Immobilization potential of Cr through Ultrasonic-assisted water washing in MSWI fly ash and evaluation of carbon capture and product reuse in its washing liquid

This study, a method was proposed under room temperature, atmospheric pressure, additive-free, and ultrasound was used as a strengthening method to promote the original gehlenite in municipal solid waste incineration fly ash (MSWI FA) to fix soluble chromium (Cr). At the same time, CO2 was captured, and calcium salts were recovered by using the washing solution's alkaline and high calcium ion properties. Firstly, the reaction time (t), ultrasonic power (w), magnetic stirring rate (rpm), and liquid-solid ratio (L/S) of ultrasonic-assisted water washing were studied by single factor experiment. The results shown that the ultrasonic power had the most significant effect on the fixation effect of Cr, and the optimal parameters are 50 min, 800w, 500 rpm, and 8 L / kg, respectively. The fixation rate of Cr was more than 99.64%. Subsequent carbonation experiments on the washing waste liquid showed that under the flow rate of 200 ml/min of carbon dioxide gas flow, the calcium ions in the solution can be recovered in the form of calcium salts. This study provides an effective MSWI FA treatment process, which can realize the resource utilization of MSWI FA and has the potential to adsorb CO2 and recover calcium salts efficiently.