Production of Syntetic Zeolites from a volcanic rock and their potential for ammonia and heavy metals removal

This paper presents the results of an investigation carried out to explore the possibility of obtaining highly adsorbent materials from a volcanic rock for use in environmental remediation. Tests were carried out in an autoclave using solutions containing different concentrations of NaOH, varying temperature over the 25-200°C range and solution/volcanic material contact time over the range 4-24 hours. The products were characterized by diffractrometric and SEM analysis as well as specific surface area and cation exchange capacity (C.E.C.) determinations. The results showed that different types of zeolite are produced depending on the temperature, NaP1 zeolite at temperatures of 80-100°C and analcime and hydroxycancrinite at higher temperatures. The highest C.E.C., around 410 meq/100g, was exhibited at 100 °C due to the formation of the NaP1 zeolite. The products obtained after attack with a 2.5 M NaOH solution were further characterized by cation exchange tests using solutions containing NH4+, Pb, Zn and Mn.