Investigation of low concentration SO2 adsorption performance on different amine-modified Merrifield resins

Three amine-modified Merrifield resins (AMMRs) were synthesized with ethane diamine, methylamine and dimethylamine to assess the impact of amine group on SO 2 adsorption under low SO 2 concentration. The dimethylamine-modified Merrifield resin (DMAMR) grafting with tertiary amine groups showed the greatest SO 2 adsorption compared with ethane diamine-modified Merrifield resin (EDAMR) and methylamine-modified Merrifield resin (MAMR). Different amine groups had different reaction mechanisms with SO 2 . It was much easier for SO 2 to form noncovalent charge transfer complex with tertiary amine group than the zwitterion and ion/counterion products with primary and secondary amine groups under dry condition. The noncovalent charge transfer complex had a relatively weaker thermostability than the zwitterion and ion/counterion products. As the temperature increased from 25 °C to 75 °C, the SO 2 adsorption capacity on DMAMR decreased by 78.92%, which was much higher than that of EDAMR and MAMR (63.77% and 63.41% respectively). As SO 2 concentration increased from 40 ppm to 100 ppm, significant increase (∼100%) in SO 2 adsorption capacity was observed. Lower SO 2 flow rate led to a more sufficient reaction between SO 2 and amine groups, resulting the increase in SO 2 adsorption capacities. Water vapor enhanced the SO 2 adsorption performance of AMMRs significantly due to the formation of salt. However, it was more difficult for tertiary amine group to react with SO 2 in the presence of water due to its relatively weaker basicity . DMAMR showed a greater regeneration performance than EDAMR and MAMR under dry and humid condition.