High flux and complete dyes removal from water by reduced graphene oxide laminate on Poly Vinylidene Fluoride/graphene oxide membranes

Graphene oxide-chitosan coated PVDF adsorptive microfiltration membrane: Enhancing dye removal and antifouling properties

This study investigates graphene oxide (GO) modified poly(vinylidene fluoride) (PVDF) membranes focusing on their dye rejection efficiency and their antifouling properties against bovine serum albumin (BSA). These membranes were prepared by modifying commercial PVDF membrane with a thin layer of GO nanosheets and chitosan (CS) using vacuum filtration. The synergistic physicochemical properties of the GO-CS/PVDF membranes were analyzed by XRD, FTIR, Raman, and XPS spectroscopy. The surface morphologies were observed by SEM and AFM microscopy, and WCA measurements. The deposition of GO and CS in the presence of citric acid resulted in a decrease in pore size and an increase in hydrophilicity. Modified membranes showed enhanced rejection of RB and MB, with rates increasing from 13.0 to 96.0 % and 28.3 to 69.1 %, respectively. Antifouling studies using BSA on selected membranes outperformed pristine membranes, which had higher irreversible fouling due to pore blockage. GO-CS/PVDF membranes exhibited higher flux recovery and lower irreversible fouling due to increased hydrophilicity, which prevents tight cake layer formation. Minimal detachment of the GO-CS layer during the long-term stability test is confirmed by minor fluctuations in dye flux and rejection. In summary, enhancing PVDF membranes with GO and CS augments dye rejection rates and bolsters antifouling properties.

How to apply terpenoid-based deep eutectic solvents for removal of antibiotics and dyes from water: Theoretical prediction, experimental validation and quantum chemical evaluation

This study proposed a theoretical prediction method and mechanism investigation for the extraction of antibiotics and dyes from aqueous media using terpenoid-based deep eutectic solvents (DESs). Firstly, Conductor-like Screening Model for Real Solvents (COSMO-RS) approach was applied to predict selectivity, capacity and performance index in the extraction of 15 target compounds including antibiotics (tetracyclines, sulfonamides, quinolones, β-lactams) and dyes by 26 terpenoid-based DESs, and thymol-benzyl alcohol shows promising theoretical selectivity and extraction efficiency for the target compounds. Moreover, the structures of both hydrogen bond acceptors (HBA) and hydrogen bond donors (HBD) have an impact on the predicted extraction performance, which can be improved by tailoring those candidates with higher polarity, smaller molecular volume, shorter alkyl chain length and the presence of aromatic ring structures, etc. According to the predicted molecular interactions revealed by σ-profile and σ-potential, the DESs with HBD ability can promote the separation process. Furthermore, reliability of proposed prediction method was confirmed by experimental verification, indicating that the trends of theoretical extraction performance index were similar with the experimental results by using actual samples. At last, the extraction mechanism was evaluated by quantum chemical calculations based on visual presentations, thermodynamic calculations and topological properties; and the target compounds showed favorable energies of solvation to transfer from aqueous phase to DESs phase. The proposed method has been proved with potential to provide the efficient strategies and guidance for more applications (e.g., microextraction, solid phase extraction, adsorption) with similar molecular interactions of green solvents in environmental research.

Fe3O4@Gum Arabic modified polyvinyl chloride membranes to improve antifouling performance and separation efficiency of organic pollutants

Nanofiltration (NF) membranes are promising media for water and wastewater treatment; however, they suffer from their hydrophobic nature and low permeability. For this reason, the polyvinyl chloride (PVC) NF membrane was modified by iron (III) oxide@Gum Arabic (Fe₃O₄@GA) nanocomposite. First, Fe₃O₄@GA nanocomposite was synthesized by the co-precipitation approach and then its morphology, elemental composition, thermal stability, and functional groups were characterized by various analyses. Next, the prepared nanocomposite was added to the casting solution of the PVC membrane. The bare and modified membranes were fabricated by a nonsolvent-induced phase separation (NIPS) method. The characteristics of fabricated membranes were assessed by mechanical strength, water contact angle, pore size, and porosity measurements. The optimum Fe₃O₄@GA/PVC membrane had a 52 L m^-2. h^-1. bar^-1 water flux with a high flux recovery ratio (FRR) value (82%). Also, the filtration experiment exhibited that the Fe₃O₄@GA/PVC membrane could remarkably remove organic contaminants, achieving high rejection rates of 98% Reactive Red-195, 95% Reactive Blue-19, and 96% Rifampicin antibiotic by 0.25 wt% of Fe₃O₄@GA/PVC membrane. According to the results, adding Fe₃O₄@GA green nanocomposite to the membrane casting solution is a suitable and efficient procedure for modifying NF membranes.

Photocatalytic TiO2@MIL-88A (Fe)/polyacrylonitrile mixed matrix membranes: Characterization, anti-fouling properties, and performance on the removal of natural organic matter

Photocatalytic membrane reactors (PMRs), coupling photocatalysts and membranes in a single system, have shown a considerable potential to reduce membrane fouling, which is one of the major drawbacks of using membranes to treat water and wastewater. In this study, the visible light-activated photocatalysts were incorporated into the polyacrylonitrile (PAN) casting solution to synthesize the photocatalytic composite membranes. The physicochemical properties and the morphology of the membranes and photocatalysts were characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction analysis (XRD), ultraviolet-visible diffuse reflectance spectroscopy (UV-visible DRS), photoluminescence (PL), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), Brunauer-Emmett-Teller (BET), porosimetry, and contact angle analyses. The performance of the synthesized photocatalytic mixed matrix membranes (MMMs) in treating water containing humic acid, as one of the major components in natural organic matter (NOM) existing in drinking water sources, was investigated. Under visible light irradiation, the PAN/TiO₂@MIL-88A (Fe) MMMs simultaneously adopted photocatalysis and membrane separation in the PMR and thereby enhanced humic acid removal and anti-fouling properties. The best synthesized photocatalytic membrane could remove 92.4% of the humic acid once exposed to visible light. The optimum membrane had suitable water permeability, a high flux recovery ratio (99.5%), and a 13.5% decline in the humic acid flux after a 10-h run, considerably lower compared to the corresponding decline of the pristine membrane (37.5% over the same period). The remarkable properties of the PAN/TiO₂@MIL-88A (Fe) membrane, including its high anti-fouling specification, confirm the appropriateness of the synthesized MMM for treating water involving humic acid.