The Removal Of Acetic Acid By Emulsion Liquid Membranes Technique And The Recovery Of Calcium Magnesium Acetate In The Internal Phase

At present,the quantity of which our country discharges acetic acid wastewater can amount to 400000 tons every year,the concentration of acetic acid wastewater ranges from 0.5%to 65%.Since there is not good recovery processing method,acetic acid wastewater is discharged directly.As a result,it not only pollutes environment but also wastes resource.If we can recycle acetic acid effectively,nearly 120000 tons of acetic acid can be recycled every year,which equals to 1/10 current domestic acetic acid production.Emulsion liquid membrane has advantages of quick separation speed,high efficient,good selectivity and saving energy.The removal of acetic acid by emulsion liquid membrane can make wastewater reach to national emission standard and effectively recycle acetic acid.The removal of acetic acid from simulated acetic acid wastewater using emulsion liquid membrane technique is studied.The membrane phase is consisted of the membrane solvent kerosene,span80,carrier N235 and TBP and membrane stabilizing agent liquid paraffin.The internal phase is calcium oxide and magnesium oxide suspension.Acetic acid entering into internal phase reacts with calcium oxide and magnesium oxide suspension,finally they produce CMA.CMA in the internal phase is recycled.The experiment obtains CMA.CMA is green deicer.Compare with NaCl,CMA has the advantage of water-solubility,low melting point and biodegradable.There are three aspects studied in the experiment such as stability of emulsion liquid membrane,the removal of acetic acid by emulsion liquid membrane and recovery of acetic acid.The study on the stability of emulsion liquid membrane mainly includes the concentration of surfactant,the kinds and concentration of carrier,the liquid paraffin concentration,preparation time,preparation speed,the ratio between oil phase volume and internal phase volume.The optimum conditions is that the surfactant concentration is 6%,the carrier concentration is 4%,the liquid paraffin concentration is 2%,the preparation time is 20min,the preparation speed is 2800r/min,the ratio between oil phase volume and internal phase volume is 1:1.In terms of the stability of emulsion liquid membrane,the stability of emulsion liquid membrane which consists of N235 is superior to that of TBP.During the study of the removing of acetic acid by emulsion liquid membrane,some parameters are investigated,including the kinds and concentration of carrier,the concentration of surfactant,calcium to magnesium ratio,the particle size of calcium oxide and magnesium oxide,calcium oxide and magnesium oxide suspension concentration,the ratio between oil phase volume and internal phase volume,the ratio between emulsion volume and external phase volume,mass transfer time,mass transfer speed,initial concentration of acetic acid.In this paper the orthogonal test is made in order to ensure optimal combination.We can get better the removing of acetic acid when the carrier TBP concentration is 4%,the surfactant span80 concentration is 6%,calcium to magnesium ratio is 2.9:7,the particle size of calcium oxide and magnesium oxide is from280 to 340 mesh,calcium oxide and magnesium oxide suspension concentration is 13.1g/L,the ratio between oil phase volume and internal phase volume is 1:1,the ratio between emulsion volume and external phase volume is 1:2,the stirring speed is 180r/min,the stirring time is 25min.Under optimum condition,the removal rate of acetic acid can reach to 99.8%.The optimal combination of orthogonal test is that the particle size of calcium oxide and magnesium oxide is from 280 to 340 mesh,TBP concentration is 6%,the ratio between oil phase volume and internal phase volume is 4:3,calcium oxide and magnesium oxide suspension concentration is 13.1g/L,the stirring speed is 210r/min,the stirring time is 25min,the ratio between emulsion volume and external phase volume is 1:2.In the recovery of CMA,the experiment investigates demulsification of emulsion liquid of mass transfer such as demulsification time and demulsification temperature.The optimal demulsification time is 90min,and demulsification temperature is 100?.The experiment produces CMA and characterizes it.