Mineral carbonation of ceramic brick at low pressure and room temperature. A simulation study for a superficial CO2 store using a common clay as sealing material

This research explores the possibilities of CO2 sequestration on ceramic bricks in a short time and at surface conditions. The experiment was carried out in a specially designed reaction chamber, filled with brick wastes and sealed with common clays. The brick used were composed of quartz, wollastonite, diopside, orthoclase and anhydrite, and the common clay was a marl composed of calcite, quartz, illite, smectite and kaolinite. Experimental condition in the reaction chamber were: reaction time 5 months, pressure of CO2 0.5 bar, 4:1 solid/water ratio. The experiment was followed by XRD, XRF, BET, physical sorption by N2 and CO2, Hg porosity, TG-DTA, SEM and ICP-EOS. After the CO2 treatment, wollastonite and anhydrite were practically destroyed and some diopside and orthoclase. Calcite precipitated as new phase (up to 48 wt%), and small amount of illite was the result of orthoclase alteration. Concerning the sealing clay, the CO2 produced an increment of calcite content (from 32 to 41 wt%) and a partial destruction of smectite, particularly close to the upper part of the brick layer. These results are hopeful in relation with the possible mineral carbonation of building ceramic waste in a short time at surface conditions, and open the opportunity to use those wastes for CO2 trapping in an appropriate system, as a quarry reclamation

Las mineralizaciones de barita de Cerro del Hierro (Sevilla). Características mineralógicas y geoquímicas

En los materiales carbonatados del Cámbrico inferior del Cerro del Hierro (Zona de Ossa-Morena) existen diversos tipos de mineralizaciones de barita (estratoligadas, filonianas y kársticas). La barita está acompañada de calcita, hematites, goethita, y calcopirita accesoria, y limonitas y malaquita como fases tardías de alteración, y presenta una gran pureza química [>98% S04(Ba,Sr)]. Existe una relación entre la tipología de la barita y el contenido en Sr, en el sentido de filonianas < estratoligadas < kársticas. b34S en las baritas oscila entre 32,7 0/00 para las estratoligadas y 20,7 0/00 para las epigenéticas. Las razones 87Sr/86Sr determinadas sobre baritas epigenéticas varían entre 0.70873 y 0.71112, lo que puede interpretarse como consecuencia de la participación de diversos tipos de soluciones mineralizantes. Se propone un origen primario de las baritas estratoligadas, en relación con la diagénesis de los materiales carbonatados durante el Cámbrico inferior. Las baritas epigenéticas se formaron tras la Orogenia Hercínica, como consecuencia de la removilización de las baritas estratoligadas previas y con el aporte de Ba y Sr lixiviados de las rocas encajantes. Este último mecanismo parece haber sido más marcado en las baritas kársticas.Different barite deposits (stratabound, vein and karstic types) are occurring in the Lower Cambrian carbonatic materials of the Cerro del Hierro, Sevilla (Ossa-Morena Zone). Calcite, hematite, goethite and minor chalcopyrite are common associated minerals, with limonite and malachite as alterations. The content of barite can be as high as 98 %. There is a close relationship between barite type and Sr content (vein < stratabound < karstic deposits). b34S ranges between 32,7 %o (stratiform barites) and 20,7 %o (epigenetic barites). The 87Sr/86Sr ratio for the epigenetic barites oscillates between 0.70873 and 0.71112 which could be the result of the infiuence of different mineralization solutions. A primary origin for the stratabound barites is proposed, in relation with the diagenesis of the limestones occurred during the Lower Cambrian. Epigenetic barites were formed after the Hercynian Orogenesis by remobilization of the stratiform ores, with Ba and Sr supplied from the lixiviation of the host rocks. The last process could be much more important for the karstic barite formation

Limitations of the Standard Procedure for the Evaluation of Marble and Limestone for Use in Construction: A Critical Analysis and Proposal for Modification

The selection of natural stone for each specific use must be based on determinations which assess their technical quality and ensure their suitability for the environment in which they will be utilized. Among the criteria to be considered, a petrographic characterization is basic to deduce the behaviour of the stone to external agents. Current European regulations for the valuation and use of a stone present serious constraints in connection with the petrographic characterization and with the definition of some of the technological tests, which can endanger the suitability of a stone for use in construction. Two commercial limestones and one marble, are studied following the existing European Standards, to explain reasonably the behavior of these materials and deduce the most appropriate uses. Finally the results lead to certain recommendations to modify existing regulations

