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Valorisation of Ca and Mg by‐products from mining and seawater desalination brines for water treatment applications
Author(s) -
Casas Sandra,
Aladjem Carlos,
Larrotcha Enric,
Gibert Oriol,
Valderrama César,
Cortina José Luis
Publication year - 2014
Publication title -
journal of chemical technology and biotechnology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.64
H-Index - 117
eISSN - 1097-4660
pISSN - 0268-2575
DOI - 10.1002/jctb.4326
Subject(s) - valorisation , electrodialysis , desalination , chemistry , reagent , seawater , brine , reverse osmosis , electrolysis , gehlenite , brackish water , nuclear chemistry , membrane , waste management , salinity , geology , biochemistry , oceanography , organic chemistry , electrode , phase (matter) , engineering , electrolyte
BACKGROUND Brines from the drainage of potash mine tailings and from seawater reverse osmosis ( SWRO ) desalination were previously evaluated as sources of NaCl for the chlor‐alkali industry. Valorisation of NaCl as raw material is required to meet the membrane electrolysis specifications of NaCl saturation and control of interferences (Ca, Mg and sulphate). Brines concentration in NaCl was previously achieved for SWRO brines using electrodialysis ( ED ). In this work, valorisation of Ca and Mg by‐products via selective recovery was evaluated.RESULTS Recovery of Ca( II ) and Mg( II ) using chemical precipitation with Na 2 CO 3 and NaOH was evaluated at 25°C and 65°C using one single reagent and mixtures of reagents. The excess of reactants needed to achieve the maximum removal efficiency ranged from 0.35 to 14 g L −1 Na 2 CO 3 and 0.85 g L −1 NaOH . Selective concentration of SWRO brines by ED benefited the purification, as it slightly diluted the antiscalants. The increase of temperatures also benefited their removal process.CONCLUSIONS Total chemical analysis of Ca and Mg by‐products showed the presence of mixed salts of Ca and Mg when Na 2 CO 3 was used and more pure precipitates of Mg when NaOH was used. In both cases, small amounts of minor traces initially present in the brines were found. © 2014 Society of Chemical Industry.