Degradation of 2,4-dichlorophenol by nanoscale calcium peroxide: Implication for groundwater remediation

• Nanoscale CaO2 was synthesized by nanoscale Ca(OH)2 and H2O2.
• 2,4-Dichlorophenol could be eliminated in 5 d by nanoscale CaO2.
• The destruction pathways of 2,4-Dichlorophenol were proposed.
• Hydroxyl radicals are the dominant reactive species.

In this study, a newly emerging oxidant nanoscale calcium peroxide (nCaO2) was synthesized to degrade 2,4-dichlorophenol (2,4-DCP). nCaO2 was prepared from nanoscale Ca(OH)2 and H2O2 and confirmed to be less than 150 nm in diameter and 62.23 m2 · g−1 in specific surface area (SSA). For treating 2,4-DCP, the optimal ratio between Ca(OH)2 and H2O2 was 1:5. Compared with conventional CaO2, nCaO2 was found to be more efficient for destructing 2,4-DCP. 2,4-DCP was completely degraded in 5 d by nCaO2 while only 75.0% 2,4-DCP was destructed by conventional CaO2. The effects of solution pH and water matrix, including SO42−, HCO3− and humic acid (HA) were examined. The reactive species in nCaO2 system was investigated by photoluminescence (PL) technique and the quenching experiments. Results showed that hydroxyl radical (OH) was the dominant reactive species for destructing 2,4-DCP. The major oxidation products identified in this study were 2-chlorophenol (2-CP), 4-chlorophenol (4-CP), phenol and benzoquinone (BQ). Our works gave an important insight into the use of nCaO2 to degrade some organic contaminants which might provide some references for the application of nCaO2 in chlorophenols contaminated groundwater remediation.