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Synthetic 11 Å tobermorite (Ca5Si6O16(OH)2.4H2O) and its Al-substituted analogue are layer-lattice ion-exchangers with potential applications in nuclear and hazardous wastewater treatment. The present study reports the facile one-pot hydrothermal synthesis of an Al-tobermorite-rich cation-exchanger from a combination of paper recycling ash, post-consumer container glass, and lime, with compositional ratios of [Ca]/[Si + Al] = 0.81 and [Al]/[Si + Al] = 0.18. The reaction products were characterized by powder X-ray diffraction analysis, 29Si magic angle spinning nuclear magnetic resonance spectroscopy, and scanning electron microscopy. Hydrothermal processing in 4 M NaOH(aq) at 100 °C for 7 days yielded an Al-tobermorite-rich product that also contained katoite (Ca3Al2SiO12H8), portlandite (Ca(OH)2), calcite (CaCO3), and amorphous silicate gel. The hydrothermal product was found to have a Cs+ cation exchange capacity of 59 ± 4 meq 100 g−1 and selective Cs+ distribution coefficients (Kd) of 574 ± 13 and 658 ± 34 cm3 g−1 from solutions with molar ratios [Cs+]:[Na+] and [Cs+]:[Ca2+] of 1:100. In a batch sorption study at 20 °C, the uptakes of Pb2+, Cd2+, and Cs+ were determined to be 1.78 ± 0.04, 0.65 ± 0.06, and 0.36 ± 0.03 mmol g−1, respectively. The kinetics of Pb2+, Cd2+, and Cs+ removal were described by the pseudo-second-order rate model, which gave respective rate constants (k2) of 0.010, 0.027, and 1.635 g mmol−1 min−1, and corresponding correlation coefficients (R2) of 0.997, 0.996, and 0.999. The metal ion sorption properties of the tobermorite-rich product compared favorably with those of other waste-derived tobermorites reported in the literature. Potential strategies to improve the yield, crystallinity, and sorption characteristics of the product are discussed.

Cement is widely used for the solidification of low- and intermediate-level radioactive waste materials. Radioactive borate solution with a high concentration of boron is one of the main radioactive wastes produced in nuclear stations. It is difficult to solidify this solution by using cement because borate has a great inhibitory effect on the cement hydration process. In this study, the hydration kinetics, strength, durability, phase assemblage, and transportation and transformation of the silicon of the paste that blended Portland cement with 5 M borate solution were investigated. After the addition of sodium hydroxide and sodium metasilicate to the paste, the cement hydration process was restarted, and the 28-days strength of samples met the requirements of the Chinese standard. The mechanism of overcoming the retardation of cement hydration by the borate solution was attributed to the formation of calcium metaborate, ettringite, portlandite, and calcium silicate hydrate with the restarting of cement hydration, without the formation of ulexite.