Felicià Plana

Synthesis of Na-zeolites from fly ash

The present study focuses on the synthesis of zeolites after fly ash activation, the major objectives being: (a) to study the activation processes; (b) to elucidate the activation conditions for maximum synthesis efficiency; (c) to optimize the conditions for the monomineral synthesis; and (d) to test synthesis efficiencies for different fly ash types. Fly ash was activated by NaOH and KOH solutions in a closed system. The zeolite conversion was studied as a function of temperature (150-200°C), reaction time (8-100h) and solution concentration (0.1-1 M). The estimated pressure during activation ranged from 0.48 MPa at 150°C to 1.55 MPa at 200°C. The activation was performed using a sample concentration of 0.055 g mL -1 . The zeolites synthesized were NaPI. NaP derivatives (mainly sodalite hydrate). analcime, gmelinite and nepheline hydrate after NaOH activation, and phillipsite after KOH activation. Subsequent experiments focused on short reaction times for high conversion efficiencies and monomineral synthesis of zeolites. High synthesis efficiencies for NaPI zeolite and analcime were obtained with the fly ash types studied. The results highlight the importance of the mineralogical composition of the fly ash. Fly ashes with very similar SiO 2 / Al 2 O 3 ratios show different zeolites synthesis behaviour under the same activation conditons. These differences could be attributed to different SiO 2 /Al 2 O 3 ratios of the glass matrix inferred from the differences in mineralogy at the same bulk chemical composition.

Seasonal evolution of suspended particles around a large coal-fired power station: particulate levels and sources

The present work focuses on the seasonal evolution of suspended particles (TSP and PM10) around the Teruel power station in NE Spain. The specific objectives are the determination of the spatial and time variability of levels of suspended particles, and their relationship with the power plant emissions and other natural or anthropogenic (local or external) particulate sources. The results show a marked seasonal trend, along the study period (July 1995–August 1996) which is characterized by particulate levels that were higher in spring–summer and decreased progressively towards winter. This trend may be related to (a) higher summer oxidation which increased levels of secondary particles, (b) higher convective circulation in summer which raised levels of soil-related particles and anthropogenic particles, (c) higher frequency of intrusion episodes of Sahara air masses in summer and spring, and (d) lower aerosol scavenging potential in summer. The similarity between the seasonal evolutions of daily mean levels of SO2 and particulates is due to the fact that both are partially controlled by the solar cycle. The long range transport particulate inputs affecting this area of the Mediterranean Basin (mainly Sahara air mass intrusions) account for major particulate peaks recorded at the monitoring stations. The influence of the emissions from the power plant in the PM10 and TSP levels is evidenced only in periods with a low background particulate levels. The results demonstrate that even PM10 levels are still highly influenced by the Saharian and European particulate inputs. Therefore, for an accurate environmental assessment, probably PM2.5 should be monitored instead of TSP or PM10, in order to quantify the influence of the power plant emissions on the bulk atmospheric particulate levels. The results obtained from the air back-trajectory analysis and their comparison with the time series of daily PM10 levels allowed the classification of the major external particulate inputs as a function of the particulate levels.

Mineral composition of atmospheric particulates around a large coal-fired power station

Abstract The present work is a mineralogical study of atmospheric particulates around a large coal-fired power station in NE Spain. After a mineralogical study of the fly ash sampled in the electrostatic precipitators of the power station, several chemical and mineralogical patterns of the fly ash were employed as tracers of the power station emissions. At the same time, the study focused on the downwind evolution of secondary particulate matter, especially particulate sulphate. The studies on the mineralogy of air borne dust allowed us to distinguish between natural and anthropogenic particles. The major mineral phases identified in the samples studied were: gypsum, calcite, clay minerals (kaolinite, clinochlore and illite), quartz, talc and hematite. In addition to these mineral phases which are frequently present in the atmospheric particulate matter of the studied area, other mineral phases, such as feldspars, mullite, and copper sulphates, were detected in minor proportions. The results show that some mineralogical and morphological characteristics of the atmospheric particulate matter may be used as tracers of the influence of coal-fired power plant emissions. These characteristics include spherical morphologies, aluminosilicate glass, mullite, hematite and sulphate-fly ash associations. The possible buffering effect of atmospheric Ca-bearing minerals to neutralize the sulphate deposition is investigated.

