Recent efforts to realize hollow fiber membranes for treatment of complex wastewater such as produced water has resulted in designing unique surfaces, for use in membrane distillation to combat wetting and fouling/scaling. However, HFMs suffer from mechanical inadequacies. Use of polyethylene terephthalate (PET) braid support to strengthen HFMs is gaining attraction, although their application in MD is scarce. Herein, we report omniphobic PET braid-reinforced HFMs (OBRMs) for application in direct contact membrane distillation (DCMD) of PW. The effects of feed type, velocity, temperature, and prolonged testing on performance OBRMs are reported. From the findings, a thin polymer layer with single-layer finger-like structure allowed for good flux (up to 15 kg/m 2 h) while omniphobic skin layer was instrumental in keeping oils and surfactants at bay. Complex PW feed is shown to have more adverse effect on strength of OBRMs than saltwater. Increased temperature negatively affects tensile strength while a turbulent flow keeps foulants at bay and mitigates fouling-assisted deterioration. Prolonged testing for nine DCMD cycles of treating PW recorded flux recovery up to 85%, with salt rejection remaining above 99.9%, a total organic carbon (TOC) rejection up to 98% and a decline in tensile strength of used membranes by 6.5%.
This work investigates the applicability of clinoptilolite, a natural zeolite, as a low-cost adsorbent for removing chromium from aqueous solutions using fixed bed studies. To improve its removal performance for the inorganic pollutant, the adsorbent is pretreated with NaCl to prepare it in the homoionic form of Na+ before undertaking ion exchange with Cr3+ in aqueous solution. This work also evaluates if treated effluents could meet the required effluent discharge standard set by legislation for the target pollutant. To sustain its cost-effectiveness for wastewater treatment, the spent adsorbent is regenerated with NaOH. It was found that the clinoptilolite treated with NaCl has a two-times higher Cr adsorption capacity (4.5 mg/g) than the as-received clinoptilolite (2.2 mg/g). Pretreatment of the clinoptilolite with NaCl enabled it to treat more bed volume (BV) (64 BV) at a breakthrough point of 0.5 mg/L of Cr concentration and achieve a longer breakthrough time (1500 min) for the first run, as compared to as-received clinoptilolite (32 BV; 250 min). This suggests that pretreatment of clinoptilolite with NaCl rendered it in the homoionic form of Na+. Although pretreated clinoptilolite could treat the Cr wastewater at an initial concentration of 10 mg/L, its treated effluents were still unable to meet the required Cr limit of less than 0.05 mg/L set by the US Environmental Protection Agency (EPA).
The use of low-cost clay materials for the fabrication of ceramic membrane has attracted much interest from researchers, and the outcome would be beneficial to the industries. In this study, low-cost bentonite was used for the preparation of hollow fiber ceramic (HFC) membrane. Bentonite powder was initially characterized by field emission scanning electron microscope (FESEM) for powder surface morphology. The bentonite membrane was fabricated through dope suspension mixing, using phase inversion-based extrusion method and sintering processes. The dope suspension was prepared by mixing quantified bentonite powder, dispersant, polymer binder, and organic solvent on a planetary ball mill. This was followed by the extrusion of the dope suspension at a bore fluid rate of 10 mL/min and air gap of 5 cm and finally subjected to the sintering temperatures of 950° C, 1000° C, 1050° C, and 1100° C. FESEM images revealed that bentonite powder has a compacted interlayer order of heterogeneous surface morphology. The resulting bentonite HFC membrane surface morphologies were examined by scanning electron microscopy (SEM), and the structures exhibit asymmetric structure, which was composed of sponge-like and finger-like structures. Due to, its superhydrophilic property and pore size; the membrane contact angle and water flux performance were obtained at 1.90° and ~326 L/m2 .h, respectively. Overall, the results suggest that bentonite can be used in the fabrication of ceramic-based hollow fiber membrane and in addition, can as well be utilized in microfiltration for wastewater treatment.
usage which contributes to the environmental issues. Among the type of existing renewable energy, fuel cells is the most promising renewable energy sources since the energy can be directly converted from combustible of fuel. The proton exchange membrane (PEM) is the heart of the fuel cells system. The research and development on proton electrolyte membrane is keep burgeoned. Even though the studies of the electrolyte nanocomposite membrane for fuel cell application are quite various but only a few studies focused on the effect of electrospun nanocomposite membrane on the performance of proton electrolyte membrane. This review is focusing on the electrospinning process for the preparation of electrospun fiber membrane. This review is concentrates on polymer based membrane electrospun nanofiber and their influence on proton conductivity as well as on fuel crossover barrier properties. The proton conductivity and fuel crossover can be improved by fully exfoliated structure of nanocomposite electrolyte membrane via electropinning process and thus the membrane can be an alternative PEM for DMFC applications.
