Advanced Materials Research Vol. 825

Abstract: 800x600 Mining waste disposal and treatment is one of the biggest environmental challenges that mining confront at present. A promising approach is the phytoremediation technology, where living plants are used to remove metals from impacted sites or to stabilize mine tailings. The aim of this work was to evaluate several plant species for phytoremediation of a mining waste from gold ores concentration plant in Andacollo, Neuquén-Argentina, to propose the execution of an environmental restoration plan in this area. For the forestation assays Pinus ponderosa, Pinus murrayana, Populus nigra species and a herbaceous plant, Festuca arundinacea, were selected. The tailings used in this study was physicochemically characterized and resulted to be non-potentially acid generating and presented very low organic matter and macronutrients contents. The sequential extraction showed that no metals were present in the water soluble fraction minimizing the risks of spreading heavy metals. Phytoremediation assay showed that all vegetable species could grow on the mine tailing. The dry vegetal biomass for F. arundinacea was only 28 % lower than the one obtained in the control soil. Pinus species and P. nigra presented high values of translocation factor only for Zn. These preliminary results suggest that the forestation of this tailing dam with Pinus species and F. arundinacea could be an adequate strategy to phytoremediate this particular area. Normal 0 21 false false false ES-AR X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Tabla normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman","serif";}

Abstract: The remediation of large heavy metal/radionuclide (HM/R) contaminated areas by conventional ex-situ techniques (excavation or chemical treatment/-stabilization) is expensive, and low cost strategies with a long-term stabilization effect of such sites are a task of next years research. Phytoremediation can be an alterative solution and sustainable technology since low treatment costs make it feasible even for such sites. Field scale investigation is applied to an area of the former uranium mining in East Thuringia, Germany. On this area, a low grade uranium ore leaching dump was situated, which was later removed during the remediation process of the site. Now, an underground remains that is slightly to moderately contaminated with heavy metals and radionuclides (HM/R) with restrictions of land use. Concepts for remediation of HM/R-contaminated sites and for the subsequent utilization of the HM/R-loaded plant residues are developed in a joint project. Plant experiments with Triticale, Helianthus annuus, Brassica juncea and Sorghum bicolor were performed revealing the influence of biological additives (mycorrhiza, HM-resistant streptomyces) and soil amendment strategies (increasing pH and organic matter) on biomass production and plant tolerance to heavy metals. The addition of mycorrhiza and streptomyces (MS) had a significant effect on biomass, and decreased the bioavailable parts of HM/R (e.g. Ni, Sr, U) in soil in comparison to untreated polluted soil with all studied plants. In lysimeter experiments it was figured out, that the different soil improvement strategies, addition of MS and of calcareous top soil (MIX) resulted in a reduction of the concentration of contaminants in the seepage water, as well as of the seepage water rates and loads, thus decreasing the risk of groundwater contamination. Finally, the processing of the heavy metal loaded plant residues was investigated by different methods. Fermentation experiments carried out with Solanum tuberosum and Secale cereale achieved good results compared with industrial standards. Remaining plant parts can be processed in a biogas process, or combusted. Fermentation sludges and combustion ashes act as sinks for HM/R. As results of the project, phytoremediation is a convenient method for the stabilization and remediation of large sites with slight to medium contaminations, and a further utilization of the plant residues by fermentation and biogas production is feasible.

Abstract: Solid waste from sulphuric acid production contains high concentrations of metals that are harmful if released to the environment. The purpose of this study was to evaluate the acid bioleaching of metals from a sample of pyritic ashes, consisting mainly of hematite. Bioleaching was tested in shake flasks and continuously stirred tank reactors (CSTR) inoculated with iron and sulphur oxidising acidophiles. Solubilisation of metals was mainly achieved through acid attack due to the formation of sulphuric acid by sulphur oxidising bacteria.

Abstract: Normal 0 21 false false false ES-CL X-NONE X-NONE MicrosoftInternetExplorer4 Cr(VI) is frequently used in several industrial activities, due to its uncontrolled spill this contaminant has generated serious damage to the environment: chromium hexavalent has a high oxidation potential and is able to go through biological membranes. As consequence Cr(VI)is described as a persistent contaminant with a high toxicity. It has been searched for alternative methods to remediate or detoxify environments contaminated with Cr(VI). The use of microorganisms able to absorb or reduce this type of contaminant is discerned as a potential biotool for remediation of metals-enriched industrial wastes. In order to isolate and identify environmental microorganisms with this capacity, we isolated a bacterium named LMA-2 with a selective pressure of 60 mM of Cr(VI) from contaminated marine sediment. In the morphologic analysis, this marine microorganism evidenced that corresponds to a Gram-positive cocci. This resistant bacterium has a minimal inhibitory concentration for Cr(VI) of 750 mM. The characterization and identification of this strain was made through 16S ribosomal RNA gene, this result revealed that it corresponds to Staphylococcus equorum. Assays using atomic absorption spectrophotometer (AAS) shows that this strain is able to ireduce the concentration of soluble Cr(VI) The capacity of this strain to remediate Cr(VI) was determined in 142.8 mg/L at 10 h of exposition. Our results showed the high resistance and the ability for Cr(VI) remediation by Staphylococcus equorum. These results suggest that this marine bacterium could be a prospect for future use as a biofilter for seabed marine environment decontamination. st1\:*{behavior:url(#ieooui) } /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Tabla normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin;}

Abstract: 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.

