Modification of Polysulfone Membrane for Separation of Compound Substance in Natural Rubber Serum

Abstract

Natural rubber product is the one significant exporting products of Thailand. Nevertheless, bad smells and wastewater from latex and rubber processing pollute the environment. Since the usable rubber particles in natural rubber latex are collected by chemical processing, the wastewater from the operation comprises the beneficial components in the residual fraction (NR serum). The NR serum consists of proteins, carbohydrates, fats, residual rubber particles, water, and other compounds. That compound will be transformed into products in the future, and value might be added to NR serum waste when it is separated from rubber particles and increased the concentration of the proteins and other components. Membrane technology is one popular technique that does not degrade organic molecules, and presents a more viable solution to the problem of separating NR serum from water. Nonetheless, membrane filtering of NR serum has been difficult due to tiny residual rubber particles in the serum, which are sticky and tend to clog the membrane, blocking pores and causing irreversible fouling. Improving the hydrophilic characteristics of the membrane surface is an essential factor in anti-fouling and preventing the accumulation of hydrophobic rubber molecules on the membrane surface. Thus, this research has the objective to enhance the hydrophilicity of the membrane surface by ultraviolet irradiation (UV-ray) with poly (ethylene glycol) (PEG) grafting, and by an electron beam to induce the acrylic acid/sodium styrene-sulfonate (AAc/SSS) grafting on the membrane surface. The results showed that the difference in wavelength of UV-ray had a different grafting effect. The UV-ray at a wavelength of 312 nm had better grafting and hydrophilic than 254 nm. Moreover, UV at treatment with 312 nm and the PEG grafting on the membrane showed a higher water flux than the untreated membrane. The electron beam energy at 10 MeV and dose of 50 kGy had shown the best condition for AAc/SSS grafting on the membrane surface. The modified membrane had been used for NR serum filtration, and the results showed after 2nd cycle filtrations of NR serum had the flux recovery ratios of 95.9 %, the rejection rates of the total solid content (TSC), and total protein in NR serum were 72.1 % and 91.5 %, respectively. So, the modified membrane had good anti-fouling properties toward the natural rubber particles and organic molecules found in NR serum.