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.

中文翻译：

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机械化学改性工艺对溴改性粉煤灰脱汞的影响

机械化学作为一种新的修饰方法，具有操作过程简单，能耗低，化学修饰容易，适合工业化的显着优点。在这项工作中，通过全向行星式球磨机通过机械化学方法对燃煤副产品粉煤灰进行了改性。研究了机械化学改性工艺参数对粉煤灰除汞性能和理化性质的影响以及除汞效率与理化性质之间的关系。实验结果表明，在单机械球磨条件下，粉煤灰（FA）的除汞效率略高于原料FA。经过NaBr修饰后，FA的除汞效率随着球磨时间和速度的增加而显着提高，而随着磨球尺寸的增加而降低。但是，由于FA中未燃烧的碳含量有限，随着球磨时间和速度的进一步增加，它不再得到显着改善。最佳的改性工艺参数由1 h的球磨时间，400 rpm的球磨速度和5 mm的球尺寸确定。表征结果表明，在各种机械化学修饰过程之间，FA的物理性质没有太大差异。但是，修饰的FA上的羰基和羧基/酯基团和C-Br共价基团的含量显示出在促进除汞性能方面的关键作用。羰基和羧基/酯基团和C-Br共价基团的含量与除汞率成正比，并且在汞吸附过程中被消耗。结果证实，改性FA的除汞效率的提高主要由表面化学性质决定。与羰基和羧基/酯基相比，C-Br共价基团是汞的主要化学吸附位点⁰。