Andrés Alastuey

Synthesis of zeolites from coal fly ash: an overview

Coal combustion by-products production in USA and EU is estimated in around 115 million tons per year. A large portion of this production is accounted for the coal fly ash (CFA). Cement and concrete manufacturing consumes most of the CFA produced. Zeolite synthesized from CFA is a minor but interesting product, with high environmental applications. Zeolites may be easily obtained from CFA by relatively cheap and fast conversion processes. This paper provides an overview on the methodologies for zeolite synthesis from CFA, and a detailed description of conventional alkaline conversion processes, with special emphasis on the experimental conditions to obtain high cation exchange capacity (CEC) zeolites. Zeolitic products having up to 3 meq g 1 may be easily obtained from high-glass CFA by direct conversion. A review of potential applications of different zeolitic products for waste water and flue gas treatment is also given. The examination of the data presented by different authors reveals that one of the main potential application of this material is the uptake of heavy metals from polluted waste waters. The zeolitic material may be also used for the uptake of ammonium from polluted waters but high concentrations of other cations may considerably reduce the ammonium absorption efficiencies due to ion competition. Some of the zeolites synthesized may be also used as molecular sieves to adsorb water molecules from gas streams or to trap SO2 and NH3 from lowwater gaseous emissions. D 2002 Elsevier Science B.V. All rights reserved.

Coarse particles from Saharan dust and daily mortality.

Background: Winds from the Sahara-Sahel desert region regularly transport large amounts of dust to the Americas, North Africa, and Europe. The presence of high dust concentrations for long periods of time, and the interaction between dust and man-made air pollution, raise concerns about adverse health effects and appropriate interventions by health authorities. This study tested the hypothesis that outbreaks of Saharan dust exacerbate the effects of man-made pollution, specifically fine and coarse particulate matter (PM2.5 and PM10-2.5, respectively) on daily mortality. Methods: We investigated the effects of exposure to PM10-2.5 and PM2.5 between March 2003 and December 2004 in Barcelona (Spain) on daily mortality; changes of effects between Saharan and non-Saharan dust days were assessed using a time-stratified case-crossover design. We studied the chemical composition of particulate matter to explain changes of effects. Results: The study included 24,850 deaths. During Saharan dust days, a daily increase of 10 &mgr;g/m3 of PM10-2.5 increased daily mortality by 8.4% (95% confidence interval = 1.5%–15.8%) compared with 1.4% (−0.8% to 3.4%) during non-Saharan dust days (P value for interaction = 0.05). In contrast, there was no increased risk of daily mortality for PM2.5 during Saharan dust days. Although coarse particles seem to be more hazardous during Saharan dust days, differences in chemical composition did not explain these observations. Conclusions: Saharan dust outbreaks may have adverse health effects. Further investigation is needed to understand the role of coarse particles and the mechanism by which Saharan dust increases mortality.

Wet and dry African dust episodes over eastern Spain

[1] The impact of the African dust on levels of atmospheric suspended particulate matter (SPM) and on wet deposition was evaluated in eastern Iberia for the period 1996–2002. An effort was made to compile both the SPM and wet episodes. To this end, the time series of levels of TSP and PM10 in Levantine air quality monitoring stations were evaluated and complemented with the computation of back trajectories, satellite images, and meteorological analysis. Wet deposition frequency was obtained from weekly collected precipitation data at a rural background station in which the African chemical signature was identified (mainly pH and Ca 2+ concentrations). A number of African dust episodes (112) were identified (16 episodes per year). In 93 out of the 112 (13 episodes per year) the African dust influence caused high SPM levels. In 49 out of 112 (7 episodes per year), wet deposition was detected, and the chemistry was influenced by dust. There is a clear seasonal trend with higher frequency of dust outbreaks in May-August, with second modes in March and October. Wet events followed a different pattern, with a marked maximum in May. Except for one event, December was devoid of African air mass intrusions. On the basis of seasonal meteorological patterns affecting the Iberian Peninsula, an interpretation of the meteorological scenarios causing African dust transport over Iberia was carried out. Four scenarios were identified with a clear seasonal trend. The impact of the different dust outbreak scenarios on the levels of PM10 recorded at a rural site (Monagrega, Teruel, Spain) in the period 1996–2002 was also evaluated.

