Characterization of ash derived from combustion of paper mill waste sludge: Comparison with municipal solid waste incinerator ash

Fly ash derived from incineration of Malaysian paper mill waste sludge (PMWS) was physically and chemically characterized in order to determine its potential toxicity as well as its application as cement replacement material. The results were compared with results obtained from similar characterization on Malaysian municipal solid waste incineration (MSWI) bottom ash. Principal analyses conducted include particle size distribution, elemental analysis, toxicity characteristic leaching procedure (TCLP) as well as thermogravimetric, x-ray diffractometry and FTIR analyses. TCLP result indicated that both the PMWS and MSWI ashes should not be classified as hazardous wastes in terms of heavy metal leachability, since leachable copper, cadmium, lead and nickel concentrations were detected below the stipulated leachability limits. Both ashes could be reused as cement replacement materials since both contained SiO2 which is one of the main building components in cement and concrete utilizations. Nonetheless, PMWS ash could be more suitable as a cement replacement material as compared to MSWI ash, as the former had significantly smaller particle size distribution and lower organic content