• Resources Recycling
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• v.20 no.2
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• pp.30-44
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• 2011

This review describes the involvement of different microorganisms for the recovery of uranium from the ore. Mainly Acidithiobacillus forrooxidans, Acidithiobacillus thiooxidans and Leptospirillum ferrooxidans are found to be the most widely used bacteria in the bioleaching process of uranium. The bioleaching of uranium generally follows indirect mechanism in which bacteria provide the ferric iron required to oxidize $U^{4+}$. Commercial applications of bioleaching have been incorporated for extracting valuable metals, due to its favorable process economics and reduced environmental problems compared to conventional metal recovery processes such as smelting. At present the uranium is recovered through main bioleaching techniques employed by heap, dump and in situ leaching. Process development has included recognition of the importance of aeration of bioheaps, and improvements in stirred tank reactor design and operation. Concurrently, knowledge of the key microorganisms involved in these processes has advanced, aided by advances in molecular biology to characterize microbial populations.

• Journal of Soil and Groundwater Environment
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• v.21 no.1
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• pp.86-93
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• 2016

Fenton is the reaction using the OH· radicals generating by interaction between hydrogen peroxide and Fe²⁺ which can oxidize the contaminants. Fe²⁺ ions are oxidized to Fe³⁺ ions by reaction with H₂O₂ and formed OH· radicals. UV-Fenton process includes the additional reaction that generates the OH· radicals by photodegradation of H₂O₂. In methylorange (MO) decolourization experiment with UV-Fenton, optimal Fe²⁺: H₂O₂ ratio was obtained at 1 : 10. Based on the obtained condition (H₂O₂= 10mM, Fe²⁺ = 1 mM) with/without UV-fenton experiment was carried out. Removal efficiency and sludge production were measured at 30 min. The case of w/o UV irradiation and only H₂O₂ was hardly treated and only Fe²⁺ showed 65% removal owing to coagulation. When UV-Fenton process in optimal ratio (Fe²⁺: H₂O₂ = 1 : 10), UV irradiation showed better removal efficiency than of w/o UV irradiation. Also, MO decolourization was a function of the hydrogen peroxide concentration (x₁), Fe²⁺:H₂O₂ ratio (x₂), and numbers of UV lamp (x₃) from the application of the response surface methodology. Statistical results showed the order of significance of the independent variables to be hydrogen peroxide concentration > numbers of UV l amp > Fe²⁺: H₂O₂ ratio.

• Journal of the Korean Applied Science and Technology
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• v.35 no.4
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• pp.1013-1030
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• 2018

Biodiesel is a fuel produced in the form of a fatty acid methyl ester by using raw materials such as animal fat, vegetable oil and its by-products, and is being seen as a biofuel that can replace petroleum energy. However unsaturated fatty acid methyl esters in biodiesel causes to oxidize during storage and distribution, resulting in poor fuel quality and corrosion of vehicle engine components. In this study, the influence of quality and oxidation characteristics of biodiesel on the oxidation stability is investigated and the evaluation method related it is described. We also propose a method to improve the drawback of oxidation stability in biodiesel.

• Journal of Microbiology and Biotechnology
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• v.28 no.12
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• pp.2057-2063
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• 2018

Laccases can oxidize a variety of phenolic and non-phenolic substrates including synthetic dyes. In this research, a laccase gene Lcc9 from Laccaria bicolor was chemically synthesized and optimized to heterogeneous expression in Pichia pastoris and Arabidopsis thaliana. The properties of recombinant laccase expressed by P. pastoris were investigated. The laccase activity was optimal at 3.6 pH and $40^{\circ}C$. It exhibited $K_m$ and $V_{max}$ values of $0.565mmol\;l^{-1}$ and $1.51{\mu}mol\;l^{-1}\;min^{-1}$ for ABTS respectively. As compared with untransformed control plants, the laccase activity in crude extracts of transgenic lines exhibited a 5.4 to 12.4-fold increase. Both laccases expressed in transgenic P. pastoris or A. thaliana could decolorize crystal violet. These results indicated that L. bicolor laccase gene may be transgenically exploited in fungi or plants for dye decolorization.

