Arsenic removal with iron(II) and iron(III) in waters with high silicate and phosphate concentrations

Roberts, Linda C. and Hug, Stephen J. and Reuttimann, Thomas and Billah, Md. Morsaline and Khan, Abdul Wahab and Rahman, Mohammad Tariqur (2004) Arsenic removal with iron(II) and iron(III) in waters with high silicate and phosphate concentrations. Environmental Science & Technology, 38 (1). pp. 307-315. ISSN 0013-936X

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Abstract

Arsenic removal by passive treatment, in which naturally present Fe(II) is oxidized by aeration and the forming iron- (III) (hydr)oxides precipitate with adsorbed arsenic, is the simplest conceivable water treatment option. However, competing anions and low iron concentrations often require additional iron. Application of Fe(II) instead of the usually applied Fe(III) is shown to be advantageous, as oxidation of Fe(II) by dissolved oxygen causes partial oxidation of As(III) and iron(III) (hydr)oxides formed from Fe(II) have higher sorption capacities. In simulated groundwater (8.2 mM HCO3 -, 2.5 mM Ca2+, 1.6 mM Mg2+, 30 mg/L Si, 3 mg/L P, 500 ppb As(III), or As(V), pH 7.0 ( 0.1), addition of Fe(II) clearly leads to better As removal than Fe(III). Multiple additions of Fe(II) further improved the removal of As(III). A competitive coprecipitation model that considers As(III) oxidation explains the observed results and allows the estimation of arsenic removal under different conditions. Lowering 500 íg/L As(III) to below 50 íg/L As(tot) in filtered water required >80 mg/L Fe(III), 50-55 mg/L Fe(II) in one single addition, and 20-25 mg/L in multiple additions. With As(V), 10-12 mg/L Fe(II) and 15-18 mg/L Fe(III) was required. In the absence of Si and P, removal efficiencies for Fe(II) and Fe(III) were similar: 30-40 mg/L was required for As(III), and 2.0-2.5 mg/L was required for As(V). In a field study with 22 tubewells in Bangladesh, passive treatment efficiently removed phosphate, but iron contents were generally too low for efficient arsenic removal.

Item Type:	Article (Journal)
Additional Information:	5128/29703
Uncontrolled Keywords:	Arsenic removal, iron(II, iron(III), waters with high silicate, phosphate concentrations
Subjects:	T Technology > TD Environmental technology. Sanitary engineering > TD895 Industrial sanitation. Industrial wastes
Kulliyyahs/Centres/Divisions/Institutes (Can select more than one option. Press CONTROL button):	Kulliyyah of Science > Department of Biotechnology
Depositing User:	Dr Mohammad Tariqur Rahman
Date Deposited:	26 Apr 2013 17:30
Last Modified:	26 Apr 2013 17:30
URI:	http://irep.iium.edu.my/id/eprint/29703

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