DEGRADATION OF 1,1,1-TRICHLOROETHANE BY NANOSCALE ZERO VALENT IRON (NZVI) SUPPORTED ON POWDERED ACTIVATED CARBON (PAC)

Nanoscale Zero Valent Iron (NZVI) is a potent reductant of chlorinated organic pollutants, like 1,1,1-Trichloroethane (1,1,1-TCA) in aqueous systems. However, the agglomeration of NZVI particles due to van-der-waals and magnetic forces can alter the effective size of the NZVI particles, degradation byproducts and reaction kinetics. Support materials, such as clay and activated carbon, have been used to stabilize NZVI particles in aqueous solution. In this study, NZVI supported on Powdered Activated Carbon (PAC) were synthesized to study the degradation of 1,1,1-TCA in bench-scale experiments. The results with 1,1,1-trichloroethane shows that (1) PAC/NZVI composite can have both adsorption and degradation capability toward chlorinated organic pollutants in drinking water aquifers; and (2) negatively charged, fine PAC prepared from woody material has high porosity to accommodate and it can support NZVI, which may prevent NZVI agglomeration and its oxidation. Experiments carried out with variable amounts of PAC (0.2 g/L – 0.8 g/L) and NZVI (0.2 g/L – 0.6 g/L) loading showed high efficiency in adsorption and degradation of 1,1,1-TCA. Further, the results also show that 1,1,1-TCA sorption increased with increasing PAC loading, whereas lower PAC concentration yielded faster degradation kinetics and higher byproduct generation. NZVI supported on PAC has remained active for more than four months, suggesting its effectiveness and longevity. Finally, addition of Copper (Cu) as secondary metal catalyst resulted in faster degradation and higher byproduct generation.