therefore crucial to properly remove them from water. In this work, a nano-composite adsorptive membrane based on Zirconium Phosphate (ZrP) adsorbent supported on Polyethersulfone (PES) was synthesized and evaluated for the removal of CPFX from synthetic aqueous solutions. The membranes described here showed a very high antibiotic removal rate. The effect of various parameters such as the initial concentration of the antibiotic, the adsorbent dosage, contact time, pH, and temperature was studied. The equilibrium data were found to reasonably best fit with the Temkin isotherm model. The membranes showed a high ciprofloxacin removal (99.7%) as opposed to (68%) when PES membrane alone was used. Moreover, a significant improvement in the membrane's water flux (100.84 L/m².h) and permeability (97.62 L/m².hr.bar) were noticed as opposed to pure PES membrane's flux and permeability. The adsorptive membranes were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET). The results confirmed the successful formation of ZrP nanoparticles adsorbent within the membrane matrix, and with enhanced hydrophilic properties. The membrane was successfully regenerated and reused up to 5 times. The results of this work showed the potential of such membranes for the removal of ciprofloxacin and at a high efficiency.

Promoting a well-dispersion of MoO3 nanoparticles on fibrous silica catalyst via one-pot synthesis for enhanced photoredox environmental pollutants efficiency

The coexistence of pharmaceutical compounds and heavy metals in the aquatic environment has resulted in complications in the treatment process and thus, causing uproar among the citizens. The radical-based photocatalysis technology has aroused as an excellent method to eliminate both heavy metal and pharmaceutical compounds in the water. Herein, reported the utilization of the microemulsion technique for the preparation of nanoporous fibrous silica-molybdenum oxide (FSMo) towards simultaneous photocatalytic abatement of hexavalent chromium (Cr(VI)) and tetracycline (TC). The FESEM analysis showed the spherical morphology of the FSMo catalyst with dendrimeric silica fiber. The synthesized FSMo catalyst exhibited narrowed bandgap, high crystallinity, and well Mo element dispersion for enhanced photo-redox of Cr(VI) and TC. Remarkably, simultaneous remediation of the Cr(VI) and TC over FSMo demonstrated superior photocatalytic efficiency, 69% and 75%, respectively, than in the individual system, possibly due to the effective separation of photoinduced charges. The introduction of the Mo element to the silica framework via microemulsion technique demonstrated better dispersion of Mo compared to the incipient wetness impregnation method and thus, yielded higher photocatalytic activity towards simultaneous removal of TC and Cr(VI). Besides, quenching experiments revealed the electrons and holes as the active species that play a dominant role in the simultaneous photo-redox of Cr(VI) and TC. Lastly, the FSMo catalyst demonstrated high stability after four continuous cycles of simultaneous photocatalysis reactions, implying its potential as a suitable material for practical wastewater treatments.

Investigation of photocatalytic performance of titania based hybrid nanocomposite structure for dilapidation of organic contaminants

This research paper attempt to provide the photocatalytic performance of nitrogen ion (N⁺) entrenched anodized Ti with hydroxyapatite hybrid nano-sctructure meant for dilapidation of organic contaminant from the environment. The N⁺ was entrenched at 70 keV with varying doses (1 × 10¹⁶, 5 × 10¹⁶, 1 × 10¹⁷ and 2.5 × 10¹⁷ N⁺/cm²) into anodized Ti surface. Functional groups, phase structure, topographic and morphologic characterizations of the synthesized hybrid nano-sctructure were analyzed using Infra Red Spectroscopy, X-ray diffraction and Microscopic techniques, respectively. Wettability of the specimens was found out using contact angle measurements. The anodized Ti specimens without N⁺ have exhibited less surface energy than the specimens with N⁺. Porous shell gets smoothened after the entrenchment of N⁺. Compared to all the doses of nitrogen implantation, better performance was observed for 5 × 10¹⁶ N⁺/cm² dose. Moreover, the samples with N⁺ showed better charge transfer resistance indicating enhanced photocatalytic performance of N⁺ entrenched titania than other samples.