Dual effects of NaCl on the high temperature adsorption of heavy metals by montmorillonite

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2024-08, Vol.494, p.152661, Article 152661
• Main Authors: Zhu, Zhicheng, Huang, Yaji, dong, Lu, Xu, Wentao, Yu, Mengzhu, Li, Zhiyuan, Xiao, Yixuan, Cheng, Haoqiang
• Format: Article
• Language: English
• Subjects: Capture; Dual effects; Montmorillonite; NaCl; PbCl2
• ISSN: 1385-8947
• DOI: 10.1016/j.cej.2024.152661

[Display omitted] •The dual effects on the heavy metal adsorption by NaCl correlated to its content.•The NaCl directly competed with PbCl2 for the adsorption by forming NaAlSiO4.•The eutectic melting effectively compensates for the competitive adsorption by NaCl.•The adsorption efficiency of PbCl2 increased by 17.22% with 2.5% NaCl loaded. The effect of alkali metals on the heavy metals capture by aluminosilicates during the combustion of solid wastes was not unified. In the experiment of PbCl2 adsorption by montmorillonite at 900 ℃, the influence of alkali metals on the adsorption behavior was quantitatively analyzed by loading different contents of NaCl. It was found that the loaded NaCl has dual effects on the heavy metal adsorption properties by montmorillonite at 900 ℃, and the effects were highly correlated with the amount of NaCl loaded. On one hand, the loaded NaCl will directly compete with PbCl2 for the reactive sites of montmorillonite at high temperatures by forming NaAlSiO4. On the other hand, an appropriate addition of NaCl will cause the eutectic melting and change the physical characteristics of sorbent. Both of them jointly influence the adsorption behavior of PbCl2, and the results are highly correlated with the NaCl content. After 2.5% NaCl was loaded to montmorillonite, the eutectic melting helped expose more reactive sites for the high-temperature adsorption, which can effectively compensate for the limited competitive adsorption. In this work, the adsorption efficiency of PbCl2 increased from 25.11% to 42.33% when 2.5% NaCl was doped, with the percentage of chemisorption also increased from 38.26% to 66.82%. However, the adsorption efficiency decreased to 30.85% and 21.18% when 5% and 10% NaCl was loaded due to the excessive occupancy of adsorption sites. This work aimed to provide a quantitative analysis of the effect of alkali metals on the high-temperature adsorption of heavy metals, which may help capture more heavy metals when faced with alkali metals.