Development Of Emulsion Liquid Membrane For Cadmium Removal
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Date
2014-07
Authors
Kusumastuti, Adhi
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
Although cadmium is basically available in very low concentration; it should be removed due to the toxicity to human body and environment. Among the existing methods, emulsion liquid membrane (ELM) is a promising method by providing high interfacial area and the ability to remove a very low concentration of the solute. However, ELM faces problems in emulsion stability and breaking loaded emulsion. Selection of suitable liquid membrane components and the use of ultrasound emulsification, counter-current Taylor-Couette column (TCC) permeation as well as centrifuge demulsification are expected to minimise emulsion instability, increase extraction and demulsification efficiencies. The optimal tiny emulsions were produced using commercially supplied ultrasonic. The drop size was measured by the aid of microscope and image J software. Initially, cadmium in simulated wastewater was extracted using a stirrer followed by an extraction using TCC. Cadmium content was determined using Atomic Absorption Spectrophotometer (AAS). The loaded emulsion was broken by centrifuge. Demulsification efficiency was determined by comparing water content of pre and post demulsified using Karl Fischer titrator whilst organic membrane solution was analysed using Gas Chromatography-Mass Spectrophotometry (GC-MS). The overall performance of ELM system can be predicted by the developed mathematical model. The results showed that emulsification time, surfactant concentration, carrier concentration and volume ratio of membrane to internal phase affect the emulsion diameter, ranging from 0.878 to 2.46 m. The highest removal capacity of 0.493 mg Cd/mL emulsion and the lowest membrane breakage of 1.494x10-5% were obtained at the smallest emulsion droplets diameter. Study on Cd(II) extraction using stirred vessel showed that HCl concentration in feed phase governs the process. More than 90% of Cd(II) could be extracted after 35 minutes under the following conditions: 15 minutes of emulsification time, 4 wt. % of Span 80 concentration, 4 wt. % of TOA concentration, 600 rpm of stirring speed, 150 ppm of initial feed concentration, volume ratio of emulsion to feed phase of 1:5, and HCl concentration of 0.1 M. For TCC under the same condition, extraction efficiency reached more than 96% in 10 minutes. This is very promising because the mass transfer area is much larger, the extraction occurs along the column. The loaded emulsion was successfully demulsified using centrifuge with efficiency of >97% in 15 minutes at 3500 rpm. The system able to recover up to 99% of kerosene and TOA. A study on mass transfer model for cadmium extraction covers the mass transfer in the external phase and emulsion globule, stripping reaction, and diffusion of the complex showed that the model can predict well the experimental concentration profile of Cd(II).
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Keywords
Development of emulsion liquid membrane , for cadmium removal