Calcium peroxide (CP) combined persulfate (PS) oxidation is an emerging in situ chemical oxidation (ISCO) technology for ground water remediation. Many field cases also confirm its effectiveness in ground water remediation while few research articles document it. This study investigated the performance of α-methylnaphthalene (MN) degradation by PS/CP to further understand this dual oxidant application in ISCO. Results showed that MN could be completely oxidized in 72 h with 1 g L −1 PS and 1 g L −1 CP. The degradation rates of MN increased with the increase of PS and CP concentration. MN degradation was significantly enhanced with the solution pH decrease, because CP was easier to dissolve and generated more radicals in acidic condition. Solutes in ground water including chloride ions, alkalinity and natural organic matters presented inhibitory effect on MN degradation in this dual oxidant system. Plausible mechanisms of the sulfate and hydroxyl radicals in the system were proposed based on the results of radical scavenging experiments and electron spin resonance (ESR) tests. It appeared that surface OH of CP was also responsible for the MN removal. The major oxidation products in this study were 1-naphthaldehdye, naphthalene-1-ylmethanol and 4-hydroxy-4-methylnaphthalen-1(4H)-one. 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 some detail information of PS/CP dual oxidant in degradation organic contaminants, which might provide some references for the application of this technology in ISCO.
The immobilization of sedimentary phosphorus (P) by capping sediments with amended calcium peroxide material (ACPM) and CaO 2 was investigated, the sediments and overlying water from a black-odor river. Under the capping with ACPM and CaO 2 , the pH and dissolved oxygen (DO) in the overlying water were higher than in the control. This contributed to the more loss of external P under the ACPM (the phosphate sorption was fitted well by the Langmuir equation, the maximum P sorption capacity up to 29.28 mg P g −1 ). Additionally, ACPM improves the decrease of the reduction materials (e.g., NH 4 + -N, Fe 2+ ) in the pore water compared to that associated with CaO 2 , resulting in a less obvious dissolved inorganic P (DIP) in the pore water, but the accumulation of DIP in the pore water with CaO 2 suggested an explosive release once the micro-environment conditions encounters adverse conditions. The sharp reduction of Fe/Al-P and Res-P contributes to the increase of DIP in the pore water, with a release of up to 390.60 mg P kg −1 DW (dry weight), whereas the value is only 62.55 mg P kg −1 DW when capped with ACPM. Correspondingly, the percentage of the bioavailable P to Tot-P decreases rapidly from 17.27% (control, 0–2 cm) to 7.21% (ACPM, 0–2 cm) and 10.57% (CaO 2 , 0–2 cm), indicating the obvious P immobilization. The implication is that the application of CaO 2 is not suitable for direct use, while the combination with other materials (e.g., WPS) is a better choice.
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