Angel M. Estévez

Remediation of soils contaminated with pesticides: a review.

The aim of this work is to address the problem of soil contamination with pesticides and present a review of the existing techniques for remediation of these types of soils. First, a brief discussion of the soil structure and complexity is presented, and the impact of its contamination by pesticides is examined. Then, the main existing and emerging techniques for soil remediation, particularly for the elimination of pesticides, is discussed, and their relative advantages and disadvantages presented. In order to choose the best remediation technology, one must take into consideration the soil and site characteristics, the technique suitability, the costs and the environmental footprint. The comparison of existing technologies will be a helpful tool for a preliminary selection of the most promising techniques to use for a particular soil decontamination problem.

Fluidization and elutriation of iron oxide particles. A study of attrition and agglomeration processes in fluidized beds

Abstract Elutriation is a way of separating particles by means of fluidodynamic forces as well as a very common method to generate solid aerosols to be used for many different purposes. In this work, a study of the elutriation of different size iron oxide particles from a fluidized bed has been carried out in order to determine the elutriation rate constants and the magnitude of the attrition and agglomeration processes in a fluidized bed of this sort of powder, which can be considered as C-type in Geldarts particle classification. The fluidized bed was formed by a mixture of sand and iron oxide particles. Sand particles were much bigger than iron oxide particles and the weight of the latter particles, which were elutriated was very small compared with the initial weight in the bed so that the weight of the bed could be considered as a constant. Theory about elutriation and its application to study the iron oxide behaviour and to determine the elutriation rate constants are presented. Experimental results showed the importance of attrition and agglomeration in iron oxide powders. The smallest iron oxide particles were not those most easily elutriated from fluidized beds of mixed size particles. These particles may be agglomerated between them or with larger sand particles. Elutriation results were compared with previous literature and it was found that a correlation similar in form to Yagi and Aochis correlation fits the experimental results quite well.

Comparative study of different fabrics in the filtration of an aerosol using more complete filtration indexes

Abstract The influence of the yarn number (or titre) of several polyester/wool fabrics on their behaviour as filter media has been studied. The main purpose of the study was to determine the relationship between their structures and their performance as filters, especially when the fluid to filter is an aerosol composed of solid particles of iron oxide of very small size (to a large extent submicron) and air at ambient temperature. The study has been accomplished by testing two nonwoven fabrics, under the same conditions as the woven fabrics, that are also appropriate for filtering applications. Three filtration indexesm δ, I F and F have been defined, in order to provide complementary information to tha given by the quality parameters already defined in the literature. This information will be very useful in quantifying the performance of filtering fabrics in solid/gas separation processes and, more importantly, to compare them mutually.

Preparation, Characterization, and Testing of Magnetic Carriers for Arsenic Removal From Water

To remove arsenic from water we are developing a research project that applies magnetic separation methods. In order to increase the removal efficiency we are using magnetic aggregates. These magnetic aggregates are iron-based and were all (except for one) prepared by us. In this paper we report the preparation steps and some of the results of the characterization and absorption tests we have performed in order to conclude about its structure and efficiency in what concerns arsenic removal.

Magnetically Stabilized and Fluidized Beds: Heat and Mass Transfer

Research and applications of magnetically stabilized and fluidized beds begun several decades ago, and have maintained their rate of interest during all these years. During last years their applications was diversified, and the application of these beds in the processing of biological materials and in environmental issues has nowadays focused the main attention within this area. In this work we present a brief review of magnetically fluidized and stabilized beds, mainly concerning their theoretical background, heat and mass transfer topics, some industrial and laboratorial setups and applications.

Landfill leachate treatment by sorption in magnetic particles: preliminary study

Leachates are still an open issue in environmental protection. Many of the applied methods for their treatment present low efficiency and thus need to be used collectively. In practice reverse osmosis is mostly used, as it is the most effective option, regardless of its cost. Magnetic methods to treat effluents have been used for water and wastewater treatment by the use of magnetic particles together with magnetic separation for the removal of contaminants. However, large-scale applications are few or even non-existent when we deal with complex contaminated media such as landfill leachates, for which not even research studies at laboratorial scale with real samples have been done yet. In this work, we apply for the first time magnetic sorption for the treatment of leachates, and close the full cycle by studying the regeneration and re-use of the magnetic particles; we also study the influence of the concentration of magnetic particles, the use of several pre-treatment methodologies and the type of particle used in the process, in real landfill samples from the waste treatment plant of Salamanca (Spain), for the removal of COD, NO3-, NO2-, NH4+, Total-N, PO43-, SO42- and Cl-. Regeneration of the magnetic particles after being used in the sorption stage is also studied, as well as their efficiency regarding their re-use. It is also determined the optimum number of batches for complete desorption and for regeneration of the particles, the effect of successive regeneration and re-use cycles, the use of two different regeneration methods, the efficiency of the desorption, the effect of the quantity of solvent and the influence of the time of sorption. Due to its innovative character and the complexity of the media, this work represents a first preliminary approach and, although some promising results have been obtained, further studies are required to completely understand and evaluate the proposed treatment process.

Designing Cryogenic Vapour-Cooled Current Leads

Constructing a new device we had to design some vapour-cooled current leads. This current leads are made of Low-Tc material connected with copper wires and some parts of High-Tc material. Its design is calculated keeping in mind the heat transfer by diffusion to a vapour-cooled stream that surrounds the conductive materials. The design and the calculations performed to achieve it, and also the background theory of the heat diffusion applied in this part of the device will be described.

Influence of the processing variables on the performance of MAGCLA?: friction coefficient and radius of the particles

This work presents simulation results for the behaviour of different particles in a new magnetic-classifier (MAGCLA™), which is capable of separating and classifying particles according to their magnetic susceptibilities. In a previous article the results for a blank simulation were reported. In this paper the blank simulation is compared with the results obtained for the variation of two of the main processing variables: friction coefficient, μ, and the radius of the particles, rpart, in the outcome results.