ENVIRONMENTAL CHEMISTRY

Author: ROZADA GÓMEZ FERNANDO.
Year: 2004.
University: LEÓN.
Place of defense: E.S.T. DE INGENIEROS ARÓNOMOS.
Place of preparation: INSTITUTO DE RECURSOS NATURALES.

Summary: In this paper we study the potential for use of two resiguos of complicated management through generation of activated carbons. This is the sludge of sewage plant, and solid waste resulting from the thermal recovery through pyrolysis tire outside use. Preliminary tests show that the best precursor is chemically activated sludge with ZnCl2 (Lz). Following optimization studies conducted on the same, the method of production that employs a 1:1 fango-activante a ramp in the warming phase pyrolysis of 5Â ° C / min to 650Â ° C and timpo of resisdencia 5-minute appears as the under most promising tests carried out in liquid phase compared with methylene blue. But neither ill adsorbents are derived from tire pirolizado (Np), and therefore no need to introduce epata activation chemistry. All adsorbents generated underwent different characterization studies. Their surfaces chemical and physical structures vary by virtue of its origin and production process. In addition, it has impact on the problem of leaching Zn by these adsorbents Lz, with the introduction of a series of stages of washing with HCl 10% more effective than other solutions such as coverage with polymer from acetonitrile in a team plasma. It has analyzed the ability of adsorption and modeled the behavior of activated carbons generated compared with methylene blue and bright red Sandolan N-BG 125 (dye industry) systems and turbulent regime batch of food. We studied the effect of temperature and pH. Regarding the effect of temperature, systems adsorbieron more when it was increased. Using the model Freundlich has been calculated thermodynamic parameters associated with each test result that all of them were spontaneous and also showed character endotérmico. Regarding the pH dependence of adsorbato employee there, adsorbiéndose more red in a more acidic, and more blue metilen working around pH 4. It is also studying the feasibility of using the adsorbent sproducidos in fixed-bed adsorption and under a continuous supply. The studies are carried out in front of the same colors: methylene blue and bright red. There have been break characteristics curves, adjusting the data obtained show that, as with previous studies in batch, the activated sludge with ZnCl2 (Lz) is the most effective lso adsorbents, and it is bright red dye the pollutant be better retained. But it is clear that the adsorbent obtained from the carbonization of the tire (Np) is not feasible for use in this type of testing in column due to its texture pulverulenta. Trials of thermal regeneration made products Lz showed a progressive loss of effectiveness of adsorbent under the number of cycles carried out, and an estimate of economic viability shows that a management process integrated with the procurement of energy, especially tire could be very profitable.

Author: GUITART FERRARONS CARLOS.
Year: 2004.
University: POLITÉCNICA DE CATALUÑA.
Place of defense: aula 002, mòdul c1.
Place of preparation: EDIFICI D1 Campus NORD.

Author: GRIVE SOLE MIREIA.
Year: 2004.
University: POLITÉCNICA DE CATALUÑA.
Place of defense: sala c1, 002, campus nord.
Place of preparation: ETSEIB, EDIFICI H PLANTA 10 Campus SUD.

Summary: The presence of radionuclides in soils and waters due to nuclear waste management facilities and uranium mining tailings is a problem of major environmental concern. The mobility of these radionuclides in oxic groundwaters is linked to the iron cycle and controlled by geochemical processes such as adsorption on major mineral surfaces and precipitation/dissolution. In this context, iron oxides and oxyhydroxides are of particular importance due to the fact that they are ubiquitous in nature and to their large capacitiy to sorb radionuclides, among them hexavalent uranium. The iron and uranium cycles are linked to the carbon one since aqueous carbonate plays a major role in the transport of radionuclides due to its high affinity to form complexes with some radionuclides, specially with uranium. Furthermore, dissolved carbonate can compete for the sorption sites of the iron oxides, promoting the dissolution of these oxides and consequently increasing the mobility of the associated radionuclides in natural systems. The ability to develop adequate models for predicting the fate of inorganic contaminants in surface environments is highly dependent on accurate knowledge of the distribution of these constituents between the solid and solution phases and ultimately on the capability to provide molecular-level information on chemical species distributions in both of these phases. Most of the information we have about interactions of cations or anions at mineral/water interfaces comes from macroscopic measurements. In the last years, efforts to quantify observed sorption reactions at solid/liquid interfaces by means of surface complexation models have been developed. However, it is very difficult to precisely study these sorption reactions without spectroscopic evidence, mainly due to the uncertainty in the definition of the nature of the surface species formed. The objective in this thesis is to characterize the bonding environments of uranium onto Fe-oxide surfaces and to study the most probable mechanism of uptake of this metal in carbonated solutions. Three different systems have been mainly studied: 1) the effect of carbonate on the dissolution of iron oxides as they are representative of one of the most widespread oxides in nature behaving as a sink of trace metals, 2) the effect of carbonate on schoepite, which is one of the main secondary phases of uranium to form under oxidizing conditions, and 3) given that the formation and dissolution of Fe minerals can imply the incorporation of U into these Fe oxide structures or the sorption of U onto these newly formed minerals, the effect of carbonate on a co-precipitate of Fe(III) and U(VI) has been also studied. The outcome of the use of combined information gathered from thermodynamic and kinetic macroscopic studies together with information from EXAFS spectroscopy will be shown. The coupling of such different studies has been helped both qualitative and quantitative to characterize bonding environments of uranium onto Fe-oxide surfaces and to study the most probable mechanism of uptake of these metals in carbonated solutions.

