Structure and properties of zeolites synthesized from 2:1 illite clay for phenol decomposition in contaminated solutions
M. Randers, G. Sedmale, M. Rundans

Riga Technical University
martins.randers@rtu.lv


Zeolites are versatile microporous materials used as ion exchangers, molecular sieves, sorbents and catalysts. Most of synthetic zeolites are produced from sodium alumosilicate gels, a relatively expensive method. Clay minerals offers cheaper alternative for raw material that can be used for zeolite synthesis using different alkaline and thermal treatment methods [1].
This study investigates mechanical and catalytic properties of hydrosodalite type zeolites synthesized from natural illite clays using alkali activation with concentrated NaOH solutions and subsequent different thermal processes.
Alkaline treatment was conducted on calcined illite (at 600°C) using NaOH solutions with concentrations of 6M and 10M, with following curing processes: 1) at 120°C for 24h; 2) hydrothermally at 180°C for 24h. Structure and morphology of raw and syntesized materials was investigated by SEM (Nova NanoSEM 650, The Netherlands) and XRD (model D8 Advance, Bruker, with CuKα radiation in a scanning interval of 2θ =10–60° at a speed of 4°/ min). Compressive strength was determined with ToniNorm compression test plant. Catalytic activity was evaluated by phenol decomposition degree in water solution using spectrophotometer (Genesis 10S UV).
Main phase that forms after alkaline treatment is hydrosodalite (Na8[AlSiO4]6(OH)2∙2H2O). Use of higher concentration of NaOH and hydrothermal conditions leads to significant increase in hydrosodalite formation. Catalytic decomposition of phenol by using alkali treated illite clay as catalyst is in accordance with fenton reaction, where presence of Fe2+ and Fe3+ ions in structure of synthesized material has key role in decomposition process.

This research was supported by Riga Technical University's Doctoral Grant programme SAM 8.2.2.0/20/I/008

References
[1] A. Z. Khalifa et al., “Advances in alkali-activation of clay minerals,” Cem. Concr. Res., vol. 132, no. March, p. 106050, 2020, doi: 10.1016/j.cemconres.2020.106050.