Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing, 210096, China.
School of Energy Science and Engineering, Central South University, Changsha, 410083, China.
Chemosphere. 2021 Jul;274:129637. doi: 10.1016/j.chemosphere.2021.129637. Epub 2021 Jan 18.
Current approaches for Mechanochemical bromination (MCB) modified fly ash have been focusing on the efficiency and mechanism of mercury removal, but the MCB activation mechanism is still not clear. Selecting activated carbon (AC), hematite (He), anatase (An), and mullite (Mu) to simulate four main fly ash components, and the above samples were MCB modified by omni-directional planetary ball mill with NaBr crystal as modifier. Based on the physicochemical properties and mercury removal ability of each pure component before and after modification, the activation mechanism of MCB was obtained. The results indicate that single mechanochemical modification has almost no effect on the mercury removal ability of each component. The mercury removal ability of fly ash improved by MCB is mainly due to the C-Br generated by reaction between NaBr and AC, and the covalently bonded Br (M-Br) on He also provides a certain contribution. However, the contribution of An and Mu is a little. The MCB activation mechanism is verified that original AC and He are firstly converted into unsaturated carbon and He with surface lattice defects by MCB process, then react with Br free radicals to form C-Br and M-Br, while An and Mu do not mechanochemically react with NaBr during the MCB process.
目前，机械化学溴化（MCB）改性粉煤灰的方法主要集中在汞去除的效率和机制上，但 MCB 的激活机制仍不清楚。本研究选择活性炭（AC）、赤铁矿（He）、锐钛矿（An）和莫来石（Mu）来模拟四种主要的粉煤灰成分，并采用全方位行星球磨机用 NaBr 晶体作为改性剂对上述样品进行 MCB 改性。基于各纯组分改性前后的物理化学性质和汞去除能力，得到了 MCB 的活化机制。结果表明，单一机械化学改性对各组分的汞去除能力几乎没有影响。MCB 提高粉煤灰的汞去除能力主要归因于 NaBr 与 AC 反应生成的 C-Br，He 上的共价键合 Br（M-Br）也提供了一定的贡献。然而，An 和 Mu 的贡献较小。MCB 活化机制得到验证，即 MCB 过程首先将原始的 AC 和 He 转化为具有表面晶格缺陷的不饱和碳和 He，然后与 Br 自由基反应形成 C-Br 和 M-Br，而 An 和 Mu 在 MCB 过程中与 NaBr 不发生机械化学反应。