Interaction of dexamethasone and montmorillonite

3 pages, 1 figure, 7 references.-- Congreso celebrado del 7-10 septiembre 1987 en Sevilla, España.-- EUROCLAY'87.Clay-drug interactions have been widely studied during the last decade. However, the reaction mechanisms responsible of these interactions only have been elucidated in sorne cases (1,2), most of them when cationic drugs are ínvolved. Neutral molecules are known to interact with clays by physical adsorption (3), and/or by hydrogen bonding (4). Dioxin is adsorbed onto montmorillonite by a reversible adsorption mechanism (5) and degrades by acid-catalyzed hydrolisis. The mechanism of ad sorption and degradation of the neutral steroid hydrocortisone by palygorskite and sepio1ite has be en recently studied (6,7). Two types of ferric iron present in these clays may be responsible for the different degradation rates of hydrocortisone.Peer reviewe

Problemática de las emisiones de flúor, cloro y azufre durante la cocción de materiales de la industria ladrillera.

proceso de cocción de materias primas cerámicas lleva implícito la emisión de elementos contaminantes (F, Cl, SO2, B, NOx ). En el caso de emisiones de F, Cl, y S la contaminación depende de la concentración de estos elementos en las materias primas (filosilicatos, pirita, yeso, halita, apatito, carbonates), de la temperatura, del tiempo de cocción, del tipo de combustible y del horno empleados. Los contenidos en F, Cl y S varían en función de la génesis y la composición mineralógica de las materias primas. Los valores tienen un rango de variación entre 150-6500 ppm , media 800 ppm para el F; 10-1000 ppm, media 100 ppm para el Cl, y <100-6000 ppm, media 2000 ppm para el S. Las emisiones para el F a 850°C son menores del 40% del total, especialmente si las materias primas tienen altos porcentajes de carbonatos, y superan el 70% cuando se cuecen a temperaturas superiores a 1100°C. Las de Cl suelen alcanzar más altos porcentajes pero no son significativas debido a los bajos contenidos de este elemento en las materias primas. Las emisiones de S son muy variables incluso algunos ladrillos contienen más S que la muestra original debido al aporte del combustible. Se realizan algunas recomendaciones para disminuir la contaminación, pero es necesario una mayor investigación para profundizar en el estudio de los parámetros que controlan las emisiones de estos elementos

Contribución al conocimiento de los depósitos caoliníferos de Pontevedra

[Resumo] Encétase o traballo cunha escolma dos depósitos caoliníferos que poidan ter interés dende o punto de vista económico ou polas características peculiares da súa xénesis. Destes depósitos elixidos fíxose, en base a unha labor de campo, o seu estudo xeolóxico e a recolleita de mostras que foron identificadas mineralóxicamente coas técnicas instrumentais usuais, describindo seguidamente os resultados. Os materiais que ofreceron un maior interés, estudáronse con vistas a súa aplicación na industria dos refractarios, feito que ven xustificado por existir naquela comarca algunhas fábricas en actividade, unha delas xa centenaria. No derradeiro capítulo, fáise unha valoración dos resultados obtidos e conclúese que os depósitos caoliníferos da provincia de Pontevedra, veñen da meteorización de rochas graníticas ou metamórficas de carácter ácedo, ou son sedimentarios o que vai influír nas súas propiedades técnicas. Dende o punto de vista mineralóxico, tanto uns como outros, compóñense de caolinita, halloisita, seixo, micas e feldespato potásico, presentando pequenas diferencias na súa cristalinidade e no contido de minerais minoritarios. Polo que respecta ao aspecto técnico, encontráronse depósitos aproveitables, uns para a produción de caolín lavado e outros como arxilas refractarias tipo "fire-clay", ou plásticas, tipo "ball-clay", axeitadas para a fabricación de materiais refractarios aluminosos, chamotas e gres, aínda que é necesario profundar máis o aspecto técnico, o que ata hoxe non se fixo

