Abstract
A relatively low voltage can be favor of e- transfer and peroxide generation from dominant 2e--reduction of O2 on carbon materials as cathode, with low energy loss. In this study the conversion of As(III) in simulated high arsenic groundwater at low voltage was compared in a mixed and a anode–cathode separated electrolytic system. With applied voltages (the potential difference between cathode and anode) from 0.1 V to 0.8 V, As(III) was found to be efficiently converted to As(V) in the mixed electrolytic cells and in separated anodic cells. The complete oxidation of As(III) to As(V) at 0.1–0.8 V was also achieved on graphite in divided cathodic cells which could be long-running. The As(III) conversion process in mixed electrolytic cells, anodic cells and cathodic cells all conformed to the pseudo first-order kinetics equation. The energy consumed by As(III) conversion was decreased as the applied voltage declined. Low voltage electrolysis is of great significance for saving energy consumption and improving the current efficiency and can be applied to in-situ electrochemical pre-oxidation for As(III) in high arsenic groundwater.
Highlights
Arsenic (As) is a toxic metalloid element in nature, and arsenic contamination is widely recognized as a global health problem
The transformation from As(III) to As(V) in simulated high arsenic groundwater was performed under low voltage conditions in mixed electrolytic systems and anode-cathode separated electrolytic systems
Total arsenic was effectively removed in mixed electrolytic cells and anodic cells of divided systems
Summary
Arsenic (As) is a toxic metalloid element in nature, and arsenic contamination is widely recognized as a global health problem. Arsenic mainly occurs in its inorganic form As(III) and As(V) oxo-anions in natural waters. Since As(III) is prevalent in anoxic groundwater [1], more toxic, more mobile and more difficultly removed than As (V) [2], pre-oxidation of As(III) to As(V) is highly desirable for the sequent arsenic removal technologies such as coagulation, sorption [3] and membrane filtration [4]. As an environmentally friendly advanced oxidation technology, electrocatalytic oxidation has been reported to be an emerging, and considerably potential pre-oxidation method for As(III), due to its advantages of no manual chemical addition, less land-area requirement, less sludge, and less capital costs [6], compared with traditional physicochemical oxidation. Iron (Fe) [7], aluminum (Al) [8], zinc (Zn) [9], copper (Cu) [9], titanium (Ti) [10], and dimensional stable anodes (DSAs) [11] had been used as anode materials for
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