Comparison of naphthalene degradation by hydrogen peroxide, nano-calcium peroxide, peroxydisulfate, and peroxymonosulfate in the Fe(II)-citric acid catalytic environments

Naphthalene (NAP) was chosen as a target contaminant due to its increasing environmental concern in this work. Using hydrogen peroxide (H2O2), nano-calcium peroxide (nCP), peroxydisulfate (PDS), and peroxymonosulfate (PMS) as oxidants activated by Fe(II)-citric acid (CA) in aqueous solution, 92.8, 95.0, 97.5, and 99.9% of NAP were removed, respectively, in which CA could significantly enhance NAP degradation. HO center dot was demonstrated to be the major radical responsible for NAP removal in H2O2/Fe(II)/CA and nCP/Fe(II)/CA processes; both HO center dot and SO4 center dot- were major radicals in PDS/Fe(II)/CA process, whereas SO4 center dot- was the sole dominant radical in PMS/Fe(II)/CA process. The impacts of water matrices (anions, natural organic matters, and surfactants) and initial solution pH on NAP removal as well as the practicalities of these four systems in groundwater were explored. The efficient NAP degradation of nCP/Fe(II)/CA and PMS/Fe(II)/CA processes in the actual groundwater indicated that these two systems have great potential and advantages in the remediation of NAP-contaminated groundwater.