Nota sobre la presencia de mineralizaciones de barita al sur de Llerena (Badajoz, España)

Barite mineralizations occur within Lower Cambrian detrital-carbonatic materials in the Zafra-Monesterio sector (Ossa-Morena zone, Iberian Massif), mainly associated to shales containing siliceous limestones layers. Four types of mineralization can be differentiated: 1) disseminate barite in carbonatic rocks, 2) centimetric concretions, 3) stratiform bodies of up 50 m long and <2 m thick, and 4) veins which are filling post-Hercynian fractures. According to the geological setting, and morphological, mineralogical and chemical characteristics a sedimentary and/or diagenetic origin may be supposed for stratiform barite deposits. Barite recrystallization took place during Hercynian deformation. Later barite was remobilized and concentrated in post-Hercynian fractures. Stratiform mineralizations described above can be considered of a commercial interest because occurrences are very abundant in this area, and grades are many times richer than 90% of BaS04with only silica as the major impurity.Las mineralizaciones estratiformes de barita aparecen asociadas a un conjunto de materiales detrítico-carbonatados de edad Cámbrico inferior en el denominado Dominio de Zafra-Monesterio (Zona de Ossa- Morena), encajando en pizarras con niveles de calizas con sílex, que presentan frecuentes cambios laterales de facies. Se pueden distinguir varios tipos de mineralizaciones: 1) barita diseminada en las rocas carbonatadas, 2) barita en concrecciones centimétricas, 3) barita en niveles estratiformes de hasta 50 m de longitud y espesores inferiores a 2 m, y 4) baritas con morfología filoniana que rellenan fracturas posthercínicas. Atendiendo a las características del entorno geológico y a las consideraciones morfológicas, mineralógicas y químicas, es posible asignar a estas mineralizaciones un origen sedimentario y/o diagenètico, con recristalizaciones durante las etapas de deformación hercínica (tipos 1, 2 y 3). Posteriormente la barita ha sido removilizada y depositada en fracturas posthercínicas (tipo 4). Las mineralizaciones estratiformes descritas pueden ser de interés económico, ya que en la zona aparecen frecuentes indicios de este tipo que alcanzan leyes superiores al 90%, con sílice como impurezas más significativa

Assessing soil quality in areas affected by sulphide mining. Application to soils in the Iberian pyrite belt (Sw Spain)

The characterization, evaluation and remediation of polluted soils is one of the present environmental challenges to be addressed in the coming years. The origin of trace elements in soils can be either geogenic or anthropogenic, but only the latter is interesting from a legal point of view. The hazard of the pollutants in the soils not only depends on their total concentration, but particularly on their availability. The mobility of the trace elements depends on their speciation, and it is also affected by several soil parameters. Mining activity is one of the most important anthropogenic causes of soil pollution. As a case study, this work is focused in the Riotinto mining area (Iberian Pyrite Belt, IPB, SW Spain). The IPB is one of the most important metallogenic provinces in the world and it has been exploited for thousands of years. The disposal of mining residues has produced important sources of contamination by trace elements and acidic waters affecting soils and rivers. In addition to these problems, the closure of mines in the Pyrite Belt at the end of the 20th Century has led to a great loss of employment, which has caused the development of an intensive agriculture of citrus fruits as a new source of income. The intensive growing of citrus fruits and the traditional subsistence agriculture have been developed surrounding the mining areas and on floodplains near to mining sites. The level of soil pollution has not been taken into account in these cases, nor has its impact on the health of the inhabitants of these areas. Therefore, it is of great interest to study the current state of the cultivated soils and the sources and types of contaminants derived from mining activity in order to program its decontamination, where appropriate, according to legislation. In order to know the present and future hazard posed by the soils chemical and mineralogical speciation has been carried out, given that the availability of a metal depends on the phase in which it is found. The results showed that mining activity has caused high levels of As, Cu, Pb and Zn in several cultivated soils. Moreover, Cu, Pb and Zn showed a high bioavailability. This suggests that at least other studies are necessary to preserve health in the inhabitants of this area. The methodology carried out in this work allowed to select potentially polluted areas where agricultural activities are not recommended