Heavy metal adsorption by different minerals: application to the remediation of polluted soils

Abstract We studied the heavy-metal adsorption capacity of various minerals in order to evaluate their potential for the reduction of metal mobility and bioavailability and their possible application for the remediation of polluted soils in the Guadiamar valley. The study (batch tests) of zinc adsorption capacity of clays (sepiolites, palygorskites, and bentonite from different mineral deposits) and a soil unaffected by the toxic spill at the P3 site (Puente las Doblas) showed a relative low adsorption capacity for Zn 2+ . In the case of the sepiolite from Orera deposit, the maximum retention capacity was obtained for Cd 2+ (8.3 mg g −1 ), followed by Cu 2+ (6.9 mg g −1 ), and finally Zn 2+ (5.7 mg g −1 ). We conclude that the capacity of adsorption of the clays and soil P3 is insufficient to immobilise heavy metals because of the high pollution levels of the soils in the Guadiamar valley. Only goethite (from Cerro del Hierro and Sierra de la Culebra) has sufficient adsorption capacity (between 3 and 4 mg g −1 ) to immobilise As in the highly polluted soil. Zeolite (NaP1), synthesised from Los Barrios fly ash, showed high retention efficiency for monovalent and divalent cations. Thus, the leaching and ionic exchange tests performed with mixtures of soil with pyrite slurry and NaP1 zeolites showed a high reduction on the mobility of Tl, Zn, Cd, Mn and Co (between 63 and 100%). The retention efficiency (for some of the metals considered) depended, not only on the ionic exchange capacity of the NaP1 zeolite, but also on the decrease of the acidity induced by the zeolitic product.

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.

Influence of African dust on the levels of atmospheric particulates in the Canary Islands air quality network

Abstract Time series of levels of atmospheric particulate matter (TSP and PM10) were studied at 19 air quality monitoring stations in the islands of Tenerife and Gran Canaria (Canary Islands) during the period 1998–2000. After analysing seasonal variations, attention was focused on the detection of high TSP and PM10 events and on the identification of their natural or anthropogenic origins. Back-trajectory analysis and TOMS-NASA aerosol index as well as satellite imagery (SeaWIFS-NASA) were used to identify three types of African dust outbreaks differing in seasonal occurrence, source origin and impact on TSP/PM10 levels. Mean annual and daily TSP and PM10 levels were compared with the forthcoming limit values of the EU Air Quality Directive EC/30/1999, and the results showed that the annual and daily limit values established for 2010 would only be met at rural stations. PM levels at urban background, urban and industrial sites would exceed the 2010 objectives. Only the levels at the urban-background stations would meet the requirements for 2005 despite the fact that the trade winds result in lower levels of atmospheric pollutants in the Canary Islands than in continental environments. The results highlight the role of African dust contributions when implementing the limit values of the EU directive.

Synthesis of zeolites from fly ash at pilot plant scale. Examples of potential applications

This study focuses on the synthesis of zeolites from Spanish fly ashes at laboratory (g and kg sample size) and pilot plant (metric ton sample size) scales, and on the potential application of the synthesized zeolitic material. To this end, eleven Spanish fly ashes were selected and characterized in detail. A matrix of experimental parameters was built to optimize the synthesis of mono-mineral zeolite products from the different fly ashes. This was achieved by using Parr digestion bombs, KOH and NaOH as activation agents, under experimental conditions ranging from T = 150 to 200°C, t = 3 to 48 h, C = 0.5 to 5 M, P = 4.7 to 15.3 atm, and solution/sample ratio from 2 to 18 ml g 1 . Subsequently, experiments to synthesize NaP1 zeolite were scaled up to kg sample and pilot plant scale. The zeolitic material obtained at these two scales was very similar. The NaP1 zeolite content was estimated as 40%. The major potential applications of the zeolites obtained were tested by determining the cation exchange capacity (CEC) with ammonium and different heavy metals. The results showed CEC values from 160 to 260 meq. 100 g 1 for NaP1, herschelite, KM, linde F and K-chabazite for the majority of the cations investigated. The zeolitic material synthesized at pilot-plant scale yielded the following CECs for these heavy metals: 68 meq. 100 g -1 for Ni 2+ , 90 meq. 100 g -1 for Cd 2+ , 95 meq. 100 g -1 for Zn 2+ , 98 meq. 100 g -1 for Pb 2+ , 110 meq. 100 g -1 for Fe 2+ , 130 meq. 100 g -1 for Ba 2+ , 210 μeq, 100 g -1 for Cu 2+ and 260 meq. 100 g -1 for Cr 3+ .

