Hydrothermal-assisted synthesis of Sr-doped SnS nanoflower catalysts for photodegradation of metronidazole antibiotic pollutant in wastewater promoted by natural sunlight irradiation.

In this study, we report a facile hydrothermal synthesis of strontium-doped SnS nanoflowers that were used as a catalyst for the degradation of antibiotic molecules in water. The prepared sample was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and ultraviolet-visible absorption spectroscopy (UV-Vis). The photocatalytic ability of the strontium-doped SnS nanoflowers was evaluated by studying the degradation of metronidazole in an aqueous solution under photocatalytic conditions. The degradation study was conducted for a reaction period of 300 min at neutral pH, and it was found that the degradation of metronidazole reached 91%, indicating the excellent photocatalytic performance of the catalyst. The influence of experimental parameters such as catalyst dosage, initial metronidazole concentration, initial reaction pH, and light source nature was optimized with respect to metronidazole degradation over time. The reusability of the strontium-doped SnS nanoflowers catalyst was investigated, and its photocatalytic efficiency remained unchanged even after four cycles of use.

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(PVDF-HFP) porous membrane for the remediation of a wide range of contaminants from wastewater withdrawn from industrial applications.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.

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.

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.

Polymer-Based Membranes for Oily Wastewater Remediation.

The compounds found in industrial wastewater typically show high toxicity, and in this way, they have become a primary environmental concern. Several techniques have been applied in industrial effluent remediation. In spite of the efforts, these techniques are yet to be ineffective to treat oily wastewater before it can be discharged safely to the environment. Membrane technology is an attractive approach to treat oily wastewater. This is dedicated to the immobilisation of TiO2 nanoparticles on poly(vinylidene fluoride-trifluoro ethylene) (PVDF-TrFE) porous matrix by solvent casting. Membranes with interconnected pores with an average diameter of 60 µm and a contact angle of 97°, decorated with TiO2 nanoparticles, are obtained. The degradation of oily wastewater demonstrated the high photocatalytic efficiency of the nanocomposite membranes: Under sunlight irradiation for seven hours, colourless water was obtained.

Membranes based on polymer miscibility for selective transport and separation of metallic ions.

Polymer inclusion membranes (PIM) used for selective transport and separation of metallic ions have emerged in recent times. Their expansion depends on the method of preparation and their suitable structure and physico-chemical characteristics. In this paper, a novel category of membranes for ions separation is reported. The membranes were synthesized by thermally induced phase separation using a mixture of polyvinylidene fluoride (PVDF) and cellulose triacetate (CTA) plasticized by tris(2-ethylhexyl) phosphate (TEHP) and with di-(2-ethylhexyl) phosphoric acid (D2EHPA) incorporated into the polymer as carrier to increase specific interactions between polymers. PIM membrane exhibited a hydrophobic (∼100°) and thermally stable up to ∼200°C porous homogenous structure. The transport of Ni(II), Zn(II) and Pb(II) from aqueous solutions was studied by competitive transport across polymer inclusion membranes (PIM). Competitive transport of ions in solution across PIM provide the selectivity order: Ni2+ (45%)>Pb2+ (35%)>Zn2+ (5%). A long-term transport experiment was carried out to study the durability of the system.