Stability Study Of Supported Liquid Membrane To Extract And Recycle Phenol From Coal Chemical Wastewater

In recent years, with the rapid development of Chinese coal chemicalindustry whose consumption of water is huge, more and more wastewatercontaining phenols is discharged into the environment. And as a kind ofimportant organic chemical raw materials, phenols are widely used in industrialproduction, so recycling phenolic compounds from coal chemical wastewater cannot only produce some economic benefits, but also reduce the difficulty ofwastewater treatment, certain environmental benefits. Supported liquidmembrane system has many advantages, such as low capital investments andoperating costs, low energy consumptions, low liquid membrane requirements,simple to operate and easy to scale up, etc. But, there have been few large-scaleapplications, mainly due to its insufficient and longtime membrane stability andshort lifetime. Therefore, it is significant to study the mechanism of instability ofthis technique.In this study, the stability of hollow fiber supported liquid membrane hasbeen studied using polyvinylidene fluoride(PVDF) as supported membrane,tributyl phosphate(TBP) and kerosene as liquid membrane, sodium hydroxide asstripping solution. The research mainly investigates factors affecting stability ofthe system; the analysis of common mechanisms on the membrane liquid loss;re-impregnation to maintain the stability; composite membrane to enhance thestability.It could be concluded that flow rate, solution temperature and carrierconcentration can obviously affect the stability of the system, while others arenot remarkable, but, they work together to accelerate membrane liquid loss. After500hours operation, the phenol concentration of effluent is less than440mg/L.The mass transfer flux after three times re-impregnation could still reach about96%of the first time in the slowly decreasing stage. In the scale-up experiment,with the increase of feed or stripping solution flow rate, the effluentconcentration of phenol is decreased, and more than80%of phenol can beremoved, and the effluent concentration of phenol can reach about200mg/L. Themass ratio as PDMS:(3-cyanide propyl) triethoxy silane: DBTL=20:3:1,concentration of PDMS15wt%, coated40min, the composite hollow fibersupported liquid membrane possesses the best mass transfer performance. Themass transfer rates of traditional and composite hollow fiber supported liquidmembrane respectively are4.87×10-6m/s and3.97×10-6m/s. The mass transferrate of composite membrane reduces about18.5%, but the stability increasesabout8%. And compared to traditional supported liquid membrane, the composite supported liquid membrane is more accommodative to high flow rate,high temperature and other complex environment.