Xiaoxia Liu,Yangyang Wang,Ronghao Liu,Ping Lv,Wenfeng Xue,Jinxin Guo,Huiying Wei,Yanzhao Yang
With environmental problems and a shortage of resources, it is urgent to recover gold from electronic waste (e-waste). Meanwhile, it is necessary to explore the relationships between the structures and extraction performances of ionic liquids (ILs) to further improve the extraction capacities of ILs for gold. Herein, three pyrrolidinium-based ILs with various N-substituents were synthesized for solvent-free extraction of Au(III). The three pyrrolidinium-based ILs exhibited ultrahigh extraction capacities for Au(III) with the order of [Pyr-EA][NTf2] (524.6 mg·g–1) > [Pyr-Bu][NTf2] (457.3 mg·g–1) > [Pyr-C2OC2][NTf2] (403.5 mg·g–1). The effects of N-substituents on extraction performances were quantitatively investigated by electrostatic potential (ESP) and quantitative NMR. Among them, the ester group (−COOR) is the most beneficial to the extraction process, which is associated with an increased ESP value and boosted hydrophobicity. Notably, [Pyr-EA][NTf2] displayed outstanding selectivity in multimetal solutions; especially, it could selectively and efficiently extract Au(III) from the actual CPU. Furthermore, [Pyr-EA][NTf2] possesses significant reuseability and can maintain superior extraction efficiency of 84.3% after five cycles. These excellent performances together with low cost ($0.44·g–1 [Pyr-EA][NTf2]) and considerable profit ($29.72·g–1 [Pyr-EA][NTf2]) confirmed that [Pyr-EA][NTf2] is a promising prospect for sustainable recovery of gold from e-waste.
The thermo- and pH/CO2-responsive poly[N-[2-(dialkylamino)ethyl]acrylamide]s containing a polyacrylamide backbone but different N-substitutes of dialkylamine were synthesized and their solution properties were comparatively checked. A controllable RAFT synthesis of poly[N-[2-(dialkylamino)ethyl]acrylamide]s was achieved when a typical trithiocarbonate containing an easily cleavable R group was employed. The RAFT polymerization rate decreases with the increasing C-number in the N-substitutes. The thermo- and pH/CO2-responsive property of poly[N-[2-(dialkylamino)ethyl]acrylamide]s is firmly correlative to the N-substitutes. With the C-number in the R-substitute increasing, the solution properties of poly(N-[2-(dialkylamino)ethyl]acrylamide)s undergo a soluble-to-thermoresponsive-to-insoluble evolution, and the critical pH of poly[N-[2-(dialkylamino)ethyl]acrylamide]s gradually decreases. The dialkylamine moieties in the poly[N-[2-(dialkylamino)ethyl]acrylamide]s lead to a characteristic CO2-response during CO2/N2 bubbling. The present study reveals the structure-dependent solution properties of the thermo- and pH/CO2-responsive poly[N-[2-(dialkylamino)ethyl]acrylamide]s, and these multistimuli-responsive polymers are believed to be very useful due to the controllable RAFT synthesis and tunable solution properties.
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