Papers by Ana Claudia Queiroz Ladeira
Brazilian Journal of Radiation Sciences
Acid mine drainage (AMD) is one of the main environmental issue caused by chemical and bacterial ... more Acid mine drainage (AMD) is one of the main environmental issue caused by chemical and bacterial oxidation of pyrite (FeS2) and other sulfite minerals when exposed to atmospheric conditions during mining. In Brazil, AMD occurs in a former uranium mine and contains radionuclides and other elements, which are precipitated from acidic water by liming. Due to the inefficiency of the treatment, contaminants overflow to the water reservoir of Indústrias Nucleares do Brasil – INB in Caldas. The multiplicity of interactions that can occur between the contaminants and the sediments of the reservoir requires a broader approach in order to understand the fixation and/or transport of these elements. In this work the natural remediation approach is reviewed and an initial chemical and radiochemical characterization of the reservoir sediments is presented. Uranium was determined by spectrophotometry, Ra-226, Ra-228 and Pb-210 by gamma spectrometry and zinc by ICP-OES. Twenty-six sediment samples ...
Brazilian Journal of Radiation Sciences
Radionuclides may contaminate lubricant oils in nuclear power plants. In Brazil, this kind of was... more Radionuclides may contaminate lubricant oils in nuclear power plants. In Brazil, this kind of waste has been stored in the generator’s facilities, awaiting treatment alternatives. This work intends to investigate a process to treat it for final deposition, using bentonite as sorbent material. This process will result in decontaminated oil, free from radiological control, and radioactive loaded sorbent, with considerable volume reduction of the radioactive waste. The study focuses in cobalt removal from a simulated oil waste (non-active). The production of the simulated waste is described. Benton-ite was used for equilibrium time determination, kinetic and adsorption studies. Cobalt adsorption equilibrium was rapidly attained after 30 minutes. The data was used for modelling the system’s kinetic, applying the pseudo first and pseudo second order equation models. Experimental data fitted to pseudo second order model, supporting the assump-tion that the adsorption is due to chemisorpti...
Journal of Geoscience and Environment Protection
This work presents a Principal Component Analysis (PCA) study using Pbisotope signatures and U, T... more This work presents a Principal Component Analysis (PCA) study using Pbisotope signatures and U, Th and Pb concentrations from groundwater, sediments and rocks (granites and orthogneisses) of the Complex of Lagoa Real (Bahia, Brazil). This area is naturally enriched in U and Th, with the occurrence of Pb derived from the radioactive decay of the elements (238 U, 235 U and 232 Th) in the form of their stable isotopes 206 Pb, 207 Pb and 208 Pb in addition to the natural isotope 204 Pb. Sampling was carried out in the rainy season (December to January) and the points were selected according to regional hydrology and geology. Thirty samples were analyzed: 12 of groundwater (AP) and 18 of sediments (S). The results show that the use of isotopic ratios allows discrimination between geogenic and anthropogenic samples. This information is not obtained using only the analysis of concentration data. Statistically, the isotopic data of Pb stand out as an efficient tool in the characterization of sources in the scenario investigated, allowing an effective environmental monitoring and a better management of the mining activities.
Brazilian Journal of Geology, 2017
ABSTRACT: This work presents the investigation in an environment that contains uranium deposits b... more ABSTRACT: This work presents the investigation in an environment that contains uranium deposits by using Pb isotope signatures. The study area, southeast of Brazil, is characterized by the lack of surface water and, as a consequence, the groundwater plays an important role in the economy of the region, such as the supply to the uranium industry and, above all serving the needs of the local population. The objective of the present investigation is the determination of the signatures of Pb in groundwater and sediments as well as the identification of environments under influences of geogenic and/or anthropogenic sources. It was determined that the Pb in the majority of sediments was geogenic in origin. Although data from the literature, related to the environmental studies, consider 206Pb/207Pb isotopic ratio values below or close to 1.2 as an indicative of anthropogenic Pb, the 206Pb/ 207Pb determined for the majority of groundwater samples ranged from 1.14 to 1.19, and are similar t...