Comparative PM10-PM2.5 source contribution study at rural, urban and industrial sites during PM episodes in Eastern Spain

In this study a set of 340 PM10 and PM2.5 samples collected throughout 16 months at rural, an urban kerbside and an industrial background site (affected by the emissions from the ceramic manufacture and other activities) were interpreted. On the regional scale, the main PM10 sources were mineral dust (mainly Al2O3, Fe, Ti, Sr, CaCO3, Mg, Mn and K), emissions derived from power generation (SO4=, V, Zn and Ni), vehicle exhausts (organic and elemental carbon, NO3- and trace elements) and marine aerosol (Na, Cl and Mg). The latter was not identified in PM2.5. At the industrial site, additional PM10 sources were identified (tile covering in the ceramic production, petrochemical emissions and bio-mass burning from a large orange tree cultivation area). The contribution of each PM source to PM10 and PM2.5 levels experiences significant variations depending on the type of PM episode (Local-urban mainly in autumn-winter, regional mainly in summer, African or Atlantic episode), which are discussed in this study. The results show that it would be very difficult to meet the EU limit values for PM10 established for 2010. The annual mean PM levels are 22.0 microg PM10/m3 at the rural and 49.5 microg PM10/m3 and 33.9 microg PM2.5/m3 at the urban site. The natural contribution in this region, estimated at 6 microg/m3 of natural mineral dust (resulting from the African events and natural resuspension) and 2 microg/m3 of marine aerosol, accounts for 40% of the 2010 EU annual limit value (20 microg PM10/m3). Mineral dust concentrations at the urban and industrial sites are higher than those at the rural site because of the urban road dust and the ceramic-production contributions, respectively. At the urban site, the vehicle exhaust contribution (17 microg/m3) alone is very close to the 2010 EU PM10 limit value. At the rural site, the African dust is the main contributor to PM10 levels during the highest daily mean PM10 events (100th-97th percentile range). At the urban site, the vehicle exhaust product is the main contributor to PM10 and PM2.5 levels during the highest daily mean PM events (100th-85th percentile range). Mineral dust concentrations during African dust events accounts for 20-30 microg/m3 in PM10 and 10-15 microg/m3 in PM2.5. During non-African dust events, mineral dust derived from anthropogenic activities (e.g. urban road dust) is also a significant contributor to PM10, but not to PM2.5.

Transport of desert dust mixed with North African industrial pollutants in the subtropical Saharan Air Layer

An analysis of chemical composition data of particulate matter samples (TSP, PM 10 and PM2.5) collected from 2002 to 2008 in the North Atlantic free troposphere at the Izãna Global Atmospheric Watch (GAW) observatory (Tenerife, Canary Islands) shows that desert dust is very frequently mixed with particulate pollutants in the Saharan Air Layer (SAL). The study of this data set with Median Concentrations At Receptor (MCAR) plots allowed the identification of the potential source regions of the dust and particulate pollutants. Areas located at the south of the southern slope of the Atlas mountains emerge as the most frequent source of the soil desert dust advected to the northern edge of the SAL in summer. Industrial emissions occurring in Northern Algeria, Eastern Algeria, Tunisia and the Atlantic coast of Morocco appear as the most important source of the nitrate, ammonium and a fraction of sulphate (at least 60 % of the sulphate<10 μm transported from some regions) observed in the SAL. These emissions are mostly linked to crude oil refineries, phosphate-based fertilizer industry and power plants. Although desert dust emissions appear as the most frequent source of the phosphorous observed in the SAL, high P concentrations are observed when the SAL is affected by emissions from open mines of phosphate and phosphate based fertilizer industry. The results also show that a significant fraction of the sulphate (up to 90 % of sulphate <10 μm transported from some regions) observed in the SAL may be influenced by soil emissions of evaporite minerals in well defined regions where dry saline lakes (chotts) are present. These interpretations of the MCAR plots are consistent with the results obtained with the Positive Matrix Factorization Correspondence to: S. Rodŕıguez (srodriguezg@aemet.es) (PMF2) receptor modelling. The results of this study show that North African industrial pollutants may be mixed with desert dust and exported to the North Atlantic in the Saharan Air Layer.

Variability of Particle Number, Black Carbon, and PM10, PM2.5, and PM1 Levels and Speciation: Influence of Road Traffic Emissions on Urban Air Quality

Measurements of particle number concentration (N), black carbon (BC), and PM 10 , PM 2.5 , and PM 1 levels and speciation were carried out at an urban background monitoring site in Barcelona. Daily variability of all aerosol monitoring parameters was highly influenced by road traffic emissions and meteorology. The levels of N, BC, PM X , CO, NO, and NO 2 increased during traffic rush hours, reflecting exhaust, and non-exhaust traffic emissions and then decreased by the effect of breezes and the reduction of traffic intensity. PM 2.5–10 levels did not decrease during the day as a result of dust resuspension by traffic and wind. N showed a second peak, registered in the afternoon and parallel to O 3 levels and solar radiation intensity, that may be attributed to photochemical nucleation of precursor gases. An increasing trend was observed for PM 1 levels from 1999 to 2006, related to the increase in the traffic flow and the diesel fleet in Barcelona. PM composition was highly influenced by road traffic emissions, with exhaust emissions being an important source of PM 1 and dust resuspension processes of PM 2.5–10 , respectively.