Geochemical modeling of brine remediation using accelerated carbonation of fly ash

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+, SO42-, Cl-, Ca2+, Mg2+, and K+ as the major ions with trace concentrations of other ions. The brine can thus be classified as Na2SO4--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 SO42-(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 SO42- as well as being in their free forms. SO42- 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.