Alena Luptáková

Remediation of Acid Mine Drainage by Means of Biological and Chemical Methods

The formation and treatment of acid mine drainage is the biggest environmental problems relating to mining and processing activities in the worldwide. Various methods are used for the sulphates and heavy metals removal from acid mine drainage in the world, but any of them is universal. Main aim of the paper is the interpretation of chemical and biological-chemical methods for the metals and sulphates removal from acid mine drainage sample. The chemical method is based on the sulphates precipitation by the sodium aluminate in combination with the calcium hydrate. The biological-chemical method is based on the application of sulphate-reducing bacteria (SRB). A sample of acid mine drainage from the abandoned and flooded deposit of Smolník located in Slovak republic was used in this study.

Testing Silica Fume-Based Concrete Composites under Chemical and Microbiological Sulfate Attacks

Current design practices based on descriptive approaches to concrete specification may not be appropriate for the management of aggressive environments. In this study, the durability of cement-based materials with and without the addition of silica fume, subjected to conditions that leach calcium and silicon, were investigated. Chemical corrosion was simulated by employing various H2SO4 and MgSO4 solutions, and biological corrosion was simulated using Acidithiobacillus sp. bacterial inoculation, leading to disrupted and damaged surfaces; the samples’ mass changes were studied following both chemical and biological attacks. Different leaching trends were observed via X-ray fluorescence when comparing chemical with biological leaching. Lower leaching rates were found for concrete samples fortified with silica fume than those without silica fume. X-ray diffraction and scanning electron microscopy confirmed a massive sulfate precipitate formation on the concrete surface due to bacterial exposure.

Application of Granulated Blast Furnace Slag in Cement Composites Exposed to Biogenic Acid Attack

The deterioration of cement-based materials used for the civil infrastructure has led to the realization that cement-based materials, such as concrete, must be improved in terms of their properties and durability. Leaching of calcium ions increases the porosity of cement- based materials, consequently resulting in a negative effect on durability since it provides an entry for aggressive harmful ions, causing corrosion of concrete. The use supplementary cementing composite materials have been reported to improve the resistance of concrete to deterioration by aggressive chemicals. The paper is focused on the investigation of the influence of biogenic acid attack on the cement composites affected by bacteria Acidithiobacillus thiooxidans. The concrete specimens with 65 wt. % addition of antimicrobial activated granulated blast furnace slag as durability increasing factor as well as without any addition were studied. The experiments proceeded during 150 days under model laboratory conditions. The pH values and chemical composition of leachates were measured after each 30- day cycle. The calcium and silicon contents in leachates were evaluated using X - ray fluorescence method (XRF). Summarizing the results, the 65% wt. addition of antimicrobial activated granulated blast furnace slag was not confirmed to be more resistant.

Bio-Corrosion Resistance of Concretes Containing Antimicrobial Ground Granulated Blastfurnace Slag BIOLANOVA and Novel Hybrid H-CEMENT

The article deals with the study of biocorrosion of concretes by sulphuric acid induced by oxidizing bacteria Acidithiobacillus thiooxidans. The concretes were prepared from reference cement CEM I 42,5 N, the mixtures of CEM I 42,5 N and antimicrobial ground granulated blastfurnace slag BIOLANOVA (GGBS) (with amount of GGBS 65 mass % - CEM III/A 32,5 N, 75 mass % - CEM III/B 32,5 N, 85 mass % - CEM III/C 32,5 N a 95 mass % - CEM III/C 32,5 N) and novel hybrid cement H-CEMENT (HC). The experiments were carried out in model laboratory conditions at 30 °C during 91 days. The degree of deterioration of concrete samples has been studied on the base of the pH changes of leachate, the concentrations of selected ions such as S, Ca and Si and the mass changes. It has been clearly confirmed, that in the presence of bacteria, the pronounced degradation of the samples occurred with exception of HC sample, which behaviour proved differences to the other samples. The HC concrete possessed more alkali leachate in comparison with the others. The concentration of sulphur S in leachate was increased by metabolic activity of bacteria due to biogenic H2SO4 formation. The increase of S concentration acidified leachate and so promoted leaching next substances from the samples. The concentration of silicon Si in leachate was promoted by metabolic activity of bacteria, as well. The development of Ca leaching concentration has been similar at all composite samples as in the case of reference CEM I 42,5 N concrete, however the smallest portion of leached Ca has been determined at HC concrete. The Ca leaching concentration has been increasing with the amount of GGBS being added to the composite CEM III concretes. The different tendency has been also observed at the HC samples in regards to the mass changes. The increase in mass has been measured at all concrete samples with exception of HC concrete, at which the mass decrease has been found out. The results confirmed the resistance of the concrete composite samples containing GGBS and HC to the sulphate attack and the HC sample showed the highest resistance to the sulphate biocorrosion.

Performance of Fiber-cement Boards in Biogenic Sulphate Environment

The paper presents the results of the study of selected fiber-cement boards parameters influenced by sulphur-oxidising (Acidithiobacillus thiooxidans) and sulphur-reducing bacteria (Desulfovibrio desulfuricans) attack. The experiments proceeded during 80 days under laboratory model conditions. The surface changes, chemical composition and pH of leachates as well as weight changes were investigated. The more extensive leaching of silicon and calcium ions from the cement matrix was confirmed under bacteria influence. The pH of liquid media has been settled to 7 and 9 for Acidithiobacillus thiooxidans and Desulfovibrio desulfuricans, respectively after initial increasing. Very small decrease in weight of samples in range 0.001 - 0.93 % was measured after the experiments.

