Enhanced detoxification and valuable metal extraction from electroplating sludge via ultrasonic-assisted ferric sulfate bio acid

Electroplating sludge (ES) is a hazardous waste containing toxic heavy metals, yet it is also a valuable secondary source of metals, necessitating its recycling for environmental and economic benefits. This study presents an innovative ultrasonic-assisted ferric sulfate bio acid (FSBA) process aimed at extracting chromium (Cr), copper (Cu), and nickel (Ni) from ES. The bacterial supernatant of Acidithiobacillus ferrooxidans was utilized to produce ferric ions and sulfuric acid for the leaching experiments. We systematically investigated various parameters influencing leaching efficiency, demonstrating that ultrasonication significantly enhanced metal extraction rates while reducing leaching time. The process achieved extraction efficiencies of 92.51% for Cr, 86.91% for Cu, and 91.25% for Ni in just 8 minutes under optimal conditions (S/L ratio of 10 g/L, 400 rpm, and 45 °C). Elemental analyses confirmed the improved extraction facilitated by ultrasound, and further analyses such as field emission scanning electron microscopy and X-ray diffraction identified the formation of hydronium jarosite on residue surfaces at elevated temperatures. Overall, both synthetic precipitation leaching and toxicity characteristic leaching procedure tests validated the effectiveness of the FSBA process for detoxifying the ES.