Gustavo Curutchet

CHARACTERISATION OF URANIUM(VI) SORPTION BY TWO ENVIRONMENTAL FUNGAL SPECIES USING GAMMA SPECTROMETRY

Abstract Uranium(VI) sorption by two highly uranium‐resistant air‐borne fungi in a low‐pH medium was measured by means of gamma spectrometry. Growth kinetics and stoichiometry of the two fungal species were also studied. Results show acceptable growth rates in synthetic medium with glucose and ammonia as carbon and nitrogen sources, respectively. Typical oxidative metabolism of carbohydrates was found. In vivo uptake of the radionuclide was negligible, but biosorption dry biomass presented a remarkable performance. The fungal strains showed potential for use in bioremediation.

Removal of Humic Acid by Organo-Montmorillonites: Influence of Surfactant Loading and Chain Length of Alkylammonium Cations

In this study, the characterization and adsorption properties of montmorillonite (MMT) and organomontmorillonites with different surfactant/cationic exchange capacity (CEC) ratios (1 and 2) of tetradecyl trimethylammonium (TDTMA+) and hexadecyl trimethylammonium (HDTMA+) cations were evaluated. The particle apparent diameter, determined by laser and scanning electron microscopy showed aggregate formation, which varied with loading and cation length of the surfactant used. X-ray diffraction analysis revealed the formation of a pseudotrilayer arrangement of both surfactants in the interlayer space, FTIR showed the characteristic bands of the surfactants and micelle formations, and zeta potential determinations indicated neutral or negative surface charge values, except for sample obtained with one CEC concentration exchanged with HDTMA+ (HDTMA1-MMT) where a charge reversal to positive was found. Higher adsorption amounts of humic acid (HA) were found for HDTMA1-MMT and TDTMA1-MMT samples than for MMT sample, while the increase in the loading of both surfactants decreased the amounts of HA adsorbed could be assigned to a higher micelle formation and different packing density of alkyl chain, in the external surface. The correlation found between the total surface area and negative zeta potential values and the HA adsorption rate, within each surfactant, indicated the strong influence that these properties have on HA adsorption.

Metal bioleaching from anaerobic sediments from Reconquista River basin (Argentina) as a potential remediation strategy

Anaerobic sediments of urban watercourses are subjected to industrial pollution and frequently tend to accumulate heavy metals. The biocatalyzed oxidation and reduction of sulphur compounds that occur within the sediment are key reactions that determine mobility of metals such as that occurred in mine acidic drainage reactions. The aim of this work was to study the application of these processes using heap leaching technology for the remediation of anaerobic contaminated sediments from Reconquista River basin. The bioleaching potentiality for remediation was demonstrated through batch tests in shake flasks with different pulp densities of anaerobic sediment containing 338xa0mgxa0kg−1 of Zn and 117xa0mgxa0kg−1 of Cu. Subsequently, bioleaching heap systems were compiled into columns of 12-cm height and 6-cm diameter, fitted with perlite to improve drainage. In order to assess the effect of elementary sulphur over the mobility of metals from the bioheap to the aqueous solution, increasing concentrations of elementary sulphur (1, 2, 5xa0% w/w) were added. After 3xa0months of acidification generated by periodic watering, the extraction of 70xa0% of the initial Zn and 43xa0% of the initial Cu was achieved. Polluted sediments from waterways as Reconquista River should not be indiscriminately manipulated if acid drainage is possible. Remediation by a simple and economically viable strategy like heap leaching is feasible.

Acid Drainage and Metal Bioleaching by Redox Potencial Changes in Heavy Polluted Fluvial Sediments

Sediments from polluted urban streams act as a sink of contaminants. The high content of organic matter and sulphides makes the system appropriate for binding heavy metals. However, changes in the redox potential leads to processes in which sediments acts like a low sulphidic ore in an oxidizing environment, and could generate acid drainages. Human and not human disturbances of the sediments could derive in its oxidation catalyzed by sulphur oxidizing bacteria (SOB). This process leads to acidification and metal release. In this study we analyze the acidification potential of anaerobic sediments of polluted streams near Buenos Aires with static and kinetic methods. The results remark the necessity to consider this process before any sediment management action.

Biocatalysed acidification and metal leaching processes in sediments of polluted urban streams

Sediments of fluvial streams are a sink for pollutants such as heavy metals and organic recalcitrant compounds. In anoxic conditions, sulphide generation and alkalinisation cause precipitation of heavy metals. The redox potential of the system could change to higher values, mainly owing to oxygen exposition generated by anthropogenic disturbances of the sediment such as dredging operations. Knowledge about the mechanisms involved is fundamental to assess the risk of acid generation and rise in heavy metals bioavailability. In this paper, the characterisation and assessment of acidification risk of sediments of a contaminated stream near Buenos Aires was carried out by static and kinetic assays. Speciation of heavy metals was determined after metal sequential extraction procedure. Also, re-suspension of sediments assay in batch mode, with and without Acidithiobacillus ferrooxidans inoculum, was carried out to assess the chemical changes that occur at oxygen exposure, verifying the acidification and heavy metal release processes.

