Effect of Supercritical Carbonation on Leach Ability of Cement-Solidified Heavy Metals

Haiyang Wang, Xiaoxiong Zha

Abstract


Cement solidification body (CSB) has been widely used in treating heavy metals before land filling or recycling. Super critical carbonation, under the conditions of CO2 pressure above 7.39MPa and temperature above 31.26°C, has been found to significantly improve carbonation efficiency.  Supercritical carbonation may also be beneficial in modifying the CSB material or improving the deficiency of the porosity of CSB. The leaching rates of Cu and Cd ions were analyzed at a leaching time of up to 42 days with leaching liquid temperatures of 25°Cand 70°Cunder natural and supercritical carbonation conditions to investigate the effect of supercritical carbonation on treating CSB. The results showed that supercritical carbonation significantly reduced the leaching rate of Cu ion in early leaching time. However, the leaching rate of Cd ion increased steadily under supercritical carbonation.  Furthermore, liquid temperature has an effect on the leaching rate. The higher the temperature of the leachate, the higher the leaching rate of ion is. The full-life simulation method using the combination of PHREEQC and COMSOL is discussed utilizing the experimental data. The full-life simulation method is also used to analyze the hydration reaction, supercritical carbonation, solidification, and migration of heavy metals in CSB.


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