CHARACTERIZATION OF VITRIFIED SLAG FROM MIXED MEDICAL WASTE SURROGATES TREATED BY A THERMAL PLASMA SYSTEM

Various mixed medical waste surrogates have been vitrified by a plasma system built at Institute of Nuclear Energy Research (INER) in Taiwan , Republic of China. Characterizations of vitrified slag were carried out in order to evaluate the effectiveness of an indirect plasma heati ng used in the INER system. After vitrification, a monolithic metal nu gget was separated from the vitrified slag as a result of the gravity effect, The vitrified slag consisted of mostly amorphous state of SiO2 , which in turn dissolved other minor constituents from waste feeds an d crucible container. In the slag, dispersive metal-bearing second pha ses in different shapes were observed. Due to their insoluble nature, these phases were embedded in the slag matrix, and no macroscopic segr egation was detected. This observation indicates the presence of mixin g state during the vitrification treatment. The formation of second ph ases was closely related to the metallic waste treated, as evidenced b y the increased slag densities for the high metallic feed samples, Lea chability analysis results revealed that the encapsulation of these se cond phases by the slag matrix was very effective. Therefore, with opt imal feed compositions, the indirect plasma heating condition used in this study has been shown to be satisfactory for the thermal vitrifica tion of mixed medical wastes. (C) 1998 Elsevier Science B.V.