Synthesis of hydroxysodalite zeolite by alkali-activation of basalt powder rich in calc-plagioclase

- Calcic-plagioclase (anorthite) can be alkali activated resulting in hydroxysodalite.
- Maximum mechanical strength (57 MPa) is obtained using NaOH/basalt ratio of 0.12.
- Reaction product has a mesoporous structure and BET surface area of 21 m2 g−1.

Hydroxysodalite (H-SOD) microcrystalline particles were synthesized from basalt powder rich in calcic-plagioclase (anorthite) by alkali activation at 80 °C/24 h. Sodium hydroxide (NaOH) solution was used as alkaline activator. The reactivity of the natural solid precursor basalt was studied using differential scanning calorimetry (DSC), and a maximum reaction enthalpy of (−ΔH) of 170 J/g was obtained. The chemical, mineralogical, and textural properties were obtained by using X-ray powder diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and N2-adsorption-desorption measurements. The synthesized material has a specific BET surface area of 20.5 m2 g−1 approximately 200 times higher than raw basalt material (0.1 m2 g−1). The compressive strength of basalt based H-SOD/sand composite samples cured at 80 °C for 24 h upon using different amounts of the activator (NaOH) was evaluated under dry and saturated conditions. The dry samples with NaOH/basalt mass ratio of 0.12 have reached a compressive strength of 57 MPa. Wet samples, on the other hand, showed a compressive strength of 25 MPa after seven days of soaking in water and four episodes of wetting and drying. The present work illustrates that crystalline H-SOD could be synthesized from cheap basalt powder precursor.

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