Removal Of Cyanide From Wastewater Through Supported Ionic Liquid Membrane

Cyanides are toxic compound which have a good complex capacity.Therefore,many industrial activities use cyanides in their operation processes,and generate cyanides as an undesirable by-product.Cyanides are extremely hazardous because they combine with high-speed rail cytochrome,leading to tissue suffocation.In addition,any discharge of cyanide wastewater will destroy ecological environment.Thus,the treatment of cyanide from wastewater has a great attention in the environment protection.Compared with the traditional volatile organic solvents,Ionic liquids(ILs)are “green” solvents having attractive and fascinating physical and chemical characteristics:good chemical stability;no measurable vapor pressure and less volatile;high ion mobility.Therefore,ILs can be applied in SLM as the organic phase to prepare supported ionic liquid membranes(SILMs)for treatment of cyanide wastewater.In this study,hydrophobic ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate([Bmim]PF6)were immobilized into the pores of solid polymeric polyvinylidene fluoride(PVDF)support to prepare SILMs for the removal of cyanide wastewater from gold smelter.Experimental parameters such as membrane immersion time,feed phase concentration,pH and strip pahse concentration were studied to explore the optimization conditions of removal cyanide.The stability mechanism of the supported liquid membrane for cyanide transport was studied by electrochemical impedance spectroscopy(EIS).(1)The SILMs were prepared through immersion method using PVDF as support,[Bmim]PF6 as ionic liquid and kerosene as membrane liquid.Membraneswere characterized by means of scanning electron microscopy(SEM)and contact angle(CA)to study the loss rate of membrane,membrane immobilization capacity,membrane morphology and wetting ability etc.The prepared SILMs have good performance.(2)Experimental parameters such as membrane immersion time,feed phase concentration,pH and strip pahse concentration were studied to explore the optimization conditions of removal cyanide.The optimal conditions were determined to be as follows: membrane immersion time,1h;feed phase concentration,312.24mg/L;feed phase pH,4;NaOH,3%;stirring temperature 25?,and the removal of cyanide was95.31% under the optimal conditions.Therefore,the extraction effect was good.(3)The membrane immersion time,feed phase concentration,pH,strip pahse concentration and stirring temperature were studied to explore the effects on removal of cyanide from wastewater.The permeation coefficient under different experimental conditions and the change of total cyanide concentration in the feed solution were obtained,and the transfer rate of total cyanide at different reaction times was determined.(4)The ILs loss from the membrane pores in the transfer process,and the value of the SILMs resistance decreased,the solution resistance increased conversely.It resulted the decrease of SILMs transmission efficiency,and affecting its stability.Therefore,the ILs loss was monitored continuously by the AC impedance method in real time to explain the stability of the SILMs by change of the resistance of each component.In the initial stage,the ILs on the surface of SILM fallen off easily to the strip phase.At the intermediate stage,most of the ILs lost from the membrane pores,and the membrane resistance reduced substantially.When reached to the penetration stage,almost all of the ILs lost from the membrane pores,and the aqueous solution immersed into the membrane pores,and the support was penetrated,the SILM life was failure.Therefore,AC impedance spectroscopy method was used to monitor the loss of the SILM in real time.