Regeneration of hexamminecobalt(II) under the catalysis of activated carbon modified with ZnCl 2 solution

The simultaneous scrubbing of NO and SO2 can be accomplished by hexamminecobalt(II) solution. Activated carbon acts as a catalyst to regenerate hexamminecobalt(II), Co(NH3)62+, to sustain the NO removal efficiency. In this paper, ZnCl2 solution has been used to ameliorate the catalytic performance of coconut activated carbon in the regeneration of Co(NH3)62+. The effects of the modification condition on the catalytic performance of activated carbon have been investigated in a batch stirred cell. The change of the surface chemical characteristics of the activated carbon caused by ZnCl2 treatment was measured by determining the concentrations of acidic and basic groups as well as their points of zero charge (pHpzc) with Boehm titration and mass titration. The alteration of the surface physical characteristics of the carbons was determined with an ASAP2000 Surface Analyzer using N2 as the adsorbate. The experiments demonstrate that the catalytic performance of the coconut activated carbon may be improved when the carbon is treated by ZnCl2 solution with concentration above 0.30moll−1. The best ZnCl2 concentration may be 0.50moll−1. The optimal impregnation duration is 9h. High activation temperature is propitious for the amelioration of the catalytic capability of carbon. 4h may be the best time for the activation of activated carbon. In our experiment, the NO removal efficiency is maintained at a level of 73% when the regeneration of Co(NH3)62+ is under the catalysis of modified carbon while that is 57% with the regeneration of Co(NH3)62+ catalyzed by original carbon. It can be concluded that such modification can improve the catalytic performance of coconut activated carbon in the simultaneous removal of SO2 and NO with Co(NH3)62+ ammonia solution.