(152an) Biomass Based Activated Carbon Electrodes for Capacitative Deionization in the Context of Nitrate and Phosphate Removal.

Clean water is a fundamental need for any society. However, access to clean water is a major challenge, and water treatment presents a possible solution to ensure an adequate clean water supply. Major contaminants include nitrates and phosphates from agricultural runoffs. The removal of nitrate and phosphate is particularly important in the context of health and environmental aspects. High levels of nitrate in the drinking water can cause birth defects and other diseases. High levels of phosphate can result in explosive algal bloom, which affects the oxygen levels in water can affect the aquatic life.

Present techniques for water treatment include biological treatment, adsorption, membranes, and ion-exchange resins. The biggest issue with some of the existing treatment methods is that they can generate secondary waste which requires further chemical treatment. In the last few years, the capacitative deionization (CDI) technique is gaining increased attention for wastewater treatment as it does not leave secondary waste and operate at low voltages < 1.2V vs. reversible hydrogen electrode (RHE). Besides, the CDI uses carbon-based electrodes with excellent electrical properties and cost benefits. Although the CDI has been successfully studied for desalination processes [1], this technique is also being employed for nitrate and phosphate removal [2].

In this work, carbon-based electrodes made from commercial coal-based activated carbons are electrochemically evaluated for nitrate and phosphate removal through CDI. The electrodes are investigated through cyclic voltammetry in a 3-electrode setup and batch tests (Figure 1), where adsorption-desorption tests were carried out at different voltages and different nitrates and phosphates concentrations. The electrochemical studies provided information on the adsorption capacity and the time constants (kinetics) for the electrosorption process. The batch tests were complemented by flow cell experiments to study the removal of these ions from aqueous solutions.Based on the information from the characterization of the electrodes, technical and economic analysis was carried out and the sensitivity of the cost to the different electrode properties were evaluated. In particular, the effect of the electrode life time, the capacitance and the ion concentration on the capital and operating expenses were evaluated. these results will be discussed in this presentation.

References:

1. Suss et al., Energy Environ. Sci., 2015, 8, 2296
2. Pastushok et al., Chem Eng J, 375 121943