Sustainable recovery of zinc and silver from Algerian leaching residues for ecological valorization

Abstract This study demonstrates the ecological valorization of zinc leaching residues from ALZINC (Ghazaouet, Algeria). Under optimized conditions (pH 1.8, 70 °C, 90 min, 2.55 mol/L H₂SO₄), zinc recovery reached ~ 92% and silver recovery ~ 20% using thiourea, with pH adjustment by lime (CaO) or NaOH ensuring iron and heavy metal precipitation. Residue characterization using X-ray fluorescence (XRF), Inductively Coupled Plasma–Optical Emission Spectrometry (ICP-OES), and X-ray diffraction (XRD) revealed zinc ferrite and iron-rich phases that hinder conventional leaching, while Response Surface Methodology (RSM) and Analysis of Variance (ANOVA) identified the operating parameters that maximize recovery. Compared with our earlier work (Begar et al. in Min Sci 28:117–26, 2021), this dual-step leaching process improves zinc recovery by more than 20% and, for the first time in Algeria, demonstrates silver recovery as a valuable by-product. The process was validated through rigorous quality assurance/quality control (QA/QC) procedures (replicates, blanks, certified standards, > 95% recoveries) and the preliminary cost–revenue estimation suggests potential economic viability at scale, with silver potentially contributing ~ 8–10% of the total revenue despite its low concentration. Beyond its technical performance, the approach reduces hazardous waste toxicity and supports Algeria’s strategy for circular economy and sustainable metallurgy.