Removal of Pentachlorophenol in Water by Electrochemical Treatment Process
2008
Hochschulschrift
Zugriff:
96
This study addressed the application of electrochemical technology on the detection of chlorophenols and the removal of pentachlorophenol in water. The reactor used in this study is a 50 mL double-jacketed glassware, which is established a Pt electrode as working electrode, a Pt wire as counter electrode, and an Ag/AgCl electrode as reference electrode. The electrochemical analyzer is employed to precisely control a constant potential during the experiments, and the currency passing through the electrodes in the reactor was recorded by the 61/2 multimeter. In the detection experiments, the scan rate is set at 0.3 V/s under the analysis of linear sweep voltammetry (LSV). On the cyclic voltammetry (CV) plot, each pair of clear redox peaks was observed for 4-chlorophenol (4-CP), 2,4-dichlorophenol (2,4-DCP), and penta- chlorophenol (PCP). The potentials of the redox pairs were 1.218 and -0.460 V for 4-CP, 1.128 and -0.448 V for 2,4-DCP, and 1.037 and -0.473 V for PCP. Based on the liner relationship between the concentrations of chlorophenols and the corresponding peak current, the suitable quantification ranges were 0.2~1 mg/L for 4-CP, 0.3~2 mg/L for 2,4-DCP, and 0.1~4 mg/L for PCP by the LSV analysis. The detection experiments demonstrated a quick measurement method to quantify the trace levels of chlorophenols in water by the electrochemical analyzer. As using 1.00 M KI as electrolyte in the degradation experiments, a complete removal of PCP was achieved by the electrolysis at 500 mV. However, the same controls of degradation experiments did not result in a similar result as using 1.00 M KCl or Na2SO4. A possible contribution is ascribed to the formation of the redox couple I3-/I-, which might play the role of mediator to initiate indirect oxidation. On the contrary, PCP can be completely removed for 1.00 M KI, KCl, or Na2SO4 by the electrolysis at -1200 mV. The possible mechanism is that the forming H atoms from water electrolysis might dechlorinate the adsorbed PCP on the electrode surface. Thus, the degradation of PCP synchronized with the dechlorination of PCP. As using 0.50 M KCl as electrolyte in the degradation experiments, a complete removal of PCP was achieved by the electrolysis at -1500 mV. The same controls of experiment conditions did not result in a similar result as using NaNO3 or CaCO3. The removal of PCP is only 88% under the initial pH 9.97, while the removal efficiency is over 99% under the initial pH 3.86. As a consequence, the strong basic condition of initial pH is not favorable for the electrochemical degradation of PCP. Based on the analysis of GC/MS, the intermediates of PCP degradation are determined as 1,2-dichloro-cyclohexane, trans-2-chloro-cyclohexamol, and 3-hexen- 1-yne. Accordingly, PCP can be successfully dechlorinated by a proper control of electrochemical treatment process.
Titel: |
Removal of Pentachlorophenol in Water by Electrochemical Treatment Process
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Autor/in / Beteiligte Person: | Wang, Jr-Wei ; 王志偉 |
Link: | |
Veröffentlichung: | 2008 |
Medientyp: | Hochschulschrift |
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