Water with Switchable Ionic Strength

Abstract

A method and system for reversibly converting water between an initial ionic strength and an increased ionic strength, using a switchable additive, is described. The disclosed method and system can be used, for example, in distillation-free removal of water from solvents, solutes, or solutions. Following extraction of a solute from a medium by dissolving it in water, the solute can then be isolated from the aqueous solution or “salted-out” by converting the water to a solution having an increased ionic strength. The solute then separates from the increased ionic strength solution as a separate phase. Once the solute is, for example, decanted off, the increased ionic strength aqueous solution can be converted back to water having its original ionic strength and reused. Switching from lower to higher ionic strength is readily achieved using low energy methods such as bubbling with CO2, CS2 or COS. Switching from higher to lower ionic strength is readily achieved using low energy methods such as bubbling with air, heating, agitating, introducing a vacuum or partial vacuum, or any combination or thereof.

Description

FIELD OF THE INVENTION[0001]The field of the invention is solvents, and specifically an aqueous solvent composition that can be reversibly converted between low ionic strength and higher ionic strength.BACKGROUND OF THE INVENTION[0002]Conventional solvents have fixed physical properties which can lead to significant limitations in their use as media for reactions and separations. Many chemical production processes involve multiple reactions and separation steps, and often the type of solvent that is optimum for any one step is different from that which is optimum for the next step. Thus it is common for the solvent to be removed after each step and a new solvent added in preparation for the next step. This removal and replacement greatly adds to the economic cost and environmental impact of the overall process. Therefore, there exists a need for a solvent that can change its physical properties.[0003]Solvents are commonly used to dissolve material in manufacturing, cleaning, dyeing,...

AI Technical Summary

Benefits of technology

The present invention provides a system for switching the ionic strength of water or an aqueous solution. This system includes an additive that is sufficient to be protonated by carbonic acid, and the addition of this additive to water or a solution results in a mixture with switchable ionic strength. The system also includes a system for controlling the amount of dissolved salt in an aqueous mixture. The switchable water can be used in a hydrophobic liquid or a solvent for desalination purposes. The system can also be used to control the ionic strength of a solution by adding or removing an ionizing trigger.

Problems solved by technology

Conventional solvents have fixed physical properties which can lead to significant limitations in their use as media for reactions and separations.

This removal and replacement greatly adds to the economic cost and environmental impact of the overall process.

Such a separation can be expensive to achieve, especially if the solvent is removed by distillation, which requires the use of a volatile solvent, which can lead to significant vapor emission losses and resulting environmental damage, e.g., through smog formation.

Furthermore, distillation requires a large input of energy.

Water is a particularly desirable solvent because of its low price, non-toxicity, nonflammability, and lack of adverse impact on the environment, but the separation of water from a product or other material by distillation is particularly expensive in terms of energy because of the high heat capacity of water and the high heat of vaporization of water.

This “salting out” method requires no distillation but is not preferred because of the expense of using very large amounts of salts and, more importantly, because of the expense of removing the salt from the water afterwards.

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