In southeastern Brazil, a closed uranium mine produces acid mine water at pH 2.7 which contains s... more In southeastern Brazil, a closed uranium mine produces acid mine water at pH 2.7 which contains significant concentrations of uranium and other elements like manganese, sulfate, iron and zinc. The contaminants are removed from the acid water to acceptable limits through precipitation of the elements using lime. The precipitation procedure has been used for more than fifteen years and generates a sludge which is disposed of into the mine opening. The present study consists of the characterization of different samples of the sludge and their classification according to leaching standard procedures in order to assess the resolubilization of the contaminants and their migration to the environment. Despite being classified as non toxic, the samples are not inert, which means that a specific site is required for their disposal instead of into the mine. Fluoride and sulfate are responsible for the chemical instability of the samples. Other elements, like Fe, Zn, Mn, U and Al, are present in significant concentrations. Uranium is present as an amorphous oxide. The main minerals of the samples, according to X-ray diffraction, are ettringite, gypsum and calcite (CaCO 3) and minor constituents are fluorite (CaF 2), gibbsite (Al 2 O 3 .3H 2 O) and portlandite (Ca(OH) 2).
Uranium extraction can be accomplished by polymeric ion exchange resin or solvent extraction. The... more Uranium extraction can be accomplished by polymeric ion exchange resin or solvent extraction. The choice of the technique and type of extradant depend on the uranium concentration and the presence of other ions in aqueous medium. In solutions with low uranium concentration, polymeric resin is more suitable. However, in solutions with high uranium content, solvent extraction is more appropriate. The influence of competitive species on uranium removal using resin and solvent extraction techniques was studied. Samples consisted of different industrial effluents which contained carbonate, ammonia, fluoride, sulfate and chloride. Results showed that although the resin has a great affinity for uranium, carbonate concentration should be below 2.5g/L and fluoride content below 6.0g/L to remove more than 95% of uranium. Conversely, the presence of ammonia up to 18 g/L did not decrease uranium recovery. The presence of chloride ion is a great problem in uranium mills. Alternative routes were ...
Minerals Engineering, 2005
One of the most serious environment problems created by the mining industry is acid mine drainage... more One of the most serious environment problems created by the mining industry is acid mine drainage. In one plant of Nuclear Industries of Brazil-INB, this problem is a matter of concern. The presence of iron sulfites, such as pyrite, generates water with acidity above the levels allowed by the legislation and therefore, inappropriate for releasing straight into the environment. The industry maintain a high cost treatment in acid water from mines and waste disposal which consists in neutralizing and precipitating heavy metals. The treatment of acid water using sulfate-reducing bacteria (SRB) has been used in other countries with quite good technical results as well as economical advantages and thus, the object of this research. A seasonal study was carried out on the sulfate-reducing bacteria present in the liquid effluent discharged from two wastes disposal of the uranium mine, in phase of decommission, in Poços de Caldas. This study shows the presence of SRB in the analyzed environmental, as well as some factors that are related with the amount of SRB presents, such as: dissolved oxygen, pH and organic matter.
Journal of Chemistry, 2013
Although oxidative precipitation by potassium permanganate is a widely recognised process for man... more Although oxidative precipitation by potassium permanganate is a widely recognised process for manganese removal, research dealing with highly contaminated acid mine drainage (AMD) has yet to be performed. The present study investigated the efficiency of KMnO4in removing manganese from AMD effluents. Samples of AMD that originated from inactive uranium mine in Brazil were chemically characterised and treated by KMnO4at pH 3.0, 5.0, and 7.0. Analyses by Raman spectroscopy and geochemical modelling using PHREEQC code were employed to assess solid phases. Results indicated that the manganese was rapidly oxidised by KMnO4in a process enhanced at higher pH. The greatest removal, that is, 99%, occurred at pH 7.0, when treated waters presented manganese levels as low as 1.0 mg/L, the limit established by the Brazilian legislation. Birnessite (MnO2), hausmannite (Mn3O4), and manganite (MnOOH) were detected by Raman spectroscopy. These phases were consistently identified by the geochemical mo...
