Supported liquid membrane extraction to treat coal gasification wastewater containing high concentra

Journal of Harbin Institute of Technology( New Series),Vol. 19,No.1,2012Supported liquid membrane extraction to treat coal gasificationwastewater containing high concentrations phenolYAO Jie", HE Zhi-ru, LUO An-guo, ZHAO Qi, JIA Li, SHAO Ze-hui, LI Biao-ming'杰,何志茹,雒安国,赵琪,贾丽,邵泽辉,李彪铭(1.schooLofMunicipalandEnvironmentalEngineeringHarbinInstituteofTechnology,Harbin150090,China,yaojiejie@@hotmail.com:2.natiOnalEngineering Research Center of Urban Water Resources, Harbin150090, China; 3. Dongying Running Water Company, Dongying 257091, ChinaAbstract: The hollow fiber supported liquid membrane extraction was introduced to treat coal gasificationwastewater to recover phenolic compounds, with tributyl phosphate( TBP)as carrier, kerosene as the mem-brane solvent, sodium hydroxide solution as the stripping agent and PVDF as the membrane material. Factorshaving strong impact on the extraction efficiency were studied in detail, including the mass transfer mode, two-phase flow rate, stripping phase concentration. As extraction system with 20% TBP-kerosene, parallel flowmass transfer, stripping phase concentration 0. 1 mol/L, the optimal operating conditions could be obtainedUnder the optimum operating conditions, the time required to reach equilibrium for the extraction is 50 minnd extraction efficiency of phenol is 86. 2% and the phenol concentration of effluent is 98. 64 mg/L.Key words: supported liquid membrane; coal gasification wastewater; phenol; extraction efficiencyCLC number: X703Document code: AArticle ID:10059113(2012)01005503During the process of pressurized gasification of kerosene, sodium hydroxide of analytical grade, andcoal, the phase of crude coal gas cooling and washing PVDF hydrophobic hollow fiber membrane were used ingenerates large amount of complicated and high CoD this research. Raw coal gasification wastewater withwastewater,which contains high concentration of phenolic phenol concentration of 1762 mg/L was obtained fromcompounds, ammonia, single ring and polycyclic aromatic Lurgi Gasifier at Harbin Coal Chemical Industry Cohydrocarbons, heterocyclic aromatic hydrocarbons withLtd, and concentration was tested with 4-AAP spectrotrogen, sulfur or oxygen and a portion of tar and cyanide. photometric methodIt is one of the most refractory wastewater to be treated. 1.2 Experimental MethodCoal gasification wastewater causes environmental pollution, and on the other hand, phenol is one type of impor-Basir.ig. I shows the experiment setup of treating coalication wastewater by means of supported liquidtant raw material for chemical industry. Therefore, trea- membrane extraction, in which organic liquid film flowsting wastewater containing phenol and reclaiming phenols in circulation inside the tube of membrane system foravegreat significance. Supported liquid membrane ex5-10 min driving by peristaltic pump so that mem-traction has the advantage of both liquid-liquid extraction brane pores were filled with organic liquid phrase, andInd membrane system, such as high efficiency, less ener- then wastewater( liquid phase) and extraction systemgy consuming, good selectivity, ease of realizing industri- was fully mixed according to certain proportions so thatalization, and many studies have been done on liquid film it can flow in circulation inside the tube of membranecomposition, transmission mechanism and industrial appli- system. At the same time, reverse extraction phase so-cation. In this paper, the feasibility and operating condi- dium hydroxide flow in shell of the membrane systemtion of treating coal gasification wastewater by means of The phenol concentration variation with time was testedsupported liquid membrane extraction, with PVDF hydro- under different operating conditions, and the extractionphobic hollow fiber membrane serving as the liquid film efficiency was calculated, so the optimized operatingsupporter,TBP( Tributyl phosphate )as mobile carrier condition was obtainedand kerosene as membrane solventastewater volume V is 0.5 L: volume and con-ntration of stripping phase VA1 Experiment1.0 moL/L, and ratio of two phases is 0-1/25. THliquid and organic phase flow rate Q are 50-150 mL/1.1 Apparatus and Materialsmin and o中国煤化工 ectively.Magnetic stirrer, Visible Spectrophotometer, TBPCNMHG55Journal of Harbin Institute of Technology( New Series), Vol 19, No 1, 2012crease in stripping phase concentration, extraction efficiency increases firstly, and then keeps stable. This il-lustrates that stripping