Treatment of sulphate wastewater by freeze desalination

N. Zikalala, J. P. Maree, C. Zvinowanda, V. Akinwekomi, T. Mtombeni, L. Mpenyana-Monyatsi

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)


Cooling and freezing can be used to produce fresh water from brackish water, industrial brines and leachates from industrial wastes. The aim of this study was to identify how cooling and/or freezing can be used for the recovery of drinking water from sulphate rich solutions associated with various cations. It was found that: (i) If the solution contains only Na2SO4, after pre-treatment with sodium alkalis, it can be removed from solution through cooling down to 0.33 mol/L (31.7 g/L SO4) through crystallization of Na2SO4·10H2O; (ii) the solubility of Na2SO4 upon cooling is influenced by the Cl-concentration; (iii) the Reverse Osmosis-Cooling (ROC) process is most suitable for treatment of saline solutions rich in Na2SO4, as it can be precipitated through cooling as Na2SO4·10H2O, followed by reverse osmosis to produce drinking water; (iv) The energy required to cool water, containing 100 g/L Na2SO4, from 25°C to 0°C, amounts to 10.66 kWh/t water. When the water is further cooled down to freeze 90% of the water, the energy consumption increased from 10.66 kW/h to 37.74 kWh/t.

Original languageEnglish
Pages (from-to)93-102
Number of pages10
JournalDesalination and Water Treatment
Publication statusPublished - Jun 2017


  • Freeze desalination
  • Reverse osmosis cooling

ASJC Scopus subject areas

  • Water Science and Technology
  • Ocean Engineering
  • Pollution


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