Full-membrane separation method for producing lithium extraction mother liquor from salt lake brine multistage nanofiltration

Abstract

The invention discloses a total membrane separation method of producing lithium extracting mother liquor with multi-stage nanofiltration salt separation of salt lake brine. The total membrane separation method comprises the following steps of (1) using a microfiltration purification system to perform pretreatment on the salt lake brine, removing suspended matters, colloid and other impurities in the salt lake brine, and then diluting the salt lake brine with fresh water to acquire microfiltration pretreated brine; (2) feeding the obtained microfiltration pretreated brine into a nanofiltrationsalt separation system, and performing separation to acquire a filtrate with monovalent cation as a priority and a concentrated solution with multivalent cation as a priority; (3) feeding the filtratein the step (2) into a membrane concentration system, and performing concentration to obtain a lithium-enriched concentrated solution; and (4) feeding the lithium-enriched concentrated solution obtained in the step (3) into a nanofiltration deep magnesium removing system, and performing deep magnesium removal with a nanofiltration membrane to obtain the lithium extracting mother liquor. The technology is low in energy consumption, high in recovery rate, low in production cost, continuous and controllable in technology, high in reliability, low in magnesium-lithium ratio of the prepared lithium extracting mother liquor, high in lithium ion concentration and stable in quality and can be used for large-scale production.

Description

technical field [0001] The invention belongs to the technical field of membrane separation, and in particular relates to a full-membrane separation process for producing lithium-extracting mother liquor by multi-stage nanofiltration and salt separation of salt lake brine. Background technique [0002] Lithium and its compounds play an extremely important role in energy, petrochemical, metallurgy, ceramics, medicine, aerospace, refrigeration and other fields, and are called "energy metals in the 21st century". Salt lake brine is an important source of lithium. At present, more than 80% of the world's total lithium salt production comes from salt lake brine. [0003] At present, the main methods for extracting lithium from salt lake brine include evaporation crystallization separation method, precipitation method, calcination leaching method, organic solvent extraction method, ion exchange adsorption method, electrodialysis method, Xu's method and nanofiltration method, etc. T...

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Problems solved by technology

[0004] The Chinese patent application with the application number 201310571755.2 discloses the separation of magnesium ions and lithium ions through the nanofiltration system, the enrichment of lithium ions by the reverse osmosis system, and the evaporation and concentration of salt fields, which can make the concentration of lithium ions reach the concentration required for refining lithium carbonate; however, the application The series of the designed nanofiltration system is only one level, the separation capacity of magnesium and lithium is limited, and the treatment effect on brine with high magnesium-lithium ratio is not good, which has certain limitations; in addition, it still takes a long time to Salt field evaporation and further concentration can make the lithium ion concentration meet the requirements for lithium carbonate production

The Chinese patent application publication with the application number 201610751304.0 pointed out that the use of forward osmosis system can concentrate lithium-containing solution and enrich lithium ions. It is still necessary to add alkali to remove magnesium in depth, and to further concentrate the refined lithium-containing solution through high-energy multi-effect evaporation to increase the concentration of lithium ions; and the forward osmosis system uses ammonium bicarbonate solution as the drawing solution, which cannot be obtained locally and fully utilized Salt obtained from drying in salt pans

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