Tailoring Carbon Materials for Next-Generation Desalination

Abstract

Mounting stressors to existing water supplies, whether by increased human consumption or changing environmental conditions, are creating water shortages worldwide. Consequently, meeting future water demand will require more sophisticated water treatment technologies. In particular, the next generation of water treatment will need to operate with less energy, treat a wider range of contaminants, and offer a greater degree of selectivity for contaminant removal. One way this can be accomplished is through the use of electrochemical water treatment in which electricity is used to remove contaminants by inducing faradaic or electrolytic reactions in solution. Although there are a number of open questions within the field of electrochemical water treatment, this dissertation aims to address two main issues. First, techniques are presented to improve the material properties of carbon-based materials that are frequently used as electrodes in electrochemical water treatment. Carbon is favored for its chemical stability and high surface area, and tailoring the nanoscale structure of the electrodes can further improve desirable properties like ion transport, electrical conductivity, and electrode stability. Methods are presented to control the electrical properties of carbon nanotube and graphene-based electrodes through changes in microscopic morphology and chemical surface doping. Second, the effect of flow-cell architecture on capacitive deionization (CDI) performance is studied in depth. CDI is an electrolytic separation process that removes ions from solution using a pair of charged porous electrodes. Differences in salt storage capacity, the average salt adsorption rate, and charge efficiency were observed depending on the direction of flow relative to the electric field. By addressing fundamental questions in the field of electrochemical water treatment, these studies contribute to future progress in water treatment.