• Microbiology and Biotechnology Letters
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• v.47 no.1
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• pp.116-124
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• 2019

The rapid development of the poultry industry has led to the production of large amounts of manure, which produce substances like hydrogen sulfide ($H_2S$) that contribute to odor pollution. $H_2S$ is a highly undesirable gas component and its removal from the environment is therefore necessary. Sulfur-oxidizing bacteria (SOB) are widely known to remove contaminating $H_2S$ due to their ability to oxidize reduced sulfur compounds. In this study, three potential SOB (designated AH18, AH25, and AH28) that were previously isolated from a hot spring in Malaysia were identified by 16S rRNA gene analysis. Laboratory-scale biological deodorization experiments were conducted to test the performance of the three isolates-in the form of pure or mixed cultures, with the cells immobilized onto alginate as a carrier-in reducing the $H_2S$ from chicken manure. On the basis of 16S rRNA phylogenetic analysis, isolate AH18 was identified as Pseudomonas sp., whereas isolates AH25 and AH28 were identified as Achromobacter sp. The most active deodorizing isolate was AH18, with an $H_2S$ reduction rate of 74.7% (p < 0.05). Meanwhile, the reduction rates for isolates AH25 and AH28 were 54.2% and 60.8% (p > 0.05), respectively. However, the $H_2S$ removal performance was enhanced in the mixed culture, with a reduction rate of 81.9% (p < 0.05). In conclusion, the three potential SOB isolates were capable of reducing the $H_2S$ from chicken manure in the form of a pure culture immobilized on alginate, and the reduction performance was enhanced in the mixed culture.

• The Plant Pathology Journal
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• v.35 no.3
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• pp.234-242
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• 2019

Thirty-four strains of bacteria were isolated from Phellodendron amurense. Using Nectria haematococca as an indicator strain, the best strain, B18, was obtained by the growth rate method. The morphological, physiological and biochemical characteristics of strain B18 and its 16S DNA gene sequence were identified, and the biocontrol effect of strain B18 was assessed in pot and field tests, as well as in a field-control test. Drilling methods were used to determine the antibacterial activity of metabolites from strain B18 and their effects on the growth of pathogen mycelia and spores. The best bacteriostatic rate was 85.4%. B18 can hydrolyse starch and oxidize glucose but does not produce gas; a positive result was obtained in a gelatine liquefaction test. According to 16S DNA gene sequencing, strain B18 is Bacillus methylotrophicus (GenBank accession number: MG457759). The results of pot and field-control trials showed 98% disease control when inoculating $10^8cfu/ml$ of the strain. The disease control effect of the B18 culture liquid (concentrations of $10^8$, $2{\times}10^6$, $10^6$, $5{\times}10^5$ and $2.5{\times}10^5cfu/ml$) in the field-control test was higher than 80%, and the cure rate of the original delivery solution was 96%. Therefore, in the practical forestry production, a $2.5{\times}10^5cfu/ml$ culture liquidshould be applied in advance to achieve good control effects.

• Korean Journal of Chemical Engineering
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• v.35 no.11
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• pp.2172-2184
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• 2018

The production of isophthalic acid (IPA) from the oxidation of m-xylene (MX) by air is catalyzed by $H_3PW_{12}O_{40}$ (HPW) loaded on carbon and cobalt. We used $H_2O_2$ solution to oxidize the carbon to improve the catalytic activity of HPW@C catalyst. Experiments reveal that the best carbon sample is obtained by calcining the carbon at $700^{\circ}C$ for 4 h after being impregnated in the 3.75% $H_2O_2$ solution at $40^{\circ}C$ for 7 h. The surface characterization displays that the $H_2O_2$ modification leads to an increase in the acidic groups and a reduction in the basic groups on the carbon surface. The catalytic capability of the HPW@C catalyst depends on its surface chemical characteristics and physical property. The acidic groups play a more important part than the physical property. The MX conversion after 180 min reaction acquired by the HPW@C catalysts prepared from the activated carbon modified in the best condition is 3.81% over that obtained by the HPW@C catalysts prepared from the original carbon. The IPA produced by the former is 46.2% over that produced by the latter.

