Recycling and detoxification process of waste tire ash via acid leaching and neutralization

Abstract

The possibility of a novel process of recycling and detoxification for waste tire ash, which contains hazardous Zn and Al, using acid leaching and neutralization was investigated. The waste tire ash mainly contains Zn, Al, Fe, Ca and Si. The leached contents of Zn, Al, and Fe with 1 mol/L of sulphuric acid (H2SO4) and hydrochloric acid (HCl) are almost same and the highest, while those of Ca with HCl is high and with H2SO4 is almost zero due to the formation of gypsum (CaSO4·2H2O). The optimum leaching condition is that waste tire ash was treated with 1 M H2SO4 for 1 h at 60 °C (solid-liquid ratio is 125 g/L). The elution of Zn and Al from the residue via H2SO4 leaching are 0.7 mg/L and 0.15 mg/L, respectively, which are lower than Japanese elution standard (Zn: 1 mg/L, Al: 0.2 mg/L), while those from raw ash are 3.3 mg/L and 1.4 mg/L. Zn-type layered double hydroxide (Zn-LDH) can be synthesized from leached liquor at 40 °C for 1 h by neutralization at pH 7. These results suggested that detoxified ash and environmental friendly material can be obtained from waste tire ash using H2SO4 acid leaching and neutralization.