EVALUATION OF THE TIME-DEPENDENT NEUTRALIZING BEHAVIORS OF MSWI BOTTOM ASH AND STEEL SLAG

A long-time batch pH titration was used to investigate the time-depend ent neutralising behaviours of municipal solid waste incineration (MSW I) bottom ash and steel slag. The neutralising processes of the solid wastes were evaluated by using reaction path modelling. The experiment s showed that the acid neutralising capacity increased with reaction t ime. Thus, a short-time pH titration should lead to a large underestim ation of the neutralising capacity since relatively slow matrix dissol ution reactions of the solid waste may give a considerable contributio n in a long-time process. The characteristics of the two investigated wastes differed in their neutralising processes. The differences appea red in the pi-I-dependent behaviour as well as in the distribution of the acid neutralising capacity at different pH levels. The pH-dependen t behaviour was closely related to the dissolution kinetics of the was te matrix. The key factor of the neutralising processes was the dissol ution of calcium-containing minerals or materials. In addition, the se condary minerals, which may precipitate and later redissolve, were als o important to the neutralising processes. (C) 1998 Elsevier Science B .V.