Browsing by Author "Kondo, Hiroaki"
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Item Applicability of solar photo-Fenton process to the remediation of water polluted with pesticides(Science Pub, 2013-12-21) Sakugawa, Hiroshi; Hasan, Nahed; Olasehinde, Emmanuel F; Takeda, Kazuhiko; Kondo, HiroakiThe applicability of solar photo-Fenton process to the degradation of three pesticides in pure and natural waters was investigated in Fe(III)/H2O2/UV–Vis and Fe(III)/H2O2 UV–Vis oxidation systems at pH 2.8 and 7.2. The pesticides concentrations were determined by HPLC analysis. Furthermore, total mineralization of the pesticides in these systems was evaluated by monitoring the decreases in DOC concentrations with solar simulator irradiation time by TOC analysis. The results obtained indicate that the spontaneous degradation due to solar illumination by Fe3+/H2O2/UV–Vis system is more effective than Fe2+/ H2O2/UV–Vis system in Milli-Q water and river water at pH 2.8. This great enhancement in the pesticides degradation rate in the photo-Fenton reaction system Fe3+/H2O2/UV– Vis compared to Fe2+/H2O2/UV–Vis systems at pH 2.8 is due to the higher rate of ·OH generation in this system in Milli-Q water and river water (4.01 and 5.26 uM/min) compared to Fe2+/H2O2/UV–Vis systems 2.44 and 2.90 uM/min. respectively. At both pH values, the order of pesticides degradation was diuron > fenitrothion > fenarimol which seems to be related with their solubility. Results obtained from this study makes it plausible to apply the photo-Fenton process to the remediation of water polluted with toxic pesticidesItem Application of Fenton reaction for nanomolar determination of hydrogen peroxide in seawater(Elsevier, 2008-08-28) Olasehinde, Emmanuel F.; Makino, Shinya; Kondo, Hiroaki; Takeda, Kazuhiko; Sakugawa, HiroshiA simple and sensitive method for the determination of nanomolar levels of hydrogen peroxide (H2O2) in seawater has been developed and validated. This method is based on the reduction of H2O2 by ferrous iron in acid solution to yield hydroxyl radical (•OH) which reacts with benzene to produce phenol. Phenol is separated from the reaction mixture by reversed phase high performance liquid chromatography and its fluorescence intensity signals were measured at excitation and emission of 270 and 298 nm, respectively. Under optimumconditions, the calibration curve exhibited linearity in the range of (0–50)×103 nmol L−1 H2O2. The relative standard deviations for five replicate measurements of 500 and 50 nmol L−1 H2O2 are 1.9 and 2.4%, respectively. The detection limit for H2O2, defined as three times the standard deviation of the lowest standard solution (5 nmol L−1 H2O2) in seawater is 4 nmol L−1. Interference of nitrite ion (NO2 −) on the fluorescence intensity of phenol was also investigated. The result indicated that the addition of 10 mol L−1 NO2 − to seawater samples showed no significant interference, although, the addition of 50 mol L−1 NO2 − to the seawater samples decreases the fluorescence intensity signals of phenol by almost 40%. Intercomparison of this method with well-accepted (p-hydroxyphenyl) acetic acid (POHPAA)-FIA method shows excellent agreement. The proposed method has been applied on-board analysis of H2O2 in Seto Inland seawater samples.Item Application of Fenton reaction for nanomolar determination of hydrogen peroxide in seawater(Elsevier, 2008-08-28) Olasehinde, Emmanuel F.; Makino, Shinya; Kondo, Hiroaki; Takeda, Kazuhiko; Sakugawa, HiroshiA simple and sensitive method for the determination of nanomolar levels of hydrogen peroxide (H2O2) in seawater has been developed and validated. This method is based on the reduction of H2O2 by ferrous iron in acid solution to yield hydroxyl radical (•OH) which reacts with benzene to produce phenol. Phenol is separated from the reaction mixture by reversed phase high performance liquid chromatography and its fluorescence intensity signals were measured at excitation and emission of 270 and 298 nm, respectively. Under optimum conditions, the calibration curve exhibited linearity in the range of (0–50) × 103 nmol L−1 H2O2. The relative standard deviations for five replicate measurements of 500 and 50 nmol L−1 H2O2 are 1.9 and 2.4%, respectively. The detection limit for H2O2, defined as three times the standard deviation of the lowest standard solution (5 nmol L−1 H2O2) in seawater is 4 nmol L−1. Interference of nitrite ion (NO2−) on the fluorescence intensity of phenol was also investigated. The result indicated that the addition of 10mol L−1 NO2− to seawater samples showed no significant interference, although, the addition of 50mol L−1 NO2 − to the seawater samples decreases the fluorescence intensity signals of phenol by almost 40%. Intercomparison of this method with well-accepted (p-hydroxyphenyl) acetic acid (POHPAA)-FIA method shows excellent agreement. The proposed method has been applied on-board analysis of H2O2 in Seto Inland seawater samples.