Research On Dissolution Of Metals In Ionic Liquids

Ionic liquids which are completely composed of anions and cations, are liquids at ambient temperature. Many metals can be eletrodeposited from ionic liquids because they have wide electrochemical windows.In this paper, 1-buty-3-methylimidazolium chloride ([bmim]Cl) intermediate,[bmim]BF4,[bmim]PF6 and [bmim]Cl-AlCl3 ionic liquid were prepared. Dissolution of metals in ionic liquids with or without the oxygen and under different temperatures was investigated.Dissolution of metals (Al,Cu,Fe) in ionic liquids under the conditions of hermetic and oxygen involved were measured. The experimental results showed that the dissolution rate of metals and saturation concentrations of metal ions in ionic liquids increased with increase in the temperature. Air involved appears to play a significant role in dissolution of metals in ionic liquids, which can change the dissolution mechanism.Al can hardly be dissolved in [bmim]BF4 and [bmim]PF6. Al and the ionic liquids were obstructed by the Al2O3 film. If Al2O3 layer was destroyed, Al can dissolve soon. Whereas Al in [bmim]Cl-AlCl3 was corroded by Cl-.Fe can be dissolved in three kinds of ionic liquids. Moreover, the dissolution magnitude of Fe in [bmim]Cl-AlCl3 was the largest, and the dissolution rate was basically constant. The apparent activation energy varied greatly under different conditions.The dissolution magnitude of Cu in [bmim]PF6 was little. But Cu in [bmim]Cl-AlCl3 was corroded significantly. Cu can only be dissolved in BMIMBF4 in the present of oxygen. According to the experimental data, the value of apparent activation energy was found to be 21760 J/mol in the temperature range from 25 to 70℃under the air atmosphere.The dissolution of Cu,Fe,Al in ionic liquids were different. The dissolution order of Cu,Fe,Al in [bmim]BF4 is expressed as follows Cu>Fe>AlSimilarly, the dissolution order of Cu,Fe,Al in [bmim]PF6 is expressed as follows Fe>Al>CuThe saturation concentrations of Cu2+ in [bmim]BF4 increased with increase in the oxygen partial pressure. Compared with [bmim]BF4 and [bmim]PF6, the saturation concentrations of Cu2+ in [bmim]Cl-AlCl3 was the largest due to the present of Cl-.Dissolution of Cu in BMIMBF4 is a diffusion-controlled process, the rate of that mainly depends on the diffusion of Cu2+ from the solid-liquid interface to the bulk solution. The rate equation of Cu dissolution in BMIMBF4 under different oxygen partial pressures and temperatures can be expressed asThe corrosion potential of Cu in [bmim]BF4 shifts negatively with increase in the temperature, and the current density and corrosion rate increased with increase in the temperature. The corrosion potential,current density and corrosion rate were maximal under the oxygen atmosphere. The corrosion potential shifts negatively with decrease in oxygen partial pressure, and the corrosion rate decreased gradually with decrease in oxygen partial pressure.The [bmim]BF4 potential is maximal under the oxygen atmosphere comparing with air and argon, and which increased with increase in oxygen partial pressure. The dissolution rate of metals can be accelerated with the [bmim]BF4 potential improved.