Cobalt oxyhydroxide as an efficient heterogeneous catalyst of peroxymonosulfate activation for oil-contaminated soil remediation

The persulfate/Fe2+ system has been proposed for the chemical oxidation for soil remediation, however, the homogeneous iron catalyst was hard to reuse which limited the further application. Cobalt oxyhydroxide (CoOOH) existed as a mineral in nature, which was environmentally friendly. Thus, in this study, CoOOH was selected as an efficient heterogeneous catalyst for peroxymonosulfate (PMS) activation to remediate oil contaminated soil by chemical oxidized reaction. 88.3% of oil at the initial concentration of 78-99 mg/kg can be removed within 24 h under the conditions of 1.0 g/L CoOOH and 0.1 M PMS at room temperature. The residual oil content was approximately 11.5 mg/kg which was lower than the standard of petroleum hydrocarbons for residential land (30 mg/kg), published by the Canadian Council of Ministers of the Environment (CCME). Specifically, the PMS/CoOOH system had a relatively high apparent reaction rate constant (0.3078 h-1), which was approximately twice that of the PS/Fe2+ system (0.1601 h-1). Furthermore, multiple radicals and reactive oxygen species (ROS), such as SO4-, O2- and 1O2, were involved in the oil removal oxidation reaction. Moreover, 73% total organic carbon (TOC) had been removed after the reaction. The findings of this study suggested that the oil-contaminated soil and CoOOH could both be recycled after remediation using the PMS/CoOOH system. In summary, the results indicated that CoOOH is a promising heterogeneous catalyst, and the PMS/CoOOH system could be considered as a feasible alternative to the PS/Fe2+ system for the remediation of oil-contaminated soil.