This page has only limited features, please log in for full access.
Determining the degree of the reducing power of multi-walled carbon nanotubes (MWCNTs) and granular activated carbon (GAC) enables their effective application in various fields. In this study, we estimate the reducing power of carbon nanotubes (CNTs) and GAC by measuring the reduction degree of various compounds with different reduction potentials. MWCNTs and GAC materials can reduce Cr(VI), Fe(III) and PMo12O403−, where the reduction potentials range from +1.33 V to +0.65 V. However, no reduced forms of PW12O403− and SiW12O404− compounds were detected, indicating that the reducing power of MWCNTs and GAC is insufficient for reduction potentials in the range +0.218 V to +0.054 V. MWCNTs exhibit a short reduction time (5 min), whereas GAC exhibits a gradually increasing reduction degree of all the compounds assessed until the end of the reaction. This indicates a higher reduction degree than that of MWCNTs systems. Acidic initial pH values favor reduction, and the reduction degree increases as the pH becomes lower than 4.0. Moreover, large quantities of MWCNTs and GAC increase the concentrations of the reduced compounds.
Heesoo Woo; Ilho Kim; Saerom Park. Estimating the Reducing Power of Carbon Nanotubes and Granular Activated Carbon Using Various Compounds. Water 2021, 13, 1959 .
AMA StyleHeesoo Woo, Ilho Kim, Saerom Park. Estimating the Reducing Power of Carbon Nanotubes and Granular Activated Carbon Using Various Compounds. Water. 2021; 13 (14):1959.
Chicago/Turabian StyleHeesoo Woo; Ilho Kim; Saerom Park. 2021. "Estimating the Reducing Power of Carbon Nanotubes and Granular Activated Carbon Using Various Compounds." Water 13, no. 14: 1959.
For effective ultrasonic algae removal, several studies have considered the ultrasound equipment linked factors, such as power and frequency. However, studies on the response of mixed algal cultures and associated water quality parameters to ultrasound are limited. In this lab-scale sonication, the removal of cyanobacteria at a pre-set frequency of 200 kHz on mixed algae suspensions collected from a eutrophic lake was investigated. The caution (17.5 µg/L) and outbreak (1450 µg/L) alert levels in terms of chlorophyll-a (Chl-a) concentrations of the initial samples were each sonicated for 10, 15, and 20 min, and then kept in an incubator. Fifteen minutes of sonication resulted in best removal efficiency of 0.94 and 0.77, at an ultrasonic dose of 30 kWh/m3 at the outbreak and caution level concentrations, respectively. Immediately after 15 min sonication, and after standing in the incubator for a day, chlorophyll-a removal efficiencies of 0.28 and 0.90 were achieved in the outbreak level, respectively, and the matching removal efficiencies for the caution level were 0.23 and 0.64. Even though the removal was substantial in both cases, the final 147 µg/L chlorophyll-a concentration of the outbreak, which is itself still in the outbreak level range, shows that ultrasonication is not effective to satisfactorily remove algae from a concentrated suspension. Total dissolved nitrogen and chemical oxygen demand were reduced, overall, due to sonication. However, total dissolved phosphorus of the concentrated level was increased during the treatment. Although sonication needs further replicated experimental testing in whole-lake systems, our results show that 200 kHz sonication was able to reduce chlorophyll-a concentrations in small-scale laboratory tests.
Andinet Tekile; Ilho Kim; Jai-Yeop Lee. 200 kHz Sonication of Mixed-Algae Suspension from a Eutrophic Lake: The Effect on the Caution vs. Outbreak Bloom Alert Levels. Water 2017, 9, 915 .
AMA StyleAndinet Tekile, Ilho Kim, Jai-Yeop Lee. 200 kHz Sonication of Mixed-Algae Suspension from a Eutrophic Lake: The Effect on the Caution vs. Outbreak Bloom Alert Levels. Water. 2017; 9 (12):915.
