Kinetics and extraction of heavy metals resources from automobile shredder residue

• Water of pH 2 is highly effective for the extraction of metals from ASR.
• Extraction of metals increased greatly with decreasing pH and particle size of ASR.
• An increasing L/S ratio also greatly increased metals extraction.
• A second order reaction kinetics was best fitted for extraction of metals.

Automobile shredder residue (ASR) has been considered as risky waste due to presence of high concentration of toxic metals, which can pose an environmental threat of being leached out under acidic conditions in the landfill. The present study investigated the extraction of Zn, Cu, Pb and Cd from ASR using water over a range of pH (2–8), temperature (25–55 °C), liquid/solid (L/S) ratio (10–100 mL g−1) and particle size (0.0–4.75 mm). The extraction kinetics of Zn, Cu, Pb and Cd from ASR using water were also analyzed by the shrinking core model (SCM) and second-order reaction model. The extraction rates of metals from ASR were improved by increasing different temperatures and liquid to solid ratios. A maximum extraction of metals was achieved at pH—2, temperature—25 °C and liquid to solid ratio—100 mL g−1. Metal extractions were not efficient at alkaline pH of water. The smallest size fraction of ASR was highly recommended for extraction of heavy metals rather than the larger fractions. The extraction data were best fitted (R2 ≥ 0.95) by the second order reaction model, but not by the SCM (R2 < 0.95).

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