• Journal of Microbiology and Biotechnology
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• v.26 no.3
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• pp.511-520
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• 2016

The most energy-demanding step of wastewater treatment is the aeration-dependent elimination of organic carbon. Microbial fuel cells (MFCs) offer an alternative strategy in which carbon elimination is conducted by anaerobic microorganisms that transport respiratory electrons originating from carbon oxidation to an anode. Hence, chemical energy is directly transformed into electrical energy. In this study, the use and stability of barcode-containing exoelectrogenic model biofilms under non-axenic wastewater treatment conditions are described. Genomic barcodes were integrated in Shewanella oneidensis, Geobacter sulfurreducens, and G. metallireducens. These barcodes are unique for each strain and allow distinction between those cells and naturally occurring wild types as well as quantification of the amount of cells in a biofilm via multiplex qPCR. MFCs were pre-incubated with these three strains, and after 6 days the anodes were transferred into MFCs containing synthetic wastewater with 1% wastewater sludge. Over time, the system stabilized and the coulomb efficiency was constant. Overall, the initial synthetic biofilm community represented half of the anodic population at the end of the experimental timeline. The part of the community that contained a barcode was dominated by G. sulfurreducens cells (61.5%), while S. oneidensis and G. metallireducens cells comprised 10.5% and 17.9%, respectively. To the best of our knowledge, this is the first study to describe the stability of a synthetic exoelectrogenic consortium under non-axenic conditions. The observed stability offers new possibilities for the application of synthetic biofilms and synthetically engineered organisms fed with non-sterile waste streams.

• Advances in environmental research
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• v.6 no.2
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• pp.127-137
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• 2017

Cotton is the major fiber crop in Pakistan that accounts for 2% of total national gross domestic product (GDP). After picking of cotton, the dry stalks are major organic waste that has no fate except burning to cook food in villages. Present research focuses use of cotton stalks as feedstock for biochar production, its characterization and effects on soil characteristics. Dry cotton stalks collected from agricultural field of Bahauddin Zakariya University, Multan, Pakistan were combusted under anaerobic conditions at $450^{\circ}C$. The physicochemical analysis of biochar and cotton stalks show higher values of % total carbon, phosphorus and potassium concentrations in biochar as compared to cotton stalks. The concentration of nitrogen was decreased in biochar. Similarly biochar had greater values of fixed carbon that suggest its role for carbon sequestration and as a soil amendment. The fourier transformation infrared spectroscopic spectra (FTIR) of cotton stalks and biochar exposed more acidic groups in biochar as compared to cotton stalks. The newly developed functional groups in biochar have vital role in increasing surface properties, cation exchange capacity, and water holding capacity, and are responsible for heavy metal remediation in contaminated soil. In a further test, results show increase in the water holding capacity and nutrient retention by a sandy soil amended with biochar. It is concluded that cotton stalks can be effectively used to prepare biochar.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.10
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• pp.787-793
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• 2015

In response to the growing interest in supercritical carbon dioxide ($S-CO_2$) power cycle technology because of its potential enhancement in compactness and efficiency, the $S-CO_2$ cycles have been studied intensively in the fields of nuclear power, concentrated solar power (CSP), and fossil fuel power generation. Despite this interest, there are relatively few studies on waste heat recovery applications. In this study, the $S-CO_2$ cycle that has a split flow with preheating was modeled and simulated. The variation in the power was investigated with respect to the changes in the value of a design parameter. Under the simulation conditions considered in this study, it was confirmed that the design parameter has an optimal value that can maximize the power in the $S-CO_2$ power cycle that has a split flow with preheating.

• Journal of the Korean Society of Food Science and Nutrition
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• v.30 no.2
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• pp.344-349
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• 2001

The removal of chlorine from aqueous solutions on dried Chlorella vulgaris(DCV) and green tea powder(GTP) were investigated as a function of contact time, pH and initial chlorine concentration. Removal by DCV and GTP reached equilibrium after 3hrs and 0.5hr, respectively. Optimum removal pH values of DCV and GTP were determined as above 10. Both Langmuir and Freundlich adsorption models were suitable for describing the short-term removal of chlorine by DCV and GTP. According to Langmuir adsorption isotherms the maximum removal capacity of DCV (2.75mg $Cl_2/mg$) was nearly two times greater than those of GTP (1.53mg $Cl_2/mg$) and activated carbon (1.47mg $Cl_2/mg$). These results suggested that Chlorella vulgaris biomass might potentially be used as an alternative to traditional water treatment materials for removal of residual chlorine in drinking water or process waste-water.

• Analytical Science and Technology
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• v.23 no.5
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• pp.429-436
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• 2010

The present research evaluates the efficiency of mixed resins between anion exchange resin and active carbon. We expected synergic effect from advantages of both adsorbents. Especially, this research focused on the removal of high cencentrated perchlorate ion from demilitarization solution. The total amount of the adsorbed perchlorate ion is increased considerably with mixed resins between mono functional anion exchange resin and granular active carbon from a single adsorbent. Results demonstated that this process not only improve the efficiency of adsorbing perchlorate, but save the time, space and cost for treating perchlotrate waste solution, because of reducing organic contaminant removing process. The interference effects from coexisting anions are not significant and can successfully applied to real demilitarization sample.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.10
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• pp.704-710
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• 2014

Biomass is considered an alternative energy which can solve an greenhouse gas problem like $CO_2$ which is a major contributor to global warming. The biomass can be converted to various energy sources through thermochemical conversion. In this study, a continuous gasifier was engineered for a wood biomass gasification. The biomass was used a waste wood. The experiments of $CO_2$ gasification were achieved as the gasification temperature, moisture content and input $CO_2$ concentration. The results showed that the yield of producer gas increased with an increasing the gasification temperature. The amount of the light tar increased due to the decomposition of gravimetric tar by the thermal cracking, and the char was confirmed pore development through the SEM analysis. The CO concentration was increased with an increased input $CO_2$ concentration from Boudouard reaction. Through the parametric screening studies, the hydrogen and carbon monoxide concentration were 32.91% and 48.33% at the optimal conditions of this test rig.

