Experimental study of viscosity modification coupled with phase transfer catalysis for enhanced remediation of non-aqueous phase trichloroethene polluted heterogeneous aquifer.

The degradation of dense non-aqueous phase liquid trichloroethene in low permeability zone is a challenging issue due to limited mass transfer between water-soluble oxidants (i.e., MnO4-) and residual phase trichloroethene and the bypassing of amendments in low permeability zone. This work accomplished trichloroethene oxidation enhancement through coupling viscosity modification by using xanthan with phase transfer of MnO4- by using phase transfer catalyst (PTC). Experiments were conducted by sand columns and 2D-tanks, and results revealed that after ~11.7 g of trichloroethene was injected in each tank, the mass of trichloroethene degradation was 1.3, 5.9, 6.9 and 8.5 g in MnO4-, MnO4- + xanthan, MnO4- + PTC and MnO4- + PTC + xanthan reaction systems, respectively. Combining PTC and xanthan with MnO4- increased the rate of continuous formation of Cl-, reflected in the acceleration of heterogeneous reactions and MnO4- transport enhancement in low permeability zone by PTC and xanthan. Moreover, PTC promoted dissolved Mn (Ⅱ) and Mn (Ⅲ) formation in the process of MnO4- reduction, and thus effectively inhibited MnO2 generation. In conclusion, the results revealed that PTC and xanthan could perform their respective contributions to mass transfer and amendment transport for jointly enhanced the remediation of trichloroethene polluted heterogeneous aquifer.