Caratterizzazione tecnologica di una Pb-clinoptilolite

A Sardinian clinoptilolite rich-rock was submitted to a mineral separation process aimed to increase zeolite content. The material enriched in zeolite was subjected to exchange processes in Na- and Pb- solutions, to conduct the clinoptilolite in Pb-form. The behaviour of the Pb-clinoptilolite was studied measuring the Pb2+ release in 0.5 M NaCH3COO solution at 20°C. This release was compared with lead releases of the same material heated at 200, 300, 400, 500, 600, 675, 700, 800, and 900°C. The rehydration capacity (R.C.) after heating was also evaluated. TG analyses were performed to evaluate the R.C. also after repeated heating-cooling cycles. XRPD results of unheated and heated materials were related with R.C. and lead releases results. The Pb-clinoptilolite was characterized also by means of DTA analyses. The ternary system SiO2-Al2O3-PbO was used to explain the transformations recorded at temperatures higher than 700°C, keeping in consideration DTA and XRPD results.