Method for extracting and separating lithium and alkaline earth metal from salt lake brine with high sodium-lithium ratio

Abstract

The invention discloses a method for extracting and separating lithium and alkaline earth metal from salt lake brine with a high sodium-lithium ratio, which comprises the following steps of providing an extraction water phase: taking the salt lake brine with the high sodium-lithium ratio as the extraction water phase which contains Li<+>, Na<+>, Ca<2+> and Mg<2+>, wherein the mass ratio of Na<+> to Li<+> is (10: 1)-(200: 1), providing anextraction organic phase: mixing an extraction agent, a synergistic extraction agent and kerosene, and preparing the extraction organic phase, wherein the extraction agent is a diketone compound, and the synergistic extraction agent is a halogen-containing organic phosphine compound, in an extraction step, mixing the extraction organic phase and the extraction water phase, performing counter-current extraction of more than one stage, and performing phase splitting after the extraction is balanced to obtain raffinate and a first loaded organic phase, and sequentially conducting sodium reverse extraction, lithium reverse extraction, calcium reverse extraction and magnesium reverse extraction on the first loaded organic phase, so that a sodium salt solution, a lithium salt solution, a calcium salt solution and a magnesium salt solution are obtained through separation. Sodium, lithium, calcium, magnesium and other alkaline earth metals are effectively separated from the salt lake brine with the high sodium-lithium ratio.

Description

technical field [0001] The invention belongs to the technical field of salt lake chemical industry, and specifically relates to a method for extracting and separating lithium and alkaline earth metals from salt lake brine with a high sodium-lithium ratio. Background technique [0002] Lithium is the lightest metal in nature and has extremely strong electrochemical activity. Its metals and compounds are widely used in glass, ceramics, aluminum smelting, organic chemical industry, aerospace, nuclear fusion and other industries and fields as thermonuclear fusion (hydrogen bomb) explosives, high-performance propellant for aircraft, rockets and missiles, and shielding materials for nuclear reactors. Lithium batteries have 4 to 30 times higher energy storage than ordinary batteries and have good performance. They have long been used as the propulsion of torpedoes, submarines, and spacecraft. Lithium-aluminum and lithium-magnesium alloys are high-strength and light-weight, and are...

AI Technical Summary

Problems solved by technology

[0003] Currently effective methods for extracting lithium from salt lake brine include solvent extraction, and solvent extraction inevitably uses FeCl 3 As a co-extraction agent, the density of the extracted organic phase is increased, and the density difference between the two phases is reduced. The requirements for extraction and separation equipment are high. Traditional mixing and settling tanks are difficult to meet the process requirements. High-efficiency centrifugal extraction equipment must be used, which is expensive; At the same time, the introduction of FeCl 3 Finally, it is very difficult to regenerate the extractant with alkali, and very precise flow control is required, otherwise it will cause problems such as a decrease in extraction rate or emulsification failure of the extractant

In addition, since the organic phase contains co-extractant FeCl 3 , this requires that the extraction liquid (brine) must be kept weakly acidic, otherwise Fe will be hydrolyzed, and the brine entering the extraction section must be acidified. Lithium and boron generally exist together in Qinghai Salt Lake, and boric acid must be precipitated during the acidification process. Filtration is required, so it is not suitable for the extraction of lithium in alkaline systems

Moreover, most of the extraction agents currently used for lithium can only realize the separation of lithium and magnesium, and the extraction effect for alkali metal systems is very poor.

[0004] In addition, salt lake brine usually contains Na + , when Na + When the concentration is too high, it will give Li + The extraction and separation of

For example, Na in salt lake brine in South America + with Li + The mass ratio is usually above 50 / 1, and the ratio of sodium to lithium is very high. For salt lake brine with high sodium-lithium ratio, when lithium needs to be extracted from it, the current process needs to pretreat the salt lake brine with high sodium-lithium ratio to reduce Na + with Li + mass ratio, and then extract lithium by precipitation, which requires a huge area of ​​salt fields, low utilization rate of lithium resources, and long production cycle

At present, the solvent extraction method can only be applied to salt lake brine with high magnesium-lithium ratio, and there is no effective extraction system for lithium extraction from salt lake brine with high sodium-lithium ratio.

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