磁性Fe_3O_4-Ag复合纳米颗粒吸附剂脱汞性能实验研究

Experimental study on mercury removal efficiencies of magnetic Fe_3O_4-Ag composite nanoparticles

目前Fe_3O_4纳米颗粒由于其优秀的物理、化学性能及特有的磁性能,在吸附剂领域有着很好的应用前景。为此,使用共沉淀法制备Fe_3O_4纳米颗粒,以3-氨丙基三乙氧硅烷(APTES)为修饰剂,根据甲酸钠与乙酸银的特异性反应,制备出磁性Fe_3O_4-Ag复合纳米颗粒吸附剂。通过固定床吸附实验考察吸附剂对模拟烟气中汞的脱除能力,讨论其对汞的脱除机理。研究结果表明:磁性Fe_3O_4-Ag复合纳米颗粒吸附剂可脱除90%以上模拟烟气中的汞,且具有很好的抗酸性气体性能。包裹Ag提高了纳米颗粒的稳定性,提高了纳米颗粒的比表面积和总孔容积,且Ag可以与元素汞发生汞齐反应。温度的提高会抑制吸附剂对汞的吸附及汞齐反应的进行,降低吸附剂的脱汞能力。吸附剂对汞的脱除机理为物理吸附为主,且高温下被吸附的汞会从吸附剂中脱附。吸附剂还具有很好的再生性能,重复脱附吸附多次后仍保持很好的脱汞能力。

Fe_3O_4 nanoparticles have great application prospect as sorbents because its excellent physical,chemical and uniquely magnetic properties. CH_3 COOAg was added in Fe_3O_4 nanoparticles solution modified by APTES to form coordination composite,and then Ag＋ was reduced to Ag by HCOONa. Thus, Fe_3O_4-Ag magnetic composite nanoparticles was made. This study investigated the mercury removal efficiencies of Fe_3O_4-Ag nanoparticles and its mechanism. Fe_3O_4-Ag nanoparticles have high mercury removal efficiency and good performance against acidic gases because the stability,the specific surface and the pore volume of nanoparticles are improved. The mercury removal efficiency decreased with increasing temperature because the adsorption process and the amalgam reaction were inhibited. When Fe_3O_4-Ag nanoparticles were used to remove mercury,Hg-0 was adsorbed in the nanoparticles physically and Hg-0 can be desorbed at high temperature. Fe_3O_4-Ag nanoparticles were also reproducible since they had high mercury removal efficiency after several times of desorption.