Antônio Thomé

Review of Nanotechnology for Soil and Groundwater Remediation: Brazilian Perspectives

The soil remediation field is still in development in Brazil. Currently, it is not known how many contaminated sites exist across the country; however, due to the country’s large size and its extensive urbanization and industrialization, it can be postulated that the number of contaminated sites must be very high. To remediate these sites, new sustainable technologies should be identified and evaluated. A technology that was born in the 1990s in the USA, and has been fairly investigated, is the use of nanoparticles (NPs) to degrade contaminants in soils and groundwater. This study aims to present a bibliographic review of nanotechnology application to remediation of soils and groundwater, as well as assess the potential of conducting research in this field in Brazil. This paper first presents an overview of the number of contaminated areas identified in the USA and Europe. The basic concepts of nanomaterials followed by classification, synthesis, and characterization of nanomaterials are explained. The main types of contaminants for which the technique was already applied as well as the chemical reactions between them and NPs are presented. The issues related to delivery and migration of NPs in the porous media is discussed. Concerns regarding the toxicity of nanomaterials are discussed. The in situ applications of nanomaterials for contaminated site remediation are presented. It is concluded that the issues involving remediation of soils and groundwater are site specific and it is not possible to directly transfer knowledge gained from sedimentary soils of temperate climates for residual soils found in tropical and subtropical climate regions. The research on nanotechnology for site remediation in Brazil has just begun, and more efforts are required from the technical and academic professionals to develop nanotechnology as practical technology for the remediation of contaminated sites.

Field Tests on Laterally Loaded Rigid Piles in Cement Treated Soils

AbstractA series of laterally loaded pile tests carried out both in natural ground and in cemented treated soil is presented in this paper. The length to diameter ratio L/D of the piles was selected as 5, representing the behavior of a free-headed, short pile that will move as a rigid body in the direction of the applied load without structural damage. The extent of the treated soil layer around the pile ranged from 2–4 times the pile diameter and 0.1–0.3 times the pile length. The treated layer was a mixture of Osorio sand and early strength portland cement. Experimental results show a significant increase in lateral load resistance of short piles when the soil is treated with cement.

RETENÇÃO DE METAIS EM SOLO DA ANTIGA ÁREA DE DISPOSIÇÃO DE RESÍDUOS SÓLIDOS URBANOS DE PASSO FUNDO - RS

A crescente contaminacao de solos e aguas subterrâneas pelos residuos solidos produzidos diariamente nas cidades ascende a necessidade de estudos que elaborem diagnosticos capazes de determinar a retencao desses contaminantes no solo. Este trabalho teve como objetivo a caracterizacao de metais no solo e a investigacao da capacidade de retencao de metais em um solo de uma antiga area de disposicao de residuos solidos urbanos na cidade de Passo Fundo, RS. A caracterizacao dos metais foi realizada atraves do metodo de extracao por digestao e analise em espectrofotometro de absorcao atomica. Dois ensaios de coluna foram realizados para simular o fluxo dos contaminantes por um solo original e nao-contaminado da area, sobre o qual foi realizada disposicao do lixo. Os metais analisados foram: Cromo, Zinco, Cobre e Manganes. Um lixiviado artificial, com concentracoes de metais inseridas, foi percolado pelo solo. A retencao de metais no solo original do aterro foi relevante, sendo maior para os metais Cobre, Cromo e Zinco. Apenas o Manganes atingiu o limite de retencao. Portanto, o solo natural da area possui alta capacidade de remediar estes metais. Palavras-chave: residuos solidos; retencao; ensaio de coluna. ABSTRACT Metals retention in soil of ancient area of disposal of urban solid waste in Passo Fundo – RS. The crescent soil contamination by urban solid waste (USW) denotes the necessity to find a solution to determine the soils attenuation capacity. The aim of this paper is the characterization of metal soil and metals natural attenuation capacity in a soil from one ancient disposal site of USW in Passo Fundo city, located in the south of Brazil. The characterization of metals was realized using the method of extraction by digestion and analysis in atomic absorption spectrometer. Two column tests were carried out to stimulate the flux of contaminants by na original and non-contaminated soil of the area. The metals analyzed in this work were: Chromium, Zinc, Copper and Manganese. An artificial leaching, with concentrations of metals, was used in soil percolation. The metals attenuation in the soil was relevant and it was higher for Copper, Chromium, and Zinc. Only Manganese reached the limit of attenuation. Thus, the natural soil has high capacity to mitigate these metals. Key words: solid waste, attenuation, columns test

Produção de biossurfactantes por microrganismos isolados de solo contaminado com óleo diesel

The aim of this work was to produce biosurfactants through submerged fermentation using microorganisms isolated from soil contaminated with diesel. Microorganisms were isolated, characterized by the production of biosurfactants, and used to study the influence of type, induction and concentration of ammonium sulfate as a nitrogen source in the culture medium. The microorganisms that showed best results, in terms of production of biosurfactants, were identified as being of the genus Pseudomonas and Bacillus. The biosurfactants produced proved capable of reducing the surface tension of the media to 39 mN/m and 34 mN/m, respectively. Higher biosurfactant production was obtained in the medium containing 1% soybean oil without ammonium sulfate.

