Synthesis of Zeolites from Volcanic Ash (tajogaite, Spain) for the Remediation of Waters Contaminated by Fluoride

In the eruptive event of Tajogaite (2021) in La Palma, Canary Islands, large quantities of volcanic ash were accumulated, affecting the local environment and urban areas. In this study, volcanic ash sampled from urban areas (catalogued as municipal waste (20 03 03) by the European Wastes Catalogue) were converted into zeolites by hydrothermal synthesis at 100 °C with previous alkaline fusion at 550 °C with distilled water. During this process, new phases of zeolite principally type X and sodalite have been identified by XRD at 2 h of incubation. These zeolites, with the course of incubation time, present competitive processes where the transformation into sodalite develops after 24 h as the predominant phase. The synthesized zeolitic material presents a high concentration as impurities in Fe2O3 (13.70 wt