Search

Membrane gas-liquid separation technology has garnered significant attention in applications such as membrane desalination, distillation, and gas absorption due to its operational flexibility, compact design, and large specific interfacial area. However, the currently used membranes are prone to pore wetting under high operational pressures, transitioning from a non-wetted state to partially or fully wetted conditions. This undesired wetting increases mass transfer resistance for water vapor molecules, ultimately leading to reduced removal efficiency. To address this issue and enhance wetting resistance, membrane hydrophobicity needs to be improved. In this study, a highly hydrophobic polyvinylidene fluoride (PVDF) membrane was developed using the phase inversion method for membrane distillation applications. We mixed a 16wt% polymer concentration with N-Methylpyrrolidone (NMP) as a solvent at 50°C for 24 hours. Subsequently, the polymer solution was cast and exposed to different non-solvents, namely water and methanol, to investigate their impact. Surface morphology and hydrophobic properties of the synthesized membranes were analyzed using Scanning Electron Microscope (SEM) and a Goniometer. Our findings indicate that the PVDF membrane fabricated with methanol as the non-solvent exhibited a significantly higher water contact angle of 126°, compared to 70° when deionized water was used as the non-solvent. This change from water to methanol as the non-solvent resulted in a more symmetrical membrane structure, enhancing the water contact angle from 70° to 126°. It is interesting to note that increase in the water contact angle increases the hydrophobicity of the PVDF membrane.

This paper was focused on the use of allicin as inhibitor which binded with less valuable by-product, palm stearin on urea fertilizer as to increase its efficiency in soil. The coated urea was prepared in three models: urea + palm stearin (UPS), urea + allicin (UAL), urea + allicin + palm stearin (UALPS), whereas pure urea prills act as control (U) sample. The efficiency of the coating materials were investigated through characterization study and this followed by investigation on its N-transformation in soil through quantification of urea-N and ammonium-N remained in soil. Fourier Transformed Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA) results proved palm stearin as a compatible binder for urea-allicin system as no significant chemical reaction or weight losses occurred compared to control sample, based on their spectrum respectively. Scanning Electron Microscope (SEM) images demonstrated that the micro-structure of UALPS resulted in a smoother coated layer besides hardness test exhibits higher crushing strength. All coated urea fertilizer showed significantly higher nitrogen in urea form (urea-N) in soil compared to control sample. Consequently, nitrogen in ammonium form (ammonium-N) in coated urea fertilizer was lower than uncoated urea as this has proved the coating material has delayed the urea-N release. Besides, UALPS and UAL possess lowest ammonium-N content since the presence of allicin in their coating material had reduced the urease activity in the soil. In overall UALPS, found to be more efficient in reducing the hydrolyzation rate due to the dual effects of material, which may inhibit urease activity and reduce nitrogen (N) releases rate from fertilizer microenvironment. [ABSTRACT FROM AUTHOR]

Hydrogel has been used as an alternative to replace biocide-based paint in preventing biofouling. However, hydrogel has low adhesion on metallic substrate, hindering its application for coating. Therefore, the aim of this project is to enhance the adhesion strength and anti-biofouling properties of the poly(acrylamide-co-acrylic acid)/polyethylene-glycol hydrogel, poly(AAm-co-AAc/EG) coating via the incorporation of fly ash-based geopolymer that range from 0.5 wt% to 2.5 wt%. The hydrogel coating was synthesised via free radical polymerisation with the aid of N,N-methylenebisacrylamide (MBA) as the crosslinker, and ammonium persulfate (APS) as the initiator. The Fourier transform infrared (FTIR) spectra of the hybrid hydrogel had proved the presence of geopolymer with the availability of significant peaks at 3,294 cm-1 (N-H bond), 2,946 cm-1 (O-H bond), 1,545 cm-1 (C-O-C bond) and 1,113 cm-1 (Si-O-Si or Al-O-Si bond). The average swelling capacity of the hybrid hydrogel coating in distilled water (up to 50,000 %) was significantly higher than in artificial seawater (up to 5,000 %) due to osmotic pressure difference. The anti-biofouling performance test by using algae (Chlorella vulgaris sp.) suspension showed that the incorporation of 2.0 wt% geopolymer into hybrid hydrogel coating had successfully reduced the algae attachment on the substrate by 92 % as compared to the control sample. The adhesion strength of all hydrogel coatings was investigated by using the pull-off adhesion test in accordance to ASTM D4541. The incorporation of 2.0 wt% geopolymer into hydrogel matrices demonstrated an increment of 58% in adhesion strength on steel plate as compared to neat hydrogel. The results showed that geopolymer has the potential to improve the anti-biofouling and adhesion strength of hydrogel coating. [ABSTRACT FROM AUTHOR]