Crystal morphology control of synthetic giniite for enhanced photo-Fenton activity against the emerging pollutant metronidazole

Sonophotocatalytic removal of organic dyes in real water environments using reusable BiSI@PVDF-HFP nanocomposite membranes

Focusing on the uncontrolled discharge of organic dyes, a known threat to human health and aquatic ecosystems, this work employs a dual-functional catalyst approach, by immobilizing a synthesized bismuth sulfur iodide (BiSI) into a poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) polymeric matrix for multifunctional water remediation. The resulting BiSI@PVDF nanocomposite membrane (NCM), with 20 wt% filler content, maintains a highly porous structure without compromising morphology or thermal properties. Demonstrating efficiency in natural pH conditions, the NCM removes nearly all Rhodamine B (RhB) within 1 h, using a combined sonophotocatalytic process. Langmuir and pseudo-second-order models describe the remediation process, achieving a maximum removal capacity (Qmax) of 72.2 mg/g. In addition, the combined sonophotocatalysis achieved a degradation rate ten and five times higher (0.026 min-1) than photocatalysis (0.002 min-1) and sonocatalysis (0.010 min-1). Furthermore, the NCM exhibits notable reusability over five cycles without efficiency losses and efficiencies always higher than 90%, highlighting its potential for real water matrices. The study underscores the suitability of BiSI@PVDF as a dual-functional catalyst for organic dye degradation, showcasing synergistic adsorption, photocatalysis, and sonocatalysis for water remediation.

Exceptional photo-elimination of antibiotic by a novel Z-scheme heterojunction catalyst composed of nanoscale zero valent iron embedded with carbon quantum dots (CQDs)-black TiO2

Passivation of nanoscale zero valent iron (nZVI, Fe0) impaired its longevity while black TiO2 (b-TiO2) suffered from restricted optical properties. Using a facile approach, a novel Z-scheme heterojunction catalyst (Fe0@CQDs-TiO2(b)) of nZVI decorated with carbon quantum dots (CQDs) implanted into b-TiO2 was designed. Characterization results revealed the optical potential of the passivation coating of nZVI. The incorporation of CQDs stimulated the creation of active •OH during the dark reaction, and led to an accelerated mobility of photo-excited carriers of b-TiO2 and optimized its band gap (narrowing from 2.36 eV to 2.15 eV) during the light reaction. The photo-elimination capacity of metronidazole (MNZ) on Fe0@CQDs-TiO2(b) (99.36%) was 2.64, 8.25 and 1.34 fold beyond that on nZVI, b-TiO2 and Fe0@b-TiO2, respectively. The assembled material offered excellent adaptability to environmental substrates, in addition to being virtually unaffected by tap (95.62%) and river water (92.62%). The mechanism of MNZ degradation was elaborated, and the combination of density functional theory (DFT) calculations and LC-MS discerned 12 intermediates and 3 routes. Toxicity assessment of these products was conducted to ensure no inadvertent negative environmental impacts arose. This work proposed an original direction and mechanism for the application of passivation layers in nZVI-based materials for environmental restoration.

Wastewater Treatment of Real Effluents by Microfiltration Using Poly(vinylidene fluoride-hexafluoropropylene) Membranes

Over the last decades, the growing contamination of wastewater, mainly caused by industrial processes, improper sewage, natural calamities, and a variety of anthropogenic activities, has caused an increase in water-borne diseases. Notably, industrial applications require careful consideration as they pose significant threats to human health and ecosystem biodiversity due to the production of persistent and complex contaminants. The present work reports on the development, characterization, and application of a poly (vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) porous membrane for the remediation of a wide range of contaminants from wastewater withdrawn from industrial applications. The PVDF-HFP membrane showed a micrometric porous structure with thermal, chemical, and mechanical stability and a hydrophobic nature, leading to high permeability. The prepared membranes exhibited simultaneous activity on the removal of organic matter (total suspended and dissolved solids, TSS, and TDS, respectively), the mitigation of salinity in 50%, and the effective removal of some inorganic anions and heavy metals, achieving efficiencies around 60% for nickel, cadmium, and lead. The membrane proved to be a suitable approach for wastewater treatment, as it showed potential for the simultaneous remediation of a wide range of contaminants. Thus, the as-prepared PVDF-HFP membrane and the designed membrane reactor represent an efficient, straightforward, and low-cost alternative as a pretreatment step for continuous treatment processes for simultaneous organic and inorganic contaminants' remediation in real industrial effluent sources.