This work aims at evaluating Al-based adsorbents (gibbsite and calcined gibbsite) for arsenic rem... more This work aims at evaluating Al-based adsorbents (gibbsite and calcined gibbsite) for arsenic removal in water treatment. The thermal treatment consisted in the calcination in temperatures from 70 and 400°C. Both the specific surface area and the adsorption capacity were found to increase up to 20 and 10 times, respectively, as a result of the treatment. Leaching and elution procedures for arsenic-loaded substrates were performed in order to evaluate arsenic remobilization and elution. Among the leaching solutions tested, distilled water, acetic acid and sulfate solutions, the latter was the one that most favored both As(III) and As(V) remobilization. The leaching data also showed a high tendency for As(III) remobilization. Up to 10% of As(III) was released from the loaded solid, the solid was classified as toxic to the environment. The treated gibbsite retained arsenic much more strongly than the raw sample. Elution with 3% and 0.5% NaOH solutions showed up to 80% of arsenic removal.
Journal of Molecular Structure-Theochem, 2006
It is well known that As(III) has a higher mobility compared to As(V) in the environment. This fa... more It is well known that As(III) has a higher mobility compared to As(V) in the environment. This fact is explained by the high reversibility of As(III) adsorption on minerals such as Al (hydr)oxides. Nevertheless, experimental results pointed out that adsorption of As(III) leads to innersphere complexes, which appears to be in conflict with the high mobility of these species as inner-sphere complexes should be strongly attached. In this work we used density functional methods and cluster models to study two different mechanisms for the H 3 AsO 3 adsorption on gibbsite-g-Al(OH) 3 , one of the most abundant aluminum hydroxide minerals. Our results show that, differently from the As(V) case, As(III) is not adsorbed via an acid/base, but by a non-dissociative mechanism in which O-H bonds are not being broken. This non-dissociative mechanism also conciliates the high remobilization of As(III) with the apparently inconsistent formation of inner-sphere adsorption complexes.
Water Pollution X, 2010
Acid mine drainage (AMD) is one of the main environmental issues faced by the mining industry. Th... more Acid mine drainage (AMD) is one of the main environmental issues faced by the mining industry. The acid mine water generally contains metals above the permissible discharging levels. Manganese is particularly present in this effluent and its removal is notoriously difficult due to its high solubility over a wide range of pH. While most of the metals precipitates at a pH below neutrality, the pH necessary for manganese precipitation is very high, above 10. Most systems that effectively removes this element from mine waters uses the oxidation of Mn (II) followed by precipitation at an elevated pH. Precipitation consumes a great amount of lime, which implies in a high operational cost. Besides, the process generates a large amount of sludge containing metals which have to be disposed of. The objective of this study is to optimize the removal of manganese by using a laboratory prepared acid solution and an acid effluent from Poços de Caldas uranium mine (Brazil), in order to achieve the Mn permitted level for discharging (<1mg/L) and to reduce the amount of sludge generated. The precipitation process has been studied using lime, limestone and a nonconventional catalyst/adsorbent (MnO 2 residue). The results obtained showed that both lime and limestone are effective in the removal of Mn in a pH higher than 10. However, there is a slight difference between the two reagents and lime shows a better performance. The volume of precipitate generated by the addition of lime was 50% smaller than that obtained when limestone was used. The use of the non-conventional material made the removal of almost 100% of the Mn possible as the concentration of manganese was reduced from 140mg/L to <1mg/L at a pH near neutrality (6.8 to 7.2). The final effluent complies with the recommended value for manganese discharge.
