Study On The Preparation And Phenols Wastewater Treatment Of PDMS Pervaporation Membranes

Phenols, i.e. highly toxic hydroxy compounds of aromatic hydrocarbons, pose great harm to environment and become one of key controlling objects in wastewater treatment field. Phenols are common pollutants of wastewater streams from petroleum refineries, petrochemical industries, the production of phenolic resins, pesticides, etc. Recovery phenols methods include solvent extraction, activated carbon and polymer adsorption and biochemical technology. However, it is difficult to get a satisfying result by these processes.Polydimethylsiloxane(PDMS), a kind of non-porous polymeric material, exhibits high permeability to phenols and can be used as membrane material for the extraction of these compounds from wastewaters, provided that an organic activity gradient is maintained across the membrane. During last several years, PDMS membrane technologies and pervaporation processes have attracted great attention for removal of volatile organic compounds (VOCs) from wastewaters.In this paper, a series of PDMS membranes are prepared by using polydimethylsiloxane(PDMS) as material,β-cyclodextrin (β-CD) and coronary aether as additive. The structure morphology, the physical and chemical parameters of the membranes are obtained by FT-IR, SEM, contact angle experiment, swelling experiment, breaking strength and thickness mensurated. The effect of the additive quantity on the separation performance of the membranes is investigated, the results showed that: with the increasing of theβ-CD quantity in the membranes, the permeation flux first decreased and then increased, the selectivity of the membranes increased; the selectivity and the permeation flux of the membranes both increased as the quantity of the coronary aether increased, the chemical additive enhanced separation performance of the membrane.The effect of operation condition on the separation performance of the pervaporation is also investigated. the selectivity of the membranes increased while the permeation flux decreased as the vulcanization temperature increased; the selectivity of the membranes decreased while the permeation flux increased as the feed temperature increased; the selectivity and the permeation flux of the membranes both increased as the feed concentration increased; the selectivity and the flux also both increased as the feed flow rate increased; the selectivity increased while the permeation flux decreased as the separation press increased. When the proportion of the PDMS, solvent, cross linker and catalyst were immobile, The permeation flux and separation factor could be 87mg/(m~2·h) and 4.75 when the vulcanization temperature was 40℃, feed temperature was 60℃, feed concentration was 0.1 g/L, feed flow rate was 0.4L/min and separation press was 6KPa.The modified Methyl-block-PDMS membranes were prepared by using triethoxy methylsilane as cross linker, the methyl content in the membrane structure were increased, the hydrophobic performance of the membranes were improved, the physical and chemical parameters of the modified membranes are also obtained, the effect of solvent and cross linker dosage on the separation performance of the pervaporation is investigated, the permeation flux and the selectivity of the modified membranes separately increased 14% and 22%, The modified Methyl-block-PDMS membranes obtained very good effect.Study on the applied treatment performance of the PDMS pervaporation membranes on the actual phenols wastewater, the effect of salty ion and sulfuric acid, hydrochloric acid on the separation performance of the pervaporation is investigated, research the performance of the membranes on phenols wastewater with high concentration and low concentration, the results showed that: the permeation flux increased while the content of the NaCl increased, the permeation flux also increased while the content of the sulfuric acid increased, but the permeation flux decreased while the content of the hydrochloric acid increased. The elimination rate of phenol is 87% and 75.2% while using the PDMS pervaporation membranes treat the phenols wastewater with high concentration and low concentration, the elimination rate of COD is 89.6% and85.5%, obtained very good effect. Moreover, the elimination performances of the PDMS pervaporation membranes on other familiar VOCs are also wonderful.