Insights into the pyrolysis/gasification mechanism of cation ion exchange resins based on ReaxFF simulation and DFT computation

Massive spent ion exchange resin (IER) would be generated in water treatment, which require proper disposal. Pyrolysis/gasification are regarded as effective treatment methods. The degradation mechanism of IER in pyrolysis/gasification was investigated using reactive force field molecular dynamics (ReaxFF-MD) simulation and density functional theory (DFT). The linear carbon backbone showed higher reactivity than CC bonds and single carbon bonds attached to benzene. The C–C bond linking styrene and divinylbenzene had lowest bond dissociation energy (365.5 kJ/mol). Activation energies for gasification were 27.5 % and 38.2 % lower than pyrolysis for the first and second stages. The gasification of carbonization products was an additional third stage in gasification. The average degradation rates for pyrolysis/gasification were 52 % and 60 %, indicating a catalytic effect of steam. The generation of CO and H2 was enhanced by H2O. The findings would offer valuable data for future studies on the thermal conversion of spent IER.