Abstract: 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.

Abstract: This paper focuses on the application of biotechnological stabilization of arsenic from (bio-) leaching operations. One of the latest applications of the Thioteq technology is arsenic immobilization. The Thioteq-scorodite biorecovery reactor is an aerobic system to immobilise arsenic in bio-scorodite crystals. In this patented process, biological arsenite oxidation, biological ferrous iron oxidation and crystallisation reactions are simultaneously taking place. Bio-scorodite crystals can be easily harvested by sedimentation due to their relative large size of up to 160 μm. This biogenic material is classified as non-hazardous due to its very low arsenic leaching rates. Furthermore, bioscorodite crystals resemble the colour, crystal morphology, iron and arsenic content, structural water of the mineral scorodite. The operational costs related to scorodite bio-crystallization can be reduced at least 50% compared to chemical precipitation because the use of biological reactions to induce the crystallization of scorodite and the good stability properties of the produced crystals. The Thioteq-scorodite process is a reliable cost effective solution to arsenic removal and immobilization by using biological processes. The stabilization of arsenic in the form of biologically produced scorodite is an attractive technology for the compact and safe immobilization of arsenic from medium to high concentrations of arsenic in acidic process streams.

Abstract: The objective of this work was to identify one bacterial consortium adapted to the cultivation in the presence of trivalent arsenic (AsIII). Samples were cultured in flasks containing modified Postgate C liquid medium (selective for sulfate-reducing bacteria, SRB). Six different As concentrations were used: 0.5, 1.0, 2.0, 4.0, 8.0 and 16 mg l^-1. The growth of sulfate reducing microorganisms was indirectly observed by the formation of an iron sulfide black precipitate and also by the Eh measures.100 ml aliquots of cultured media were centrifuged and stored at-20°C for DNA extraction by phenol/chloroform method. Universal primers 968F-GC 1392R (Bacteria domain) were used for 16S ribosomal DNA amplification. Microbial diversity was evaluated by denaturing gradient gel electrophoresis (DGGE). After DGGE analysis 7 different bands were selected, cut, sequenced and analyzed using the Ribosomal Database Project Release. Consortium microorganisms identified were: Pantoea agglomerans, Enterobacter sp, Citrobacter sp, Cupriavidus metallidurans, Ralstonia sp, Burkholderia cepacia and Bacillus sp. Thus the microbial consortium here identified is a good candidate for bioremediation of arsenic contaminated areas and effluents.

Abstract: This study aims to build and operate an experimental system to observe the metabolic activity of a mixed culture of SRB on removing sulphate and arsenic (AsIII). The experimental apparatus was operated semi-continuously. The synthetic medium utilized was modified Postgate C increased with a NaAsO₂ solution (As concentrations ranging from 2 to 8 mg/L). Powdered chicken feathers (PCF) was used as nutrient and solid support for microbial growth. It is a cheap waste material produced by poultry industry and it was previously studied for As biosorption. Growth parameters analyzed were pH, Eh, sulphate and As(III) concentration. After 6 months of operation, As was introduced into the system, initially 2mg.L^-1. The main results obtained are: pH changes were quit negligible, varying between 7 and 8, Eh decayed to a maximum of -400 eV, compatible with a reducing condition. Sulphate removal was of about 80%, and up to 90% of the arsenic was removed from the system. The methodology here presented is effective and innovative since arsenic is removed without any oxidation step. Considering the low cost of the waste material some operation costs may be reduced.

Abstract: Ouro Preto/MG/Brazil soils are rich in arsenic containing minerals that once solubilized may contaminate water or food. Arsenic (As) is toxic if ingested or inhaled. Microorganisms and organic matter plays an important role in the dynamics of As in soils and sediments affecting its mobilization. Aims: to study the mobility of arsenic in the presence of organic matter and sulfur reducing bacteria (SRB) and also to obtain some As resistant bacterial cultures. Materials: Soil samples were collected from abandoned gold mines named Old Mine, Chico Rei and Santa Rita. As content in solid samples were in a range of 465 to 1829 mg Kg^-1. Soil samples (5 g) were mixed with 35 ml of 2.5 M, CaCl₂, stirred (5 min) and allowed to rest at 21.0°C for 1, 30, 60, 90 and 120 days. Other set of experiments were prepared following the previous procedure with some modifications: (i) group 1, flasks with bacterial inoculum (4 ml) from an enrichment of 5 g of soil and 45 ml of liquid medium B Postgate, pH 7.0, incubated at 35°C under anaerobic conditions; (ii) group 2, flasks with (5 g) of organic matter with As (III) adsorptive capacity (powdered chicken feathers - PCF), and (iii) group 3, flasks containing bacterial inoculum and organic matter. Results: As solubility was inversely proportional to time and depends on Fe and Mn contents. The influence of microorganisms on As immobilization was more relevant than the presence of organic matter. Surprisingly, in some cases, As solubility enhanced in the presence of PCF besides its As adsorptive capacity. One microbial consortium adapted to the culturing at pH 5.0 was obtained and this is an interesting feature considering the acid pH of the studied arsenic soils. Indigenous bacteria phenotypically similar to SRB may contribute to As immobilization in natural or impacted environment.