CO2-triggered draw agents for forward osmosis

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The primary goal of the research is to create a new process that lowers the environmental and economic cost of recovering fresh water from wastewater or seawater. Methods for obtaining fresh (potable) water include distillation, reverse osmosis (RO) and forward osmosis (FO). RO requires the least energy but unfortunately it still requires too much energy to make desalination of seawater and recycling of wastewater economically viable. We are developing a new FO technology that uses low-grade or waste heat as its primary energy source. Waste heat is low-grade (< 80 °C) heat produced as a byproduct of processes such as power generation or cement manufacture and is available at little or no cost at these types of facilities. However a water purification system primarily powered by low-grade heat could also be used for the generation of drinking water or agricultural water, including at remote sites and communities. For example, solar energy can be used to generate heat at the low temperatures required for our process. Similarly, low-grade geothermal sources of hot water could supply both the feed water and the heat required for the production of clean water. We will design new materials for use in FO systems that are "switchable", meaning their properties can be changed by changing their environment. Our materials will be able to undergo dramatic in properties simply by adding or removing carbon dioxide (CO2), similarly to what is done with carbonated beverages. CO2 is an ideal "trigger" in that it is non-toxic, environmentally benign, inexpensive and plentiful. Furthermore, our process uses CO2 but does not produce CO2. By using these CO2-switchable materials, we will address critical shortcomings in current FO technology since the switchability of the materials we are using will allow us to obtain a desired combination of properties not attainable with any other single material. Our three industry partners span the range from developers of FO technology to end users of water treatment systems, providing across the spectrum expertise from new idea inception to technology implementation.