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Ansan, South Korea

Bae Y.,Hanyang University | Bae Y.,Daeil Development Co. | Kim D.,Dankook University | Cho H.-H.,Hanyang University | And 3 more authors.
Water Research

In this research, we conducted trichloroethylene (TCE) reduction in a column filled with iron and iron-reducing bacteria (IRB) and developed a mathematical model to investigate the critical reactions between active species in iron/IRB/contaminant systems. The formation of ferrous iron (Fe(II)) in this system with IRB and zero-valent iron (ZVI, Fe(0)) coated with a ferric iron (Fe(III)) crust significantly affected TCE reduction and IRB respiration in various ways. This study presents a new framework for transformation property and reducing ability of both dissolved (Fe(II)dissolved) and solid form ferrous iron (Fe(II)solid). Results showed that TCE reduction was strongly depressed by Fe(II)solid rather than by other inhibitors (e.g., Fe(III) and lactate), suggesting that Fe(II)solid might reduce IRB activation due to attachment to IRB cells. Newly exposed Fe(0) from the released Fe(II)dissolved was a strong contributor to TCE reduction compared to Fe(II)solid. In addition, our research confirmed that less Fe(II)solid production strongly supported long-term TCE reduction because it may create an easier TCE approach to Fe(0) or increase IRB growth. Our findings will aid the understanding of the contributions of iron media (e.g., Fe(II)solid, Fe(II)dissolved, Fe(III), and Fe(0)) to IRB for decontamination in natural groundwater systems. © 2012 Elsevier Ltd. Source

Kim J.-Y.,Daeil Development Co. | Kim J.-Y.,Hanyang University | Shin C.-H.,Daeil Development Co. | Choi H.,Daeil Development Co. | Bae W.,Hanyang University
Separation and Purification Technology

Etching processes during the production of semiconductors generate mixed waste acids containing acetic acid (HAc), nitric acid (HNO 3) and phosphoric acid (H 3PO 4) with aluminum (Al) and/or molybdenum (Mo) as impurities. Diffusion dialysis with newly developed anion exchange membrane method followed by vacuum distillation was carried out to recover phosphoric acid from mixed waste acids. Experiments examined dialyzer performance under different operating conditions of various inlet acid and water flow rates, phosphoric acid and Al concentrations in the feed solution, and operational temperature. The recovered H 3PO 4 in this process was found to be 85 wt.% whereas the concentration of Al leakage was of 3.68 mg/kg. Although, diffusion dialysis was very effective for this purpose, it failed to achieve the multi-target of more than 80% H 3PO 4 recovery yield with 50% acid concentration and less than 1 mg Al/kg of 85% H 3PO 4 simultaneously. Complete separation of HNO 3 and HAc from H 3PO 4 was achieved using vacuum distillation at 730 mm Hg vacuum pressure and 125°C temperature. © 2012 Elsevier B.V. All rights reserved. Source

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