摘要
For revealing the effect of calcium on heavy metal in-furnace capture by kaolinite,gaseous PbCl_(2) and CdCl_(2) adsorptions by calcium-doped kaolinite at high temperatures and their mechanisms were investigated through experiments in a fixed-bed furnace,where factors of temperatures and the mixing proportion of limestone and kaolinite were considered.The results show that the adsorption efficiency of cadmium by the mixed sorbents is lower than that by single sorbents,mainly due to the consumption of lime or limestone,whereas that of lead varies at different reaction temperatures.Two kinds of areas,named as Ca-rich zone and Ca-low zone,are found in the sorbents of calcium-doped kaolinite.The Ca-rich zone tends to lessen the capture efficiencies for the two metals,whereas the Ca-low zone can enhance their adsorption.The heterogeneous distributions of calcium have multiple effects on metal sorption,including the diffusion enhancement through the eutectic effect by forming low-melting-point substances,the inhibition by the competitive occupation of reaction sites,and the block of pores caused by sintering at a high temperature.
为探究钙质对高岭土高温吸附重金属的影响,在固定床反应器上采用不同的反应温度和掺混比研究了掺钙高岭土对气态氯化铅和氯化镉的高温吸附过程,分析了矿物相互反应的影响机理.结果表明,混合吸附剂对镉的吸附效率低于高岭土或石灰石的单一吸附剂,而对铅的吸附能力随温度变化存在差异.吸附剂中存在富钙区和贫钙区,富钙区的生成会降低2种金属的捕集效率,而贫钙区有助于促进吸附过程.由此说明,钙在高岭土中的非均相分布对金属吸附具有复合效应,既可通过共晶熔化作用促进重金属扩散,又会竞争性占据反应位点,阻止吸附,同时还会造成高温烧结,堵塞孔结构,从而抑制反应进行.
基金
The National Natural Science Foundation of China(No.51976036)
the Scientific Research Foundation of the Graduate School of Southeast University(No.3203009748)。
