Na2SO4 modified low-carbon cementitious binder containing commercial low-reactivity metakaolin for heavy metal immobilization: Mechanism of physical encapsulation and chemical binding

被引：11

作者：

Liu, Minghao ^{[1
,2
,3
]}

Xia, Yan ^{[1
,2
,3
]}

Zhao, Yading ^{[1
,2
,3
]}

Chi, Xiaofeng ^{[1
,2
,3
]}

Du, Jianxin ^{[1
,2
,3
]}

Du, Donghang ^{[1
,2
,3
]}

Guo, Junzhen ^{[1
,2
,3
]}

Cao, Zhenggang ^{[1
,2
,3
]}

机构：

[1] Harbin Inst Technol, Sch Civil Engn, Harbin 150090, Peoples R China

[2] Harbin Inst Technol, Key Lab Struct Dynam Behav & Control, Minist Educ, Harbin 150090, Peoples R China

[3] Harbin Inst Technol, Key Lab Smart Prevent & Mitigating Ind & Informat, Harbin 150090, Peoples R China

来源：

JOURNAL OF BUILDING ENGINEERING | 2022年 / 60卷

关键词：

Low -carbon cement; Modification; Immobilization mechanism; Pore structure; C-A-S-H; CALCIUM-SILICATE-HYDRATE; C-S-H; FLY-ASH; MERCURY POROSIMETRY; PORE STRUCTURE; MICROSTRUCTURE; STRENGTH; SLAG; POROSITY; SODIUM;

D O I：

10.1016/j.jobe.2022.105194

中图分类号：

TU [建筑科学];

学科分类号：

0813 ;

摘要：

In this study, a Na2SO4 modified low-carbon cementitious binder based on commercial low -reactivity metakaolin (MK) and cement was utilized for the immobilization heavy metals (Cu2+, Ni2+, Cd2+ and Zn2+). The compressive strengths and leaching concentrations of the immobilization systems were investigated to evaluate the immobilization effect for heavy metals. Meanwhile, the pore structure and chemical compositions of the immobilization systems were characterized to study the immobilization mechanisms. Results demonstrate that the MK-blended systems exhibit excellent heavy metal immobilization effect and low releasing risk under the effect of Na2SO4. The incorporation of Na2SO4 significantly improve the compressive strength of the MK-blended systems due to the promotion effect on the early hydration kinetics of cement, the formation of ettringite and the pozzolanic reaction of MK. Moreover, the incorporation of Na2SO4 decreases the capillary porosity and/or increases the tortuosity of the MK-blended sys-tems, which enhances the physical encapsulation to heavy metals. The MK-blended systems have higher chemical binding capacities to heavy metals than pure cement immobilization systems. This is due to the increase in the Si/Ca and Al/Ca atom ratios of calcium aluminosilicate hydrate that introduces more negative charged silicon and aluminium sites to bind heavy metal cations.

引用

页数：19