Seasonal evolution of suspended particles around a large coal-fired power station: Chemical characterization

Abstract The present work focuses on the seasonal evolution of total suspended particles (TSP) around the Teruel power station in Northeastern Spain. The results show a marked seasonal trend, along the sampling period (July 1995–July 1996), which is characterized by levels of the elements studied in TSP that were higher (up to one order of magnitude) in spring-summer and decreased progressively towards winter. This trend contrasts with the seasonal evolution reported by most of the studies carried out in industrial and urban areas in Central and Northern Europe. The origin of this seasonal TSP trend may be related to: (a) higher summer oxidation which increased levels of secondary TSP; (b) higher convective circulation in summer which raised levels of soil-related particles and primary anthropogenic particles; (c) higher frequency of intrusion episodes of Sahara air masses in summer and spring; and (d) lower aerosol scavenging potential in summer. A clear grain-size fractionation was observed for the different ions determined. SO 4 2− and NH 4 + were concentrated in the finest grain-size fraction (0.3−0.6 μm); NO 3 − , Cl − , K + , Mg 2+ , Na + and minor amounts of NH 4 + were concentrated in the 1.2−5.0 μm fractions; and Ca 2+ increased with the particle diameter. S-bearing species were (NH 4 ) 2 SO 4 (mascagnite), (NH 4 ) 2 Ca(SO 4 ) 2 · H 2 O (koktaite) and CaSO 4 · 2H 2 O (gypsum). Mascagnite was the dominant species in the finest grain size fraction (0.3−0.6 μm), whereas koktaite was also present in the 0.6−1.2 μm fraction, and gypsum predominated in the other fractions.

How mudrock and soil physical properties influence badland formation at Vallcebre (Pre-Pyrenees, NE Spain)

Abstract Soils, regoliths and their parent materials were investigated in relation to the development of badlands in the Pre-Pyrenees, in NE Spain, on Late Cretaceous mudrocks under a mountain Mediterranean climate. Whilst all the soils in the area which are developed on mudrocks show a good structure and support a dense plant cover, the bare parent materials slake very rapidly giving rise to badlands characterized by high erosion rates. Several physical, chemical, mineralogical and micromorphological properties of soils, regoliths and related parent materials were analyzed in order to explain their different susceptibility to erosion and to determine which of all these properties are better related to such erosive behaviour. Only micromorphological and porosity properties were able to explain the erosion susceptibility, whilst mineralogical, chemical and physico-chemical (specific surface area) properties were not. Among the aggregate stability tests performed to estimate the relationships of soil components with the susceptibility to erosion, the Emerson test for macroaggregate evaluation, was particularly well suited. Although no good correlation was found between the Emerson test classes and organic matter content, we observed that the degree of slaking in organic-rich horizons, was always lower than in subsurface horizons and regoliths. Consequently, as far as organic rich aggregates are present in the soil surface, the influence of water in producing slaking, swelling and then erosion, will be minimum. However, when regoliths and rocks are uncovered, the influence of water in these particular materials, through freeze-drying and swell-shrinking, will give rise to mudrock desintegration leading to accelerated erosion.

