The pollution caused by heavy metals is one of the major environmental problems that is imperative to be solved. New technologies, easy to implement and to adapt to any system, deserve special attention and are a focus of this work. The ability of a biofilm of Escherichia coli supported on kaolin to remove Cr(VI), Cd(II), Fe(III) and Ni(II) from aqueous solutions was investigated in batch assays for the treatment of diluted aqueous solutions. The biosorption performance, in terms of uptake, followed the sequence: Fe(III) > Cd(II) > Ni(II) > Cr(VI). The equilibrium data in batch systems were described by Langmuir, Sips and Redlich-Peterson model isotherms. The best fit for chromium and nickel was obtained with the Redlich-Peterson model and for cadmium the best fit was obtained with the Sips model. The presence of functional groups on the cell wall surface of the biomass that may interact with the metal ion was confirmed by FTIR. Kaolin samples have been fully characterized by chemical analyses. The results obtained are very promising for the removal of metal ions from effluents.
The area around the São Domingos copper mine (Iberian Pyrite Belt) is subject of great environmental concern as acid mine water occurs several kilometres downstream of the mine. In addition thousands of tons of mine waste are present. Erica australis and Erica andevalensis, which are two spontaneous plant species of this area, have been studied with regard to their potential for phytostabilization.Soils and plants from São Domingos and from a reference site (Moreanes) were analysed for soil characteristics, chemical element content in soils (total and AB-DTPA bioavailable fraction) and in plants. Superficial and seepage water as well as waste material leachates were also analysed. Seepage water showed high redox potential (mean 481 mV), high conductivity (mean 4337 μS cm − 1 ) and low pH values (mean 2.6), being classified as mining water. Leachate solutions possessed mainly high levels of Fe, Al and SO 4 2− . Soils in the mining area were highly contaminated in Pb, As and Sb. Locally also high values of Cu and Zn were encountered and the soil available fraction of the majority of the elements showed also quite high values.E. andevalensis grows in soils with pH between 3 and 4, whereas E. australis was only found in soils with pH above 3.5. Both species grow spontaneously in soils, highly contaminated with Pb, As and Sb. These plants, even in the non contaminated soils, are Al-tolerant and Mn-accumulators. In contaminated soils these species are also As-tolerant.Considering the tolerant behaviour in extreme environmental conditions, these Erica species may be of major importance for the recovery of the sulphide mining areas, with climate conditions compatible with its breeding and growing, by physical and chemical stabilization of contaminated soils and even waste materials.
The aim of this study is the preparation and characterization of new catalytic materials to be used in oxidation reactions through the recovery of heavy metals in wastewater. The recovery of Cr(III) and Cr(VI) from aqueous solutions by an Arthrobacter viscosus biofilm supported on NaY zeolite was investigated. Experiments were repeated without the bacteria for comparison purposes. The batch method has been employed, using solutions with chromium concentrations of 10 mg L À1 , 25 mg L À1 , 50 mg L À1 and 100 mg L À1. Cr(III) was easily removed from solution due to its positive charge which allows the entrapment in the framework zeolite by ion exchange. However, due to its anionic form Cr(VI) was only removed in the presence of the biofilm that performs its reduction to Cr(III), followed by ion exchange in the zeolite. The best uptake was achieved for initial concentration of 100 mg L À1 : 14 mg g À1 zeolite for Cr(III) by both systems and 3 mg g À1 zeolite for Cr(VI) by the zeolite with the bacterium biofilm. The modified zeolite samples have been fully characterized by surface analysis (XRD, XPS), chemical analyses (ICP-AES), spectroscopic method (FTIR) and microscopic analysis (SEM). The results show that the biofilm of A. viscosus supported on NaY zeolite is able to recover chromium from dilute solutions and the framework zeolite remains unchanged after chromium biosorption.
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