饱和膨润土复合颗粒吸附剂吸附的重金属离子的固定及其再生

Immobilization and regeneration of heavy metal ions by composite saturated bentonite adsorbent

采用Na_2S化学再生法对吸附Fe^(2+)、Mn^(2+)、Cu^(2+)和Zn^(2+)饱和的膨润土-钢渣复合颗粒吸附剂分别进行重金属离子的固定及其再生实验研究,探究该吸附剂吸附的重金属离子的固定问题及其再生的可能性和多次再生后的吸附效果,同时根据SEM图进一步揭示固定、再生机理。结果表明:在对Fe^(2+)的固定、再生实验中,可形成Fe S沉淀而实现固定,但再生后再吸附时,膨润土复合颗粒中蒙脱石结构改变使得颗粒坍塌变成粉末状,因此,吸附Fe^(2+)饱和的膨润土复合颗粒吸附剂不适合用Na_2S再生;而对Mn^(2+)、Cu^(2+)和Zn^(2+)的固定、再生实验中,均可形成S化物沉淀而实现固定,颗粒结构未改变,经过3次再生后,吸附剂对Mn^(2+)、Cu^(2+)和Zn^(2+)的去除率还可达到94.22%、83.2%和76.30%,远比未经再生的吸附剂吸附效果好,同时,由SEM表征分析进一步揭示:Na_2S再生溶液既可使重金属离子形成MS沉淀固定,又可使复合颗粒吸附剂获得再生,实现了同步固定、再生的目的,且吸附剂经多次再生后吸附效果保持良好。

Using Na_2 S as the regeneration agent,this study investigated the fixation of heavy metal ions by a bentonite-steel slag composite granular adsorbent and its regeneration after adsorption saturation with Fe^2＋,Mn^2＋,Cu^2＋,and Zn^2＋. Specifically,this study explored the fixation of heavy metal ions by the adsorbent,the possibility of regeneration,and the adsorption capability after repeated regeneration. The mechanisms of the fixation of metal ions and the regeneration of the adsorbent were explored using SEM（ scanning electron microscopy） images. The experimental results showed that Fe^2＋was fixed by the adsorbent in the form of Fe S precipitate. However,after regeneration by Na_2 S,the structure of montmorillonite in the adsorbent was altered,resulting in the collapse of the adsorbent into powder. This result indicated that Na_2 S was not suitable for the regeneration of the adsorbent saturated with Fe^2＋. In the case of Mn^2＋,Cu^2＋,and Zn^2＋,these metal ions were fixed owing to the formation of metal sulfide precipitates,while the structure of the granular adsorbent was not modified in the regeneration process. After regeneration was performed three times,the removal efficiencies of the adsorbent for Mn^2＋,Cu^2＋,and Zn^2＋were 94. 22%,83. 2%,and 76. 30%,respectively,which were far better than the case without regeneration. SEM images further revealed the synergistic effect of Na_2 S solution as the regeneration agent in terms of enhancing the fixation of metal ions as metal sulfide precipitates and the repeated regeneration of the adsorbent without compromising the adsorption capability.