Process for fixing filter dust containing heavy metals in ceramic mouldings.

摘要

Produced comprises moulding a mixt. of clay, water, heavy metal-contg. filter dust and flux and firing at 900-1070 deg.C, the flux type and amt for formation, at the selected firing temp. below the softening pt, of a molten phase obtd. in vitrification and permanent containment of heavy metals in the moulding. The clay pref. contains at least 25 (more than 30) wt.% AP2O3 (on dry basis) and is mixed with up to 350 g water (w.r.t. 1000g. dry mixt), up to 50 wt.% filter dust (on dry basis w.r.t. clay flux and filter dust). The flux may be silicic acid, nepheline, syemite, glass powder, borax, fluorspar, enamel or even electroplating sludge. The mixt. is pref, extruded to green bodies, dried at max. 150 deg. C for day(s) and fired pref. at 950-1020 deg.C Heavy metal cpd. emissions during firing are filtered pref. using a mol. sieve which is used to prepare further mixts.