This study aimed to develop innovative photothermal materials derived from agricultural by-products (rice husk), with a primary focus on assessing the potential of both rice husk ash (RHA) and rice husk char (RHC) powders as effective photothermal for localised heating. A comparative analysis of their feasibility for membrane integration and photothermal performance was conducted through comprehensive physical, chemical, and optical characterisations. The RHC powder demonstrated superior qualities for utilisation in comparison with RHA. This superiority is attributed to several key factors: a notably high production yield (40.3 %), a smaller particle size of z-average (0.65 μm), a significantly larger effective BET surface area (301.78 m2 g−1), smaller pore size (2.78 nm) and an elevated total pore volume (0.21 cm³.g−1). Dominated by a significant carbon content of 38.5 %, RHC powder showcased minimal light reflection (<5 %) and excellent light absorption across the entire spectrum, while RHA exhibited reflectance of more than 40 %, with light absorption occurring solely in the UV region. Moreover, RHC powder displaced superior light-to-thermal conversion, evident in a 20.9 °C temperature rise (83.6 %) from a 90-min exposure to a 0.4 kW m−2 full spectrum light source. The findings of this study firmly established RHC powder as the preferred alternative option for sustainable photothermal materials, given its physical properties compatible with membrane integration and exceptional photothermal conversion ability.
This investigation aimed to enhance the hydrophobicity of a polytetrafluoroethylene (PTFE) hollow fiber membrane, transforming it into an omniphobic surface. This was achieved by coating the membrane with a mixture of zinc oxide nanoparticles (ZnO-NPs) and polyvinylidene fluoride-cohexafluoropropylene (PVDF-HFP) using the universal spray technique. The membrane's morphology and performance were evaluated based on the number of spray cycles, which influenced the coating thickness on the membrane surface. The spraying process was varied up to 4 cycles to determine the membrane with the most effective deposition of ZnO NPs in terms of water contact angle and liquid entry pressure (LEPw). Results indicated that the membrane spray-coated up to 4 cycles, denoted as PTFE-4, exhibited a rough hierarchical re-entrant morphology, imparting omniphobic characteristics. The optimized membrane demonstrated a high water contact angle of 170° and a liquid entry pressure of 2.6 bar. Fourier-transform infrared (FTIR) and energy dispersive analysis of X-rays (EDX) confirmed the successful chemical integration of ZnO NPs onto the commercial membrane. This research holds significance for the future of membrane distillation in treating wastewater containing low surface tension pollutants.
A systematic study of the air gap effects on morphology and mechanical strength of Nickel Oxide (NiO) hollow fiber membranes has been carried out. The hollow fibers were prepared using the dry-jet wet spinning process using a dope solution containing NiO/N-methyl-2-pyrrolidone (NMP)/Arlacel/Poly(ethylene sulphide) with a weight ratio of 70/22.9/0.1/7. Tap water was used as internal and external coagulants. The cross-sectional structure of precursors hollow fiber membrane was studied by scanning electron microscopy (SEM). The results showed that both inner and outer finger-like voids of the hollow membrane were determined by the air gap distance. Experimental results indicated that an increase in air gap distance, from 100 mm to 200 mm, gave a hollow fiber with a lower mechanical strength and higher percentages of cross section surface area covered by finger-like voids structures. This study also revealed that the air gap introduced an elongation stress because of gravity on the internal or external surfaces of the NiO hollow fibers. A more effective hollow fiber membrane which is in asymmetric structure instead of symmetric structure can be produced by using air gap higher than 200 mm.
This work developed and applied a CuO-impregnated bauxite hollow fibre membrane (BHFM) using hydrothermal method for bisphenol A (BPA) photodegradation. BHFM was synthesized through a phase inversion method at optimum sintering at 1300 °C. Subsequently, the physico-chemical properties of CuO-coated BHFM were characterized, while its performance for the BPA degradation was investigated at varying time of hydrothermal exposure and compared to ceramic hollow fibre membrane from alumina (AHFM) as control and commercial membranes. Oxidation by-products, resulting from BPA photodegradation, were identified and after treatment, the saturated membrane was regenerated to sustain its cost-effectiveness. As compared to the pristine BHFM membrane, we found that functionalizating BHFM surface with CuO significantly improved its mechanical strength by 130 % from 18.5 to 42.5 MPa. The removal of BPA was enhanced with the increasing hydrothermal time to 5 h due to the even distribution of CuO-impregnated BHMF on its membrane surface. 97 % of BPA removal with 10 mg/L concentration was substantially attained by the same CuO-impregnated BHFM under visible light (VIS) irradiation. Treated effluents, resulting from the BPA photocatalysis, could meet the required effluent limit of 20 mg/L set by national legislation. The possible oxidation by-products cover 4-(2-hydroxy-2-propanol)phenol, 4-isopropylphenol and dihydroxybenzene. With 25 % of efficiency, the saturated CuO-impregnated BHMF was subsequently regenerated for consecutive five cycles. This implies that functionalizing BHMF surface with CuO enabled it to possess outstanding stability and removal performance for treatment of BPA-laden wastewater.
