This study investigated the activation of persulfate (PS) by calcium peroxide (CP) to further understand this dual oxidant application in in-situ chemical oxidation (ISCO). The degradation of a-methylnaphthalene (MN), a target contaminant, was studied to evaluate the performance of PS/CP combined system. The results showed that PS could be effectively activated by CP. MN was found to be completely oxidized in 72 h with 1 g/L PS and 1 g/L CP. The degradation rate constants of MN increased with the increase of PS and CP concentration. Several factors affecting the performance of PS/CP combined system were investigated. Results showed that MN degraded faster at lower initial pH. The pH-dependent CP dissolution and radicals distribution was account for this. Solutes in ground water including chloride ions, alkalinity and natural organic matters presented inhibitory effect on MN degradation in this dual oxidant system. Furthermore, the reactive species in the PS/CP system were identified as sulfate radical and hydroxyl radical by electron spin resonance (ESR) spectroscopy and radical scavenging experiments. Surface hydroxyl radicals were also found to play an important role in the MN degradation in neutral pH conditions. GC/MS was applied to identify the major oxidation products, which included 1-naphthaldehdye, naphthalene-1-ylmethanol and 4-hydroxy-4-methylnapht-halen-1(4H)-one. The reaction scheme was proposed in this study. To better understand PS/CP in ISCO, the degradation of MN was tested in ground water matrix, which showed satisfactory efficiency. The results of this study provided detail information of PS/CP dual oxidant in degradation organic contaminants, which might provide some references for the application of this technology in ISCO.

Performance of combined persulfate - calcium peroxide dual oxidant system on the degradation of methylnaphthalene

248th National Meeting (2014)

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