Ion sequestration for scale prevention in high-recovery desalination systems

摘要

Cations that can precipitate from an aqueous composition (22) to produce scaling are sequestered by adding a multi-dentate ligand (24) to the aqueous composition (22). The multi-dentate ligand bonds with the cation to form a non-scaling ionic complex; and the aqueous solution with the ionic complex (26) is used in a process (28) that produces substantially pure water (32) from the aqueous composition, where the cation, absent formation of the ionic complex, is subject to scaling. The pH of the aqueous composition (or a brine including components of the aqueous composition) is then reduced (36) to release the cation (40) from the multi-dentate ligand (42); and the multi-dentate ligand (42), after the cation is released, is then reused in a predominantly closed loop.