Removal Of Carbamazepine By Forward Osmosis Membranes

In recent years, a variety of trace organic pollutants, pharmaeeutieals and personal care products have been detected. These organic pollutants from the people’s daily life and and industrial production are disorderly emitted which have characteristics of strong activityand slow biodegradation. These pollutants have caused a lasting harm to human health. Carbazepine which can be used for the treatment of epilepsy, neuralgia and nervous system uremia and hyperuresis is widely used because of its remarkable efficiency. Carbazepine tends to increase cancer risks,and exposure to these pharmaceutical compounds without medical surveillance is dangerous due to the fragile health of high-risk life forms such as developing fetuses,or people with existing diseases taking medications.Removal of organic compounds by reverse osmosis(RO)and nanofiltration(NF) membranes has previously been studied. The rejection mechanisms of organic compoundsby RO/NF membranes include size exclusion, electrostatic repulsionand hydrophobic interactions between solute and membrane.Although RO/NF membrane processescan be powerful options to remove pharmaceutical compounds. These pressure-driven membraneprocesses are limited by membrane fouling and high energy consumption. ForwardOsmosis(FO) is a new type of membrane treatment technology. It offers many advantages over pressure-drivenmembrane processes such as lower fouling potential, low energy comsumption, simplicity and operation condition of room temperature. FO is attractingincreasing interests for its potential applications in wastewaterreclamation, energy and medicine field.In this study, rejection of carbamazepine(CBZ) by three commercial forward osmosis(FO) membranes was investigated. The effects of membrane orientation, draw solution concentration, flow velocity, and draw solute were also explored. The results shows the rejection of CBZ in the PRO mode was lower than that of FO mode because of the high concentration gradient caused by the porous support layerconcentration polarization. As draw solution centration increased from 0.5mol/L to 1.5mol/L, the increase of CBZ rejection became slow and high draw concentration caused serious reverse salt flux. Effect of flow velocity on a thin-film composite with embedded polyester screen(TFC-ES) is more significant than the other two membranes.The cellulose triacetate with a cast nonwoven(CTA-NW) membrane displayed a lower rejection as the flow velocity increased from 8cm/s to 24cm/s. NaCl was the most suitable draw solute for CBZ rejection. The rejection of CBZ increased with water flux, but high reverse salt flux may result in decrease of CBZ rejection. The cellulose triacetate with embedded polyester screen(CTA-ES) membrane showed constantly higher CBZ rejection than that of CTA-NW membrane, while TFC-ES membrane was even lower compared to CTA membranes. The results of membrane fouling resistance test of three commercial membrane shows that three kinds of membranes show good water flux stability(only 20% decline) in FO mode while significant decline in PRO mode(about 40% decline).On the other side, the PSf composite nanofibers were prepared by electrospin with PET as the support layer, and then the composite membrane was prepared by interfacial polymerization on PSf/PET nano composite fibers. After optimizing the spinning condition by changingdifferent spinning voltages and polymer concentration, the results shows that 25 KV is the best condition. As psf concentration increases from 15%-25%, The water flux of the three kinds of membranes first increases and then decreases both in FO and PRO mode, and the three kinds of FO membranes all shows high flux(25-36L/m2.h)as well as low salt flux(0.02-0.1g/m22h).The pure water flux of FO mode are smaller than that of PRO model, while the reverse salt flux is opposite to that.the electrospun nanofiber supported-polyamide composite membranes exhibited two to four times(two to seven in PRO mode) higher flux with up to 100 times lower salt flux than standard commercial forward osmosis membranes. The carbamazepine rejection experiment demonstrated that carbamazepine was efficiently removed with rejection ranging from approximately 84%-95%, while rejection rate of FO is higher than that of PRO which are quite better than those of commercial CTA membranes and much better than TFC membrane. The results of membrane fouling resistance test of PSF composite membrane prepared by electrospinning shows that the water flux of the three composite membranes decreased significantly, and the water flux decreased by about 30%, and the water flux of PRO decreased by about 45%. Compared to commercial membranes, The electrospun PSF composite membrane is subjected to membrane fouling more easily.