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With the growing need for sustainable solutions to manage desalination by-products and reduce carbon emissions, mineralization offers a promising approach converting CO2 into valuable and stable metal carbonates. This study investigated the effects of pH and reaction time on calcium carbonate precipitation from a Qatari desalination reject brine. The experiments involved a two-step synthesis, where (1) CO2 reacted with NaOH, producing Na2CO3, (2) the produced solution was mixed with reject desalination brine at equimolar molar ratio of Ca2+ to CO32− 1:1. The initial synthesis pH was adjusted by adding concentrated NaOH solution. Reactions were carried out at pH levels from 9.25 to 10.5 and the influence of pH on precipitation speed, phase formation, and magnesium interaction as evaluated. The study found that the 9.5 pH optimal for calcium carbonate precipitation with the highest Ca2+ recovery. The presence of magnesium and its inhibitory effect on crystallization was a significant factor in the process, especially at higher pH levels.

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Valorization of Desalination Reject Brine for Calcium Recovery

  • 会议论文

  • 发表日期：

    2025年

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  • Aiste Zukaityte,
  • Roneta Chaliulina,
  • Bryant Montenegro,
  • Yousef Alhorr

摘要

With the growing need for sustainable solutions to manage desalination by-products and reduce carbon emissions, mineralization offers a promising approach converting CO2 into valuable and stable metal carbonates. This study investigated the effects of pH and reaction time on calcium carbonate precipitation from a Qatari desalination reject brine. The experiments involved a two-step synthesis, where (1) CO2 reacted with NaOH, producing Na2CO3, (2) the produced solution was mixed with reject desalination brine at equimolar molar ratio of Ca2+ to CO32− 1:1. The initial synthesis pH was adjusted by adding concentrated NaOH solution. Reactions were carried out at pH levels from 9.25 to 10.5 and the influence of pH on precipitation speed, phase formation, and magnesium interaction as evaluated. The study found that the 9.5 pH optimal for calcium carbonate precipitation with the highest Ca2+ recovery. The presence of magnesium and its inhibitory effect on crystallization was a significant factor in the process, especially at higher pH levels.