• A hydrothermal method using scorodite formation selectively removes arsenic from acid polymetallic solutions containing high concentrations of Cd and Zn.
• Thermodynamic analysis identified a pH range of 1.8–3.9 for selective As removal as FeAsO4, preventing Cd precipitation as Cd5H2(AsO4)4.
• Under optimized conditions (pH adjusted to 1.0), 88.96% of As was removed as scorodite with minimal loss of Cd (2.44%) and Zn (1.13%).
• The study provides a practical approach to recover valuable metals from arsenic-bearing metallurgical wastes while achieving stable arsenic disposal.