The removal of chlorinated aliphatic hydrocarbons from water using reactive activated carbon: the influence of synthesis factors and reaction environments

Granular activated carbon (GAC) composite incorporated with nanoscale zerovalent iron (nZVI) particles (reactive activated carbon, RAC) was synthesized by the liquid phase precipitation method and used to remove chlorinated aliphatic hydrocarbons (CAHs) from water. The influence of synthesis factors, such as base carbon types and annealing treatment temperature, and environmental factors, such as the molecular structure of CAHs, common ionic species and natural organic matter, on the removal capacities of RAC for CAHs was investigated. Mesoporous carbon with high hardness is a good candidate for base carbon, and high annealing treatment (up to 700 degrees C) enhanced the total removal capacity of RAC for CAHs. The removal capacities of RAC for CAHs are consistent with the following order: tetrachloroethene >1,1,1-trichloroethane > trichloroethylene, and the CAH removal processes fit the pseudo-first-order reaction kinetics model well. The removal mechanism of CAHs might be in accordance with a sequence of adsorption, diffusion and dechlorination in two heterogeneous GAC and nZVI materials. The presence of other CAHs, common ionic species and humic acid all inhibited the removal of CAHs. The removal ability of aged RAC for CAHs decreased slightly compared with that of fresh RAC, which demonstrated its good application potential in underground water remediation.