Encapsulation of Cs/Sr contaminated clinoptilolite in geopolymers produced from metakaolin

Abstract The encapsulation of caesium (Cs) and strontium (Sr) contaminated clinoptilolite in Na and K based metakaolin geopolymers is reported. When Cs or Sr loaded clinoptilolite is mixed with a metakaolin geopolymer paste, the high pH of the activating solution and the high concentration of ions in solution cause ion exchange reactions and dissolution of clinoptilolite with release of Cs and Sr into the geopolymer matrix. The leaching of Cs and Sr from metakaolin-based geopolymer has therefore been investigated. It was found that Na-based geopolymers reduce leaching of Cs compared to K-based geopolymers and the results are in agreement with the hard and soft acids and bases (HSAB) theory. Cs ions are weak Lewis acids and aluminates are a weak Lewis base. During the formation of the geopolymer matrix Cs ions are preferentially bound to aluminate phases and replace Na in the geopolymer structure. Sr uptake by Na-geopolymers is limited to 0.4 mol Sr per mole of Al and any additional Sr is immobilised by the high pH which causes precipitation of Sr as low solubility hydroxide and carbonate phases. There was no evidence of any other phases being formed when Sr or Cs are added to metakaolin geopolymers.

[1]  S. Berger,et al.  Formulation of caesium based and caesium containing geopolymers , 2009 .

[2]  S. Cohn,et al.  I. CESIUM-137 METABOLISM IN MAN. , 1963, Radiation research.

[3]  J. Sharp,et al.  Indirect determination of the Ca/Si ratio of the C-S-H gel in Portland cements , 1999 .

[4]  J. Deventer,et al.  The coexistence of geopolymeric gel and calcium silicate hydrate at the early stage of alkaline activation , 2005 .

[5]  Caijun Shi,et al.  Stabilization/solidification of hazardous and radioactive wastes with alkali-activated cements. , 2006, Journal of hazardous materials.

[6]  J. Deventer,et al.  Geopolymers : structure, processing, properties and industrial applications , 2009 .

[7]  Ralph G. Pearson,et al.  HARD AND SOFT ACIDS AND BASES , 1963 .

[8]  M. Degteva,et al.  Age-Dependent Model for Strontium Retention in Human Bone , 1994 .

[9]  M. Murat.  Hydration reaction and hardening of calcined clays and related minerals. I. Preliminary investigation on metakaolinite , 1983 .

[10]  Waltraud M. Kriven,et al.  Formation of ceramics from metakaolin-based geopolymers , 2009 .

[11]  J. V. Deventer,et al.  Effects of Anions on the Formation of Aluminosilicate Gel in Geopolymers , 2002 .

[12]  J. Rundo.  THE METABOLISM OF BIOLOGICALLY IMPORTANT RADIONUCLIDES. VI. A SURVEY OF THE METABOLISM OF CAESIUM IN MAN. , 1964, The British journal of radiology.

[13]  D. Roy.  Alkali-activated cements Opportunities and challenges , 1999 .

[14]  H. Manzano,et al.  A model for the C-A-S-H gel formed in alkali-activated slag cements , 2011 .

[15]  C. Shi,et al.  Alkali-Activated Cements and Concretes , 2003 .

[16]  A. Cotton,et al.  Dissolution kinetics of clinoptilolite and heulandite in alkaline conditions , 2008 .

[17]  E. Merz,et al.  Immobilization of intermediate-level wastes in geopolymers , 1994 .

[18]  J. Deventer,et al.  Geopolymerisation kinetics. 3. Effects of Cs and Sr salts , 2008 .

[19]  Brian H. O'Connor,et al.  Chemical optimisation of the compressive strength of aluminosilicate geopolymers synthesised by sodium silicate activation of metakaolinite , 2003 .

[20]  J. Deventer,et al.  39K NMR of Free Potassium in Geopolymers , 2006 .

[21]  K. MacKenzie,et al.  Synthesis and characterisation of materials based on inorganic polymers of alumina and silica: sodium polysialate polymers , 2000 .

[22]  Erez N. Allouche,et al.  Effect of geopolymer cement on microstructure, compressive strength and sulphuric acid resistance of concrete , 2006 .

[23]  Ángel Palomo,et al.  Immobilization of cesium in alkaline activated fly ash matrix , 2005 .

[24]  H. Spencer,et al.  Strontium85 and calcium45 metabolism in man. , 1957, The Journal of clinical investigation.

[25]  J. Bollinger,et al.  Coordination Chemistry Reviews , 2017 .

[26]  Á. Palomo,et al.  Compatibility studies between N-A-S-H and C-A-S-H gels. Study in the ternary diagram Na2O–CaO–Al2O3–SiO2–H2O , 2011 .

[27]  I. Smičiklas,et al.  Removal of Cs1+, Sr2+ and Co2+ from aqueous solutions by adsorption on natural clinoptilolite , 2007 .

[28]  J.S.J. van Deventer,et al.  Geopolymerisation kinetics. 2. Reaction kinetic modelling , 2007 .

[29]  Hua Xu,et al.  Effect of Source Materials on Geopolymerization , 2003 .

[30]  Syed Sakhawat Shah,et al.  Colloids and Surfaces A , 1999 .

[31]  R. Pearson.  Hard and soft acids and bases ― the evolution of a chemical concept , 1990 .

[32]  Vesa Penttala,et al.  The pH measurement of concrete and smoothing mortar using a concrete powder suspension , 2004 .

[33]  G. G. Stokes.  "J." , 1890, The New Yale Book of Quotations.

[34]  J. Phair.  Green chemistry for sustainable cement production and use , 2006 .

[35]  N. Hyatt,et al.  Encapsulation of caesium-loaded Ionsiv in cement , 2010 .

[36]  R. C. Weast.  Handbook of chemistry and physics , 1973 .

[37]  C. Dobson,et al.  The characterization of hardened alkali-activated blast-furnace slag pastes and the nature of the calcium silicate hydrate (C-S-H) phase , 1994 .

[38]  Waltraud M. Kriven,et al.  The effect of alkali and Si/Al ratio on the development of mechanical properties of metakaolin-based geopolymers , 2007 .

[39]  J. C. Swanepoel,et al.  Utilisation of fly ash in a geopolymeric material , 2002 .

[40]  T. Cheng,et al.  Fire-resistant geopolymer produced by granulated blast furnace slag , 2003 .

[41]  Haihong Li,et al.  Synthesis and mechanical properties of metakaolinite-based geopolymer , 2005 .

[42]  Christopher R. Cheeseman,et al.  Ambient Temperature Drying Shrinkage and Cracking in Metakaolin-Based Geopolymers , 2012 .

[43]  J. Provis,et al.  In situ ATR-FTIR study of the early stages of fly ash geopolymer gel formation. , 2007, Langmuir : the ACS journal of surfaces and colloids.

[44]  J. Morales,et al.  On the thermal decomposition mechanism for dehydroxylation of alkaline-earth hydroxides , 1976 .

[45]  Joel Davis,et al.  Aqueous leachability of metakaolin-based geopolymers with molar ratios of Si/Al = 1.5 4 , 2008 .

[46]  X. Cong,et al.  Effects of the temperature and relative humidity on the structure of CSH gel , 1995 .

[47]  W. Loveland,et al.  Elements beyond uranium , 1990 .

[48]  J. Deventer,et al.  Reaction mechanisms in the geopolymeric conversion of inorganic waste to useful products. , 2007, Journal of hazardous materials.

[49]  S. Ito,et al.  Formation and carbonation of C-S-H in water , 1985 .