Remediation of groundwater contaminated with hexavalent ‎chromium using a mixture of Zero-Valent Iron and Pyrite ‎

Waseem Yousef Daoud*(1)

(1). Department of Civil and Environmental Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran

(*Corresponding author: Dr. Waseem Yousef Daoud. E-Mail: waseem.daoud@yahoo.com).  

Received: 13/09/2020                               Accepted: 17/10/2020

Abstract

Permeable Reactive Barriers (PRBs) with Zero Valent Iron (ZVI) have been used to remediate groundwater contaminated with metals such hexavalent chromium Cr(VI). Cr(VI) is of particular environmental concern due to its toxicity and mobility and is challenging to remove from industrial wastewater. It is a strong oxidizing agent that is carcinogenic and mutagenic, and diffuses quickly through soil and aquatic environments. It does not form insoluble compounds in aqueous solutions, so separation by precipitation is not feasible. While Cr(VI) oxyanions are very mobile and toxic in the environment, trivalent Cr(III) cations are not. Like many metal cations, Cr(III) forms insoluble precipitates. Thus, reducing Cr(VI) to Cr(III) makes its removal from effluent easier and also reduces its toxicity and mobility. At high pH values iron precipitations are expected to occur which lead to changes in ZVI surface, therefore the reactivity and hydraulic performance of ZVI decrease over time.  ZVI reactivity was prolonged by adding pyrite (FeS2) to ZVI for scavenging oxygen in feed water as well as neutralizing the effects of . An increase in Cr(VI) removal was found in ZVI preceded by FeS2.

Keywords: Permeable reactive barriers; Polluted groundwater; Hexavalent chromium; Zero valent iron; Pyrite.

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