Method for removing Al impurity from KCl-LiCl lithium electrolyte

Abstract

The invention relates to an alkali metal Li purification process, which belongs to the field of electrochemical metallurgy and is a process for removing an impurity by a molten salt electrochemical method. The invention adopts an electrochemical method for removing an Al impurity from KCl-LiCl lithium electrolyte. The method comprises: determining the deposition potential of metal aluminum by cyclic voltammetry; performing constant potential electrolysis at the potential; precipitating the metal aluminum on a carbon steel strip cathode; and after electrolyzing for 4.5 to 10 hours, removing the carbon steel strip cathode out from the electrolyte, and removing the carbon steel strip cathode from a reactor completely. According to the researches on the impurity-removing effect by the electrochemical method and the analysis on the Al content of the electrolyte by a fluorescence flame spectrum ICP-AES (Varian 710-ES), and the Al content of the purified electrolyte is lowered greatly. In the invention, the method is simple and convenient to operate, and over 96 percent of Al in the molten salt can be removed after 10 hours of electrolysis.

Description

technical field [0001] The invention relates to a purification process of alkali metal Li, belonging to the field of metallurgy, in particular to a process for removing impurity Al by a molten salt electrochemical method. Background technique [0002] Currently, the only industrial production method for lithium metal is lithium chloride-potassium chloride molten salt electrolysis. The LiCl-KCl system is a simple binary eutectic system, and the composition of LiCl at the eutectic point is about 50 (wt)%. During industrial electrolysis, the lithium chloride content in the electrolyte is 55 (wt)%, the potassium chloride content is 45 (wt)%, the electrolysis temperature is between 390-450°C, and potassium chloride acts as a supporting electrolyte to stabilize and reduce the melting point. effect. The industrial lithium electrolyzer adopts graphite anode and low-carbon steel cathode under the action of direct current, the anode produces chlorine gas, and the cathode produces li...

AI Technical Summary

Problems solved by technology

Vacuum distillation is carried out in a stainless steel distillation furnace at 600-800°C. This distillation method needs to evaporate most of the lithium, and each kilogram of pure lithium needs to consume 52 degrees of electricity. The power consumption is large and the distillation efficiency is low.

At the same time, due to the high distillation temperature, severe corrosion occurs to the equipment, which obviously increases the production cost of high-purity metal lithium. It is estimated that the purification of metal lithium with a purity of 98.5wt% to 99.9wt% costs about 100,000 yuan / ton

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