KAGAKU KOGAKU RONBUNSHU, Vol.29, No.1, 118-123, 2003
Elution control of arsenic ion from sewage sludge-ash by coating with coal bottom-ash
A unique control method was developed for toxic ion elution from sewage sludge-ash in an acid solution. Coated sewage sludge-ash pellets were prepared by covering with bottom ash from a coal-fired boiler. Since the melting temperature of inner sewage sludge-ash was lower than that of outer coal bottom-ash, coated sewage sludge-ash was heated rapidly in order to melt only the surface of a pellet. The heating conditions were determined based on the observed thermal conductivities of sewage sludge -ash and coal bottom-ash. Elution tests were carried out in hydrochloric acid and nitric acid solution for the sewage sludge-ash pellets with and without coal bottom-ash coating. The coating of sewage sludge-ash completely suppressed the elution of arsenic ion in both solutions, whereas the uncoated pellets showed considerable elution.