Simultaneous Extraction And Stripping Of Cu(II) Ions Through Vegetable Oil-Based Bulk Liquid Membrane
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Date
2011-12
Authors
Chang, Siu Hua
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Publisher
Universiti Sains Malaysia
Abstract
This research aims to examine the feasibility of replacing the classical petroleum-based organic solvents, which are non-renewable and invariably toxic, with the vegetable oil-based ones, that are more renewable and environmentally benign, as the membrane phase of a bulk liquid membrane (BLM) for simultaneous extraction (removal) and stripping (recovery) of Cu(II) ions in a single unit. The liquid-liquid extraction results revealed that soybean oil-based organic solvent (soybean oil loaded with di-2-ethylhexylphosphoric acid (D2EHPA) (extractant (carrier)) and tributylphosphate (TBP) (phase modifier)) and sulphuric acid (H2SO4) of 1.5 M were the most suitable organic solvent and efficient stripping agent, respectively, for Cu(II) ion extraction and stripping. By means of Response Surface Methodology (RSM), the optimum conditions for maximum Cu(II) ion extraction were determined as follows: D2EHPA concentration ([D2EHPA]) of 85.43 mM, equilibrium pH of 4.47, mixing time of 3 min, organic to aqueous phase ratio of 1, sodium sulphate (inert salt) concentration of 200 mM, and TBP concentration of 30 mM. The stoichiometry (stoichiometric ratio of D2EHPA to Cu(II) ion of 4:1) and structure (inner sphere) of Cu-D2EHPA complexes (extracted species), as well as the loading capacity (2400 mg/L (37.82 mM) of Cu(II) ions) and reusability (up to 10 consecutive extraction-stripping cycles) of soybean oil-based organic solvent were also investigated. The suitable design parameters (stirring of all phases and stripping/membrane to feed/membrane interface area ratio of 2.5:1) for a soybean oil-based BLM were selected and its operating parameters ([D2EHPA], H2SO4 concentration ([H2SO4]), stirring speed, temperature and operating time) were optimised for maximum Cu(II) ion stripping by RSM as follows: [D2EHPA] of 87.43 mM, stirring speed of 150 rpm, temperature of 313 K, operating time of 24 h, and [H2SO4] of 1.5 M.
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Keywords
Simultaneous extraction and stripping of Cu(II) Ions , through vegetable oil-based bulk liquid membrane