Osmotic desalination process

摘要

An energy efficient desalination process that does not produce waste products involves the extraction of water from a first solution, such as seawater, by using a second concentrated solution to draw the water from the first solution across a semi-permeable membrane. By manipulating the equilibrium of the soluble and insoluble species of solute within the second solution in favor of the soluble species of the solute, a saturated second solution can be used to generate osmotic pressure on the first solution. Also, by adjusting the equilibrium in favor of the less soluble species after the water has been drawn from the first solution, a portion of the solute can easily be precipitated out. Heating the second solution decomposes the solute into its constituent gases. The constituent gases and precipitated solute may be recycled through the process to affect the changes in equilibrium and eliminate waste products. Additionally, by using the waste steam from industrial sources and a heat pump to effectively distribute heat through the present method, the present method exhibits greater energy efficiency than prior art methods.

主权项

1. A method for extracting a solvent from a solution using forward osmosis, the method comprising the steps of:
providing a semi-permeable membrane; introducing a first solution to a first surface of the semi-permeable membrane; introducing a second solution to a second surface of the semi-permeable membrane, wherein the second solution comprises at least two species of a solute, a soluble species of the solute and a less-soluble species of the solute, where the ratio of the soluble species of the solute to the less-soluble species of the solute is greater than 1:1 at equilibrium so as to generate an increased osmotic pressure on the first solution; drawing a solvent from the first solution through the semi-permeable membrane and into the second solution, thereby creating a solvent-enriched second solution; and removing at least one of the at least two species of the solute from the solvent-enriched second solution, wherein the step of removing at least one of the at least two species of the solute comprises at least one of precipitation or filtration.