Author: LATORRE FERNÁNDEZ ANA M..
Year: 2005.
University: BARCELONA.
Place of defense: UNIVERSITAT DE BARCELONA.
Place of preparation: DEPARTAMENT DE QUÍMICA AMBIENTAL, IIQAB-CSIC.

Summary: Although in recent years there has been progress in the study and characterization of the effluent from paper industries, it is still a need for more identification of new pollutants, assess their toxicity and determine necessary treatment for their total elimination. This requires sensitive and selective develop methods for identifying and quantifying organic compounds responsible for the toxicity of these effluents. That is why in this thesis were developed based on analytical methodologies and LC-Ms for GC-MS analysis of pollutants originating from the raw materials (fatty acids and resínicos) as of different additives used (biocides, surfactants and plasticizers) . Combining the results obtained by applying these methodologies to the analysis of different types of industries with the assessment of the toxicity using a standardized system, ToxAlert 100, helped identify compounds that contribute more significantly to the toxicity of the samples. In addition assessed the efficiency of some of the treatments commonly used in the paper industry, such as treatment aerobic, anaerobic, the combination of anaerobic and aerobic as well as ozone for reducing the COD and toxicity of the samples . In this sense, assessed the persistence of two biocides used in such industries through photodegradation studies. Finally, given the presence of nonylphenol and octilfenol in the process water, its adsorption was studied in the final product. The presence of both compounds showed the potential toxicological risk they represent, especially in the wrapping paper, used widely in the area of food, and the tissue, since their contact with the skin.

Author: ZELEDON TORUÑO ZORAIDA DEL CARMEN.
Year: 2006.
University: POLITÉCNICA DE CATALUÑA.
Place of defense: E.P.S. d'Enginyeria de Manresa.
Place of preparation: EPSEM, EDIFICI MN1 --- MN.

Summary: Adsorption by activated carbons is a treatment widely used for the efficiency of the method to eliminate significant amounts of polluting agents. With the purpose of reducing the costs of the current treatments, in this study, the potential of the adsorbent leonardite as a natural and low cost material, has been evaluated for reduction of heavy metals and polycyclic aromatic hydrocarbons (PAHs) in aqueous solutions. The effect of factors such as pH, contact time, concentration and hardness of the metallic solution on adsorption has been studied. In addition, comparative experiments of adsorption capacity of leonardite with other alternative materials and widely used commercial activated carbon has been carried out. Previously to the adsorption studies, a physic-chemical characterization of the material has been performed. The results show that leonardite has heterogeneous nature, acid character and has high capacity of ion exchange provided by interchange among the H+ ions of carboxylic and phenolic functional groups. It has been demonstrated that pH has a significant influence upon adsorption of Ni, Cu, Zn, Cd and Pb. The best results were obtained in the rank of pH 5-6. In the study of contact time has been observed that all the metals reach maximum levels of retention after two hours. These data have been fitted with three kinetic models: Lagergren, Pseudo-second order and Hyperbolic. Of these models, Pseudo-second order adjusts best to the data. The kinetic constant or transference coefficient determined with the Pseudo-second order model for each metal has shown to depend on the concentration, nature of solute and adsorbent as well as of contact time. The maximum adsorption capacity of each metal has been determined varying the concentration of the metal and maintaining constant the dose of adsorbent (1 g/L). The obtained experimental data adjust to Langmuir and extended Langmuir (for a binary system) isotherms. According to the results, the decreasing order of affinity of metals with respect to their capacity to adsorb itself to leonardite is: Pb, CD, Zn, Cu and Ni. Also it has been found that the levels of metal retention are smaller in binary and multicomponent systems than those found in individual systems. The adsorption studies realized with other coals (coal of Mequinenza, activated carbon) indicate that leonardite has greater capacity to retain metals. The experimental data of adsorption capacity considering the effect of water hardness show that the ion Ca interferes in the metal retention by leonardite, being more affected some metals than others. On the other hand, the adsorption studies carried out with galvanic industry effluents, showed similar results to those obtained from aqueous solutions prepared in the laboratory. Adsorption experiments of five PAHs (FLE, PYR, B(k)F, B(a)P and B(g, h, i)P) with leonardite show that pH is not a determining factor in the retention of the heaviest PAHs. Also, according to the experimental data, the contact time has been established in 24 hours. From the results obtained by varying the concentration of the PAHs at constant dose of adsorbent, the adsorption capacity of leonardite has been determined, by means of the partition coefficients leonardite/water of each PAH. These coefficients are obtained from the relation of Freundlich constant and the carbon fraction of leonardite. The coefficients determined demonstrate that retention of the polluting agents to the adsorbent increases with the increase of aromaticity of the compound and its Kow coefficient. In addition, it has been observed that the levels of individual retention of the PAHs do not decrease in multicomponent systems. Finally, the comparison of the results obtained of heavy metal and PAHs adsorption with other adsorbent materials mentioned in literature, suggest that leonardite can be 8 used as 2d7 an alternative to reduce levels of the studied contaminants in the water cycle.