phase concentration should becontrolled at certain extent in supported liquid mem-brane extraction system80一0.01000501-Magnetic stirrer; 2-Feed tank; 3--Stripping extraction solvent tankpump; 4--Peristaltic pump: 5--Pressure gauge: 6-Valve: 7-Hollow0.500fiber membrane module020406080Fig 1 Flow chart of supported liquid membrane extractionT/minto treat coal gasification wastewaterFig 3 Effect of stripping extraction phase concentration orextraction efficiency2 Result and Discussion2.3 Effect of Ratio of Two Phases on Extraction2.1 Effect of Mass Transfer on Extraction Effi-EfficiencyciencyIt can be inferred from Fig. 4 that the ratio of twoAs shown in Fig. 2, mass transfer modes have phases has little effect on extraction efficiency which ilgreat influence on phenol extraction, and when the bal- lustrates that there is limited liquid phases flashing aance reaches, parallel mass transfer shown highest ex- way in the membrane. Because wastewater flow is tootraction efficiency while reverse mass transfer has lower less to cause strong sheer force for liquid phase in theextraction efficiency. Parallel flow leads to higher two- membrane pores and so little liquid washed away in thephase relative rate, thinner mass transfer boundary laysystem is observeder, higher transfer efficiency, and longer contact timeof two phases, all of which is beneficial to the transferprocess and therefore extraction efficiency. In addi-tion, if the feed liquid flows like reverse, the strippinghase cannot fully soak all the membrane silk. In thisexperiment, it was found that only 1/3 of the mem-brane silk get contacted with stripping phase, resultingn lower utilization rate of stripping phase and low ex-1:25traction efficiency.020406080100120140T/minFig 4 Effect of ratio of two phases on extraction efficiency2. 4 Effect of Two-Phase Flow Rate on the Extraction EfficiencyReverse mass transfer 1From Figs. 5 and 6, it can be concluded that withthe increase in volume flux of two phases, extractionParallel mass transferefficiency increases firstly, and then keeps stableThats because that greater mass transfer coefficient of6080100120140tube and shell causes high total transfer coefficientT/minwhich is beneficial for extraction. But when the volumeFig2 Effect of mass transfer on extraction efficiency with flux of two phases got too large, the solute distributionertical membranecoefficient in the organic phase will deecrease and was2. 2 Effect of Stripping Phase Concentration on tract中国煤化工 celerated, so the exCNMH Gme flux of strippingFrom Fig 3, it can be concluded that with the in. extractiExtraction Efficiencyuvaave on extraction ratethan liquid phase does, which can be explained by theJournal of Harbin Institute of Technology( New Series),VoL 19, No. 1, 2012fact that mass transfer resistance in liquid phase ac- current mass transfer. Stripping extraction phase con-counts for greater proportion in total resistance than centration has great influence on extraction efficiencythat in the stripping extraction phaseProportion of organic phase has little effect on extraction efficiency, which means that little organic phase iswashed away from the system. Two-phase flow三certain effect on extraction efficiency and withof flow rate of two phases, extraction efficiency-5.0ses firstly and then keeps stable7.5LhThe optimal operating conditions of supported liq-100Lh-12.5Ihuid membrane extraction to treat coal gasification150I/hwastewater are parallel mass transfer, stripping extrac-tion phase concentration of 0. 1 mol/L, ratio of two100120140phases of 0, membrane fill proportion of 19%.Underthis condition, it will take 50 min to reach the balance,with extraction efficiency of 86. 2% and phenolFig 5 Effect of liquid phase flow rate on the extraction ef-concentration phenols of 98. 64 mg/LficiencyReferences[1] Huang Yunbing. The new coal chemical industry technologyprogress. Enterprise Science and Technology Develop-ment,2009,12(258):31-335.0I/h[2] Messikhab N, Samar M H. Neural network analysis ofid-liquid extraction of phenol from wastewater using10.0Lholvent. 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Beijing: Chemical Industrycontaining high concentrations phenol, it can be con-Press,2007,100-103cluded that mass transfer modes have great effect on[7 Rhlalou T, Ferhat M, Froujietal M A. Facilitated transportextraction efficiency and parallel flow mass transferof sugars by a resorcinarene through a supported liquidmembrane. Journal of Membrane Science, 2000, 168(1mode leads to higher extraction efficiency than counter2):63-73中国煤化工CNMHG57