(512c) Advanced Redox-Based Electrochemical Separations for Wastewater Treatment

Water scarcity is one of the principal challenges for
the 21^st century, both from a geographical and an economic
standpoint. Developing novel, more energetically efficient technologies for wastewater
treatment, retreatment and reuse is crucial for long-term water sustainability.
One of the principal challenge for water remediation, both in the U.S. and
worldwide, is to target contaminants of emerging concern, such as complex
organic molecules including pharmaceuticals, chemical precursors, endocrine
inhibitors and pesticides.^[1]
These originate from chemical processes and organic synthesis, the food
industry, electronic manufacturing among others. Many of these pollutants
disperse in remote locations, such as agricultural locations, in which
large-scale purification systems cannot be implemented. Electrochemical methods
are particularly attractive for addressing these problems due to their
modularity, fast kinetics and integration with renewable energy sources.^[2]

We
have developed an redox-mediated separation method based on
organometallic-functionalized electrodes (e.g. ferrocene or cobaltocene)
for the sorption and release of specific ions from the liquid-phase under
oxidizing and reducing conditions.^[3]
Many of the organic contaminants are anionic in nature (e.g. carboxylates, sulfonates or phosphonates), thus
selectivity based on chemical interactions with their functional groups is
essential in chemical design. Rather than rely solely on charge or size, our
immobilized redox-centers targets these compounds through the activation of a
specific chemical binding. Moreover, in the charging and discharging steps,
electrochemical charge can be stored by ion-selective adsorption onto the
porous electrodes, thus dramatically decreasing energetic costs.

This
modular system can then be easily implemented at the point-of-exit in chemical
manufacturing and wastewater treatment. Here,
we present a complete asymmetric redox-system in both batch and flow for (1)
water remediation, through the specific separation of anionic and cationic
contaminants in water, (2) tandem energy recovery due to pseudocapacitive
charge storage and (3) increasing sustainability in chemical processes, through
the recovery of expensive synthesis products from complex organic reactions,
thus reducing organic waste and decreasing water usage during separation
steps.

References

[1] a) Gilliom R.; Hamilton P. U.S. Geological Survey. 2014. (USGS fact
sheet: http://pubs.usgs.gov/fs/2006/3028/

). b) Doughton, C.G. and Thomas, A. T. (1999). Pharmaceuticals
and personal care products in environment: agents of suble
change? EHP 107 (6), 907-938.

[2] Suss, M. E.; Porada, S.; Sun, X.; Biesheuvel, P. M.;
Yoon, J.; Presser, V. Energy &
Environmental Science 2015.
Zhao, R.; Satpradit, O.; Rijnaarts, H. H.; Biesheuvel, P. M.; van der Wal, A. Water Res 2013, 47, 1941.

[3] Su, X.; Kulik, H; Jamison, T.F.; Hatton, T. A. 2016. Anion-selective redox electrodes:
electrochemically-mediated separation with organometallic interfaces. Advanced
Functional Materials. Advance Article Online. DOI:
10.1002/adfm.201600079