Synthesis of Ion-Exchange Polypyrrole/Activated Carbon Composites and Their Characterization as Electrodes for Capacitiv
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Note www.springer.com/13233 pISSN 1598-5032 eISSN 2092-7673
Synthesis of Ion-Exchange Polypyrrole/Activated Carbon Composites and Their Characterization as Electrodes for Capacitive Deionization Oneeb ul Haq1 Jae-Hwan Choi*,2 Youn-Sik Lee*,1
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Division of Chemical Engineering, Jeonbuk National University, 567 Baekje-Daero, Deokjin-gu, Jeonju, Jeonbuk 54896, Korea
Department of Chemical Engineering, Kongju National University, 1223-24, Cheonan-daero, Seobuk-gu, Cheonan, Chungnam 31080, Korea Received November 27, 2019 / Revised March 9, 2020 / Accepted March 23, 2020
1. Introduction Capacitive deionization (CDI) uses a low electrical potential to adsorb ions from ion-rich feed flow onto electrode surfaces, and remove ions from the solution, resulting in deionization (or desalination). In CDI cells, the ions are adsorbed onto oppositely charged electrode surface and co-ions are repelled, suggesting that ion adsorption and desorption may occur simultaneously in the pores of carbon electrodes, leading to substantial reduction in adsorptiondesorption efficiency. The efficiency was improved significantly by placing ion-exchange membranes between either anode or cathode and a spacer, which is called membrane CDI (MCDI). The membranes increase counter-ion flux by allowing only counterions to pass through during the adsorption step1 and prevent oxidation and reduction reactions at anode and cathode.2 However, the high price of commercial ion-exchange membranes limits the practical application of CDI cells. It had been discovered that electrodes functionalized with ionic groups became polarized and intrinsically more coulombically efficient.3,4 Recently, Yan et al. prepared a polyaniline/AC (PANI/AC) composite electrode for CDI cells.5 They found that the pristine AC particles were compacted, enriching the composite in mesopores and leading to rapid diffusion of ions. Furthermore, the electrical conductivity of the composite electrode was higher than that of the pristine AC electrode. Thus, the composite-based CDI cell exhibited much higher salt adsorption capacity (SAC) than the pristine AC electrode-based cell (3.15 mg/g vs. 1.98 mg/g). More recently, Haq et al. synthesized ion-exchange PANI/AC composites and used them as electrodes of CDI cell. The resulting cell exhibited higher performance than the simple (non-ionic exchange) PANI/AC cell (SAC = 17.7 mg/g vs. 14.7 mg/ g), which was at least comparable to that of MCDI cell (15.5 mg/g).6 The improved performance of the ion-exchange PANI/AC-based CDI cell compared with the PANI/AC cell was attributed to the functional groups in the PANI chains that acted similar to those of ion-exchange membranes in the MCDI cell. Polypyrrole (PPy) is another common electro-conducting Acknowledgment: This study was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (grant No. 2017R1D1A1B03028365). *Corresponding Authors: Youn-Sik Lee ([email protected]), Jae-Hwan Choi ([email protected]) Ma
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