Use of Sawing Waste from Zeolitic Tuffs in the Manufacture of Ceramics

This paper investigates the thermal transformation of powders of volcanic tuffs that are used as building stones and aims at thermally transforming them into ceramics. The following positive indications concerning this thermal transformation were found: (1) the structural evolution which brings products similar to traditional ceramics, (2) the good ability to give rise to dense and compact final products, and (3) the good mechanical properties and the lovely appearance of the final products. Nevertheless, the high values of linear shrinkages recorded in this work seem to strongly hinder the thermal transformation of this powder-like waste into ceramics. However, mixing this by-product with other powder-like waste exhibiting higher-dimensional stability, such as those deriving from sawing of granites, appears proper

Italian zeolitized rocks of technological interest

Large areas of Italian territory are covered by thick and widespread deposits of zeolite-bearing volcaniclastic products. The main zeolites are phillipsite and chabazite spread over the whole peninsula, and clinoptilolite recorded only in Sardinia. A trachylic to phonolitic glassy precursor accounts for the formation of the former zeolites characterized by low Si/Al ratios (≤3.00), while clinoplilolite is related to more acidic volcanism. The genesis of most of these zeolitized deposits is linked to pyroclastic flow emplacement mechanisms characterized by quite high temperatures and by the presence of abundant fluids. The main utilization of these materials has been and still is as dimension stones in the building industry. Currently, limited amounts are also employed in animal farming (dietary supplement, pet litter and manure deodorizer) and in agriculture as soil improvement and slow-release fertilizers. New fields of application have been proposed for these products on account of their easy availability, very low cost, their high-grade zeolites (50-70%), and good technological features such as high cation exchange capacities and adsorption properties

Comparative ion-exchange characterization of zeolitic and clayey materials for pedotechnical applications. Part 2: interaction with nutrient cations

With the purpose to evaluate the possible use of a phillipsite-rich tuff, in place of the naturally occurring clay minerals, as inorganic ion-exchanger component of organo-mineral aggregates of pedotechnical interest, the ion-exchange behavior of Neapolitan yellow tuff and a reference montmorillonite-rich material towards some nutrient cations was investigated. Accordingly, exchange kinetics and isotherms of Na+, K+, and NH4+ for Ca2+, at 25 °C and 0.1 total normality, were determined, and the related kinetic and thermodynamic quantities computed. The obtained results point out that the zeolitic material, apart from a higher cation exchange capability, exhibits selectivity performances towards nutrient cations comparable or even better than those of the montmorillonitic material, confirming, on the basis of the previous data concerning noxious cations, that phillipsite-rich tuffs can be considered potential substitutes of clay materials to recover and/or rebuild polluted and degraded soils

Evaluation of natural phillipsite and chabazite as cation exchangers for copper and zinc

Chabazite and phillipsite, two zeolites widespread in many volcaniclastic deposits in central-southern Italy, were evaluated as cation exchangers for the removal of copper and zinc from aqueous solution. Equilibrium and kinetics of copper and zinc exchange reactions for sodium were investigated in order to verify the selectivity and the uptake rate of both zeolites for these heavy metals. Thermodynamic quantities, such as equilibrium constant, K-a, and Delta G degrees, as well as rate constant, K, were computed, and they showed that Na-chabazite displays a moderate selectivity and a favorable kinetics for copper, whereas in ail the other cases uses in wastewater treatment are not recommended