Physico-chemical characterisation of atmospheric aerosols in a rural area affected by the aznalcollar toxic spill, south-west Spain during the soil reclamation activities

High levels of atmospheric contamination due to the re-suspension of pyrite particles from the mining waste slurry were recorded in the Guadiamar valley (the Guadiamar is a tributary of the Guadalquivir river) after the toxic spill of Aznalcóllar, north of the Doñana Natural Park (SW Spain). Major high-particulate events occurred during the extraction of the pyrite-rich mud layer, which covered an extensive area of the valley downstream of the confluence of the Agrio and Guadiamar rivers. This study deals with the monitoring of the ambient air quality at two stations near the village of Aznalcázar in the central part of the flooded area. Although the Spanish legal limit for atmospheric particles and lead in environmental air were not exceeded, high daily levels of total suspended particles (TSP) and of some elements with an environmental significance (As, Cd, Cu, Mn, Ni, Pb, Sn, Tl and Zn) were recorded at Aznalcázar and in the Guadiamar valley during soil reclamation (July-August 1998). Despite a progressive decrease in TSP levels through September-October 1998, background was higher than the levels for the May-June period. Evolution of levels for most of the elements studied showed a similar trend. The exceptions were copper, which was partially increased by other emission sources such as fumigation activities, and sodium, which remained at relatively constant levels during the study period because of its marine origin. The physico-chemical characterisation of the atmospheric particulates allowed us to determine the major grain size modes of the pyrite related elements and the solubility of the potentially toxic elements, and to identify the major particulate types present in the atmosphere in the area. Secondary and tertiary aromatic amines (i.e. alkyldiphenylamines and phenylcarbazoles, respectively) were identified in the suspended particles and in the vapour phase collected at the same station as the TSP samples. As some of these aromatic amines had been previously identified in the pyrite sludge, it is assumed that fine sludge particles containing aromatic amines were re-suspended in the atmosphere. The highest concentrations of aromatic amines in the particulate phase were recorded in August 1998 during the pyrite slurry extraction in the proximity of the Aznalcázar sampling site. Despite a sharp drop in the suspended particles of the aromatic amine concentrations, a significant concentration was detected in the vapour phase (< 1.2 mm) during autumn, probably because of longer residence time in the atmosphere. Although health hazards associated with the presence of these aromatic amines are unknown, their acute toxicity exceeded that of urban aerosols.

Physicochemical characterization of Spanish fly ashes

This article summarizes the results obtained from the physical, chemical, and mineralogical characterization of 14 fly ash samples. Major features that influence the utilization of each fly ash for zeolite synthesis are evidenced, and several fly ash types were selected as potential high-quality starting material for zeolite synthesis and ceramic applications. The main parameters influencing this selection were relatively small grain size; high Al and Si contents; high glass content; low CaO, S, and Fe contents; and relatively low heavy metal concentration. The Compostilla and Dou He fly ashes have high potential applications because of the low content of major impurities (such as Ca, Fe, and S) and the low content of soluble hazardous elements. The Espiel, Escucha, Los Barrios, As Pontes, Soto de Ribera, Meirama, Narcea, and Teruel fly ashes have important application potential, but this potential is slightly limited by the intermediate content of nonreactive impurities, such as Fe and Ca. The La Robla f...

Fly ash content and distribution in lake sediments around a large power station: inferences from magnetic susceptibility analysis.

The bulk magnetic susceptibility of sediments from artificial and natural lakes around a large coal-fired power station in NE Spain has been measured. Higher magnetic susceptibility values are found in lake sediments located SE of the power station. This distribution of susceptibility values is compatible with environmental and meterological studies of emissions from the power station, which indicate a dominant SE plume direction. Mineralogical studies, by means of X-ray diffraction and scanning electron microscopy, show that the highest susceptibility values found in the sediments are caused by magnetic iron spinels in the fly ash that is transferred to the environment by the power station particulate emissions. After the quantitative mineralogical studies of fly ash, two different methods of fly ash content determination in the sediments have been devised, showing very similar results. The low background magnetic susceptibility of the sediments in the study area and the high susceptibility resulting from the input of magnetic fly ash particles allows both delimitation of the polluted area around the power station, and quantification of the fly ash input into the natural sediments.