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In this work we have tested the fluidized bed desulfurization performance of lime particles obtained by means of a limestone slow calcination pre-treatment technique. This performance was compared to that of the parent untreated limestone particles. The occurrence of particle fragmentation and attrition during the fluidized bed operation was also investigated with a specific test protocol for both raw limestone and pre-treated lime sorbent. Two particle size ranges were tested under typical fluidized bed coal combustion conditions ( T = 850 °C; SO 2 = 1800 ppm). The experiments were complemented by porosimetric and morphological (SEM) analyses of the sorbent. Results showed that limestone pre-treatment was able to preserve the high mechanical strength of the parent particles as opposed to the fast in situ calcination typically active in fluidized beds. In addition, a high calcium reactivity and final conversion were observed for the pre-treated lime particles, leading to a SO 2 capture capacity per unit mass of sorbent much higher than that obtained with the untreated limestone. Simple economic evaluations suggest that the use of the pre-treated lime in place of limestone can involve significant economies for fluidized bed coal combustor operators.

On the basis of a previous detailed characterization of the Sardinian bentonites for pelotherapy applications wCara, S., Carcangiu, G., Padalino, G., Palomba, M., Tamanini, M., 2000. The bentonites in pelotherapy: chemical, mineralogical and technological properties of materials from Sardinia deposits Italy.. Appl. Clay Sci. 16, 117-124 this issue.x, three commercial bentonites have been selected for detailed studies. The thermal properties of the pastes, prepared with these bentonites at different moisture, have been compared with the properties of a peloid, commonly used in the spa of Benetutti northern Sardinia.. The cooling kinetics of the bentonites along with the thermal mud have been studied using an experimental apparatus that reproduces the conditions during the application of a cataplasm. A mathematical model for the cooling kinetics has been obtained by means of a theoretical cooling equation, with instrumental constants derived from a reference paste TiO2 at 50% moisture.. The heat capacity of the pastes introduced into the model was calculated from chemical and mineralogical data. The methodology developed can be used in other laboratories of the thermal centres to determine the quality and ability of the bentonitic materials for pelotherapy. q2000 Elsevier Science B.V. All rights reserved.

Mn-rich beds occur within the “Brecce di Seravezza” Formation (BSFm) intercalated between Norian metadolostone-Megalodontic marble and Hettangian marble in the Alpi Apuane, (Italy). The BSFm is a rockfall talus deposit that accumulates at the base of the footwall scarp of normal faults bordering extensional marine coastal basins. The type sequence of metabreccia ends with a bed of chloritoid schist interpreted as the metamorphic equivalent of lateritic soils. The four main types of Mn mineral assemblages are: (1) braunite, piemontite, and rare hausmannite; (2) piemontite, braunite, hollandite and minor rhodochrosite and kutnahorite; (3) braunite, hollandite and rare piemontite. The other minerals are: quartz, calcite, muscovite, phlogopite, baryte and minor hematite, rutile and apatite. During the Alpine orogeny pressures of 4–6 kb and temperatures of 350 °–380 °C were attained; Mn assemblages with hematite and phlogopite indicate ƒO2 > 10−8 for T= 350 °C and ƒO2 ≥ 10−6 when braunite appears. On the Mn-rich rocks Ti, Fe, Nb, Sn, Ta, Hf, Th, Ga, Rb, Pr, K, Na, Nd were identified as detrital in origin and are positively correlated with Al. U is positively correlated with Co, Pb, Bi, Mo. The rare earth element patterns normalized to seawater show a negative slope towards the heavy rare earth elements, with positive Ce anomalies in some samples, positive Ce and Eu anomalies in other samples and negative Ce and positive Eu anomalies in a third group. The Eu concentrations are nearly constant and the Eu anomalies reflect differences in the concentration of other rare earth elements; for Ce, a positive correlation with Al2O3 + SiO2 indicate that a detrital signature prevails on that produced by duration of seawater exposure. But a significant good correlation of La, Tm, Lu with Mg could indicate, at least for these elements a seawater signature. Only in some samples, Ba, Eu, Sr show anomalously high concentrations, likely of hydrothermal origin. However, generally in all the chemical variation diagrams the BSFm samples fall outside the field of hydrothermal and hydrogenous deposits as defined in the literature for other Mn deposits. In addition, metabasites and metavolcaniclastic beds are absent from the BSFm sequence and BSFm coastal basins were for the most part separated from the open ocean and related streams, that must be excluded as possible Mn-sources. Owing to the arid climate of Late Triassic the runoff was negligible and the groundwater, oxidizing and alkaline, were unable to mobilize Mn. The BSFm basins are then the most suitable depositional environment for Mn. The water column was stagnant and stratified. Only where bottom of the basin was deeper than the oxic-anoxic boundary, reducing marine bottom waters percolated within the fractured basement and leached Mn from disseminated minerals of metamorphic rocks and, then, rising along fault and fractures, supplied Mn to the bottom waters. Afterwards, when tectonic uplift and sealevel drop brought the bottom into the oxic field, Mn precipitated and formed the Mn-rich matrix of the BSFm deposits.