• Journal of Soil and Groundwater Environment
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• v.25 no.4
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• pp.77-86
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• 2020

Persulfate-based advanced oxidation processes (AOPs) can oxidize various organic pollutants. In this study, persulfate/Fe(II) system was utilized in phenol removal, and the effect of various organic and inorganic chelators on Fe(II)-medicated persulfate activation was investigated. The feasibility of persulfate/Fe(II)/chelator in cleanup of phenol-contaminated sediment was confirmed through toxicity assessment. In persulfate/Fe(II) conditions, the rate and extent of phenol removal increased in proportion to persulfate concentration. In chelator injection condition, the rate of phenol removal was inversely proportional to chelator concentration when it was injected above optimum ratio. Thiosulfate showed greater chelation tendency with persulfate than citrate and interfered with persulfate access to Fe(II), making the latter a more suitable chelator for enhancing persulfate activation. In contaminated clay sediment condition, 100% phenol removal was obtained within an hour without chelator, with the removal rate increased up to four times as compared to the rate with chelator addition. A clay sediment toxicity assessment at persulfate:Fe(II):phenol 20:10:1 ratio indicated 71.3% toxicity reduction with 100% phenol removal efficiency. Therefore, persulfate/Fe(II) system demonstrated its potential utility in toxicity reduction and cleanup of organic contaminants in sediments.

• Journal of Korean Society of Water and Wastewater
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• v.36 no.3
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• pp.167-175
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• 2022

The degradation of EBT (Eriochrome Black T) in an aqueous solution was investigated at various values of pH, Ferrate (VI) dosage, initial concentration, aqueous solution temperature. The maximum degradation efficiency was 95.42% at pH 7 and in that experimental condition, the kapp value was 872.87 M-1s-1. The degradation efficiency was proportional to the dosage of Ferrate (VI). Also, the initial rate constant of EBT degradation increased with decreasing of the EBT initial concentration. In addition, the degradation rate of EBT was increased from 74.04% to 95.42% when the temperature in the aqueous solution was increased from 10℃ to 45℃. The activation energy value was 11.9 kJ/mol for EBT degradation. Overall, the results of the degradation experiment showed that Ferrate (VI) could effectively oxidize the EBT in the aqueous phase.

• Journal of the Korean earth science society
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• v.34 no.7
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• pp.681-692
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• 2013

We aimed to evaluate the effectiveness of the Giggenbach bottle method and develop the related pretreatment and analytical methods using artificial fumarolic gases. The artificial fumarolic gases were generated by mixing $CO_2$, CO, $H_2S$, $SO_2$, $H_2$, and $CH_4$ gas streams with a $N_2$ stream sparged through an acidic medium containing HCl and HF, with their compositions varied by adjusting the gas flow rates. The resultant fumarolic gases were collected into an evacuated bottle partially filled with a NaOH absorption solution. While non-condensible gases such as CO, $H_2S$, and $CH_4$ accumulated in the headspace of the bottle, acidic components including $CO_2$, $SO_2$, HCl, and HF that were dissolved into the alkaline solution. Like other acidic components, $H_2S$ also dissolved into the solution, but it reacted with dissolved $Cd^{2+}$ to precipitate as CdS when $Cd(CH_3COO)_2$ was added. The non-condensible gases were analyzed on a gas chromatography. Then, CdS precipitates were separated from the alkaline solution by filtration, and they were pretreated with $H_2O_2$ to oxidize CdS-bound sulfide into sulfate. In addition, a portion of the solution was also pretreated with $H_2O_2$ to oxidize sulfite to sulfate. Following the pretreatment, the resultant samples were analyzed for $SO_4^{2-}$, $Cl^-$ and $F^-$ on an ion chromatography. In the meanwhile, dissolved $CO_2$ was analyzed on a total organic carbon-inorganic carbon analyzer without such pretreatment. According to our experimental results, the measured concentrations of the fumarolic gases were shown to be proportional to the gas flow rates, indicating that the Giggenbach bottle method is adequate for monitoring volcanic gas. The pretreatment and analytical methods employed in this study may also enhance the accuracy and reproducibility of the Giggenbach bottle method.