Effect of a Mechanochemical Process on the Stability of Mercury in Simulated Fly Ash. Part 1. Ball Milling

As a novel method, mechanochemistry has great potential in the field of mercury stabilization. In this paper, simulated mercury adsorption saturated fly ash (SFA) was prepared, and an omnidirectional planetary ball mill was used for mechanochemical (MC) stabilization. The effect of different MC stabilization processes such as ball milling time, ball milling speed, ball size, and the mass ratio of the ball/SFA on the mercury stabilization of SFA was explored by the mercury toxicity leaching experiment. Based on the physicochemical properties of SFA before and after different MC stabilization, the mercury stabilization mechanism was discussed. The results show that the influence trends of different MC stabilization conditions on the mercury stability of SFA are different. The optimum MC stabilization process of SFA is as follows: the ball milling time is 30 min, the ball milling speed is 400 rpm, the ball size is 5 mm, and the mass ratio of the ball/SFA is 10/1. An appropriate MC process is beneficial for the stabilization of mercury in SFA because it crushes SFA particles and destroys the lattice structure, making its pore structure more developed and more surface active sites generated, which is conducive to increasing the diffusivity and adsorption ability of Hg in SFA. However, an improper MC process induces agglomeration, reduces the active sites of SFA, and destroys its pore structure, which is not conducive to the stabilization of mercury and even leads to secondary release. Nevertheless, although the mercury stability in SFA can be improved by an appropriate MC stabilization process, the stabilization performance is still insufficient.