Binding of Cu(Ⅱ) and Zn(Ⅱ) in Portland cement immobilization systems: Effect of C-A-S-H composition. (August 2022)

• Record Type: Journal Article
• Authors: Liu, Minghao; Zhao, Yading; Yu, Zhenyun; Cao, Zhenggang
• Is Part Of: Cement & concrete composites. Volume 131(2022)
• Publication Date: 2022-08
• Subjects: C-A-S-H -- EDS -- Adsorption -- Heavy metals -- Portland cement; Composite-reinforced concrete -- Periodicals; Concrete -- Periodicals; Composite materials -- Periodicals; Composites de ciment -- Périodiques; Béton -- Périodiques; Composites -- Périodiques; Béton léger -- Périodiques; Cement composites; Composite materials; Composite-reinforced concrete; Concrete; Lightweight concrete; Periodicals; Electronic journals; 620.135
• DOI: 10.1016/j.cemconcomp.2022.104602
• Languages: English
• ISSNs: 0958-9465

Abstract

Abstract: In this study, statistical EDS point analysis was conducted to understand the binding mechanisms of Cu 2+ and Zn 2+ in Portland cement immobilization systems based on their correlation with compositions of Al incorporated into calcium silicate hydrate (C-A-S-H). Cu 2+ and Zn 2+ significantly retarded early hydration and strength development within the first day but exerted an accelerating effect at later ages. The uptake of Cu 2+ by C-A-S-H occurs through two types of binding forms, which are dominated by the adsorption of Cu 2+ on the Al sites of substituted bridging silicate tetrahedra and on deprotonated silanol group sites. These binding forms result in competitive adsorption between Cu 2+ and Ca 2+ . Zn 2+ is primarily bound to the outer-product C-A-S-H. Zn anion species were adsorbed on the positively charged sites of the C-A-S-H surface, which were generated from the adsorption of Ca 2+ . Consequently, the uptake of Zn exhibits a noncompetitive relationship with Ca 2+ and increased with Ca content in C-A-S-H.