Geochemical modeling of brine remediation using accelerated carbonation of fly ash

Abstract

A protocol is proposed, where waste fly ash and CO₂ emissions from coal-fired power plants are utilized in remediating brine waste. The untreated brine sample was made up of Na⁺, , Cl⁻, Ca²⁺, Mg²⁺, and K⁺ as the major ions with trace concentrations of other ions. The brine can thus be classified as -rich water with respect to major cations and anions. Following carbonation, over 99% removal of NO₃⁻ was achieved while B³⁺, V²⁺, MO²⁺, and Cl⁻ concentrations increased. Major components removal from brine upon carbonation was as follows: Na⁺ (15–29%), Mg²⁺ (53–87%), K⁺ (70–88%), Ca²⁺ (40–73%), and (12–36%). Speciation modeling of the major components present in brine showed that Na⁺, K⁺, and Cl⁻ exist mainly as free ions, while Mg²⁺ and Ca²⁺ are associated with as well as being in their free forms. ions on the other hand were present in its free form to a great extent as well as associated with Na⁺, Ca²⁺, Mg²⁺, and K⁺, respectively, in a decreasing order. The carbonated brine effluents are therefore depleted with regards to major and trace elements concentration, when compared with the untreated brine. Mineral carbonation may therefore be a potent brine remediation protocol, which can be optimized for maximum removal of various elements.

Keywords:

• Brine
• Mineral carbonation
• Fly ash
• McNemar test
• Geochemical modeling
• Speciation

Acknowledgments

This research was financially supported by the NRF and the Water Research Commission (WRC) Project Number: K5/ 2,128.