Abstract
Mg2+is extracted from ammonium dihydrogen phosphate (NH4H2PO4) solution by an emulsion liquid membrane (ELM) using mono-(2-ethylhexyl) 2-ethylhexyl phosphonate (HEHPEHE)as a carrier, sulfonated liquid polybutadiene (LYF) as a surfactant and kerosene as a solvent. To study the extraction efficiency and advantages of the ELM process in the separation of Mg2+,the effects of various operating conditions on the extraction -HEHPEHE volume fraction, reaction temperature, treat ratio (emulsion phase / external phase), phase ratio (membrane phase / internal phase), agitation speed, extraction time, internal phase concentration, surfactant LYF concentration and initial pH of NH4H2PO4 solution are experimentally investigated and discussed. The results show that Mg2+ in NH4H2PO4 solution can be effectively removed by the ELM process. An extraction efficiency of more than 83.1% is attained at the optimized parameters and superior-grade NH4H2PO4can be obtained by two levels of extraction.
Highlights
Mg2+ is extracted from ammonium dihydrogen phosphate (NH4H2PO4) solution by an emulsion liquid membrane (ELM) using mono-(2-ethylhexyl) 2-ethylhexyl phosphonate (HEHPEHE) as a carrier, sulfonated liquid polybutadiene (LYF) as a surfactant and kerosene as a solvent
Several methods based on solvent extraction [1,2] are used to remove Mg2+ industrially, in comparison with the solvent extraction process, an ELM process has main advantages such as very high mass
HEHPEHE is employed as an extractant produced by Luo Yang Zhong Da Chemical Company (China) (AR grade)
Summary
External aqueous solution (continuous phase) is prepared by dissolving magnesium sulfate heptahydrate in NH4H2PO4 solution. A water-in-oil (W/O) emulsion (dispersed phase) is made by slow addition of the internal aqueous solution to the organic solution at optimal stirring speed (3000 rpm) by means of a motor-driven emulsifier (Shanghai Specimen Model Factory, China). This high shear-agitator produced high speeds, generating emulsions with small size droplets around 0.5–100 μm. The parameters to be optimized are the HEHPEHE volume fraction, reaction temperature, treat ratio (emulsion phase/external phase), phase ratio (membrane phase/ /internal phase), agitation speed, extraction time, internal phase concentration, surfactant LYF concentration and initial pH of NH4H2PO4 solution. The concentration of Mg2+ is determined by atomic absorption spectrophotometry (GF3000)
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