As a new modification method, mechanochemistry features the remarkable advantages of simple operation process, low energy consumption, easy chemical modification, and suitability for industrialization. In this work, the coal-fired byproduct fly ash was modified by a mechanical–chemical method through omnidirectional planetary ball mill. The effect of the mechanical–chemical modification process parameters on the performance of mercury removal and physicochemical properties of the fly ash and the relationship between the mercury removal efficiency and the physicochemical properties were studied. The experimental results showed that, under the condition of single mechanical ball milling, the mercury removal efficiency of fly ash (FA) was slightly higher than that of raw FA. After being modified by NaBr, the mercury removal efficiency of FA increased considerably with the increase of ball milling time and speed and decreased with the increase of the size of the grinding ball. However, it was no longer significantly improved with further increasing the ball milling time and speed owing to the limited unburned carbon content in FA. The best modification process parameters were determined from the ball milling time of 1 h, the ball milling speed of 400 rpm, and the ball size of 5 mm. The characterization results showed that there was no big difference in physical properties of FA between various mechanical–chemical modification processes. However, the content of carbonyl and carboxyl/ester groups and C–Br covalent groups on modified FA demonstrated a key role in promoting mercury removal performance. The contents of carbonyl and carboxyl/ester groups and C–Br covalent groups were positively proportional to the mercury removal rate, and they were consumed during mercury adsorption. The results confirmed that the improvement of mercury removal efficiency of modified FA was dominated mainly by the surface chemical properties. Compared with the carbonyl and carboxyl/ester groups, the C–Br covalent group was the major chemisorption site of Hg0.

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The Mn‐Fe‐Sn/TiO2(MFST) catalysts for NO and Hg co‐removal with SO2 resistance at low temperature were prepared by the impregnation method under different calcination temperatures (300, 400, 500, and 600°C). The influences of calcination temperatures on SO2 resistance and of SO2 concentration on both denitration and demercuration performances of the Mn‐Fe‐Sn/TiO2 catalysts were investigated in a fixed‐bed reaction system. Surface physicochemical characteristics and SO2 resistance mechanism of MFST catalysts were analyzed by means of Brunauer–Emmett–Teller (BET), X‐ray diffraction (XRD), H2‐temperature‐programmed reduction (H2‐TPR), and X‐ray photoelectron spectroscopy (XPS). The results showed that the NO and Hg0 removal efficiency of the MFST catalysts was not affected by reaction temperature between 200–280°C in the absence of SO2. However, the NO and Hg0 removal efficiency was affected mostly in SO2‐containing atmosphere. Appropriate calcination temperature can alleviate SO2 poisoning and improve catalytic activity. When the calcination temperature was below 500°C, MFST catalysts have good resistance to the SO2, and it was found that at calcination temperature of 400°C, the NO and Hg0 removal efficiency had the minimum decay from 95% to 70% and 99% to 93% at 700 ppm SO2, respectively, which was higher than that of other catalysts. That was mainly due to the abundant BET surface area and pore parameters and the high ratio of Mn4+/(Mn4+ + Mn3+), Fe3+/(Fe3+ + Fe2+), and Oα/(Oα + Oβ) on catalyst surface. At lower calcination temperature (≤400°C), the metal active ingredient did not calcined sufficiently that made the NO and Hg0 removal efficiency declined. While at higher calcination temperature (>400°C), the catalyst tended to agglomeration and MnO2 was converted into Mn2O3 gradually. Furthermore, doping Fe and Sn can effectively reduce the consumption of Mn4+, which greatly improved the catalytic activity and the SO2 resistance.

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.