MnO2 generation mechanisms in the presence of phase transfer catalyst enhanced trichloroethene oxidation by permanganate

The remediation of trichloroethylene contaminated groundwater by permanganate-based in situ chemical oxidation is limited by MnO2 formation. The application of phase transfer catalyst (PTC) is a promising alternative to enhance remediation efficiency, and the alleviation of MnO2 generation is one of crucial capacities of PTC to promote oxidation. This work has emphatically elucidated the mechanism of MnO2 alleviation by PTC, as well as the effectiveness which was researched by conducting batch and sand column experiments. The results indicated that the contents of MnO2 suspended in aqueous phase and total manganese in the media were respectively decreased by 29.5% and 26.1% attributed to PTC addition. Although PTC could not be used as a chelator for Mn(III) stabilization, the generation of dissolved Mn(II) and Mn(III) was promoted by PTC for less MnO2 generation. Further studies illustrated that redox reactions would occur between dissolved Mn(II)/Mn(III) and TCE, which benefited TCE degradation. Moreover, Smaller particle size and improved colloidal stabilization of formed MnO2 were achieved by PTC to minimize MnO2 precipitation. Overall, effective alleviation of the MnO2 generation and precipitation by PTC is collectively contributed from the promotion of dissolved Mn(II) and Mn(III) and the stabilization of MnO2 formed in situ.

Automated summary

This study focuses on elucidating the mechanism of manganese dioxide (MnO2) alleviation by phase transfer catalyst (PTC) and conducting experiments to evaluate the effectiveness. The results showed that PTC addition decreased the suspended MnO2 content and total manganese in the media. Additionally, PTC promoted the generation of dissolved Mn(II) and Mn(III), which benefited trichloroethylene degradation.