Supported Liquid Membrane Extraction And Recovery Of Phenol From High Concentration Coal Gasification Wastewater

The high concentration of phenolic compounds in the wastewater has a seriousimpact on the coal gasification wastewater treatment. However, the phenoliccompounds in the wastewater have high recovery value. Supported liquid membraneextraction technique is a new separation technology with advantages of a smallextractant use, high extraction efficiency, low running costs and no secondary pollution.These advantages make the supported liquid membrane technology has a broad spacefor development in the extraction and recovery of phenol from high concentration coalgasification wastewater.The extraction and recovery of phenol from high concentproportion coalgasification wastewater has been investigated using polypropylene (PP) hollow fibermembranes and polyvinylidene fluoride (PVDF) hollow fiber membranes as supportedliquid membrane and the mixture of extraction agent and paraffin as liquid membranephase, with sodium hydroxide as stripping agent. The main research contents of theexperiments are as follows.(1) The effect of the composition of the liquid membranephase made of N-503-kerosene, tributyl phosphate (TBP)-kerosene or trialkylphosphine oxide (TRPO)-kerosene on extraction efficiency has been studied.(2) Theeffect of membrane wire thickness and membrane pore size of the supported membraneon the extraction effect has been researched.(3) The experiments have studied the effectof operating conditions such as liquid phase temperature and the connection forms ofmembrane modules on the extraction process.(4) The continuous experiments whichcan test the stable operation ability of the supported liquid membrane system havedetermined the most suitable supported liquid membrane system from the screenedsupported liquid membrane system in the previous research.(5) The effect of liquidphase and stripping phase flow rate, membrane modules connection forms on theextraction process and testing the stable operation ability of supported liquid membranesystem are the main research contents in the scale-up experiments which can confirmand optimize the conclusions obtained in lab scale experiments.The supported liquid membrane give novel extraction result for the extraction ofphenol from high concentproportion coal gasification wastewater when proper liquidmembrane phases and liquid membrane support body materials are used in supportedliquid membrane system. Under the operating conditions of waste water temperature at20℃，pH at7.5~8.1，waste water and stripping phase flow rate at5L/h, the supportedliquid membrane using PP as the supported liquid membrane and the extraction agent ofTBP with volume proportion of20%could operate continuously and stablely more than24hours and the extraction effect be4%higher than PVDF-TBP supported liquidmembrane systems. The extraction efficiency of the PP-TBP supported liquidmembrane systems is94%and the phenol concentration of effluent is100.68mg/L. The conclusions obtained in lab scale experiments can be confirmed in the scale-upexperiments. The liquid phase flow rate has a greater effect on the extraction efficiencyof the supported liquid membrane system while the effect of stripping phase flow rateon the extraction effect is small. The combinations of membrane modules series andmembrane modules parallel can enhance the extraction effect of supported liquidmembrane system. Under the optimum operating conditions, the extraction efficiency ofthe PP-TBP supported liquid membrane system is87.02%in the scale-up experimentsand the phenols concentration of effluent is218.14mg/L. The extraction efficiency ofscale-up experiments is satisfactory and the phenols concentration of effluent meet therequirements of biodegradation.