Rem: Revista Escola de Minas, 2002
Esse trabalho consistiu da realização de estudos comparativos da capacidade de retenção de arsêni... more Esse trabalho consistiu da realização de estudos comparativos da capacidade de retenção de arsênio de 3 amostras de solos do Estado de Minas Gerais e de 1 amostra de rejeito de minério aurífero oriundo da mina do Morro do Ouro, da Rio Paracatu Mineração S.A. A capacidade de retenção foi avaliada com base no levantamento de isotermas, através das quais foi calculado o carregamento máximo de arsênio em cada material. Foi realizada, também, a caracterização química e mineralógica desses sólidos de forma a determinar os minerais constituintes das amostras e, conseqüentemente, os principais adsorventes de arsênio. Finalmente, correlacionando a capacidade adsortiva de cada solo com seus constituintes mineralógicos, foi possível fazer a seleção dos solos mais adequados para a imobilização do arsênio.
HOLOS, 2014
O zircônio e o háfnio são dois importantes metais para a indústria nuclear. O háfnio ocorrer em t... more O zircônio e o háfnio são dois importantes metais para a indústria nuclear. O háfnio ocorrer em todos os minérios de zircônio na faixa de 2 - 3%. Entretanto, o uso do zircônio na indústria nuclear exige que o háfnio esteja em concentrações menores que 100 mg Kg-1. O atual trabalho consiste na separação do par zircônio e háfnio pelo método de troca iônica a fim de se obter um concentrado de zircônio de alta pureza. Os licores de zircônio e háfnio foram produzidos a partir da lixiviação de seus hidróxidos Zr(OH)4 e Hf(OH)4 em meio nítrico por 24 horas. A partir destes dois licores foi preparada uma solução contendo 7,5x10-2 mol L-1 de Zr e 5,8x10-3 mol L-1 de Hf, acidez de 1 M. Os experimentos de troca iônica foram realizados em batelada, com as resinas Dowex 50WX4 50, Dowex 50WX8 100, Dowex 50WX8 50, Amberlite IR-120 e Marathon C a temperatura constante de 28°C. As demais variáveis tais como acidez e agitação foram mantidas constantes. A partir do ajuste dos dados a equação de Langmu...
Rem: Revista Escola de Minas, 2008
Esse trabalho visou à caracterização de resíduos e efluentes da indústria galvânica a fim de iden... more Esse trabalho visou à caracterização de resíduos e efluentes da indústria galvânica a fim de identificar os elementos que conferem periculosidade aos resíduos, assim como a classificação destes em perigosos (classe I) ou não perigosos (classe II). A caracterização das amostras mostrou que o Fe e o Zn são os elementos predominantes nas amostras, mas existem outros elementos (Ni, Cd, Al, Mn, Cu, F, Cr, Ca) como minoritários ou traços. A classificação dos resíduos, feita com base na Norma ABNT NBR10004/2004, mostrou que o Cd e o Cr são os contaminantes responsáveis pelo enquadramento destes como perigosos. As lamas de fosfatização não apresentam características de periculosidade apesar de, a priori, serem consideradas como tal. Com base neste estudo, foi possível apresentar um cenário do setor de galvanoplastia de forma a orientar as empresas quanto a necessidade de eliminação ou redução dos níveis de contaminantes de forma a reclassificar seus resíduos como não perigosos.
Water, Air, & Soil Pollution, 2013
In recent years, much attention has been devoted in developing inexpensive or alternative systems... more In recent years, much attention has been devoted in developing inexpensive or alternative systems for treating acid mine drainage (AMD). Manganese is a common component of AMD, and it is traditionally removed by precipitation. However, in order to meet the standard limits for discharging, usually <1 mg L −1 , it is necessary to raise the pH above 10 which implies in high consumption of reagents and a final pH that does not meet the required value for discharging. This study investigated the removal of manganese from an acid mine effluent and laboratory solutions by using an industrial residue consisted of manganese dioxide (MnO 2). The pH of the acid effluent is around 2.7, and the manganese concentration is approximately 140 mg L −1. Batch experiments assessed the influence of pH and the efficiency of manganese dioxide (MnO 2) in the Mn +2 removal. In the presence of MnO 2 , the metal concentration meets the discharging limit at pH range of 6.8 to 7.2. Experiments carried out with columns packed with MnO 2 assessed the influence of the flow rate on the process. Best results were obtained for columns fed with mine water neutralized with limestone at pH 7.0 and a residence time of 3.3 h. The maximum manganese loading capacity for MnO 2 was around 14 mg g −1. RAMAN spectroscopy showed that the MnO 2 is essentially constituted of pyrolusite. In addition, the solid hausmannite (Mn 3 O 4) was observed on the surface of the MnO 2 residue after its contact with the Mn +2 solution.
