Enhanced Salt Removal in an Inverted Capacitive Deionization Cell Using Amine Modified Microporous Carbon Cathodes

Environ Sci Technol. 2015 Sep 15;49(18):10920-6. doi: 10.1021/acs.est.5b02320. Epub 2015 Aug 27.

Abstract

Microporous SpectraCarb carbon cloth was treated using nitric acid to enhance negative surface charges of COO(-) in a neutral solution. This acid-treated carbon was further modified by ethylenediamine to attach -NH2 surface functional groups, resulting in positive surface charges of -NH3(+) via pronation in a neutral solution. Through multiple characterizations, in comparison to pristine SpectraCarb carbon, amine-treated SpectraCarb carbon displays a decreased potential of zero charge but an increased point of zero charge, which is opposed to the effect obtained for acid-treated SpectraCarb carbon. An inverted capacitive deionization cell was constructed using amine-treated cathodes and acid-treated anodes, where the cathode is the negatively polarized electrode and the anode is the positively polarized electrode. Constant-voltage switching operation using NaCl solution showed that the salt removal capacity was approximately 5.3 mg g(-1) at a maximum working voltage of 1.1/0 V, which is an expansion in both the salt capacity and potential window from previous i-CDI results demonstrated for carbon xerogel materials. This improved performance is accounted for by the enlarged cathodic working voltage window through ethylenediamine-derived functional groups, and the enhanced microporosity of the SpectraCarb electrodes for salt adsorption. These results expand the use of i-CDI for efficient desalination applications.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adsorption
  • Amines / chemistry
  • Carbon
  • Electrochemical Techniques / instrumentation*
  • Electrochemical Techniques / methods*
  • Electrodes
  • Equipment Design
  • Nitric Acid / chemistry
  • Sodium Chloride / isolation & purification*
  • Water Purification / instrumentation*
  • Water Purification / methods*

Substances

  • Amines
  • Nitric Acid
  • Sodium Chloride
  • Carbon