Aerobic Reduction of Uranium(VI) by Acidithiobacillus Thiooxidans Cultures

Acidithiobacillus thiooxidans was grown in the presence of uranium and its redox processes were studied in aerobic conditions for the first time. Results so far obtained may suggest an indirect uranium reduction, mediated by metabolically produced reducing compounds.

Copper Removal by Botryococcus braunii Biomass with Associated Production of Hydrocarbons

The goal of the present article is to evaluate the potential of copper (II) removal from acidic wastewater, associated with the production of hydrocarbons by the microalgae Botryococcus braunii. Results demonstrate that the growth of B. braunii is correlated with the hydrocarbon production as well as with alcalinization and copper removal from the medium. Even though B. braunii did not present high rates of copper adsorption, the increase in the pH of the media promotes the precipitation of the metal. In this way copper can be removed from solution by both, adsorption and precipitation. Results suggest that metabolic active biomass of B. braunii could be used for copper removal from solution while it produces appreciable quantities of hydrocarbons. This fact is very interesting in order to develop new remediation processes of waste water with coupled energy production.

Characterization of U(VI) Sorption and Leaching on Clay Supported Biomass Sorbents

In previous studies was demonstrated that matrixes generated from fungal biomass and a montmorillonite (BMMTs) are efficient as biosorbentes in batch uranium removal systems. The objective of this article is to evaluate the U(VI) sorption capacity of BMMT in continuous systems for its removal from effluents and to determine the reusability of the sorbent and the recovery of the uranium testing different leaching solutions. Upflow BMMT columns were performed in order to optimize the system for continuous sorption techniques. For upflow columns, the maximum total amount of U(VI) retained was 75 mg U(VI) / g BMMT. Treatment of U(VI) loaded BMMTs with leaching solutions allowed calculating U(VI) extraction percentages. These results indicated the possibility of recycling the sorbent after processes of U(VI) sorption and that the use of clay supported biomass sorbents in upflow columns presented strong potential for uranium retention.

Alternative Treatment of Recalcitrant Organic Contaminants by a Combination of Biosorption, Biological Oxidation and Advanced Oxidation Technologies

Industrial activity produces increasing amounts of effluent. Dyes and surfactants are typical examples of such pollutants, and both are present in various industries such as textiles, which are widely distributed in South-American, Indo-Asian and African countries. These industries are an important source of resources in the 3rd World Countries and also a source of pollution. Many compounds present in them are recalcitrant and therefore persistent in the environment, causing deleterious effects on the ecosystem (Padmavathy et al. 2003; Stolz et al. 2001). These compounds are usually found in very low concentrations and large volumes of effluent, characteristics that make very difficult its treatment by conventional means. Conventional techniques for removal of recalcitrant pollutants from wastewaters are based on the use of activated carbon, ionic exchange resins, chemical precipitation or membrane filtration. However, these technologies are usually not very convenient due to the large volumes to be treated and the low concentration of pollutants, excessive use of chemicals, accumulation of concentrated sludge and disposal problems, high cost of operation and maintenance of plant, sensitivity to other components of the liquid effluent (Balaji and Matsunaga 2002, Chen and Lin 2001). Traditional and alternative biological processes have received increasing interest owing to their cost, effectiveness, ability to produce less sludge and environmental benignity (Chen et al 2003; Volesky 2007) but some organic industrial and agricultural pollutants are recalcitrant to biological treatments . Several common compounds such as dyes, surfactants and pesticides, among others, are biorecalcitrant and can produce microbial death or other problems in water treatment plants. The biological treatment of liquid effluents containing this type of pollutants involves a previous separation step, or the isolation and use of specialized strains that can resist and degrade these toxic contaminants (Padmavathy et al. 2003).

Environmental biotechnology and engineering: two convergent areas to provide real solutions for a growing world

World population is growing fast, in parallel with the use of natural resources and waste generation. Therefore, it is mandatory to take actions immediately to preserve the environment and the health and living conditions of the people. In this sense, biotechnology and engineering are key tools to provide solutions to a world with serious environmental problems. The advances in both Biotechnology and Engineering are usually covered by international meetings that typically dedicate only one or two sessions to environmental applications. However, the synergistic interaction of environmental biotechnology and environmental engineering has an enormous potential for the generation of important contributions to a more sustainable development of the present society. These contributions will undoubtedly lead to the improvement of the life quality of the people and preserve the natural resources for the future generations. To help achieve this goal, the scientific community must interact in a multidisciplinary way and join efforts to come up with new ideas and thus, there was a need for an international meeting dedicated to both disciplines, with a strong vocation to share scientific and technological knowledge and promote research networking. The International Symposium on Environmental Biotechnology and Engineering (ISEBE) was conceived to present the advances in both convergent disciplines, where researches from all over the world could find a friendly ambience to share novel ideas, doubts, problems, and solutions related to these important areas of knowledge. In this way, a series of events was developed, that began in Mexico in 2004 with the First International Meeting on