Effects of loading different metal ions on an activated carbon on the desorption activation energy of dichloromethane/trichloromethane.

The effects of loading Fe(3+), Mg(2+), Cu(2+) or Ag(+) on activated carbons (ACs) on interaction of the carbon surfaces with dichloromethane (DCM) and trichloromethane (TCM) were investigated. Temperature-programmed desorption (TPD) experiments were conducted to measure the desorption activation energy of DCM/TCM on the ACs separately doped with ions Fe(3+), Mg(2+), Cu(2+) and Ag(+). The absolute hardness and electronegativity of DCM and TCM were estimated on the basis of density functional theory. The influence of loading the metal ions on the ACs on the interaction of its surfaces with DCM/TCM was discussed. Results showed that the desorption activation energy of DCM and TCM on the modified ACs followed the order: Fe(III)/AC>Mg(II)/AC>Cu(II)/AC>AC>Ag(I)/AC. Both DCM and TCM were hard base. The loading of ion Fe(3+) or Mg(2+) on the surface of the ACs enhanced the interaction between DCM/TCM and the surfaces due to Fe(3+) and Mg(2+) being hard acid, while the loading of ion Ag(+) on the surface of the AC weakened the interaction between DCM/TCM and the carbon surfaces due to Ag(+) being soft acid.