• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.04a
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• pp.260-265
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• 2004

Acid mine drainage(AMD) is one of the most serious environmental concerns associated with the mining industry around the world. The objective of this study is to assess the potential of sewage sludge as a carbon source for sulfate reducing bacteria and waste lime and steel slag as a neutralize agent for acid mine drainage bioremediation for use in permeable reactive materials. The study was performed using synthetic AMD in six column experiments. The effluent solution was systematically analysed throughout the experiments. The results of the study indicated that sewage sludge, waste lime and steel slag were the most effective for the AMD treatment as a permeable reactive materials.

• Proceedings of the Korean Environmental Health Society Conference
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• 2001.04a
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• pp.91-92
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• 2001

• Journal of Microbiology and Biotechnology
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• v.18 no.11
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• pp.1809-1818
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• 2008

Biotechnological treatment of sulfate- and metal-ions-containing acidic wastewaters from mining and metallurgical activities utilizes sulfate-reducing bacteria to produce sulfide that can subsequently precipitate metal ions. Reducing sulfate at a low pH has several advantages above neutrophilic sulfate reduction. This study describes the effect of sulfide removal on the reactor performance and microbial community in a high-rate sulfidogenic gas-lift bioreactor fed with hydrogen at a controlled internal pH of 5. Under sulfide removal conditions, 99% of the sulfate was converted at a hydraulic retention time of 24 h, reaching a volumetric activity as high as 51 mmol sulfate/l/d. Under nonsulfide removal conditions, <25% of the sulfate was converted at a hydraulic retention time of 24 h reaching volumetric activities of <13 mmol sulfate/l/d. The absence of sulfide removal at a hydraulic retention time of 24 h resulted in an average $H_2S$ concentration of 18.2 mM (584 mg S/I). The incomplete sulfate removal was probably due to sulfide inhibition. Molecular phylogenetic analysis identified 11 separate 16S rRNA bands under sulfide stripping conditions, whereas under nonsulfide removal conditions only 4 separate 16S rRNA bands were found. This shows that a less diverse population was found in the presence of a high sulfide concentration.

• Biomaterials Research
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• v.22 no.4
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• pp.328-336
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• 2018

Background: Biogenic fabrication of silver nanoparticles from naturally occurring biomaterials provides an alternative, eco-friendly and cost-effective means of obtaining nanoparticles. It is a favourite pursuit of all scientists and has gained popularity because it prevents the environment from pollution. Our main objective to take up this project is to fabricate silver nanoparticles from lichen, Usnea longissima and explore their properties. In the present study, we report a benign method of biosynthesis of silver nanoparticles from aqueous-ethanolic extract of Usnea longissima and their characterization by ultraviolet-visible (UV-vis), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) analyses. Silver nanoparticles thus obtained were tested for antimicrobial activity against gram positive bacteria and gram negative bacteria. Results: Formation of silver nanoparticles was confirmed by the appearance of an absorption band at 400 nm in the UV-vis spectrum of the colloidal solution containing both the nanoparticles and U. longissima extract. Poly(ethylene glycol) coated silver nanoparticles showed additional absorption peaks at 424 and 450 nm. FTIR spectrum showed the involvement of amines, usnic acids, phenols, aldehydes and ketones in the reduction of silver ions to silver nanoparticles. Morphological studies showed three types of nanoparticles with an abundance of spherical shaped silver nanoparticles of 9.40-11.23 nm. Their average hydrodynamic diameter is 437.1 nm. Results of in vitro antibacterial activity of silver nanoparticles against Staphylococcus aureus, Streptococcus mutans, Streptococcus pyrogenes, Streptococcus viridans, Corynebacterium xerosis, Corynebacterium diphtheriae (gram positive bacteria) and Escherichia coli, Klebsiella pneuomoniae and Pseudomonas aeruginosa (gram negative bacteria) showed that it was effective against tested bacterial strains. However, S. mutans, C. diphtheriae and P. aeruginosa were resistant to silver nanoparticles. Conclusion: Lichens are rarely exploited for the fabrication of silver nanoparticles. In the present work the lichen acts as reducing as well as capping agent. They can therefore, be used to synthesize metal nanoparticles and their size may be controlled by monitoring the concentration of extract and metal ions. Since they are antibacterial they may be used for the treatment of bacterial infections in man and animal. They can also be used in purification of water, in soaps and medicine. Their sustained release may be achieved by coating them with a suitable polymer. Silver nanoparticles fabricated from edible U. longissima are free from toxic chemicals and therefore they can be safely used in medicine and medical devices. These silver nanoparticles were stable for weeks therefore they can be stored for longer duration of time without decomposition.

