Ultrafiltration membrane based on polyacrylonitrile prepared by phase inversion method using zinc chloride as an additive showed more than 90% rejection for BSA and 90 -110 lm Ϫ2 h Ϫ1 water flux. The surface modification of this membrane was studied using ethanolamine, triethylamine, sodium hydroxide, and potassium hydroxide solutions. The effect of base treatment time and temperature on water flux and rejection was investigated. The membranes exhibited swelling by NaOH treatment followed by deswelling by HCl post-treatment, similar to pH responsive membranes. The treatment by organic as well as inorganic bases improved water flux with a slight lowering in BSA rejection by dead-end mode type treatment. A 230% increase in water flux was achieved by sodium hydroxide treatment in crossflow mode without a noticeable pore swelling by SEM. The contact angle of the modified membranes was decreased as compared to the unmodified one indicating appreciable surface modification. As the treatment time or temperature increased, the ESCA analysis showed increased population of Na-carboxylate groups.
Supported ultrafiltration (UF) membranes based on polyacrylonitrile were prepared by phase inversion method using nonwoven polyester fabric as support with different origin. The membrane preparation parameters, including dope solution composition and casting conditions, were kept same while changing the support fabric. Various analyses performed, viz. water flux, protein rejection, porosity, and membrane compaction indicated that the support used for UF membrane preparation affects the membrane properties to a great extent, and a right support need to be chosen for a preparation of membrane with desired properties.
ab s t r ac tPhosphorous containing antiscalants, which are commonly used in RO desalination process, have become an environmental concern for RO concentrate disposal. These chemicals are suspected of contributing to algal blooms in the water bodies where RO concentrate is discharged. Therefore, phosphorous-free antiscalants are increasingly being required for both brackish and seawater membrane desalination systems. Nalco recently developed a phosphorous-free antiscalant (PC-1611T) to address this environmental concern. In the laboratory testing, this product performed similar to ATMP (commonly used phosphonate based antiscalant) for CaCO 3 scale inhibition up to 3.0 LSI (Langelier Saturation Index). It also inhibited CaCO 3 scale in presence of up to 1 ppm Fe 3+ and residual levels of poly(DADMAC) based pre-treatment coagulant. It also showed 2-5× lower bio-growth contribution potential than polycarboxylates and is compatible with polyamide RO membranes. Full-scale evaluation of this product is in progress and the results for first 4 weeks show stable RO performance, indicating successful scale-control.
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