pH Manipulation: A Facile Method for Lowering Oxidation State and Keeping Good Yield of Poly(m-phenylenediamine) and Its Powerful Ag+ Adsorption Ability

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• 作者：Liyuan Zhang ; Liyuan Chai ; Jin Liu ; Haiying Wang ; Wanting Yu ; Peilun Sang
• 刊名：Langmuir
• 出版年：2011
• 出版时间：November 15, 2011
• 年：2011
• 卷：27
• 期：22
• 页码：13729-13738
• 全文大小：1055K
• 年卷期：v.27,no.22(November 15, 2011)
• ISSN：1520-5827

文摘

A method of pH manipulation has been used to improve chemically oxidative polymerization of m-phenylenediamine (mPD) through concurrent addition of NaOH when adding oxidant (NH₄)₂S₂O₈. pH detection and open-circuit potential technique were adopted to monitor the polymerization process of mPD and to explain the oxidation state鈥損H and yield鈥損H relationships. Results from Fourier transformed infrared (FTIR) and X-ray photoelectron (XPS) spectroscopies indicate that a low oxidation state is under control by regulating NaOH concentration. At 2.5 M NaOH, the oxidation state of poly(m-phenylenediamine) (PmPD) is 64.7 mol % (measured by molar content of quinoid imine from XPS), while the yield is 84%. The synthesized PmPD possesses better Ag⁺ adsorption performance when lowering its oxidation state. Moreover, the Ag⁺ adsorbance of PmPD can reach 1693 mg g^鈥?. Meanwhile, Ag⁺ adsorption mechanism was studied by pH tracking, X-ray diffraction (XRD) patterns, and X-ray photoelectron spectroscopy. The adsorption process includes redox reaction, chelation, and physical adsorption.