Thermochemical study for remediation of highly concentrated acid spill: Computational modeling and experimental validation

Abstract The release of a concentrated acid solution by a chemical accident or acid mine drainage can be disastrous for our environmental safety. Alkaline agents are often applied to remedy acid spills, however, secondary damage such as vaporization and the diffusion of acidic fumes may arise unless substantial amount of neutralization heat is properly controlled. By incorporating rigorous thermodynamic formalism proposed by the Pitzer ion-interaction model and accounting for all subsidiary reactions, we develop a systematic computational model that enables to quantitatively predict the reaction heat and the temperature change during neutralization. We apply this model to the neutralization of four acid solutions (HCl, HNO 3 , H 2 SO 4 , and HF), which is 3 M equivalent concentration with calcium hydroxide ( Ca ( OH ) 2 ) and sodium bicarbonate ( NaHCO 3 ). The evaluation is validated by experiments with remarkable consistency of linear correlation factor R 2 over 0.98. We further extend the acid concentrations up to the extremely high 50 wt% where an experimental approach is, in practice, very restricted. Remarkably, in contrast to Ca ( OH ) 2 which is extremely exothermic, NaHCO 3 even lowers the solution temperature and is suggested as a versatile neutralizer applicable to wide range of concentrated acid solutions. Our model can be useful for establishing a remediation strategy for concentrated acid spills and designing a suitable neutralizer.