A Study On The Catalytic Performance Of Modified Activated Carbon In The Regeneration Of Hexamminecobalt (Ⅱ)

The wet ammonia desulphurization process can be retrofitted to remove NO and SO2 simultaneously by adding soluble cobalt(II) salt into the aqueous ammonia solution. However, [Co(NH3)6]2+, the active constituent, may also be oxidized to [Co(NH3)6]3+ by the dissolved oxygen, which is unable to activate oxygen molecules or bind NO. In order to regenerate the active constituent [Co(NH3)6]2+ to maintain the capability of removing NO from the gas streams, modified activated carbon acts as a catalyst to regenerate hexamminecobalt(II), [Co(NH3)6]2+, to maintain a high NO removal efficiency for a long time.In this paper, the modification methods used KOH solution, ZnCl2 solution and those two solution compound with air have been studied to find out the catalytic performance of modified activated carbon in the regeneration of hexamminecobalt(II). The effects of the modification conditions, such as KOH and ZnCl2 concentration, impregnation duration, activation temperature and activation duration, on the catalytic performance of activated carbon have been investigated in a batch stirred cell. The experimental results show that the catalytic performance of the coconut activated carbon may be improved when the activated carbon is treated by KOH or ZnCl2 solutions soaked in 0.50 mol·l-1 solution for 9h and than heated under 700℃for 4h.The two-steps modification activated carbons have even better catalytic performance than KOH and ZnCl2 modified activated carbon.Boehm titration, mass titration, BET and FTIR method confirmed that changes of surface area and more micropores play important roles in affecting the regeneration of hexamminecobalt(II) in KOH modification. The micropores are key factor in affecting the catalytic performance of ZnCl2 modified activated carbon. And the critical factor in enhancing the ability of regeneration of hexamminecobalt(II) in two-steps modification is the lactonic.The modification can improve the catalytic performance of coconut activated carbon in the simultaneous removal of SO2 and NO with [Co(NH3)6]2+ ammonia solution. And the modification with KOH-air performed the best among those three methods, obtain a much higher NO removal efficiency than the original coconut activated carbon, and last for a long time.