Mineral Recovery Enhanced Desalination (MRED) Process for Desalination and Recovery of Commodity Minerals

Patent metadata

Field	Value
Publication number	US-2021317026-A1
Application number	US-202117301617-A
Country	US
Kind code	A1
Filing date	Apr 9, 2021
Priority date	Apr 9, 2020
Publication date	Oct 14, 2021
Grant date	—

Abstract

A novel process for treatment of low quality or brackish water that allows increased recovery of high quality water, recovers commodity minerals and reduces the volume of water and mass of solids that are disposed from the process.

First claim

What is claimed is:

1 . A process for treating brackish or saline water comprising, performing, in sequence, the steps of low pH degasification; high pH precipitation; ion exchange, nanofiltration, and desalination to produce high quality desalinated water; wherein
commodity materials are selectively obtained from at least one of the high pH precipitation, ion exchange, nanofiltration and gypsum precipitation unit operations.

2 . The process of claim 1 wherein the brackish or saline water has a total dissolved solids (TDS) concentration of between 1,000 mg/L to 20,000.

3 . The process of claim 1 wherein the brackish or saline water is flue gas desulfurization (FGD) wastewater.

4 . The process of claim 1 wherein the byproduct is a sodium chloride salt brine.

5 . The process of claim 4 wherein the sodium chloride salt brine is used to regenerate an ion exchange column for use in the ion exchange unit operation.

6 . The process of claim 1 wherein the commodity materials comprise magnesium hydroxide obtained from a selective precipitation unit operation at high pH.

7 . The process of claim 1 wherein byproducts from the ion exchange and nanofiltration unit operations are combined and precipitated to obtain a commodifiable product.

8 . The process of claim 1 wherein the brackish or saline water comprises concentrations of suspended solids, one or more multivalent ions or dissolved silica that cause scale formation on surfaces of thermal or membrane desalination equipment.

9 . The process of claim 8 wherein the multivalent ions are selected from the group consisting of calcium, magnesium, iron, aluminum, bicarbonate/carbonate, sulfate, and dissolved silica.

10 . The process of claim 7 wherein the commodifiable product is gypsum.

11 . The process of claim 1 wherein the step of low pH degasification comprises lowering the pH of the water to less than pH 6.

12 . The process of claim 1 wherein dissolved carbon dioxide is removed from the low pH solution by air stripping.

13 . The process of claim 1 wherein the pH of the feed water solution after degasification is raised to greater than pH 10.5 by addition of a strong base to achieve selective removal of high purity commodifiable magnesium hydroxide.

14 . The process of claim 13 wherein selectively precipitated high purity magnesium hydroxide is removed from solution by a process that removes suspended solids from solution.

15 . The process of claim 14 wherein the pH of the water is adjusted to approximately pH 7.0 after high pH selective magnesium hydroxide precipitation, during or prior to the ion exchange unit operation.

16 . The process of claim 1 wherein the desalination step produces a concentrate stream containing sodium chloride salt as a concentrate that is at greater than 1% concentration.

17 . The process of claim 1 wherein magnesium is selectively obtained via high pH precipitation of magnesium hydroxide, calcium is selectively removed by cation exchange and sulfate is selectively removed by nanofiltration.

18 . A processing plant for treating brackish or saline water wherein the processing plant performs, in sequence, the steps of low pH air stripping degasification; high pH precipitation; ion exchange, nanofiltration, and desalination to produce high quality desalinated water; wherein
commodifiable materials are selectively obtained from at least one of the high pH precipitation, ion exchange, nanofiltration, and gypsum precipitation unit operations.

19 . The processing plant of claim 18 wherein the processing plant receives and treats flue gas desulfurization (FGD) wastewater.

20 . The processing plant of claim 18 wherein the processing plant produces, as separately obtainable materials, magnesium salts, gypsum, sodium chloride, and high quality water.

Assignees

• Thomson Bruce
• Howe Kerry
• Unm Rainforest Innovations

Inventors

• Thomson Bruce
• Howe Kerry

Classifications

• C01F5/22

  from magnesium compounds with alkali hydroxides or alkaline- earth oxides or hydroxides · CPC title

• C01F11/005

  Preparation involving liquid-liquid extraction, absorption or ion-exchange · CPC title

• C01D3/06

  Preparation by working up brines; seawater or spent lyes · CPC title

• C01F11/46

  Sulfates (dehydration of gypsum {for the production of calcium sulfate cements} C04B11/02) · CPC title

• C04B11/264

  Gypsum from the desulfurisation of flue gases · CPC title