载银活性碳纤维对气态汞吸附特性的实验研究

Study on adsorption capability of silver-loaded activated carbon fibre for gaseous mercury

采用银氨溶液浸渍活性碳纤维的方法,制得载银量为14.07%的载银活性碳纤维吸附剂。利用管式炉对载银活性碳纤维筒状吸附体进行汞吸附性能试验。研究发现:气体汞浓度为5263.5μg/m3、H2O(g)体积分数为7%、吸附温度90℃、气体在吸附体的停留时间为0.1s条件下,筒式吸附体在前30min内汞吸附效率98%以上,吸附300min后汞吸附效率仍在20%以上。研究还表明,温度升高,汞吸附效率降低;停留时间延长,汞吸附效率增加;H2O(g)的存在有利于汞吸附,但H2O(g)含量过高又使汞吸附效率略有降低。扫描电镜分析发现,汞只吸附在含银活性点上,吸汞前形状不规则的银粒子与汞结合后变成形状较规则的银汞齐颗粒,且主要分布于活性碳纤维微晶的晶棱交界处。

A kind of new sorbent for gaseous mercury named silver-loaded activated carbon fibre with 14. 07% silver content was prepared from activated carbon fibre soaked with silver-ammonia solution. The sorbent in form of tube shape was tested to investigate its adsorption capability for gaseous mercury. Results showed that the adsorption efficiency of mercury was above 98% in the first 30 minutes and still higher than 200% alter 300 minutes with mercury concentration 5263.5μg/ma , H2O（g） content 7% in the nitrogen stream, and retention time 0. 1s, at adsorption temperature 90℃. The adsorption efficiency decreased with increasing adsorption temperature and increased with the increase of retention time. The existence of water steam in the nitrogen stream could promote gaseous mercury adsorption, but high content of steam slightly decreased the efficiency. The SEM micrograph of silver-loaded activated carbon after mercury adsorption run indicated that the mercury was only adsorbed at active points where silver particles exist. The silver pieces got from original irregular shapes to relative regular balls because of increase of its surface tension when adsorpted with mercury. The silvermercury pieces were all distributed on the juncture of activated carbon fibre microcrystal.