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Industrial wastewaters contain high levels of heavy metals, including lead, which are highly toxic.1 Lead is also used as an essential raw material for manufacture of batteries, pigments, fuel, photographic materials and explosives.2,3 Learning and behavioral disorders in children, damage to liver, kidney and heart and impaired immune system result from lead contamination.4 There are various methods for removing heavy metals from industrial effluents, which include chemical and biological methods. These methods include chemical deposition, adsorption, ion exchange and solvent extraction, which are still in use. However, industries are looking for competitive alternative technologies which can overcome a number of major disadvantages of these methods. One of the promising methods for separating heavy metals from wastewater is emulsion liquid membrane process.3
Emulsion liquid membrane was first introduced in 1968 by Li and was initially most used in separation of hydrocarbons.5,6,7,8,9,10,11 Separation of zinc, copper, gold, chromium and compounds such as phenols was well done by a variety of liquid membranes. If downstream processes where separation and condensation are done both preferably in one step can be designed and implemented, considerable savings can be made. Liquid membranes have this potential, that is, they can perform purification and condensation in one step.3,12,13
In the emulsion liquid membrane, the membrane is actually a liquid phase in the form of emulsion (Fig 1). Emulsion liquid membranes are necessarily double emulsions, such as water/oil/water (w/o/w) systems, which is liquid membrane of the oil phase. The emulsion liquid membrane involves the receiver phase which is placed in the membrane phase and forms the emulsion, and this emulsion is dispersed again in the feed phase and forms a double or secondary emulsion. Components are absorbed from the feed phase in the membrane phase and penetrate into the receiver phase where they are ultimately discharged into.14,15
The operation performed in an emulsion liquid membrane separation process consists of four steps (Fig 2):2
Emulsification.
Dispersion of the emulsion in contact with the continuous external phase for extraction.
Deposition for separating emulsion from external phase.
Decomposition of emulsion for membrane phase retrieval.
Taguchi’s method is a powerful statistical method for determining optimal arrangement of factors of a process, thereby achieving better process efficiency, reducing variability and producing...