Effect of pH on the flotation performance of incinerator fly ash

ABSTRACT

Flotation was proved to be effective for decarburization and removal of dioxins from hospital solid waste (HSW) incinerator fly ash, but weathering makes it difficult. The effects of three types of surfactants including nonionic (Tween 80), anionic (SDS), and cationic (CTAB) at different pulp pH values on the flotation performance of weathered HSW incinerator fly ash were investigated. Results showed that the corresponding optimal pH values of Tween 80, CTAB, and SDS were 7, 5, and 9 in terms of decarburization performance, respectively, which were validated by the measurement of Zeta potential. The total dioxins and carbon removal efficiencies showed good correlation at various pulp pH values with surfactant of Tween 80. The optimum surfactant type and pH value should be selected as Tween 80 and pH = 7 from the standpoints of the dioxin removal. Under the optimum condition, the lowest content of dioxins (2.7 ng I-TEQ/g) in the tailings was obtained. The content of heavy metals in the froths exhibited higher with addition of SDS compared with that with Tween 80 and CTAB.

KEYWORDS:

• Incinerator fly ash
• flotation
• pH value
• dioxins
• heavy metals

Acknowledgments

The authors gratefully acknowledge Tianjin Natural Science Foundation under the project number 18JCYBJC24100, National key research development program under the project number 2017YFC0703100, and National Natural Science Foundation of China under grant under the project number NSFC51378332.