RECOVERY OF SALEABLE SALTS FROM OCCURRING NATURAL BRINES REPRESENTING THE QUINARY AQUEOUS SYSTEM Na-K-Mg-Ca-Cl
RECUPERAÇÃO DE SAIS COMERCIAIS A PARTIR DE UMA SALMOURA NATURAL REPRESENTATIVA DO SISTEMA QUINÁRIO Na-K-Mg-Ca-Cl
Ruberlan Gomes da Silva; Marcelo Seckler; Sonia Denise Ferreira Rocha; Daniel Saturnino; Éder Domingos de Oliveira
Abstract
Potassium chloride (KCl) accounts for most of the potassium (K) used in world agriculture and represents 96% of the world potash capacity. The other 4% includes potassium sulfate (K2 SO4 ), potassium nitrate (KNO3 ) and potassium-magnesium based salts. In this sense, the prediction of the solubility of electrolytes in aqueous solutions is important to provide data for processes that extract potassium salts from multicomponent brines. In this work, Pitzer´s and Harvie´s models were used to calculate the amount and composition of crystallized salts after water evaporation. The process involved four crystallization steps starting from multicomponent brines represented by the quinary Na-K-Ca-Mg-Cl aqueous system at 20°C. The temperature of 20°C was chosen because it is the average process brine temperature in many dry salt lakes. The Pitzer´s and Harvie´s models allowed performing a material balance in solar ponds producing saleable salts like sodium, potassium, magnesium and calcium chlorides.
Keywords
Resumo
O cloreto de potássio (KCl) é uma das principais fontes de potássio (K) usada na agricultura e corresponde a 96% do consumo mundial desse nutriente. Os outros 4% incluem o sulfato de potássio (K2 SO4 ), nitrato de potássio (KNO3 ) e os sais duplos de potássio e magnésio. A previsão da solubilidade dos eletrólitos em soluções aquosas é importante na estimativa dos parâmetros de processos da rota de processo a ser usada na extração seletiva dos sais de potássio presentes em salmouras multicomponente. Nesse sentido, os modelos de Pitzer e Harvie foram usados nas estimativas das quantidades e das composições dos sais cristalizados após evaporação da água. A rota de processo envolve quatro etapas de cristalização de uma salmoura representativa do sistema aquoso quinário Na-K-Mg-Ca-Cl na temperatura de 20ºC. A temperatura de 20ºC foi escolhida por ser a temperatura média das salmouras verificadas nos salares Andinos. Os resultados obtidos com os modelos de Pìtzer e Harvie permitiram a elaboração do balanço de massa e energia das piscinas de evaporação e obtenção dos sais comerciais: cloretos de sódio, potássio, magnésio e cálcio.
Palavras-chave
Referências
1 Yang J, Peng J, Duan Y, Tian C, Ping M. The phase diagrams and pitzer model representations for the system KCl+MgCl2+H2O at 50 and 75°C. Russian Journal of Physical Chemistry A. 2012;86(13):1930-1935.
2 Zuvic P, Parada N, Vergana L. Recovery of potassium chloride, potassium sulfate and boric acid from the salar de atacama brine. In: Proceedings of the 66th International Symposium on Salts; May 1983; Toronto, Canada. Naples: Salt Institute; 1983. vol. II.
3 Wang X, Miller JD, Cheng F, Cheng H. Potash flotation practice for carnallite resources in the Qinghai Province, PRC. Minerals Engineering. 2014;66-68:33-39.
4 Silva RG, Secker M, Rocha SDF, Saturnino D, Oliveira EG. Thermodynamic modeling of phases equilibrium in aqueous systems to recover potassium chloride from natural brines. Journal of Materials Research and Technology. 2016;6(1):57-64. http://dx.doi.org/10.1016/j.jmrt.2016.05.006.
5 Song P, Yao Y. Thermodynamics and phase diagram of the salt lake brine system at 298.15 K: V. Model for the system Li+, Na+, K+, Mg2+/Cl−, SO42−–H2O and its applications. Calphad. 2003;27:343-352.
6 Pitzer KS. Thermodynamics of electrolytes. I. Theoretical basis and general equations. Journal of Physical Chemistry. 1973;77(2):268-277.
7 Harvie C, Eugster H, Weare J. Mineral equilibria in the six-component seawater system, Na-K-Mg-Ca-SO4 -Cl-H2 O at 25°C II: Compositions of the saturated solutions. Geochimica et Cosmochimica Acta. 1982;46:1603.
8 Harvie C, Moller N, Weare J. The prediction of mineral solubilities in natural waters: the Na-K-Mg-Ca-H-ClSO4 -OH-HCO3 -CO3 -CO2 -H2 O system to high ionic strengths at 25°C. Geochimica et Cosmochimica Acta. 1984;48:723-751.
9 Pabalan RT, Pitzer K. Thermodynamics of concentrated electrolyte mixtures and the prediction of mineral solubilities to high temperatures for mixtures in the system Na-K-Mg-Cl-SO4 -OH-H2 O. Geochimica et Cosmochimica Acta. 1987;51:2429-2443.
10 Spencer R, Moller N, Weare J. The prediction of mineral solubilities in natural waters: A chemical equilibrium model for the Na-K-Ca-Mg-Cl-SO4 -H2 O system at temperatures below 25°C. Geochimica et Cosmochimica Acta. 1990;54:575-590.
11 Marcus Y, Soffer N. Solubilities and vapour pressure in the quinary system. Journal of the Chemical Society, Faraday Transactions I. 1988;84(10):3575-3585.
12 Zeng DW, Xu WF, Voigt W, Yin X. Thermodynamic study of the system (LiCl + CaCl2 + H2O). The Journal of Chemical Thermodynamics. 2008;40(7):1157-1165.
13 Harvie C, Weare JH. The prediction of mineral solubilities in natural waters: the Na-K-Mg-Ca-Cl-SO4 -H2 O system from zero to high concentration at 25°C. Geochimica et Cosmochimica Acta. 1980;44:981-997.
14 Butts D. Theory and practice of extracting minerals from brine. Ogden: Great Salt Lake Minerals & Chemicals Corporation; 1984. (Solar Ponds; vol. 1).
Facebook
Google+
Twitter
LinkedIn
Mendeley
StumbleUpon
CiteULike
Reddit
Email