Hurt, Andrew, Coleman, Aimee, Ma, Haosen, Li, Qiu and Coleman, Nichola (2022) Calcium silicate hydrate cation-exchanger from paper recycling ash and waste container glass. Ceramics, 5 (3). pp. 301-317. ISSN 2571-6131 (Online) (doi:https://doi.org/10.3390/ceramics5030024)

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Abstract

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. Hydro-thermal 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 amor-phous 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 pseu-do-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.

Item Type:	Article
Additional Information:	This article belongs to the Special Issue Geopolymers and Ceramics.
Uncontrolled Keywords:	tobermorite; waste glass; paper recycling ash; sorbent; ion-exchange; lead; cadmium; caesium
Subjects:	Q Science > Q Science (General) Q Science > QD Chemistry
Faculty / School / Research Centre / Research Group:	Faculty of Engineering & Science Faculty of Engineering & Science > School of Engineering (ENG) Faculty of Engineering & Science > School of Science (SCI)
Last Modified:	25 Jul 2022 11:25
URI:	http://gala.gre.ac.uk/id/eprint/37073

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