Synergic thermal activation of peroxydisulfate intercalated Mg/Al layered double hydroxide at a low temperature

Abstract

In this work, for the first time, the thermal activation of peroxydisulfate (PDS, S2O82−) intercalated layered double hydroxide (LDH-PDS) was developed for efficient contaminant oxidation at relatively low temperatures (50 °C). The physical characterizations indicated successful PDS intercalation into the interlayer of LDH. The phenol oxidation percentage of LDH-PDS was 84.1% at 50 °C, which was much higher than that of PDS alone at the same temperature. This property of LDH-PDS was observed at 25–70 °C, which improved the oxidation performance of 4-bromophenol, 2,4-dibromophenol, 2,6-dibromophenol and bisphenol A. The kinetics of LDH-PDS decay with and without ethanol, as well as the dissolved small organic acid determination test, indicated that the organic contaminant was decomposed on LDH-PDS via the radical generation coordinated with the redox reaction. It thus was illustrated that at 50 °C, a part of the PDS in LDH-PDS was activated to provide the sulfate radical, the activation energy of which was decreased to 31.3 kJ/mol compared to 140.1 kJ/mol for the PDS alone. At that moment, the oxidation capacity of the residual PDS in the interlayer of LDH barely worked until its exposure to organic contaminants. Accordingly, it is supposed that the synergic thermal activation of the PDS occurred in LDH-PDS. Moreover, the intercalation structure of LDH-PDS improved the oxidation path, probably due to the strong drag force from the high basic sites in the double interlayer of LDH, which weakened the O-O bond of the intercalated PDS and decreased its activation energy in order to generate sulfate radicals. Therefore, the thermal activation of LDH-PDS at low temperatures provides a promising solid oxidant for decontamination.