Simultaneous Hydrogen Generation and Waste Acid Neutralization in a Reverse Electrodialysis System

Type
Article

Authors
Hatzell, Marta C.
Zhu, Xiuping
Logan, Bruce E.

KAUST Grant Number
KUS-I1-003-13

Online Publication Date
2014-08-15

Print Publication Date
2014-09-02

Date
2014-08-15

Abstract
Waste acid streams produced at industrial sites are often co-located with large sources of waste heat (e.g., industrial exhaust gases, cooling water, and heated equipment). Reverse electrodialysis (RED) systems can be used to generate electrical power and hydrogen gas using waste heat-derived solutions, but high electrode overpotentials limit system performance. We show here that an ammonium bicarbonate (AmB) RED system can achieve simultaneous waste acid neutralization and in situ hydrogen production, while capturing energy from excess waste heat. The rate of acid neutralization was dependent on stack flow rate and increased 50× (from 0.06 ± 0.04 to 3.0 ± 0.32 pH units min -1 m-2 membrane), as the flow rate increased 6× (from 100 to 600 mL min-1). Acid neutralization primarily took place due to ammonium electromigration (37 ± 4%) and proton diffusion (60 ± 5%). The use of a synthetic waste acid stream as a catholyte (pH ≈ 2) also increased hydrogen production rates by 65% (from 5.3 ± 0.5 to 8.7 ± 0.1 m3 H2 m-3 catholyte day -1) compared to an AmB electrolyte (pH ≈ 8.5). These findings highlight the potential use of dissimilar electrolytes (e.g., basic anolyte and acidic catholyte) for enhanced power and hydrogen production in RED stacks. © 2014 American Chemical Society.

Citation
Hatzell MC, Zhu X, Logan BE (2014) Simultaneous Hydrogen Generation and Waste Acid Neutralization in a Reverse Electrodialysis System. ACS Sustainable Chem Eng 2: 2211–2216. Available: http://dx.doi.org/10.1021/sc5004133.

Acknowledgements
This research was supported by the National Science Foundation Graduate Research Fellowship Program (NSF Grant No. DGE1255832), and a grant from the King Abdullah University of Science and Technology (KAUST) (Award KUS-I1-003-13).

Publisher
American Chemical Society (ACS)

Journal
ACS Sustainable Chemistry & Engineering

DOI
10.1021/sc5004133

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