Utilization of alkaline silicate wastes for removal of cadmium ions from aqueous solution: Comparative performances and removal mechanisms. Issue 5 (October 2019)

• Record Type: Journal Article
• Authors: Zhang, Ge; Fu, Pingfeng; Yang, Huifen; Fu, Peng; Li, Zhaofeng
• Is Part Of: Journal of environmental chemical engineering. Volume 7:Issue 5(2019)
• Publication Date: 2019-10
• Subjects: Silicate waste -- Cd2+removal -- Removal capacity -- Straw ash -- Chemical precipitation -- Surface complexation; Chemical engineering -- Environmental aspects -- Periodicals; Environmental engineering -- Periodicals; Chemical engineering -- Environmental aspects; Environmental engineering; Periodicals; 660.0286
• DOI: 10.1016/j.jece.2019.103402
• Languages: English
• ISSNs: 2213-2929

Abstract

Graphical abstract: Highlights: The Cd 2+ removal capacity of silicate wastes had the order of SA > BFS > CFA > LS. The received SA had a maximum Cd 2+ adsorption capacity of 88.75 mg/g. Cd 2+ ions were precipitated as Cd(OH)2 due to the release of OH − ions from SA. Chemical precipitation, ion exchange and surface complexation contributed to Cd 2+ removal by SA. Abstract: In this work, alkaline silicate wastes including blast furnace slag (BFS), coal fly ash (CFA), straw ash (SA) and lithium slag (LS) were used to remove Cd 2+ from aqueous solution. The removal performances of Cd 2+ by silicate wastes were compared in batch experiments, and the removal mechanisms by SA were proposed. All of four silicate wastes showed high acid neutralization capacity with solution pH increasing from 2.0 at initial to 6.27–9.70 at equilibrium. The removal of Cd 2+ by four wastes followed the pseudo‒second‒order kinetic model and the equilibrium data were well described by the Langmuir isotherm. The maximum removal capacity of Cd 2+ for four wastes had the sequence of SA > BFS > CFA > LS. The SA with the maximum removal capacity of 88.75 mg/g was the best adsorbent for Cd 2+ removal. The XRD tests showed that Cd 2+ could be chemically precipitated as Cd(OH)2 on the SA surface. The FTIR and XPS analysis exhibited that oxygen functional groups of SA could undergo surface complexation with Cd 2+ . Hydration products such as calcium silicate hydrate derived from SA could immobilize Cd 2+ ions through ion exchange. In summary, the removal of Cd 2+ by straw ash had a complicate involvement of chemical precipitation, ion exchange and surface complexation with oxygen functional groups.