In the past years, the Centro Studi Geominerari e Mineralurgici of the C.N.R. of Cagliari has carried out an investigation on sand deposits located along the coasts and the continental shelf of Sardinia. These studies determined titanomagnetite, zircon, cassiterite, monazite and V, Hf, REE, Th, etc., particularly in the Santa Margherita area (southwestern Sardinia). The economic interest of some of these mineral species and elements suggested the need for further investigation. Beneficiation tests, plasma chemical analyses and electron-microprobe analyses were therefore carried out. The most significant aspects of the research and the results obtained are reported for each sampled zone.

Raw and calcined kaolinic clays from a mid-western Sardinia (Italy) sector were investigated in order to evaluate the feasibility of lime-activated materials. The great reserves of clays in this mining district, which are not well suited to traditional ceramics because of their low kaolinite content, excess of quartz, iron oxides, alunite, and the open pit exploitation, suggest an alternative use for these materials. The kaolinic clay samples and a reference kaolin were thermally activated in a laboratory oven at 530, 630 and 800 °C temperatures. Pastes of thermally activated and non-activated materials with lime, in the ratio of 1 : 1 by weight and water / solid ratio 1 : 2, were prepared and cured at different times. The reactions that took place in the metakaolin–lime–water systems were monitored using thermogravimetric analysis, differential thermal analysis and X-ray diffraction analysis. The results of pozzolanic tests and laboratory analyses were combined and offered very interesting property relations compared with a high-grade kaolin used as reference sample, even though a slower hydration kinetics. The large availability of the Donnigazza kaolinic clay reserves encourages the use of these materials in the binders sector and particularly in the Cultural Heritage sector as pozzolanic additives for restoration mortars.

Spa centres in northern Italy use clayey admixtures for the formulation of muds to be used in pelotherapy. The basic ingredient (“virgin” clay) is a dressed bentonitic geomaterial with mineralogical composition: smectite 60–70%, illite 5–10%, kaolinite 10–15%, quartz 5–10%, calcite 5–10% and feldspars 2–3%. The peloid muds are obtained by “maturation” of the virgin clay with mineral waters gushing out in situ which have different geochemistry: sulphureous, Ca-sulphate, Ca–Mg-sulphate and Br–I-salty (after the Italian regulation DPR 105/92). The maturation treatment is varying with respect to the mixing procedure and lasting time. Peculiar parameters have been tested to verify the effects of various maturation treatments, i.e., changes with respect to virgin clay. Formation of organic matter is due to the presence of microorganisms and algae in the maturation habitat. The Noteworthy was the influence of high-pH value of the virgin clay on the pH of peloid muds (in fact, the pH of the used mineral waters is ranging around the natural value). Furthermore, the temperature reached by the peloid muds after 20 min of application (calculated after an innovative mathematical model) is influenced by water retention. An increase in plasticity index and a slower cooling are considered to improve the quality of the obtained peloid muds for pelotherapy. The observed different cation exchange behaviour and soluble salt content could be discriminant for either dermatological masks or thermal body cataplasms. A need of regulation (standard procedures) is suggested to certificate the clay geomaterials suitable for pelotherapy and also for drugs formulation.

Bentonite muds are suited for use in pelotherapy due to their typical properties of high swelling (>25 ml/2 g), specific heat (Cp) and ease of handling, generally obtained at a material viscosity of 400 cps. This paper reports chemical, mineralogical and technological properties of Sardinia bentonites, to identify the most suitable materials for pelotherapy pastes. Their characteristics have been compared to the peloid properties commonly used in the spa of Benetutti (Northern Sardinia). On the basis of the mineralogical, chemical and technological characterization of the samples, besides their proximity to the most important regional spas and/or thermal sources, Costa Paradiso, Pedroseddu, Laconi, Busachi, Siurgus-Donigala and Giba bentonites are the most suitable Sardinia materials for pelotherapy. The results of this study also show that a complete characterization of clay materials is necessary in pelotherapy paste preparation. The utilization and/or addition of bentonites, largely available in Sardinia at relatively low cost, can improve the thermal mud quality for curative purposes.