Radiochimica Acta, 2000
SummaryUranium in solution can be precipitated over a wide pH range, from acidity and alkalinity,... more SummaryUranium in solution can be precipitated over a wide pH range, from acidity and alkalinity, depending upon the solution and the precipitant used. The precipitate is generally filtered and the solution resultant contains uranium that should be recovered. This work is aimed at the selection of an appropriate resin for uranium recovery from alkaline solutions in the presence of ammonia, carbonate and fluoride. The ability of uranium extraction of 3 types of polymeric strong base resin was assessed. Laboratory solutions were prepared to determine the influence of the ions like ammonia, carbonate and fluoride on the uranium recovery by resins. The uranium concentration was 100 mg/L and the solution pH ranged from 9.2 to 10.4. The results, obtained by batch experiments, showed that excess of carbonate and fluoride completely inhibit uranium uptake in the pH range studied. Even low concentrations of fluoride and carbonate decrease uranium adsorption by resins. The optimum concentrati...
Rem: Revista Escola de Minas, 2008
The work aimed at the characterization of wastes and liquid effluents from galvanizing industry i... more The work aimed at the characterization of wastes and liquid effluents from galvanizing industry in order to identify the main elements responsible for their toxicity and the classification of the residues as hazardous or non hazardous. The characterization of the samples showed that Zn and Fe are the predominant elements. However, elements like Ni, Cd, Al, Mn, Cu, F, Cr and Ca are present as minority or as trace constituents. According to the standard procedure (Norma ABNT NBR10004/2004) the elements Cd and Cr are the main constituents responsible for the classification of the residues as hazardous. The residues that are generated in the phosphatization process may be considered as non hazardous in spite of being a priori considered as hazardous. Based on the results, it was possible to present an overall view of the galvanizing industry residues. Data can be useful as a guide to help the industry to propose alternatives to eliminate or decrease the levels of contaminants in order to classify them as non hazardous wastes.
Minerals Engineering, 1993
This work presents a comparative characterization of five samples of activated carbon and a kinet... more This work presents a comparative characterization of five samples of activated carbon and a kinetic evaluation of gold adsorption from diluted cyanide solutions. The characterization was aimed at determining and quantifying some physical and chemical properties considered important for adequate performance of carbon in gold plants. The kinetic study analyzed the influence of gold concentration in solution, temperature, pH, agitation and time on the rate of gold adsorption on carbon. The data obtained were compared with those reported in the literature. A discussion of these results based on the suggested mechanism is also presented.
Minerals Engineering, 2005
The recovery of uranium from nuclear industrial effluent has been studied using laboratory column... more The recovery of uranium from nuclear industrial effluent has been studied using laboratory column and polymeric ion exchange resin. The industrial effluent, at pH around 10, contains uranium (40 mg/L), ammonium (80 g/L) and carbonate (170 g/L) and cannot be discharged without previous treatment. Uranium is in the form of uranyl quadrivalent complex anions [UO 2 (CO 3) 3 ] 4À. The resin IRA 910 U was employed for its specific application for uranium extraction. Adsorption was carried out at flow rate of 1.0, 2.0, and 5.0 mL/min, which corresponds to a retention time of 10, 5.0 and 2.5 min, respectively. The use of ion the exchange technique makes the recovery of more than 98% of the uranium possible. Elution was carried out with ammonium carbonate solutions and also with the diluted effluent. The eluate contained uranium ranging from 2.4 to 2.7 g/L. The solution eluate might be recycled back into the process with the advantage of saving this valuable metal.
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Papers by Ana Claudia Queiroz Ladeira