Zero valent iron and amorphous boron-assisted nano calcium peroxide/Fe(III) system for naphthalene degradation: Efficient performance and diverse mechanisms

Abstract

Nano calcium peroxide (nCP) has attracted attention as an alternative for liquid H2O2-mediated advanced oxidation processes. However, the slow reduction kinetics of Fe(III) still significantly limit its application. Here, zero valent iron (ZVI) and amorphous boron (B) could remarkably promote the Fe(III)/Fe(II) cycle in nCP/Fe(III) system to generate various active species (HO•, O2−•, and 1O2) with HO• acting as the predominant role in naphthalene (NAP) degradation. nCP/Fe(III)/ZVI process could achieve 98.2% NAP degradation and 70.6% TOC removal, compared with 97.5% NAP degradation and 56.3% TOC removal in nCP/Fe(III)/B process. ZVI could donate electrons to Fe(III) to generate Fe(II) and itself could also be corroded to release Fe(II). B was stepwise oxidized (B0 to B(I)/B(II) to B2O3) and continuously supplied electrons to Fe(III) to ensure fast and long-lasting Fe(II) generation. Moreover, B2O3 was dissolved as H3BO3 in aqueous solution, which kept the B surface reactive for the continuous reduction of Fe(III). Although the two co-activators showed different promotion mechanisms in nCP/Fe(III) system, both systems exhibited excellent NAP degradation performance in different experimental conditions and various water matrixes. Overall, this study provided the strategies to overcome the limitation of nCP/Fe(III) system and extended its application potential in contaminants remediation.