Removal of metallic Al and Al/Zn alloys in MSWI bottom ash by alkaline treatment

Dongxing Xuan; Chi Sun Poon

doi:10.1016/j.jhazmat.2017.10.002

Removal of metallic Al and Al/Zn alloys in MSWI bottom ash by alkaline treatment

J Hazard Mater. 2018 Feb 15:344:73-80. doi: 10.1016/j.jhazmat.2017.10.002. Epub 2017 Oct 6.

Authors

Dongxing Xuan¹, Chi Sun Poon²

Affiliations

¹ Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong. Electronic address: d.x.xuan@polyu.edu.hk.
² Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong. Electronic address: cecspoon@polyu.edu.hk.

PMID: 29031096
DOI: 10.1016/j.jhazmat.2017.10.002

Abstract

In order to reduce the leaching of pollutants and remove the Al and Zn/Al alloy from municipal solid waste incineration bottom ash (MSWIBA), an optimized alkaline pre-treatment procedure was developed in this study. The influences of alkaline conditions on the removal rate of Al and Zn/Al alloy were investigated, including [OH]^- concentration, temperature, particle size, liquid/solid ratio and treatment duration. The experimental results showed that the optimized alkaline pre-treatment conditions to efficiently remove the Al and Zn/Al alloy was by using a minimum of 1.0mol/l [OH]^-, at 55°C and with a minimal liquid/solid ratio of 5. The removal rate of Al and Zn/Al alloy followed an S-shape curve, in which the slow beginning stage was attributed to the protection of the oxidation layer and the quenched product around the Al and Al/Zn alloy. After 3h of the optimized alkaline pre-treatment, the leaching of Cr, Cu, Pb and Zn of the treated MSWIBA was reduced by more than 90% of that of the original MSWIBA. The alkali-silica reaction test further indicated that the expansion of concrete prepared with the pre-treated MSWIBA was significantly reduced and there was no macro-crack or spalling damage on the surface of the tested specimens.

Keywords: Alkali-silica effect; Alkaline treatment; Heavy metals; Incineration bottom ash; Metallic Al and alloy.