• Resources Recycling
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• v.12 no.3
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• pp.25-30
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• 2003

The synthesis of SiC used for the parts of the gas turbine and the heat exchanger, was carried out. In this study, wire cutting slurry of silicon wafer and the graphite rod of spent zinc-carbon battery were applied to the starting materials for the synthesis. The powders of Si or Si+SiC were obtained from the waste material by filtration, gravity separation and magnetic separation. Graphite powder was produced by dismantling, grinding and gravity separation from spent zinc-carbon battery. The synthesis of SiC could be completed from the mixture powders of Si and C or Si+SiC and C at the condition of equivalent ratio of Si and C, atmosphere of Ar or vacuum, temperature of above 1$600^{\circ}C$ and 2 hours reactions. The purity of synthesized Si-C was above 99%.

• Journal of the Korean Electrochemical Society
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• v.21 no.4
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• pp.61-67
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• 2018

As emerging the new electric devices, the commercial lithium ion batteries have faced with various challenges. In this regard, many efforts to solve challenges have been tried. In order to solve the above problems in terms of development of a new secondary battery, we successfully demonstrated the two electrocatalysts, such as MCWB and PPY hydrogel, PPY hydrogel and MCWB showed typical H3-type BET isotherm, indicating that micro- and mesopores existed. Especially, in terms of voltage efficiency at the first cycle, PPY hydrogel was higher than that of MCWB, but lower than that of PtC. More interestingly, the PPY hygrogel based seawater battery exhibited charge-discharge reversibility during 20 cycles, and the voltage efficiencies ranged from 70.32 % to 77.35 % in cyclic performance test.

• Resources Recycling
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• v.28 no.5
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• pp.60-67
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• 2019

A valuable metal recovery from waste resources such as spent rechargeable secondary batteries is of critical issues because of a sharp increase in the amount of waste resources. In this context, it is necessary to research not only recycling waste lithium-ion batteries (LIBs), but also reusing valuable metals (e.g., Li, Co, Ni, Mn etc.) recovered from waste LIBs. In particular, the lithium hydroxide ($LiOH{\cdot}xH_2O$), which is of precursors that can be prepared by the recovery of Li in waste LIBs, can be reused as a catalyst, a carbon dioxide absorbent, and again as a precursor for cathode materials of LIB. However, most studies of recycling the waste LIBs have been focused on the preparation of lithium carbonate with a recovery of Li. Herein, we show the preparation of high purity lithium hydroxide powder along with the precipitation process, and the systematic study to find an optimum condition is also carried out. The lithium carbonate, which is recovered from waste LIBs, was used as starting materials for synthesis of lithium hydroxide. The optimum precipitation conditions for the preparation of LiOH were found as follows: based on stirring, reaction temperature $90^{\circ}C$, reaction time 3 hr, precursor ratio 1:1. To synthesize uniform and high purity lithium hydroxide, 2-step precipitation process was additionally performed, and consequently, high purity $LiOH{\cdot}xH_2O$ powder was obtained.

• Korean Journal of Soil Science and Fertilizer
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• v.40 no.4
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• pp.269-273
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• 2007

Occurrence of malodor could cause adverse impacts on human health and increase public interest. Therefore, scientific methods to decrease odor is required. Endeavor to decrease odor from compost however has not fully been successful. The purpose of this research is assessment of some amendments to reduce $NH_3$ from immature composts. Calcium hydroxide was applied to composts due to it's characteristics to increase pH. Activated carbon and zerovalent iron (ZVI) were selected because of their adsorption properties. The research results were as follows: Calcium hydroxide, activated carbon, zerovalent iron increased the composting temperature above $60^{\circ}C$. The addition of calcium hydroxide, activated carbon, and ZVI to compastry process increased pH 8.6 - 8.8 from $1^{st}$ day to $14^{th}$ day. During the 14 days of composting, addition of calcium hydroxide, activated carbon and ZVI changed EC from $2.15-0.66dS\;m^{-1}$, $1.48-1.11dS\;m^{-1}$, respectively and $1.77-0.68dS\;m^{-1}$. The difference in EC of the compost was due to irregularities of samples. Organic matter in the compost decreased through out theexcept control. The $NH_4-N/NO_3-N$ ratio of all experimental compost increased through the process. The addition of activated carbon, calcium hydroxide and ZVI decreased $NH_3$ from 0.1ppm, 0.7ppm and 1.7ppm more than the control (pig manure and sawdust), 9.3ppm, in 30 days of composting. In conclusion, odor from prematured compost decreased by addition of chemicals like calcium hydroxide, activated carbon, zerovalent iron. Moreover, use of these $NH_3$ reducers alone or together combined at different periods of composting etc. could decrease $NH_3$.