Prepn. of ceramic bodies, in which heavy metal-contg. residues (HMR) are bound, comprises: forming a mouldable mixt. contg. HMR, water and si moulding a green body from the mixt.; and firing the mixt. to give a dense, sintered, stone- or brick-like body. Alternatively, a mixt. contg. HMR and silt is pressed and fired to give a prod. as above. Ceramic bodies obtd. by the process are also claimed. USE/ADVANTAGE - HMR are esp. hydroxide sludges, specifically from electroplating plants, chemical pptn. or dissolution processes or waste water purificn. plants (all claimed). Such materials are utilised and made harmless in ceramics, from which heavy metals are not, or only very slowly, eluted. Silt contaminated with harmful organic components (e.g. mineral oils or polychlorinated biphenyls) can also be disposed off, as well as other problem materials (added to the ceramic-forming mixt.) such as glass grinding sludges (e.g. as waste from the glass or enamel industry), used casting sand and blasting sand, dust from dry separators (e.g. waste gas purifying filters) and fly ash. The process uses silt, rather than (more expensive) clay. In some cases addn. of flux is unnecessary, since hydroxide sludges can act as flux.
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