The selective and sustainable separation of Cd(II) using C6MImT/[C6MIm]PF6 extractant

Abstract

Cadmium has been classified as a kind of human carcinogens, and has a strong mobility in the water environment and this can result in serious harm to human health and environmental safety. Here, a new selective and efficient extraction-recovery strategy for Cd purification is provided by using C6MimT/[C6Mim]PF6 as the green extractant. Due to the high compatibility between C6MimT and [C6Mim]PF6, C6MimT-Cd was efficiently separated from the aqueous phase. When the concentration of Cd(II) was 1000 mg/L, the extraction rate could reached 99.9 %. By comparing [C6MIm]BF4 with [C6MIm]PF6, the hydrophobicity restrained the ion exchange between cation and Cd and significantly reduced the loss of extractant. The extracted Cd(II) was separated in the form of precipitation after stripping. The extraction system of C6MimT/[C6Mim]PF6 was stable after several extraction-stripping cycles. The extraction of Cd(II) by C6MimT/[C6Mim]PF6 system mainly realized by forming a neutral and extractable cadmium complexes between Cd(II) and thione. Based on the natural complexation mechanism between metal and C6MImT, Cd exists as obvious competitive advantage in coordination with C6MimT compare to Pb, Zn, Mg, Cr, Fe. This work overcomes the problems of extractant loss and organic pollution caused by volatile or ion exchange, which can only reduce environmental hazards, but also promote the recovery of cadmium and other valuable resources.