Two-Step Flotation Treatment for Removal of Toxic Matter from Hospital Solid Waste Incinerator Fly Ash

Han-Qiao Liu,Dan-Dan Zang,Fang Liu,Rui Zhang,Guo-Xia Wei

doi:10.4209/aaqr.2017.02.0090

Han-Qiao Liu, Dan-Dan Zang + Show 3 more

Open Access

https://doi.org/10.4209/aaqr.2017.02.0090

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Abstract

ABSTRACTApplication of two-step flotation for removing dioxins and heavy metals from hospital solid waste incinerator (HSWI) fly ash was studied. In the first step, decarburization flotation was executed to remove dioxins from raw fly ash. The second step of precipitation flotation was carried out to recycle the toxic metals in the residual slurry. Finally, an acid leaching-sulphide precipitation-flotation method was proposed. The results showed that carbon removal rate was 90.7%, and the dioxin removal percentage was 91.0% during decarburization flotation. And Zn, Pb and Cu in residual slurry were acid-leached with the removal efficiencies being 91.3%, 79.2% and 85.6%, respectively. The optimum sulphidation condition of heavy metals in the residual slurry were Na2S molar ratio of 1.4 and sulphidation time of 30 min. Subsequently, precipitation flotation could recover 49.9% of Zn, 42.0% of Pb and 48.7% of Cu from the raw fly ash. After the two-step flotation, the toxicity of the tailings reduced considerably, and the tailings could be disposed in landfill. Therefore, this two-step flotation treatment of HSWI fly ash may result in both detoxiﬁcation and potential resource recovery.

Highlights

Hospital solid waste incinerator (HSWI) fly ash is categorized as hazardous waste rich in toxic metals and organic pollutants such as chlorobenzenes (CBs), chlorophenols (CPs), polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs), etc. (Lee et al, 2003; Wang et al, 2005; Chen et al, 2013; Cheruiyot et al, 2015; Cheruiyot et al, 2016; Lee et al, 2016)
Raw fly ash (30 g), deionized water (600 mL), and a balanced amount of agents including methyl isobutyl carbinol (MIBC) which served as a frother and kerosene which served as a collector were mixed to obtain the slurry, which was fed from the top of the flotation column
Feng reported that heavy metal chloride complexes which were formed and absorbed onto the surface of fly ash could exchange with carbonate ions, which would improve the performance of decarburization flotation (Feng et al, 2015)

Summary

Introduction

Hospital solid waste incinerator (HSWI) fly ash is categorized as hazardous waste rich in toxic metals and organic pollutants such as chlorobenzenes (CBs), chlorophenols (CPs), polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs), etc. (Lee et al, 2003; Wang et al, 2005; Chen et al, 2013; Cheruiyot et al, 2015; Cheruiyot et al, 2016; Lee et al, 2016). Incinerator fly ash can be disposed by four main methods, namely: acid extraction, chemical stabilization, melting treatment and cement solidification, among which cement solidification is widely adopted due to its simple operation and low investment. It will only reduce the leaching amount of heavy metals and has little effect on organic pollutant removal (Huang et al, 2011). Traditional chemical stabilization is inappropriate for source recovery from such types of wastes Even more, this method may produce unexpected wastes (Deliyanni et al, 2017)

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