Investigation of the Precipitates on the Concrete Surface due to Sulphate Exposure

Abstract The aim of this study is to investigate the durability of cement-based materials subjected to the effects of sulphuric acid in terms of surface deterioration. Damaged concrete surfaces and the samples’ mass changes were studied during 270-day simulation of both chemical and biological attacks. Chemical corrosion was simulated by sulphuric acid with pH of 3.0 and 4.0, respectively, while biological corrosion was simulated by activity of bacteria Acidithiobacillus thiooxidans. XRD and SEM analyses confirmed a massive sulphate precipitate formation on the concrete surface due to chemical and biological sulphate corrosion.

Sulphates Removal from Acid Mine Drainage

Acid mine drainage (AMD) are a worldwide problem leading to ecological destruction in river basins and the contamination of water sources. AMD are characterized by low pH and high content of heavy metals and sulphates. In order to minimize negative impacts of AMD appropriate treatment techniques has to be chosen. Treatment processes are focused on neutralizing, stabilizing and removing pollutants. From this reason efficient and environmental friendly methods are needed to be developed in order to reduce heavy metals as well as sulphates. Various methods are used for remediation of acid mine drainage, but any of them have been applied under commercial-scale conditions. Their application depends on geochemical, technical, natural, financial, and other factors. The aim of the present work was to interpret the study of biological methods for sulphates removal from AMD out-flowing from the shaft Pech of the deposit Smolmk in Slovak Republic. In the experimental works AMD were used after removal of heavy metals by precipitation and sorption using the synthetic sorbent Slovakite. The base of the studied method for the sulphates elimination was the anaerobic bacterial sulphate reduction using sulphate-reducing bacteria (SRB) genera Desulfovibrio. SRB represent a group of bacteria that uses sulphates as a terminal electron acceptor for their metabolism. These bacteria realize the conversion of sulphate to hydrogen sulphide under anaerobic conditions. For the purposes of experiments a few variants of the selective medium DSM-63 culture media were used in term of the sulphates and sodium lactate contents in the selective medium as well as sulphates in the studied AMD.

Deterioration of Cement Composites with Silica Fume Addition due to Chemical and Biogenic Corrosion Processes

The paper is aimed at comparative study of resistance of Portland cement composites with addition of silica fume as durability increasing factor in various aggressive environments (sulphuric acid with pH 4, the medium of activated bacteria and the cultivating medium without bacteria) during 150 days under model laboratory conditions. Experimental studies confirmed: the leaching of silicon ions calculated to 1 g of concrete sample affected with bacteria Acidithiobacillusthiooxidans was 2.5 times lower (31.78 mg/g of sample) for concrete sample with silica fume addition comparing to concrete sample of ordinary CEM I Portland cement without any additives (82.98 mg/g of sample). The highest concentration of calcium ions released (60.808 mg/g of sample) was observed for reference sample without silica fume addition placed in the cultivating medium. Silica fume based concrete samples were found to have better performance in terms of calcium ions leaching for all environments and silicon ions leaching.

Bacterial Reduction Of Barium Sulphate By Sulphate-Reducing Bacteria

Abstract Acid mine drainage (AMD) is a worldwide problem leading to contamination of water sources. AMD are characterized by low pH and high content of heavy metals and sulphates. The barium salts application presents one of the methods for the sulphates removing from AMD. Barium chloride, barium hydroxide and barium sulphide are used for the sulphates precipitation in the form of barium sulphate. Because of high investment costs of barium salts, barium sulphide is recycled from barium sulphate precipitates. It can be recycled by thermic or bacterial reduction of barium sulphate. The aim of our study was to verify experimentally the possibility of the bacterial transformation of BaSO4 to BaS by sulphate-reducing bacteria. Applied BaSO4 came from experiments of sulphates removal from Smolnik AMD using BaCl2.

Application of Bacterially Produced Hydrogen Sulphide for Selective Precipitation of Heavy Metals

The generation of acid mine drainage (AMD) and its discharge into the environment surrounding abandoned mines is likely to cause serious environmental pollution. Numerous techniques are available for neutralization and removal of metals and sulphates from AMD. One of the best available technologies for the removal of metals from AMD is the application of the sulphate-reducing bacteria (SRB). This process is based on the production of biogenic hydrogen sulphide by SRB, which consequently reacts with metal ions in the water forming sparingly soluble metal sulphides. The main objective of this work was to study the process of the heavy metals precipitation from AMD by bacterially produced hydrogen sulphide combined with intermediate steps of metals precipitation by sodium hydroxide at various pH values. The experiments were conducted with AMD coming from the abandoned and flooded deposit of Smolnik (Slovak Republic). This process is able to sequentially precipitate Cu2+, Zn2+ and Fe3+ in the form of sulphides, Al3+, Fe2+ and Mn2+ in the form of hydroxides.