Advanced (bio)fouling resistant surface modification of PTFE hollow-fiber membranes for water treatment

Antifouling PTFE Hollow Fiber Microfiltration Membrane with a Double-Defense Mechanism

Polytetrafluorethylene (PTFE) is the preferred material for highly polluted wastewater treatment. Hydrophilic modification of the PTFE hollow fiber membrane can further enhance its filtration performance and durability. Yet, it still remains a challenge to construct a robust hydrophilic coating on the PTFE surface. Here we report a surface engineering strategy of in situ coating a PTFE hollow fiber membrane with poly(vinyl alcohol) (PVA) and polyion complex (PIC) double-layer (DL) hydrogels. The first PVA hydrogel layer was covalently bonded to N-β-(aminoethyl)-γ-aminopropyl trimethoxysilane (AEAPTS)-grafted PTFE via a glutaraldehyde (GA)-induced Schiff base reaction and aldol condensation, respectively, while the second PIC hydrogel layer was strongly anchored on PVA through hydrogen bonding and topological entanglements. The resulting PVA/PIC DL hydrogel coating exhibited favorable strength and chemical resistance. Moreover, the double-defense mechanism provided by the hydration layer and polyzwitterionic brushes endowed the membrane with durable microfiltration and antifouling performances by effectively repelling various types of pollutants.

Macroencapsulation Device with Anti-inflammatory Membrane Modification Enhances Long-Term Viability and Function of Transplanted β Cells

Treating type 1 diabetes (T1D) through β-cell macroencapsulation is a promising long-term solution, but it faces challenges such as immune-mediated fibrosis on the capsule surface, which impairs cell functionality and compromises longevity and effectiveness. This study presents an approach for including an anti-inflammatory molecule on the macroencapsulation device (MED) using initiated chemical vapor deposition for the surface modification of poly(tetrafluoroethylene) (PTFE) membranes. The surface-modified MEDs significantly reduced fibrosis, improved β-cell viability and functionality, and promoted M2 macrophage polarization, which is associated with anti-inflammatory effects. This MED displayed improved glycemic control in a streptozotocin-induced diabetic mouse model for 45 days. The findings underscore the potential of surface-modified MEDs for improving T1D management by mitigating inflammation and enhancing the therapeutic efficacy of β-cell encapsulation.

A Novel Organic-Inorganic-Nanocomposite-Based Reduced Graphene Oxide as an Efficient Nanosensor for NO2 Detection

There are three components to every environmental protection system: monitoring, estimation, and control. One of the main toxic gases with considerable effects on human health is NO2, which is released into the atmosphere by industrial activities and the transportation network. In the present research, a NO2 sensor is designed based on Fe3O4 piperidine-4-sulfonic acid grafted onto a reduced graphene oxide Fe3O4@rGO-N-(piperidine-4-SO3H) nanocomposite, due to the highly efficient detection of pollution in the air. In the first phase of the present study, the nanocomposite synthesis is performed in four steps. Afterward, the novel fabricated nanosensor is characterized through energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), Raman, surface area analysis, and field emission scanning electron microscopy (FE-SEM). To determine the optimal condition for sensor performance, graphene-based nanosensors are prepared with various weight percentages (wt%) of rGO-N-(piperidine-4-SO3H) (1 wt%, 5 wt%, 10 wt%, and 15 wt%). During the experimental process, the performance of the sensors, in terms of the sensitivity and response time, is investigated at different NO2 concentrations, between 2.5 and 50 ppm. The outputs of this study demonstrate that the synthesized nanosensor has the best efficiency at more than a 5 ppm contamination concentration and with at least 15 wt% of rGO-N-(piperidine-4-SO3H).

Role of plasma process gas on permeate flux augmentation of cellulose nitrate membrane for mud water treatment

A comparative study between Nitrogen (N2) and Argon (Ar) plasma is carried out to investigate its effect on surface morphology, hydrophilicity, permeate flux and ageing of cellulose nitrate polymeric membranes in the present work. Langmuir probe and Optical Emission Spectroscopy are used to characterize the plasma. The SEM analysis reveals the noticeable macro-void creations and pore enlargement for both N2 and Ar plasma. The AFM analysis shows a higher surface roughness for Ar plasma treatment as compared to N2 plasma treatment. XPS analysis confirms the changes in the polymer matrix along with the incorporation of various functional groups on the membrane surface as a result of the plasma treatment. A better hydrophilic nature with prolonged plasma treatment is observed for Ar plasma as compared to N2 plasma treatment. The present results show a higher permeate flux with a high rejection rate for Ar plasma treatment in comparison to N2 plasma, which might be due to the pore size and pore area enlargement of the membrane. The hydrophobic recovery for both the plasma-treated membranes is found significant for the initial ageing period of 7 days and found almost stable in nature after 7 days. A diffusion-based theoretical model is developed to study the hydrophobic recovery of plasma-treated membranes. A strong alignment between experimental and theoretical results is observed in the present work. The Cake Filtration model, derived from the Hermia model, is identified as the most suitable model for describing the fouling mechanisms for the present work.

Performance enhancement of the solar still using textiles and polyurethane rollers

The acquisition of clean drinking water in regions with limited power sources has been a challenge of paramount concern. Solar stills have emerged as a popular and sustainable option for obtaining clean water in such regions. This process involves employing solar radiation to heat up water, which is then condensed to obtain potable water. The present study introduces a solar still system that is both cost-effective and energy-efficient, while simultaneously ensuring sustainability. Fabric-coated polyurethane rollers with capillary action enhance evaporation area, leading to notable performance improvements. Water vapour condensed on the cooling chamber's inclined aluminium plate and collected in the distillate chamber within the solar still. The thermal, energetic, and economic performance and productivity of the proposed model were evaluated. The fabricated solar still boasted maximum instantaneous system efficiency and exergy efficiency of approximately 62.16% and 7.67%, respectively. This system's cost-effectiveness and performance improvements are particularly noteworthy. The daily average distillate productivity of the proposed still was estimated at 1.14 L/m2, resulting in an annual production rate of 416.54 L/year. The estimated cost of producing 1 L of distillate was 0.023 $.