Solubilization Of Cu²⁺ In Supercritical Carbon Dioxide Microemulsion

As a "green-friendly" alternative solvent, microemulsion formed in supercritical carbon dioxide has attracted considerable interest. The solubility of metal ions can be improved by W/C microemulsion. This extends the application fields of supercritical carbon dioxide, including reaction,extraction,cleaning and nano-particle preparation. However, studies on the solubilization of metal ions in literatures are not sufficiently for applications. In order to resolve this problem, a variable-volume high pressure view cell apparatus was designed and built for measuring the solubilization of Cu²⁺ in supercritical CO₂ microemulsion。Two surfactants were selected, PFPE-NH₄ and AOT. The PFPE-NH₄ W/C microemulsion can solubilize Cu²⁺.The research condition: PFPE-NH₄ was 0.0150M, W₀ was 10.00 or 20.00, PFPE-NH₄/CO₂ mol ratio was 7.64×10^-3.At five different temperatures: 308.15 K,313.15 K,318.15 K,323.15 K and 328.15 K, we found five different solubilization line. When W₀ was 10.00, the maximum solubilization amount of Cu²⁺ was from 3.541mmol/1 to 3.745mmol/1; When W₀ was 20.00, the maximum solubilization amount of Cu²⁺ was from 8.239⁸.500mmol/l. The Cu²⁺ can't solubilize in the microemulsion formed by AOT and dissolved in supercritical dioxide containing an alcohol, ethanol, 1-pentanol or octanol.The micro-polarity of PFPE-NH₄ and AOT microemulsions formed in supercritical CO₂ was studied. Methyl orange was selected as solvatochromic probe molecular, and the absorption spectrum of methyl orange was detected by a fiber optic spectrometer connected with the view cell. We found that the micro-polarity of the AOT W/C microemulsion was very small, which caused Cu²⁺ can't solubilize in the microemulsion.At the end, semiconductor nanopaparticles of CuS was synthesized in the water-in-CO₂ reverse microemulsions formed by PFPE-NH₄, than primarily analyzed by TEM.