Preparing High-Purity Lithium Hydroxide Monohydrate by the Electrochemical Conversion of Highly Soluble Lithium Salts
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NOLOGY OF INORGANIC SUBSTANCES AND MATERIALS
Preparing High-Purity Lithium Hydroxide Monohydrate by the Electrochemical Conversion of Highly Soluble Lithium Salts N. M. Nemkova, *, A. D. Ryabtseva, N. P. Kotsupaloa, L. T. Menzheresa, E. V. Mamylovaa, and O. I. Chayukovaa a
OOO Ekostar-Nautekh, Novosibirsk, 630075 Russia *e-mail: [email protected]
Received March 12, 2018; revised March 14, 2018; accepted March 27, 2018
Abstract—A series of studies on the preparation and reproduction of a solution of lithium sulfate obtained from technical salts Li2CO3 and Li2SO4 ⋅ H2O has been performed for the electrochemical conversion of lithium sulfate to hydroxide. High-purity lithium hydroxide monohydrate has been shown to be prepared from conversion alkali, namely, a LiOH solution. These studies are the basis of a waste-free technology for producing high-purity lithium hydroxide monohydrate from technical salts of lithium carbonate and sulfate. Keywords: technical salts, lithium carbonate, lithium sulfate, dissolution, purification, membrane electrolysis, reproduction, crystallization, lithium hydroxide monohydrate, washing, mother solution, utilization DOI: 10.1134/S0040579519050166
INTRODUCTION The manufacturing of lithium products from hydromineral raw materials, which has become widespread in the Americas, has been used successfully in recent years in Asia, particularly in China [1]. The final product of processing is lithium carbonate. However, many industries that use lithium products are in dire need of lithium hydroxide monohydrate. As the primary product, LiOH ⋅ H2O is used in the production of metallic lithium, in the separation of lithium isotopes, in the preparation of lubricants, in synthetic rubber, and in modern technology. To create new materials, high-purity lithium compounds are needed, including high-purity lithium hydroxide monohydrate. In previous studies [2, 3], the efficiency of applying the electrochemical conversion of a solution of lithium chloride to hydroxide for these purposes was shown. For the industrial production of LiOH ⋅ H2O from other lithium salts using this process, it is necessary to determine the optimal parameters for both the operation of the electrochemical conversion process and the associated technological operations that form the basis of the production technology of LiOH ⋅ H2O by this method. In [4], these parameters were developed for the LiCl → LiOH system. Here, we present the physicochemical principles of the process of the electrochemical conversion of technical salts of lithium sulfate and lithium carbonate to hydroxide. The aim of this study is to prepare a solution of lithium sulfate from technical lithium salts and determine
the optimal parameters for the process of electrochemical conversion of Li2SO4 → LiOH with the simultaneous selection of materials for the membrane electrolysis of sulfate solutions. EXPERIMENTAL To prepare a solution of lithium sulfate, technical salts of hydrated lithium sulfate and lithium carbonate with a basic substance content of at least 98%
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