Solar Photocatalytic Membranes: An Experimental and Artificial Neural Network Modeling Approach for Niflumic Acid Degradation

The presence of contaminants of emerging concern (CEC), such as pharmaceuticals, in water sources is one of the main concerns nowadays due to their hazardous properties causing severe effects on human health and ecosystem biodiversity. Niflumic acid (NFA) is a widely used anti-inflammatory drug, and it is known for its non-biodegradability and resistance to chemical and biological degradation processes. In this work, a 10 wt.% TiO₂/PVDF-TrFE nanocomposite membrane (NCM) was prepared by the solvent casting technique, fully characterized, and implemented on an up-scaled photocatalytic membrane reactor (PMR). The photocatalytic activity of the NCM was evaluated on NFA degradation under different experimental conditions, including NFA concentration, pH of the media, irradiation time and intensity. The NCM demonstrated a remarkable photocatalytic efficiency on NFA degradation, as efficiency of 91% was achieved after 6 h under solar irradiation at neutral pH. The NCM proved effective in long-term use, with maximum efficiency losses of 7%. An artificial neural network (ANN) model was designed to model NFA's photocatalytic degradation behavior, demonstrating a good agreement between experimental and predicted data, with an R² of 0.98. The relative significance of each experimental condition was evaluated, and the irradiation time proved to be the most significant parameter affecting the NFA degradation efficiency. The designed ANN model provides a reliable framework l for modeling the photocatalytic activity of TiO₂/PVDF-TrFE and related NCM.

Efficient eradication of antibiotic and dye by C-dots@zeolite nanocomposites: Performance evaluation, and degraded products analysis

Metronidazole (MET), a recalcitrant antibiotic from the nitro-imidazole family and commercially used Rhodamine B (RhB) dye, contributes a huge to water pollution, which needs to eliminate, preferably by photocatalytic degradation technique. The Cdots@zeolite (CDZ) nanocomposites with different weight ratios (1:1, 1:3, 1:5, 5:1, 1:7) were synthesized hydrothermally to degrade MET and RhB molecules. The CDZ composites were characterized by XRD, BET, EDS, and XPS technique which verifies the crystalline nature, incorporation of C-dots into zeolite frameworks with high surface area (∼187 m²/g). The morphology, d-spacing and lattice planes were analyzed by SEM images, HR-TEM and SAED analysis. The maximum degradation (∼79%) was achieved at an optimum catalyst dose of 0.2 g/L and pH 4 for MET and that of RhB was ∼90% at a catalyst dose of 0.4 g/L. The PZC (point of zero charge) value for CDZ composite was about pH 3.4, which justifies the maximum removal of MET at pH 4. The obtained rate constants 'k' were found to be 0.0081, 0.0041, and 0.0101 min^-1 in sun, UV, and visible light sources, respectively. The real industrial wastewater sample has been treated to give ∼68% of COD and ∼62% TOC removal. Moreover, the intermediates of plausible degradation pathways were identified by the m/z values obtained from GC-MS analysis.

Enhanced metronidazole removal by binary-species photoelectrogenic biofilm of microaglae and anoxygenic phototrophic bacteria

High efficient removal of antibiotics during nutriments recovery for biomass production poses a major technical challenge for photosynthetic microbial biofilm-based wastewater treatment since antibiotics are always co-exist with nutriments in wastewater and resist biodegradation due to their strong biotoxicity and recalcitrance. In this study, we make a first attempt to enhance metronidazole (MNZ) removal from wastewater using electrochemistry-activated binary-species photosynthetic biofilm of Rhodopseudomonas Palustris (R. Palustris) and Chlorella vulgaris (C. vulgaris) by cultivating them under different applied potentials. The results showed that application of external potentials of -0.3, 0 and 0.2 V led to 11, 33 and 26-fold acceleration in MNZ removal, respectively, as compared to that of potential free. The extent of enhancement in MNZ removal was positively correlated to the intensities of photosynthetic current produced under different externally applied potentials. The binary-species photoelectrogenic biofilm exhibited 18 and 6-fold higher MNZ removal rate than that of single-species of C. vulgaris and R. Palustris, respectively, due to the enhanced metabolic interaction between them. Application of an external potential of 0V significantly promoted the accumulation of tryptophan and tyrosine-like compounds as well as humic acid in extracellular polymeric substance, whose concentrations were 7.4, 7.1 and 2.0-fold higher than those produced at potential free, contributing to accelerated adsorption and reductive and photosensitive degradation of MNZ.

