Rapid and long-effective removal of broad-spectrum pollutants from aqueous system by ZVI/oxidants
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REVIEW ARTICLE
Rapid and long-effective removal of broad-spectrum pollutants from aqueous system by ZVI/oxidants Sana Ullah1,2, Xuejun Guo (✉)1, Xiaoyan Luo1, Xiangyuan Zhang1, Siwen Leng1, Na Ma1, Palwasha Faiz1 1 State Key Laboratory of Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China 2 Department of Environmental and Conservation Sciences, University of Swat, Mingora 19200, Pakistan*
HIGHLIGHTS
GRAPHIC ABSTRACT
• The coupling of oxidants with ZVI overcome the impedance of ZVI passive layer. • ZVI/oxidants system achieved fast and longeffective removal of contaminants. • Multiple mechanisms are involved in contaminants removal by ZVI/oxidant system. • ZVI/Oxidants did not change the reducing property of ORP in the fixed-bed system.
ARTICLE INFO Article history:
Received 22 October 2019 Revised 7 July 2020 Accepted 18 July 2020 Available online 30 August 2020 Keywords: Zero-Valent Iron (ZVI) Oxidants Heavy Metals (HMs) Metalloids Nitrate, Phosphate
ABSTRACT Zero-valent iron (ZVI) technology has recently gained significant interest in the efficient sequestration of a wide variety of contaminants. However, surface passivation of ZVI because of its intrinsic passive layer would lead to the inferior reactivity of ZVI and its lower efficacy in contaminant removal. Therefore, to activate the ZVI surface cheaply, continuously, and efficiently is an important challenge that ZVI technology must overcome before its wide-scale application. To date, several physical and chemical approaches have been extensively applied to increase the reactivity of the ZVI surface toward the elimination of broad-spectrum pollutants. Nevertheless, these techniques have several limitations such as low efficacy, narrow working pH, eco-toxicity, and high installation cost. The objective of this mini-review paper is to identify the critical role of oxygen in determining the reactivity of ZVI toward contaminant removal. Subsequently, the effect of three typical oxidants (H2O2, KMnO4, and NaClO) on broad-spectrum contaminants removal by ZVI has been documented and discussed. The reaction mechanism and sequestration efficacies of the ZVI/oxidant system were evaluated and reviewed. The technical basis of the ZVI/oxidant approach is based on the half-reaction of the cathodic reduction of the oxidants. The oxidants commonly used in the water treatment industry, i.e., NaClO, O3, and H2O2, can be served as an ideal coupling electron receptor. With the combination of these oxidants, the surface corrosion of ZVI can be continuously driven. The ZVI/oxidants technology has been compared with other conventional technologies and conclusions have been drawn. © Higher Education Press 2020
1 ✉ Corresponding authors E-mail: [email protected] Special Issue—Accounts of Aquatic Chemistry and Technology Research (Responsible Editors: Jinyong Liu, Haoran Wei & Yin Wang)
Introduction
Chemical pollution in the form of inorganic and organic pollutants is becoming a serious risk to the public health and aquatic ecosystem ( Li
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