Chicago/Turabian StyleAndinet Tekile; Ilho Kim; Jai-Yeop Lee. 2017. "200 kHz Sonication of Mixed-Algae Suspension from a Eutrophic Lake: The Effect on the Caution vs. Outbreak Bloom Alert Levels." Water 9, no. 12: 915.
This study utilized multistage orifice microbubble generator to investigate dissolved oxygen (DO) formation characteristics and to increase its efficiency, by considering saturator pressure, water supply, and gas flow rates as the main operating factors. The effect of changing the parameters was described in terms of dissolution performance using volumetric mass transfer rate, which is very important element for aerator design and scale-up. Pressure values from 1 to 6 atm were taken for the analysis. To improve the oxygen transfer efficiency of the multistage orifice, the internal supply line was controlled to circulate the bubbles water up to 300% cycling. The volumetric mass transfer coefficient was limited below 0.01 per min for air; however, the value varied from 0.10 to 0.13 per min for oxygen at 4.5 L/min flow rate, showing increasing pattern with pressure. The transfer characteristic was doubled, with circulating ratio applied, because circulation could multiply the number of microbubbles. Examining the various operating conditions within the range set for the cost to generate 1 kg of DO, under gas injection velocity of 1.27 m/s, higher liquid pressurization showed lower cost per production in case of oxygen than air. Thus, natural water bottom area environment can be economically improved using oxygen microbubbles, considering the excessive dissolution.
Tekile Andinet; Ilho Kim; Jai-Yeop Lee. Effect of microbubble generator operating parameters on oxygen transfer efficiency in water. DESALINATION AND WATER TREATMENT 2016, 57, 26327 -26335.
AMA StyleTekile Andinet, Ilho Kim, Jai-Yeop Lee. Effect of microbubble generator operating parameters on oxygen transfer efficiency in water. DESALINATION AND WATER TREATMENT. 2016; 57 (54):26327-26335.
Chicago/Turabian StyleTekile Andinet; Ilho Kim; Jai-Yeop Lee. 2016. "Effect of microbubble generator operating parameters on oxygen transfer efficiency in water." DESALINATION AND WATER TREATMENT 57, no. 54: 26327-26335.
Water quality in rivers is vital to humans and to maintenance of biotic and ecological integrity. During the Four Major Rivers restoration of South Korea, remarkable attempts have been made to decrease external nutrient loads and moveable weirs were designed to discharge silt that may deposit in pools. However, recently eutrophication of the Nakdong River, which was limited to the lower reaches, is seen to be spreading upstream. The reduction of external nutrient loads to rivers is a long-term goal that is unlikely to lead to reductions in algal blooms for many years because of the time required to implement effective land management strategies. It would therefore be desirable to implement complementary strategies. Regulating the amount of water released is effective at preventing algae blooms in weir pools; so, the relationship between discharge, stratification and bloom formation should be understood in this regard. However, pollutants are likely to accumulate in the riverbed upstream from release points. Thus, to control phosphorus levels, total phosphorus density should be lowered by applying in-river techniques as well. As many ecosystem properties are controlled by multiple processes, simultaneous river bottom improvement techniques, such as combined dissolved oxygen supply and nutrient inactivation, are likely to be effective. The purpose of this review is to present a series of technological approaches that can be used to improve the river bottom area and hence sediment nutrient release, and to illustrate the application of these techniques to the Nakdong River.
Andinet Tekile; Ilho Kim; Jisung Kim. Mini-review on river eutrophication and bottom improvement techniques, with special emphasis on the Nakdong River. Journal of Environmental Sciences 2015, 30, 113 -121.
AMA StyleAndinet Tekile, Ilho Kim, Jisung Kim. Mini-review on river eutrophication and bottom improvement techniques, with special emphasis on the Nakdong River. Journal of Environmental Sciences. 2015; 30 ():113-121.
Chicago/Turabian StyleAndinet Tekile; Ilho Kim; Jisung Kim. 2015. "Mini-review on river eutrophication and bottom improvement techniques, with special emphasis on the Nakdong River." Journal of Environmental Sciences 30, no. : 113-121.