Arsenic — a Review. Part II: Oxidation of Arsenic and its Removal in Water Treatment

Abstract

In natural waters arsenic normally occurs in the oxidation states +III (arsenite) and +V (arsenate). The removal of As(III) is more difficult than the removal of As(V). Therefore, As(III) has to be oxidized to As(V) prior to its removal. The oxidation in the presence of air or pure oxygen is slow. The oxidation rate can be increased by ozone, chlorine, hypochlorite, chlorine dioxide, or H 2 O 2 . The oxidation of As(III) is also possible in the presence of manganese oxide coated sands or by advanced oxidation processes. Arsenic can be removed from waters by coprecipitation with Fe(OH) 3 , MnO 2 or during water softening. Fixed-bed filters have successfully been applied for the removal of arsenic.The effectiveness of arsenic removal was tested in the presence of adsorbents such as FeOOH, activated alumina, ferruginous manganese ore, granular activated carbon, or natural zeolites. Other removal technologies are anion exchange, electrocoagulation, and membrane filtration by ultrafiltration, nanofiltration or reverse osmosis. Arsen -eine Übersicht. Teil II: Oxidation und Entfernung bei der WasseraufbereitungIn natürlichen Wässern liegt Arsen überwiegend in den Oxidationsstufen +III (Arsenit) und +V (Arsenat) vor. Da As(III) bis zu einem pH-Wert von 9 nicht dissoziiert, ist die Entfernung von As(III) schwieriger als die Entfernung von As(V). Die Oxidation von As (III)

The Problem of Arsenic Contamination of Groundwater

“…Several useful reviews of the techniques for removing arsenic from water supplies have been published [10][11][12][13]. Existing and emerging arsenic removal technologies include:…”

Implementation of ferric hydroxide-based media for removal of toxic metalloids

“…In natural waters, arsenic is usually present in inorganic forms, as arsenite or arsenate oxyanions. However, trivalent arsenite As(III) is dominant in more reducing conditions, whereas pentavalent arsenate As(V) is mostly present in an oxidizing environment [5][6].…”

Arsenic Sorption Using Mixtures of Ion Exchange Resins Containing N-Methyl-D-Glucamine and Quaternary Ammonium Groups

“…Two forms of arsenic are common in natural waters: arsenite (AsO 3 3-) and arsenate (AsO 4 3-), referred to as arsenic (III) and arsenic (V), respectively 17,20,21 .…”