Biossorção passiva de cromo (VI) através da microalga Spirulina platensis

Effluents containing toxic metals are dangerous and more economical, efficient and environmentally friendly treatments must be studied, with the biosorption process with microbial biomass constituting an efficient solution. Thus, the ability of Spirulina platensis biomass for removing chromium (VI) using passive and active biosorption was evaluated. Inactive microalgae biomass and synthetic solution containing chromium (VI) were used to evaluate important factors in the process and biomass biosorption ability. Results of the experiments showed that microalgae have potential for biosorption of chromium (VI), attaining removal of 100.39 mg g-1, and that pH was the variable with the greatest influence on the process.

Influence of physicochemical factors on biodiesel retention in clayey residual soil.

AbstractSoil can naturally attenuate contamination, depending on its interaction with contaminants. Soils can delay the spread of the contaminant plume and even reduce the bioavailability of the contaminant because of their contaminant retention capacity. The retention capacity may be influenced by several physicochemical factors of both the soil and the contaminant. The aim of this study was to assess the retention capacity of a clayey, basaltic residual soil to an organic contaminant (soybean biodiesel) under different variable conditions, such as moisture content, void ratio, and presence or absence of biostimulation nutrients, specifically nitrogen (N), phosphorus (P), and potassium (K). Experiments were conducted using 100-g samples of dry soil under different void ratios (1.14, 1.24, and 1.34) and different moisture contents (15, 25, and 35%). Two series of experiments were conducted: one in the absence of nutrients and another in the presence of nutrients. The soil samples were initially sterilized...

Potential of Live Spirulina platensis on Biosorption of Hexavalent Chromium and Its Conversion to Trivalent Chromium

Microalga biomass has been described worldwide according their capacity to realize biosorption of toxic metals. Chromium is one of the most toxic metals that could contaminate superficial and underground water. Considering the importance of Spirulina biomass in production of supplements for humans and for animal feed we assessed the biosorption of hexavalent chromium by living Spirulina platensis and its capacity to convert hexavalent chromium to trivalent chromium, less toxic, through its metabolism during growth. The active biomass was grown in Zarrouk medium diluted to 50% with distilled water, keeping the experiments under controlled conditions of aeration, temperature of 30°C and lighting of 1,800 lux. Hexavalent chromium was added using a potassium dichromate solution in fed-batch mode with the aim of evaluate the effect of several additions contaminant in the kinetic parameters of the culture. Cell growth was affected by the presence of chromium added at the beginning of cultures, and the best growth rates were obtained at lower metal concentrations in the medium. The biomass removed until 65.2% of hexavalent chromium added to the media, being 90.4% converted into trivalent chromium in the media and 9.6% retained in the biomass as trivalent chromium (0.931 mg.g−1).

Biorremediação de um solo argiloso contaminado com uma mistura de diesel e biodiesel através da bioventilação

O crescente consumo de combustiveis fosseis gera a necessidade de buscar fontes alternativas ambientalmente mais adequadas, como e o caso do biodiesel, em misturas com o diesel. Porem essa mistura torna-se um provavel contaminante ambiental. A bioventilacao e uma tecnica de biorremediacao que envolve apenas a insercao de ar no meio, para estimular a atividade aerobia dos microrganismos e surge como uma alternativa aos metodos convencionais de remediacao. O objetivo deste trabalho foi avaliar a biorremediacao ex situ de um solo argiloso contaminado com uma mistura B20 utilizando a bioventilacao. Os ensaios foram realizados em biorreatores de PVC, e 4% de contaminante, em relacao a massa de solo seco. Foram testadas tres vazoes de ar (2, 4 e 6 L/min), em tres intervalos de tempo distintos (1h a cada 24h, 36h e 48h), alem do controle. A degradacao do contaminante foi avaliada atraves da determinacao da fracao residual, extraido por ultrassom, em 3 tempos (15, 30 e 60 d). A maior degradacao aos 60 dias, foi obtida para a velocidade de ar de 6 L/min aplicado diariamente, com 86% de degradacao, demonstrando-se ser a bioventilacao uma tecnica de biorremediacao promissora para o tratamento de solos argilosos contaminados com mistura B20.

Bioremediation of Soil Contaminated with Diesel and Biodiesel Fuel Using Biostimulation with Microalgae Biomass

AbstractThis study evaluates the ability of biostimulation to enhance the bioremediation of soil contaminated with oily compounds as compared with natural attenuation. The soil was contaminated wit...

Toxicity Evaluation of Nano-Zero Valent Iron to Soil Indigenous Microorganisms

The objective of this study was to evaluate the toxicity of nZVI to the indigenous microorganisms of the soil. The toxicity of nZVI was assessed by the CO2 production for the soil native microorganisms. Different concentrations of nZVI were added to the soil (0, 4, 15 and 50 g/kg) for further analysis of the microbiological activity. For a better interpretation of toxicity effects, was used glucose (g/kg) as a carbon source. As soil mixtures, nZVI and glucose were inserted into sealed vials for an evaluation of the microbiological activity. The quantification of CO2 produced by the indigenous microbes respiration was performed by stoichiometry, using NaOH to absorb the gas and using HCl to determine the concentration. The analyzes were performed every 02 days, until a total monitoring time of 40 days. It was observed that at a concentration of 50 g/kg it has not released any carbon dioxide, demonstrating a maladaptation of the microorganisms under these conditions. The nZVI concentrations of 4 and 15 g/kg showed an increase of CO2 production, indicating an adaptation of the microorganisms as available conditions. Thus, the application of nZVI as remediation technology can be performed up to concentrations of 15 g/kg without causing damage to native soil microorganisms. However, applications above these may cause toxic and/or inhibitory effects to the microbes, restricting a possible combination of nano and bioremediation.