The need for fresh water has increased exponentially during the last several decades due to the continuous growth of human population and industrial and agricultural activities. Yet existing resources are limited often because of their high salinity. This unfavorable situation requires the development of new, long-term strategies and alternative technologies for desalination of saline waters presently not being used to supply the population growth occurring in arid regions.We have developed a novel environmentally friendly method for desalinating inland brackish waters. This process can be applied to either brackish ground water or produced waters (ie., coal-bed methane or oil and gas produced waters). Using a set of ion exchange and sorption materials, our process effectively removes anions and cations in separate steps. The ion exchange materials were chosen because of their specific selectivity for ions of interest, and for their ability to work in the temperature and pH regions necessary for cost and energy effectiveness.For anion exchange, we have focused on hydrotalcite (HTC), a layered hydroxide similar to clay in structure. For cation exchange, we have developed an amorphous silica material that has enhanced cation (in particular Na + ) selectivity. In the case of produced waters with high concentrations of Ca
Executive SummaryFresh water consumption has rapidly increased during the last several decades due to the increasing needs of industry and agriculture, and an exponentially growing human population. During this same time, the available natural fresh water supply remains limited -less than 0.5% of the Earth's water resources. This situation demands the development of long-term strategies and technologies for desalination of saline waters.Over 90% of the existing industrial methods for water desalination are based on distillation and reverse osmosis technologies. In our project we applied an entirely new approach based exclusively on chemical processes. Our strategy was based on in-situ crystallization, ion exchange, and precipitation of inorganic phases able to sequester the major ionic constituents of brackish water. The goal of our project was to develop new (or modify known) inorganic phases, which are able to incorporate significant amounts of ions from saline waters. In our work we focused on three main types of materials:• Anionic getters -materials that incorporate anions (Cl • Ionic getters -materials that could incorporate both anions and cations.We present herein our desalination process that can be implemented inland, used as a pretreatment step for existing RO desalination processes, and is highly cost and energy efficient. Furthermore, it is also a process that minimizes and/or eliminates the problem of salt disposal and its associated environmental concerns; though solids-management costs of ion exchanges will be a factor. 6
