| Membrane extraction is a new separation technology which combines membrane process with liquid-liquid extraction.It is a new membrane-based separation process for the removal of azeotropic compounds,volatile organic compounds,thermo sensitive and low boiling point materials from aqueous solution.By means of hydrolytic equilibrium of aromatic acid or base, combined nonporous membrane(permeable for the aromatic compounds but impermeable for the ionic species) and caustic or acidic stripping solution,the new extraction process is characterized as high efficiency,low energy consumption,simple and convenience etc. Presently,the technology is at its initial stage of industrialization application.There are still many problems that need to be investigated.In this study,o-cresol was chosen as model compound of phenolic compounds and sodium hydroxide was used as stripping solution.One kind of membrane process system was constructed by non-porous membrane(Poly Dimethylsiloxane,PDMS).The characteristics,mass transfer process and mechanism of the systems were investigated.The mathematical model was obtained.The following studies were carried out:(1) A new membrane extraction technology with single tubular non-porous silicone rubber membrane and basic stripping solution were combined into membrane extraction used for treatment of o-cresol wastewater,which operated by circulating mode.The membrane extraction research for o-cresol was investigated.Based upon the resistance-in-series model, the effects of o-cresol initial concentration,liquid flow status on the surface of membrane, stripping solution pH value,and salt ion strength,different kinds of acid and system temperature on Kov were discussed.The experiment results indicated that the wastewater of this initial concentration is suitable for membrane extraction;when Res＞1677.80 and Ref＞148.18, Kov was dominated by membrane resistance in this process using silicone rubber;When the stripping solution pH＞11,the increasing pH value influence on Kov was not remarkable;Kov was in direct proportion to the temperature in this process,the salt ion and acid in the wastewater could change the distribution coefficient of the o-cresol between two phase to effect on the whole mass transfer processes.Compared with phenol wastewater,this technology is more suitable for extracting the wastewater which contains weakly hydrophilic substance such as o-cresol. (2) A new membrane extraction technology with spiral wound tubular non-porous silicone rubber membrane and basic stripping solution were combined into membrane extraction used for treatment of o-cresol wastewater,which operated by continuous mode. Through investigating the effects of liquid flow status on the surface of membrane and system temperature on mass transfer coefficient,mass transfer mechanism and process of o-cresol through membrane were investigated.The mathematical model between flow status and temperature was obtained.The experimental result showed that the obtained correlation is acceptable and effective,in which relative error is under 5%.(3) On the basis of trail results,the pilot project of utilizing PDMS to treat wastewater from chemical industry in Shandong was designed.This process was suitable for the treatment of high strength wastewater with o-cresol.The economic benefit was obvious.The net benefit was￥113.94 per ton when initial concentration was 21928.46 mg/L for design.It was calculated that the payback period of investment is about 2.87 years.
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