Using waste to treat waste: utilizing pickling liquor for detoxification and extraction of valuable elements from electroplating sludge

Addressing the urgent need for sustainable solutions in waste management, this study focuses on the pivotal task of recycling heavy metals from electroplating sludge (ES), a critical issue both environmentally and economically. The research introduces a novel leaching process utilizing pickling liquor as a reagent to extract valuable metals from the sludge. Key parameters such as agitation speed, solid to liquid ratio (S/L), temperature, and duration were examined to optimize the leaching rate. Results revealed impressive extraction rates, with 92.33 % Cr, 89.49 % Cu, and 89.59 % Ni extracted within 120 min from S/L 10 g/L, at 300 rpm, and 25 °C. However, it was noted that increasing temperature negatively impacted the leaching rate and led to the formation of undesirable compounds. X-ray diffraction (XRD) analysis identified gypsum and potassium jarosite as predominant compounds formed on the leaching residues at different temperatures of 25 °C and 45 °C. Field emission scanning electron microscopy (FE-SEM) illustrated significant morphological changes in the residues, indicating the influence of temperature on compound formation. Additionally, environmental risk assessment of the residues was conducted using synthetic precipitation leaching procedure (SPLP) and toxicology characteristic leaching procedure (TCLP) methods. In conclusion, this research underscores the promising potential of the developed leaching process using pickling liquor to reclaim valuable metals from ES. By optimizing parameters and assessing environmental risks, this study contributes to advancing environmentally sound practices in industrial waste management.