吸汞载银活性炭纤维和吸汞活性炭纤维的热脱附特性研究

吸汞载银活性炭纤维和吸汞活性炭纤维的热脱附特性研究

  • 摘要: 70℃下分别对载银活性炭纤维(载银量14.07%)和活性炭纤维的片状吸附体进行气态汞吸附实验,测定出载银活性炭纤维汞饱和吸附量为192.3mg/g,活性炭纤维汞饱和吸附量为29.4mg/g,分别为普通活性炭的48倍~192倍和7倍~29倍。采用热重分析法(TGA)研究了两种吸附剂汞饱和后的热脱附再生特性。结果表明,汞饱和载银活性炭纤维的汞脱附发生在100℃~650℃,在70min内从50℃升温至650℃,汞脱附率为94.73%;汞饱和活性炭纤维的汞脱附发生在100℃~230℃,在40min内从50℃升温至350℃,汞脱附率为69.93%。扫描电镜分析发现,载银活性炭纤维因吸附汞而富集的银,经热脱附后变成均匀弥散于纤维表面的亚微米级和纳米级球状银颗粒;吸汞活性炭纤维经热脱附后物理吸附汞基本消失,而氧化汞颗粒反而变多,说明物理吸附的汞易于脱附,氧化汞难以脱附,同时在热脱附过程中存在金属汞向氧化汞的转化。

     

    Abstract: Both silverloaded activated carbon fibre (silver-loaded ACF) with the silver content of 14.07% and activated carbon fibre (ACF) in form of sheet shape were tested to get their saturation adsorption capacities for mercury in a nitrogen stream. Results showed that silver-loaded ACF and ACF had a saturation adsorption capacity of 192.3mg/g and 29.4mg/g at 70℃, which was 48~192 and 7~29 fold that of common activated carbon, respectively. The thermal desorption characteristics of elemental mercury of the two sorbents were investigated by thermogravimetric analysis (TGA). Mercury desorption from silver-loaded ACF occurred in the temperature range of 100℃~650℃, and mercury desorption efficiency was 94.73% as temperature increased from 50℃ to 650℃ within 70min. Mercury desorption from ACF occurred in the temperature range of 100℃~230℃, and mercury desorption efficiency was 69.93% as temperature increased from 50℃ to 350℃ within 40min. Both silver-loaded ACF samples undergoing mercury adsorption and thermal desorption run were analyzed by scanning electron microscope (SEM). Results showed that after mercury adsorption run, the silver enriched in silver amalgam particles and intensively distributed on the junctures of ACF microcrystals. And after thermal desorption run, the enriching silver got to dispersedly distribute on the surface of ACF in form of globular particles in submicronsize or nanosize. The SEM micrographs of ACF after mercury adsorption and thermal desorption run showed that the elemental mercury by physical adsorption disappeared but mercuric oxide particles by chemical adsorption had a little increase. It suggested that elemental mercury can easily be removed by thermal treatment but mercuric oxide can't be removed. Parts of elemental mercury might transform to mercuric oxide during thermal desorption run.

     

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