• Journal of the Korea Organic Resources Recycling Association
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• v.4 no.1
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• pp.13-21
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• 1996

For treating tannery wastewater containing high sulfate and heavy metals, test was performed to assess their performance, competition between SRB (sulfate reducing bacteria) and MPB (methane producing bacteria), and the activity of MPB according to change of chromium concentrations. COD removal efficiency was above 70% at VLR (volumetric loading rate) of 2.0 gCOD/I.day and HRT (hydraulic retention time) of 18hrs at $35^{\circ}C$. In the competition between SRB and MPB, about 15% of the removed COD was utilized by SRB in the begining, but it became 43% at the end. It indicated that MPB was strongly suppressed by the occurrence of significant sulfate reduction since a large electron flow was uptaken by SRB. For the entire experiment, removal efficiencies of chromium concentration were more than 90%. Despite high removal efficiencies of chromium concentration, performance of reactor did not change significantly during the experimental periods. Expecially, chromium (III) is tannery wastewater is less toxic than chromium (VI).

• Advances in nano research
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• v.6 no.1
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• pp.81-92
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• 2018

Biosynthesis of nanoparticles has acquired particular attention due to its economic feasibility, low toxicity and simplicity of the process. Extracellular synthesis of nanoparticles by bacteria and fungi has been stated to be brought about by enzymes and other reducing agents that may be secreted in the culture medium. The present study was carried out to determine the underlying mechanisms of extracellular silver nanoparticle synthesis by Pseudomonas hibiscicola isolated from the effluent of an electroplating industry in Mumbai. Synthesized nanoparticles were characterized by spectroscopy and electron microscopic techniques. Protein profiling studies were done using Sodium Dodecyl Sulphate Polyacrylamide Gel Electrophoresis (1D-SDS PAGE) and subjected to identification by Mass Spectrometry. Characterization studies revealed synthesis of 50 nm nanoparticles of well-defined morphology. Total protein content and SDS PAGE analysis revealed a reduction of total protein content in test (nanoparticles solution) samples when compared to controls (broth supernatant). 45.45% of the proteins involved in the process of nanoparticle synthesis were identified to be oxidoreductases and are thought to be involved in either reduction of metal ions or capping of synthesized nanoparticles.

• Economic and Environmental Geology
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• v.56 no.4
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• pp.421-433
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• 2023

