Cadmium stabilization via silicates formation: Efficiency, reaction routes and leaching behavior of products. (August 2018)

• Record Type: Journal Article
• Authors: Su, Minhua; Tang, Jinfeng; Liao, Changzhong; Kong, Lingjun; Xiao, Tangfu; Shih, Kaimin; Song, Gang; Chen, Diyun; Zhang, Hongguo
• Is Part Of: Environmental pollution. Volume 239(2018)
• Page Start: 571
• Page End: 578
• Publication Date: 2018-08
• Subjects: Cadmium -- Wastes -- SiO2 -- Silicates -- Transformation ratio (TR); Pollution -- Periodicals; Pollution -- Environmental aspects -- Periodicals; Environmental Pollution -- Periodicals; Pollution -- Périodiques; Pollution -- Aspect de l'environnement -- Périodiques; Pollution -- Effets physiologiques -- Périodiques; Pollution; Pollution -- Environmental aspects; Periodicals; Electronic journals; 363.73
• DOI: 10.1016/j.envpol.2018.04.035
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: Stabilizing cadmium by incorporating it into crystalline products is an effective approach to detoxify cadmium-containing wastes. In this study, two Si-rich matrices in amorphous and crystalline forms (i.e., silica fume and α -quartz, respectively) were employed to incorporate Cd. The processing parameters, namely the type of Si-rich matrix, Cd/Si molar ratio ( Г ) and sintering temperature, were thoroughly investigated using quantitative X-ray diffraction technique. Cd incorporation was more energetically favored when silica fume was used rather than when α -quartz was used because of the lower Gibbs free energy of formation for silica fume. The sintering temperature and Г values substantially affected the formation of three cadmium silicates, namely monoclinic CdSiO3, orthorhombic Cd2 SiO4, and tetragonal Cd3 SiO5 . CdSiO3 formed only in Г = 1.0 systems. Cd2 SiO4 was dominant in all reactive systems. In Г = 3.0 systems, Cd3 SiO5 rather than Cd2 SiO4 was the predominant Cd-hosting product at temperatures above 850 °C. Leaching test results demonstrated that CdSiO3 possessed the highest acid resistance among the cadmium silicates. The leachability of Cd2 SiO4 was very similar to that of Cd3 SiO5 . CdSiO3 preferred incongruent dissolution, whereas Cd2 SiO4 and Cd3 SiO5 favored near-congruent dissolution. This study delineated the feasibility of cadmium incorporation by Si-rich matrices, identifying a promising approach for cadmium detoxification. Graphical abstract: Image 1 Highlights: Cd was successfully incorporated into cadmium silicates via solid state reactions. The incorporation pathways by cadmium silicates crystallization are unraveled. The Cd leachability was substantially reduced by forming cadmium silicates.