The neutralization behavior of MSWI bottom ash on different time scales and in different reaction systems

The neutralization behavior of municipal solid waste incineration (MSWI) bottom ash is characterized according to reaction time and reaction system. Batch and flow-through pH titrations are used to determine the acid neutralizing capacity of the MSWI bottom ash in different reaction systems. A reaction path model and a reactive transport model evaluate the detailed mechanisms and titration kinetics of the experiments. The results indicate that both the neutralization kinetics and titration kinetics of the test methods are important. They determine the relation between the time scale of the experiments and that of an actual leaching environment. Current pH titration experiments account mainly for the relatively fast neutralization reactions, so that they cannot assess the long-term neutralization processes of MSWI bottom ash. It is also found that the neutralization characteristics of MSWI bottom ash in a flow-through system are very different from those in a batch system. The movement of a pH front and the washing-out of soluble buffering components have large influences on the neutralization ability of MSWI bottom ash in a reaction system with flow-through of leachant