LiCoPO4 (LCP) as an effective peroxymonosulfate activator for degradation of diethyl phthalate in aqueous solution without controlling pH: Efficiency, stability and mechanism

- LiCoPO4 (LCP) has been tested for the first time to activate PMS.
- LCP demonstrated good performance in activating PMS for DEP degradation.
- SO4− and OH were produced and made contributions to DEP removal together.
- LCP displayed good reusability on PMS activation for DEP removal.

LiCoPO4 (LCP) synthesized particles, which used a conventional solid-state method, were applied as activators for the first time to activate peroxymonosulfate (PMS) with diethyl phthalate (DEP) as the target pollutant. Contrast tests presented that LCP possessed excellent ability of activating PMS for pollutant removal without controlling pH. About 98.6% of DEP could be removed in 6 min with 0.1 g L−1 LCP and 0.15 g L−1 PMS. Rating under different concentrations of Co2+ and leaching solution, activation tests indicated that LCP/PMS system involved in heterogeneous and homogeneous reaction. To reduce the homogeneous effect of Co2+ ions, LCP dose decreased to 0.01 g L−1, and the time for entire removal of DEP was extended to 60 min. Technologies such as Scanning electron microscope (SEM), X-ray diffraction (XRD), Raman and X-ray photoelectron spectroscopy (XPS) were employed to characterize the particles before and after the reaction. It was found that characterizations of samples had little change and that the DEP removal efficiencies showed no significant reduction after 3 cycles. Sulfate radicals and hydroxyl radicals existed together to make great contributions. This study presented the proposed mechanism of radical production in LCP/PMS system for the DEP removal. Co2+/Co3+ cycle in heterogeneous surface and homogeneous solution play important roles in the process of PMS activation. This report would help to understand the mechanism of PMS activation on LCP and offered an alternative environment-friendly scheme for pollutant removal.