Triple Stimuli-Responsive N-Isopropylacrylamide Copolymer toward Metal Ion Recognition and Adsorption via a Thermally Induced Sol–Gel Transition

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• 作者：Jinjin Cheng ; Guorong ShanPengju Pan
• 刊名：Industrial & Engineering Chemistry Research
• 出版年：2017
• 出版时间：February 8, 2017
• 年：2017
• 卷：56
• 期：5
• 页码：1223-1232
• 全文大小：587K
• ISSN：1520-5045

文摘

Poly(N-isopropylacrylamide-co-maleic acid-co-1-vinylimidazole), P(NIPAM-MA-VI), has been prepared in water by free radical polymerization. The aqueous solution of low-molecular-weight P(NIPAM-MA-VI) has four distinct phases above a critical concentration. Effects of monomer ratio, copolymer concentration, and pH on the phase transition temperatures of P(NIPAM-MA-VI) were studied. The addition of divalent metal ions promoted the gelation process of P(NIPAM-MA-VI). Therefore, the adsorption behavior of P(NIPAM-MA-VI) to Cu²⁺ ions was further investigated; this adsorption behavior was pH-dependent, and the adsorption isotherm could be well fitted by the Freundlich model. The maximum adsorption capacity reaches 21.1 mg g^–1 dried copolymer at 60 °C and pH 5. The adsorbed P(NIPAM-MA-VI) can be regenerated by the treatment of hydrochloric acid and reused in the following adsorption process. X-ray photoelectron spectroscopy (XPS) and synchrotron radiation small-angle X-ray scattering (SAXS) were used to investigate the effect of Cu²⁺ ions on the phase transition behavior of P(NIPAM-MA-VI). O 1s and N 1s XPS spectra and SAXS results analyzed by the Ornstein–Zernike and generalized Ornstein–Zernike models are in agreement with the proposed mechanisms and adsorption behavior. As a thermo-, pH-, and metal ion-responsive copolymer, P(NIPAM-MA-VI) could be used for the ion recognition, water purification, and enrichment of heavy metal ions.