Mechanistic insights into the degradation of trichloroethylene by controlled release nano calcium peroxide activated by iron species coupled with nano iron sulfide

Abstract This study demonstrated a novel approach for prolonged benefits in groundwater remediation schemes utilizing PVA coated nano calcium peroxide (PVA@nCP) activated by Fe(II)/nFeS or Fe(III)/nFeS. Various techniques (SEM, TEM, XRD, EDS, FTIR, and BET) were used to characterize the synthesized nFeS and the prepared PVA@nCP. Trichloroethylene (TCE) was chosen as the target pollutant and its degradation performance was assessed in both Fe(II)/nFeS and Fe(III)/nFeS activated PVA@nCP systems, and the second-order reaction kinetics were determined. The effect of nFeS dose revealed its dominant role in Fe(III)/nFeS system by providing a surface platform, and at the same time, it also enhanced TCE removal in Fe(II)/nFeS system·H2O2 release behavior, the participation of Fe(II) in both solution and surface, and the generated (free and surface-bound) active species (HO , O2− & 1O2) determined the insights of synergistic mechanisms. Electron spin resonance (ESR) identified the active species initially, which correspondingly confirmed by quenching tests. Moreover, X-ray photoelectron spectroscopy (XPS) investigated the surface reaction mechanism, showing the dominant role of S(-II) as an efficient converter of iron species as Fe(II) increased from 35% to 45% and 45.5% and Fe(III) decreased from 65% to 55% and 54.5% in Fe(II)/nFeS and Fe(III)/nFeS systems respectively. The effects of initial solution pH and common anions (Cl−, HCO3−, NO3−, & SO42−) on TCE removal were further examined, and recycling use of nFeS was investigated for its reusability in both systems. The findings of this work suggest that both systems, i.e., PVA@nCP/Fe(II)/nFeS and PVA@nCP/Fe(III)/nFeS, are novel processes and possessing potential applicability in TCE contaminated groundwater remediation.