Nitrate removal from water using electrostatic regeneration of functionalized adsorbent

TL;DR

This study introduces a novel electrostatic regeneration method for nitrate removal using functionalized activated carbon electrodes, offering a potentially more sustainable alternative to traditional ion exchange and reverse osmosis techniques.

Contribution

The paper presents a new electrostatic regeneration approach for nitrate adsorption on functionalized activated carbon electrodes, enabling repeated use without complex chemistry or waste brine disposal.

Findings

Adsorption capacity of about 80 mg NaNO₃ per gram of activated carbon.

Electrostatic regeneration recovers approximately 40% of initial capacity.

Functionalized electrodes can be repeatedly regenerated using an applied electrostatic potential.

Abstract

Nitrate is an important pollutant in drinking water worldwide, and a number of methods exist for the removal of nitrate from water including ion exchange and reverse osmosis. However, these approaches suffer from a variety of disadvantages including requirements for supply and disposal of brine used for regeneration in ion exchange and low water recovery ratio for reverse osmosis. Here, we demonstrate the use of high surface area activated carbon electrodes functionalized with moieties having high affinity for adsorption of nitrate from aqueous solution, such as those used in ion exchange. Adsorption of surfactant molecules having a quaternary amine ionic group to the activated carbon surfaces provides functionalization of the surfaces without complex chemistries. The functionalized electrodes have adsorption capacities of about 80 mg NaNO$_3$ per gram of activated carbon material. Unlike a traditional ion exchanger, the functionalized surfaces can be repeatedly regenerated by the application of an electrostatic potential which displaces the bound NO$_3^-$ while leaving an excess of electronic charge on the electrode. The cell is completed by an inert counter electrode where Faradaic reactions occur during regeneration. Up to approximately 40% of the initial capacity of the electrode is accessible following electrical regeneration.