Capture of lithium and generation of hydrogen from lithium-containing saltwater

Abstract

This invention relates to a method for lithium capture and hydrogen generation from lithium-containing brine, including seawater, salt lake brine, or lithium-containing wastewater. The method utilizes photoactive ion sieves, one of the most selective types of lithium ions, to enrich lithium ions in the brine, while simultaneously performing photocatalytic decomposition to produce hydrogen. This method for lithium capture and hydrogen generation from lithium-containing brine is simple, environmentally friendly, and the lithium ions enriched from the brine can be further processed into high-purity lithium hydroxide, becoming a key raw material for lithium battery cathodes or for other applications.

Claims

1. A method for lithium extraction and hydrogen production from lithium-containing brine, comprising: a brine filtration step to remove solid impurities from a lithium-containing brine; a photoactive ion sieve extraction and hydrogen production step to enrich lithium ions in the lithium-containing brine with a photoactive ion sieve and photocatalyze the lithium-containing brine to produce hydrogen gas; a hydrogen purification step to purify the hydrogen gas produced by photocatalysis of the lithium-containing brine; and a lithium hydroxide production step to generate lithium hydroxide from the lithium ions enriched by the photoactive ion sieve; wherein... This photoactive ion sieve is prepared by the following synthesis method, comprising: mixing nano-titanium dioxide (TiO2) and lithium hydroxide (LiOH) in a TiO2:LiOH weight ratio of 0.5–0.8 with deionized water at a temperature of 20–40°C until homogeneous; centrifuging to separate solid lithium titanium oxide, drying at 60°C–90°C for 4–16 hours, and calcining at 600°C–800°C for 4–6 hours to synthesize a lithium titanium oxide ion sieve; and mixing the lithium titanium oxide ion sieve with a 0.2–0.5 mole / L hydrochloric acid (HCl) aqueous solution in a HCl aqueous solution to ion sieve weight ratio of 50–200, and carrying out an ion exchange reaction for 8–24 hours, thereby exchanging the lithium ions (Li+) of the lithium titanium oxide ion sieve with the hydrogen ions (H+) of the HCl aqueous solution to generate a hydrogen titanium oxide ion sieve, thereby selectively enriching lithium ions (Li+) in brine.

2. The lithium extraction and hydrogen production method of lithium-containing brine as described in claim 1, wherein the brine filtration step uses a rotary disc filter to continuously filter the solid impurities in the lithium-containing brine, and simultaneously backwashes the other half of the rotary disc filter with the lithium-extracted brine to return the suspended solids to the ocean or salt lake, thus having a continuous operation function.

3. The lithium extraction and hydrogen production method of lithium-containing brine as described in claim 1, wherein the lithium extraction and hydrogen production step of the photoactive ion sieve uses a fluidized bed filled with a uniformly dispersed photoactive ion sieve to enrich the lithium ions in the lithium-containing brine.

4. The lithium extraction and hydrogen production method of lithium-containing brine as described in claim 1, wherein the lithium extraction and hydrogen production step of the photoactive ion sieve uses a fluidized bed filled with a uniformly dispersed photoactive ion sieve, and photocatalytically decomposes the lithium-containing brine to produce hydrogen while enriching the lithium ions in the lithium-containing brine.

5. The method for lithium extraction and hydrogen production from lithium-containing brine as described in claim 1, wherein, The lithium hydroxide generation step involves enriching the lithium ions in the lithium-containing brine using a photoactive ion sieve, and then regenerating the photoactive ion sieve by forming carbonic acid with high-pressure carbon dioxide to generate an aqueous lithium carbonate solution.

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