Membrane distillation (MD) could be applicable in zero liquid discharge applications. This is due to the fact that MD is applicable at high salinity ranges which are generally outside the scope of reverse osmosis (RO) applications, although this requires proper management of precipitating salts to avoid membrane fouling. One way of managing these salts is with MD crystallisation (MDC). This paper focuses on the applicability of MDC for the treatment of mining wastewater by thermodynamically modelling the aqueous chemistry of the process at different temperatures. The paper is based on the typical brine generated from an RO process in the South African coal mining industry and investigates the effect water recovery and operating temperature have on the salts that are predicted to crystallise out, the sequence in which they will crystallise out and purities as a function of the water recovery. The study confirmed the efficacy of using thermodynamic modelling as a tool for investigating and predicting the crystallisation aspects of the MDC process. The key finding from this work was that, for an MDC process, a purer product can be obtained at higher operating temperatures and recoveries because of the inverse solubility of calcium sulphate.
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Research Article|
October 12 2015
Thermodynamic modelling of a membrane distillation crystallisation process for the treatment of mining wastewater
Jeeten Nathoo;
1NuWater SA (Pty) Ltd, Capricorn Drive, 7945 Cape Town, South Africa
E-mail: jeeten@nuwaterglobal.com
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Dyllon Garth Randall
Dyllon Garth Randall
2Process Engineering, EAWAG, Swiss Federal Institute of Aquatic Science and Technology, Überlandstrasse 133, 8600 Dübendorf, Switzerland
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Water Sci Technol (2016) 73 (3): 557–563.
Article history
Received:
June 19 2015
Accepted:
September 30 2015
Citation
Jeeten Nathoo, Dyllon Garth Randall; Thermodynamic modelling of a membrane distillation crystallisation process for the treatment of mining wastewater. Water Sci Technol 15 February 2016; 73 (3): 557–563. doi: https://doi.org/10.2166/wst.2015.515
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