Effect of the milling solution on lead stabilization in municipal solid waste incinerator fly ash during the milling processes

The wet milling process had been found to effectively stabilize lead in fly ash. This study adopts this method and looks at the effect of different milling solutions to improve the efficiency of lead stabilization. Different milling solutions (water, phosphoric acid and ethanol) and different milling times (1, 24, 48 and 96 h) were selected as parameters. Since lead oxide can be identified by XRD in this experiment’s samples, 5% lead oxide was added to the extracted mixed fly ash to make instrumental analysis easier. The experimental results indicate that the effect of stabilization of lead after milling could exceed 96%. During milling with water, considerable lead leached into the water in the initial stage (1 h) of the process, but a stable level was reached as the milling time increased. After milling with ethanol and 0.2 M phosphoric acids, the efficiency could exceed 93% after 1 h of milling time. The results of the sequential extraction procedure (SEP) results show that the residual fraction could be increased from 8.93% to 56.16% when a 0.2 M phosphoric acid solution was used. Clearly the choice of an appropriate milling solution can enhance lead stabilization in the fly ash.