Ion exchange in amorphous alkali-activated aluminosilicates: Potassium based geopolymers

Significant Statements

 Despite the high functionality of many nanostructured materials, their implementation into our everyday life is limited by few specialized applications. Solution chemistry of metal oxides and silicates offers various routes for “chemical manipulation” that, in turn, allow to design a wide range of inorganic and hybrid nanostructured solids. However, the cost of pure molecular precursors and the complexity of synthesis introduce difficulties with scaling of many technologies. This research focuses on the development of scalable and cost-effective synthetic strategies to obtain nanostructured solids, emphasizing materials functionality and sustainability of long-term materials evolution. It has been demonstrated herein the possibility of preparation of highly porous sorbents based on amorphous alkali-activated aluminosilicates, (i.e., geopolymers). Synthesis and proposed treatment of this geopolymer can be considered as environmental friendly processes, which, unlike zeolite syntheses, do not require high temperature and elevated pressure. Furthermore, the geopolymeric sorbents can be synthesized utilizing waste products, such as slag or fly ash.       

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Ion exchange in amorphous alkali-activated aluminosilicates Potassium based geopolymers copy

Applied Clay Science, Volume 87, January 2014, Pages 205-211.

Taisiya Skorina.

Department of Material Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Room 4-217, Cambridge, MA 02139, USA.

 

Abstract

 

Ion exchange properties of pure potassium-based geopolymer (pure K-GP) formulated with Si/Al = 2.1 and K/Al = 1.0 ± 0.02 atomic ratios have been studied. For pure K-GP, the maximum ion-exchange level of K+with respect to Na+ and Cs+ is 77 and 61%, respectively, as determined by exhausted exchange with 1 M solutions of appropriate nitrates at 22 ± 2 °C. The geopolymer shows a slight preference for K+ over Cs+ as indicated by the normalized Cs/K-GP isotherm obtained under noncompetitive exchange. Parent geopolymer yields a pure geopolymer when it is extensively washed with deionized water until neutral pH is obtained and equilibrated with aqueous solution of KNO3 resulting in changing in composition and textural properties. As calculated from N2 sorption–desorption isotherms, surface specific area and cumulative pore volume for parent K-GP are 5.5 m2 g− 1 and 0.01 cm3 g− 1, respectively, whereas for pure K-GP surface specific area and cumulative pore volume are 270 m2 g− 1 and 0.4 cm3 g− 1, respectively.

 

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