H₂S adsorption by municipal solid waste incineration (MSWI) fly ash with heavy metals immobilization

As a byproduct of municipal solid waste incineration (MSWI) plant, fly ash is becoming a challenge for waste management in recent years. In this study, MSWI fly ash (FA) was evaluated for the potential capacity of odorous gas H₂S removal. Results showed that fly ash demonstrated longer breakthrough time and higher H₂S capacities than coal fly ash and sandy soil, due to its high content of alkali oxides of metals including heavy metals. H₂S adsorption capacities of FA1 and FA2 were 15.89 and 12.59 mg H₂S/g, respectively for 750 ppm H₂S. The adsorption of H₂S on fly ash led to formation of elemental sulfur and metal sulfide. More importantly, the formation of metal sulfide significantly reduced the leachability of heavy metals, such as Cr, Cu, Cd and Pb as shown by TCLP tests. The adsorption isotherms fit well with Langmuir model with the correlation coefficient over 0.99. The adsorption of H₂S on fly ash features simultaneous H₂S removal and stabilization and heavy metals found in most MSWI fly ash, making fly ash the potential low cost recycled sorbent material.