Graphene-based materials for metronidazole degradation: A comprehensive review

Due to its cytotoxic effect, metronidazole (MNZ) is a drug commonly used to treat bacterial, protozoal, and microaerophilic bacterial infections. After consumption, it undergoes a series of metamorphic reactions that lead to the degradation of oxidized, acetylated, and hydrolyzed metabolites in the environment. To eliminate such pollutants, due to their high potential, adsorption and photocatalysis extensive processes are used in which graphene can be used to improve efficiency. This review analyses the use of graphene as an absorbent and catalyst with a focus on absorption and photocatalytic degradation of MNZ by graphene-based materials (GBMs). The parameters affecting the adsorption, and photocatalytic degradation of MNZ are investigated and discussed. Besides, the basic mechanisms occurring in these processes are summarized and analyzed. This work provides a theoretical framework that can direct future research in the field of MNZ removal from aqueous solutions.

Internal-electric-field induced high efficient type-I heterojunction in photocatalysis-self-Fenton reaction: Enhanced H2O2 yield, utilization efficiency and degradation performance

Herein, a type-I phosphorus-doped carbon nitride/oxygen-doped carbon nitride (P-C₃N₄/O-C₃N₄) heterojunction was designed for photocatalysis-self-Fenton reaction (photocatalytic H₂O₂ production and following Fenton reaction). In P-C₃N₄/O-C₃N₄, the photoinduced charge carriers were effectively separated with the help of internal-electric-field near the interface, ensuring the high catalytic performance. As a result, the production rate of H₂O₂ in an air-saturated solution was 179 μM·h^-1, about 7.2, 2.5, 2.5 and 2.1 times quicker than that on C₃N₄, P-C₃N₄, O-C₃N₄, and phosphorus and oxygen co-doped C₃N₄, respectively. By taking advantage of the cascade mode in photocatalysis-self-Fenton reaction, H₂O₂ utilization efficiency was remarkably improved to 77.7%, about 9.0 times higher than that of traditional homogeneous Fenton reaction. Befitting from the superior yield and utilization efficiency, the degradation performance of P-C₃N₄/O-C₃N₄ was undoubtedly superior than other photocatalysts. This work well addressed two bottlenecks in traditional Fenton reaction: source of H₂O₂ and their low utilization efficiency, and the findings were beneficial to understand the mechanism and advantage of the photocatalysis-self-Fenton system in environmental remediation.

Reusable Ag@TiO2-Based Photocatalytic Nanocomposite Membranes for Solar Degradation of Contaminants of Emerging Concern

Two significant limitations of using TiO2 nanoparticles for water treatment applications are reduced photocatalytic activity under visible radiation and difficulty recovering the particles after use. In this study, round-shaped Ag@TiO2 nanocomposites with a ≈21 nm diameter and a bandgap energy of 2.8 eV were synthesised by a deposition-precipitation method. These nanocomposites were immobilised into a porous poly (vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) matrix and well-distributed within the pores. The photocatalytic activity of Ag@TiO2/PVDF-HFP against metronidazole (MNZ) under solar radiation was evaluated. Further, an adaptive neuro-fuzzy inference system (ANFIS) was applied to predict the effect of four independent variables, including initial pollutant concentration, pH, light irradiation intensity, and reaction time, on the photocatalytic performance of the composite membrane on MNZ degradation. The 10% Ag@TiO2/PVDF-HFP composite membrane showed a maximum removal efficiency of 100% after 5 h under solar radiation. After three use cycles, this efficiency remained practically constant, demonstrating the membranes' reusability and suitability for water remediation applications.

Rational tailoring of the electronic structure for the SrxNaTayO3 semiconductor: Insights into its enhanced photoactivity and optical property

