DOI: 10.15125/bath-00590
title: Dataset for "A mild conditions synthesis route to produce hydrosodalite from kaolinite, compatible with extrusion processing"

description: Chemical characterisation data describing the cured products formed when reacting kaolinite precursor with sodium hydroxide solution at Na:Al ratios of 0-1.5.

Version 2 includes additional data for mass spectrometry results and 29Si MAS NMR peak deconvolution.
description: Fig 2 - Powder X-ray diffraction (PXRD) analysis was done to identify phases with a Bruker D8 Advance instrument using monochromatic CuKalpha1 L3 (λ = 1.540598 Å) X-radiation and a Vantec superspeed detector. A step size of 0.016⁰(2θ) and step duration of 0.3 seconds were used. 

Fig 3 - Atterberg plastic limit measurements were taken for kaolinite over a range of sodium hydroxide solution concentrations, based on BS 1377-2:1990. From these data a best fit line was plotted to extrapolate the volume of solution required to reach plastic limit consistency for a given concentration. A correction was made to exclude the mass of the sodium hydroxide from the solids mass in the plastic limit calculations. 

Fig 4 - Powder X-ray diffraction (PXRD) analysis was done to identify phases with a Bruker D8 Advance instrument using monochromatic CuKalpha1 L3 (λ = 1.540598 Å) X-radiation and a Vantec superspeed detector. A step size of 0.016⁰(2θ) and step duration of 0.3 seconds were used. 

Fig 5 - Powder X-ray diffraction (PXRD) analysis was done to identify phases with a Bruker D8 Advance instrument using monochromatic CuKalpha1 L3 (λ = 1.540598 Å) X-radiation and a Vantec superspeed detector. A step size of 0.016⁰(2θ) and step duration of 0.3 seconds were used. 

Fig 7 - Thermogravimetric analysis (TGA) was done to characterise thermal behaviour, using a Setaram Setsys Evolution TGA over a range of 30 to 1000 °C at a heating rate of 10 °C/minute. An air atmosphere was used, with a flow rate of 20 ml/minute. A connected mass spectrometer was used (Pfeiffer Omni) to identify whether evolved gas species contained OH, H2O, CO or CO2. 

Fig 8 and Fig 9 - Magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra were measured for 27Al and 29Si to characterise coordination states, using a Varian VNMRS in direct excitation. Standards used were 1M aq. Al(NO3)3 for 27Al and tetramethylsilane for 29Si. Spin rates used were 12 kHz for 27Al and 6 kHz for 29Si, and frequencies used were 104.199 kHz for 27Al and 79.435 MHz for 29Si. Sample holders were 4mm width for 27Al and 6mm width for 29Si. 

Fig 10 - Fourier Transform Infrared Spectroscopy (FTIR) was done to characterise molecular bonding, using a Perkin-Elmer Frontier with a diamond Attenuated Total Reflectance (ATR) head. Spectra were collected over a range of 4000-600 cm-1 using a resolution of 4cm-1 and 5 scans per spectrum.
description: Fig 2 - Phase identification was done using Bruker EVA software.


Fig 5 - Le Bail extractions and Rietveld refinements of the structure were performed using JANA 2006 and the Cheary Coelho fundamental approach for XRD profile parameters. 

Fig 10 - Corrections were made for ATR and background using Perkin-Elmer Spectrum software. 

Fig 11 - To understand how the Na:Al molar ratio affected the reaction of kaolinite to form a hydrosodalite, the proportion of kaolinite consumed was estimated using PXRD, TGA and 29SI MAS-NMR. For PXRD, Rietveld refinement was used as already described. For TGA, in the dTG spectrum (plotted in %mass loss / minute to normalise between samples), the peak attributed to the dehydroxylation of kaolinite was integrated. This peak area was then expressed as an area fraction of the equivalent peak in the dTG spectrum for the starting kaolinite precursor. The area fraction was then assumed as equivalent to proportion of kaolinite remaining in the sample. For 29Si MAS-NMR, peaks corresponding to kaolinite and hydrosodalite were integrated (deconvoluted as required when overlapping). The area fraction of the kaolinite peak from the total peak area in a given sample’s spectrum was assumed as equivalent to phase proportion, since 29Si is a spin-half nucleus and does not suffer quadrupolar effects. A Lorentzian profile was used for deconvolution as it gave a better fit to the measured curves than a Gaussian profile.