Study on the mechanism of arsenic removal from aqueous solution by capacitive deionization technology
Date Issued
2015
Date
2015
Author(s)
Tseng, Ssu-Chia
Abstract
Capacitive deionization (CDI), or referred to electrosorption process, has been regarded as a novel water purification technology, which has many advantages including low operating pressure, low energy consumption, no secondary waste, and easy regeneration. The mechanism behind CDI to remove ionic species from water is based on the charge separation, in which nanoporous carbon electrodes are charged and discharged to store and to release large quantities of ions, respectively. In this study, CDI process can electrostatically separate low concentration (0.2 mg/L) arsenic from aqueous solutions. Furthermore, arsenate (As(V)) can be directly removed by electrosorption at 1.2 V because of its negative charge. The results indicate that the mechanism of arsenite (As(III)) removal in CDI system could be involved with the oxidation of As(III) to As(V) which can be removed by electrosorption. In the competitive experiments, although, the presence of sodium chloride and nature organic matter (NOM) obviously interfered with the electrosorption behavior of arsenic, there was still electrosorption capacity for arsenic. Notably, the CDI system still showed good electrosorption selectivity of As. The surface of activated carbon was investigated with SEM and XPS. As evidenced, there was no visible electrodeposition of arsenic on the electrode surface, demonstrating that arsenic was removed by electrosorption.
Subjects
Capacitive deionization (CDI)
Electrosorption
Arsenic
Activated carbon electrodes
Type
thesis
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