NaTaO₃ (NTO), as a popular photocatalyst with the prominent redox ability, largely straddles across the conduction band minimum (CBM) and valence band maximum (VBM) edge over Fermi level. Pristine NTO exhibits the poor light-harvesting ability and the rapid recombination of electron-hole pairs. We proposed an effective method to improve the photocatalytic property of NTO (ABO₃-type) by substituting B site with Sr. The Sr_xNaTa_yO₃ (SNTO) exhibited the boosted photocatalytic activity toward tetracycline oxidation under solar light irradiation. The rate constant for S_0.5NTO (molar ratio of Sr: Ta = 1 : 2) was 5.1 times higher than the pure NTO. DFT results indicated that the Sr 3d orbital combining the O 2p and Ta 5d hybrid orbitals, widened the VB of SNTO. The band gap was narrowed from 3.86 to 2.82 eV after Sr substitution, which enhanced its light-harvesting ability. The VBM moved upward for 1.42 V and the CBM moved upward for 0.38 V. The shifts of the CBM and VBM, together with the more stretched Ta-O-Ta configuration, highly facilitated the electron-hole pair separation in SNTO. These electronic structure changes accounted for the significant photocatalytic performance enhancement of NaTaO₃ via Sr substitution for B-site-Ta.

Photodegradation of tartrazine dye favored by natural sunlight on pure and (Ce, Ag) co-doped ZnO catalysts

In this work, the synthesis of pure and (Ce, Ag) co-doped ZnO was successfully accomplished using a solvothermal process. The synthesized samples were characterized by ultraviolet-visible spectroscopy, X-ray diffraction, and scanning electron microscopy. The photocatalytic ability of the samples is estimated through degradation of tartrazine in aqueous solution under photocatalytic conditions. The degradation study carried out for a reaction period of 90 min at and a free pH = 6.0 found that dye degradation is 44.82% for pure ZnO and 98.91% for (Ce, Ag) co-doped ZnO samples, indicating its excellent photocatalytic ability. Tartrazine mineralization was also studied by calculating the degradation of chemical oxygen demand. The effect of operating parameters such as catalyst dose, initial concentration of tartrazine, initial reaction pH, and nature of light source has been optimized for tartrazine degradation as a function of time. The reusability of ZnO and (Ce, Ag) co-doped ZnO catalysts was studied and its photocatalytic efficiency was found to be unchanged, even after six cycles of use. The mechanism of photocatalytic activity was also proposed.

Improving the Solubility, Dissolution, and Bioavailability of Metronidazole via Cocrystallization with Ethyl Gallate

Metronidazole (MTZ) is an antibacterial drug widely used for the treatment of protozoan and anaerobic infections in humans and animals. However, its low bioavailability necessitates the frequent administration of a high dose to attain an effective plasma concentration profile for therapy. To reduce the dose of MTZ, we have prepared a new cocrystal between MTZ and ethyl gallate (EG). The solid-state properties of MTZ-EG were characterized using complimentary techniques, including thermal, spectroscopic, microscopic, and X-ray crystallographic methods. The MTZ-EG cocrystal exhibits a higher solubility and faster dissolution than MTZ. The bioavailability of MTZ in rats was increased by 36% when MTZ-EG was used.

Modulation of the Bifunctional CrVI to CrIII Photoreduction and Adsorption Capacity in ZrIV and TiIV Benchmark Metal-Organic Frameworks

The presence of hexavalent chromium water pollution is a growing global concern. Among the currently applied technologies to remove CrVI, its adsorption and photocatalytic reduction to CrIII less mobile and toxic forms are the most appealing because of their simplicity, reusability, and low energy consumption. However, little attention has been paid to bifunctional catalysts, that is, materials that can reduce CrVI to CrIII and retain both hexavalent and trivalent chromium species at the same time. In this work, the dual CrVI adsorption–reduction capacity of two iconic photoactive water-stable zirconium and titanium-based metal–organic frameworks (MOFs) has been investigated: UiO-66-NH2 and MIL-125. The bifunctionality of photoactive MOFs depends on different parameters, such as the particle size in MIL-125 or organic linker functionalization/defective positions in UiO-66 type sorbents. For instance, the presence of organic linker defects in UiO-66 has shown to be detrimental for the chromium photoreduction but beneficial for the retention of the CrIII phototransformed species. Both compounds are able to retain from 90 to 98% of the initial chromium present at acidic solutions as well as immobilize the reduced CrIII species, demonstrating the suitability of the materials for CrVI environmental remediation. In addition, it has been demonstrated that adsorption can be carried out also in a continuous flux mode through a diluted photoactive MOF/sand chromatographic column. The obtained results open the perspective to assess the bifunctional sorption and photoreduction ability of a plethora of MOF materials that have been applied for chromium capture and photoreduction purposes. In parallel, this work opens the perspective to develop specific chemical encoding strategies within MOFs to transfer this bifunctionality to other related water remediation applications.