Hydrometallurgical recovery of heavy metals from low grade automobile shredder residue (ASR): An application of advanced Fenton process (AFP)

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P> <P>To investigate the leaching and recovery of heavy metals from low-grade automobile shredder residue (ASR), the effects of nitric acid (HNO<SUB>3</SUB>) and hydrogen peroxide (H<SUB>2</SUB>O<SUB>2</SUB>) concentrations, liquid/solid (L/S) ratio, leaching temperature and ASR particle size fractions on the heavy metal leaching rate were determined. The heavy metals were recovered by fractional precipitation and advanced Fenton process (AFP) at different pHs. The toxicity characteristic leaching procedure (TCLP) test was also performed in the residue remaining after heavy metal leaching to evaluate the potential toxicity of ASR. The heavy metal leaching efficiency was increased with increasing HNO<SUB>3</SUB> and H<SUB>2</SUB>O<SUB>2</SUB> concentrations, L/S ratio and temperature. The heavy metal leaching efficiencies were maximized in the lowest ASR size fraction at 303 K and L/S ratio of 100 mL/g. The kinetic study showed that the metal leaching was best represented by a second-order reaction model, with a value of R<SUP>2</SUP> > 0.99 for all selected heavy metals. The determined activation energy (kJ/mol) was 21.61, 17.10, 12.15, 34.50, 13.07 and 11.45 for Zn, Fe, Ni, Pb, Cd and Cr, respectively. In the final residue, the concentrations of Cd, Cr and Pb were under their threshold limits in all ASR size fractions. Hydrometallurgical metal recovery was greatly increased by AFP up to 99.96% for Zn, 99.97% for Fe, 95.62% for Ni, 99.62% for Pb, 94.11% for Cd and 96.79% for Cr. AFP is highly recommended for the recovery of leached metals from solution even at low concentrations.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Nitric acid combined with H<SUB>2</SUB>O<SUB>2</SUB> greatly increased the leaching of metals from ASR. </LI> <LI> The leaching rate of metals increased with increasing temperature and L/S ratio. </LI> <LI> The second-order kinetic model was best fitted (R<SUP>2</SUP> ≥ 0.99) with the metal leaching. </LI> <LI> The leaching rates of metals were controlled by both diffusion and chemical processes. </LI> <LI> Application of the advanced Fenton process greatly increased the recovery of metals. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>