The final disposal of spent nuclear fuel(SNF) from nuclear power plants takes place in a deep geological repository. The metal canister encasing the SNF is made of cast iron and copper, and is engineered to effectively isolate radioactive isotopes for a long period of time. The SNF is further shielded by a multi-barrier disposal system comprising both engineering and natural barriers. The deep disposal environment gradually changes to an anaerobic reducing environment. In this environment, sulfide is one of the most probable substances to induce corrosion of copper canister. Stress-corrosion cracking(SCC) triggered by sulfide can carry substantial implications for the integrity of the copper canister, potentially posing a significant threat to the long-term safety of the deep disposal repository. Sulfate can exist in various forms within the deep disposal environment or be introduced from the geosphere. Sulfate has the potential to be transformed into sulfide by sulfate-reducing bacteria(SRB), and this converted sulfide can contribute to the corrosion of the copper canister. Bentonite, which is considered as a potential material for buffering and backfilling, contains oxidized sulfate minerals such as gypsum(CaSO4). If there is sufficient space for microorganisms to thrive in the deep disposal environment and if electron donors such as organic carbon are adequately supplied, sulfate can be converted to sulfide through microbial activity. However, the majority of the sulfides generated in the deep disposal system or introduced from the geosphere will be intercepted by the buffer, with only a small amount reaching the metal canister. Pyrite, one of the potential sulfide minerals present in the deep disposal environment, can generate sulfates during the dissolution process, thereby contributing to the corrosion of the copper canister. However, the quantity of oxidation byproducts from pyrite is anticipated to be minimal due to its extremely low solubility. Moreover, the migration of these oxidized byproducts to the metal canister will be restricted by the low hydraulic conductivity of saturated bentonite. We have comprehensively analyzed and summarized key research cases related to the presence of sulfates, reduction processes, and the formation and behavior characteristics of sulfides and pyrite in the deep disposal environment. Our objective was to gain an understanding of the impact of sulfates and sulfides on the long-term safety of high-level radioactive waste disposal repository.

• Journal of the Mineralogical Society of Korea
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• v.24 no.3
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• pp.217-224
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• 2011

Removal of dissolved selenium by D. michiganensis, a iron-reducing bacterium, and effects of dissolved metal elements such as iron, sulfate, and copper were investigated. Selenide that was reduced from selenite (2 mM) by D. michiganensis was gradually removed from the aqueous medium. As the reduced selenide was combined with aqueous iron, it was precipitated as a nanoparticulate iron-selenide. Sulfate and copper negatively affected the microbial selenite reduction, and the copper was especially toxic to the bacterium, inhibiting a microbial removal of dissolved selenite. These results show that it should be carefully biotreated for a selenium-contaminated site considering in situ sulfate or copper distribution and concentration. Consequently, the formation of iron-selenide by bacteria will be an important measure for preventing a long-distance migration of selenium in the subsurface environments.

• Economic and Environmental Geology
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• v.42 no.5
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• pp.471-477
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• 2009

An experimental removal of dissolved uranium (U) exsiting as uranyl ion (${UO_2}^{2+}$) was carried out using Shewanella p., iron-reducing bacterium. By the microbial reductive reaction, initial U concentration ($50{\mu}M$) was constantly decreased, and most U were removed from solution after 2 weeks. Major mechanism that U was removed from the solution was adsorption, precipitation and mineralization on the microbe surface. Under the transmission electron microscopy, the U adsorbed on the microbe was observed as being crystallized and eventually enlarged to several ${\mu}m$ sizes of minerals by combining with individual microbes and organic exudates. It seems that such U growth and mineralization on the microbial surface could affect the U behavior in a radioactive waste disposal site. Thus, the biogechemical reaction of metal-reducing bacteria observed in this experiment could give an affirmative measure that the microbial activity may retard U movement in subsurface environment.

• Journal of Korea Soil Environment Society
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• v.2 no.1
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• pp.45-50
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• 1997

The change of industrial structure has brought the sharp declination of mine products, and has made many mines closed, which results in environmental pollution by untreated acid mine drainage(AMD). AMD with low pH and high concentration of heavy metals could severely destroy the ecosystem. Many researches have been carried out for the treatment of AMD. In this study, we have treated AMD with oak compost, mushroom compost, sludge cake and cow manure which usually used in AMD treatment systems, and compared the capability of each organic matter. Cow manure and oak compost have been most effective among 4 organic materials. Oak compost removed the heavy metals by ion exchange between Ca-rich particles and soluble heavy metal ions. It also captured the heavy metals using bound functional groups like -OH and -COO-. Sulfate reducing bacteria existing in the cow manure removed effectively heavy metals by producing metal sulfide compound. Therefore, it is effective to use both organic materials in mixture on the treatment of AMD.