• Journal of Korean Society of Environmental Engineers
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• v.28 no.3
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• pp.257-264
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• 2006

This study investigated the effects of hybrid process(chemical coagulation, Fenton oxidation and ceramic UF(ultrafiltration)) on COD and color removals of commercial reactive dyestuffs. In the case of chemical coagulation, the optimal concentrations of $Fe^{3+}$ coagulant for COD and color removals of RB49(reactive blue 49) and RY84(reactive yellow 84) were determined according to the different coagulant dose at the optimal pH. They were 2.78 mM(pH 7) in RB49 and 1.85 mM(pH 6) in RY84, respectively. In the case of Fenton oxidation, the optimal concentrations of $Fe^{3+}\;and\;H_2O_2$ were obtained. Optimal $[Fe^{2+}]:[H_2O_2]$ molar ratio of COD and color removals of RB49 and RY84 were 4.41:5.73 mM and 1.15:0.81 mM, respectively. In the case of ceramic UF, the flux and rejection of supernatant after Fenton oxidation were investigated. After ceramic UF for 9 hr, the average flux of RB49 and RY84 solutions were $53.4L/m^2hr\;and\;67.4L/m^2hr$ at 1 bar, respectively. In addition, the permeate flux increased and the average flux recovery were 98.5-99.9%(RB49) and 91.0-97.3%(RY84) according to adopting off-line cleaning(5% $H_2SO_4$). Finally, COD and color removals were 91.6-95.7% and 99.8% by hybrid process, respectively.

• Journal of the Korean Chemical Society
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• v.55 no.3
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• pp.529-540
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• 2011

The purpose of this study was to analyze experiments for the rules of material change unit in 9th grade science textbooks and develop experiments applying small-scale chemistry (SSC). For this study, experimental methods for the precipitation experiment, water electrolysis experiment, decomposition of hydrogen peroxide experiment presented in the 9 science textbooks were analyzed. Problems and improvements that were needed were extracted by 13 science teachers performing the experiments. Experiments applying SSC were developed based on the improvements needed. Afterwards, 19 pre-service science teachers performed both the developed SSC experiments and the science textbooks' experiments. A questionnaire about merits and demerits of the experiments applying SSC was performed. According to the results of this study, most of the 9th grade science textbooks included the lead iodide precipitation experiment, water electrolysis experiment by Hoffman voltameter, and decomposition of hydrogen peroxide experiment using catalytic manganese dioxide. Improvements were needed on the quantity of reagents, time for performing experiments, and scale of experimental apparatus. Merits of the developed experiments applying SSC which used small amount of reagents were safety, easy waste material disposal, short reaction time, and reproducible experimental results. Demerits of the experiments applying SSC were difficulty in observing, decreased achievement, and lack of skill in handling small-scale apparatus. Therefore, if the experiments developed applying SSC were to be utilized in 9th grade science experiments, it will be possible to use less reagent and be able to teach and carry out reproducible experiments at the same time. Also, the reproducible experiments based on SSC will help students under stand the scientific concepts for the rules of material change unit.