US 2003/0201235 A1 · Fractional deionization process

Abstract

A liquid treatment process is described for sequential removal of ionic species of progressively decreasing ionic strength without precipitation or “scaling.” An embodiment of the invention includes dual electrodeionization operations. The first electrodeionization operation is performed at a voltage calculated to remove strongly ionized species such as calcium and magnesium from the feed water without scaling. The product of the first electrodeionization operation is then subjected to a second electrodeionization operation. The second electrodeionization operation is performed at a voltage greater than the first electrodeionization operation, and is designed to remove more weakly ionized species such as silica and atmospheric carbon dioxide. The danger of precipitation or “scaling” normally present during electrodeionization of weakly ionized species is not present in this invention, because the strongly ionized species responsible for scaling at higher voltages have already been removed from the feed stream through the first electrodeionization operation. More than two successive electrodeionization operations may be performed if desired. Multiple electrodeionization operations may occur in a single electrodeionization stack or in multiple electrodeionization stacks.

Claims48

Dependent claims

A liquid purification process comprising the following steps:

(a) providing a feed stream of the liquid to be purified;
(b) treating the feed stream in a first module comprising at least one anode and at least one cathode wherein a first voltage is applied across said at least one anode and said at least one cathode to substantially remove at least a first ionic species that causes scaling from said feed stream to produce a first product stream;
(c) treating the first product stream in a second module comprising at least one anode and at least one cathode wherein a second voltage different from said first voltage is applied across said at least one anode and said at least one cathode to substantially remove at least a second ionic species from said first product stream to produce a second product stream;
and
(d) recovering the second product stream.

2 more elements

A water purification process comprising the following steps:

(a) providing a feed stream of the water to be purified, said feed stream containing impurities comprising chemical species with a hardness at least five parts per million;
(b) treating the feed stream in a first electrodeionization module comprising at least one anode and at least one cathode wherein a first voltage is applied across said at least one anode and said at least one cathode to substantially remove at least a first ionic species from said feed stream to produce a first product stream, said first ionic species comprising at least calcium anions;
(c) treating the first product stream in a second electrodeionization module comprising at least one anode and at least one cathode wherein a second voltage greater than said first voltage is applied across said at least one anode and said at least one cathode to substantially remove at least a second ionic species from said first product stream to produce a second product stream, said second ionic species comprising at least silica anions;
and
(d) recovering the second product stream, said second product stream having a resistivity of up to 18.3 megaohms and a silica concentration of up to 5 parts per billion or better.

2 more elements

Dependencies are inferred from the claim text.

Fractional deionization process

Life of this patent

Fractional deionization process

Life of this patent

Abstract

Claims48