The management of cadmium-rich sludges, which are pollutant residues from the phosphorus industry, including the valorization of these sludges through the selective recovery of heavy metals, is a promising prospect. However, there is still a need to develop recovery methods that are both optimized for efficiency, cost-effectiveness, and environmentally friendly. This study aims to enhance cadmium extraction from the polymetallic sludge by optimizing the processes of sulfuric acid (SA) leaching and sodiumsulfide precipitation. Key parameters including SA concentration, temperature, solid/liquid ratio, and stirring velocity were optimized to maximize the heavy metals extraction. Over 90% of the Cd and Zn present in the sludge were successfully extracted. Subsequently, investigates the selective precipitation of metal sulfide from acidic leachates (pH < 2), focusing particularly on cadmium. Through the optimization of chemical precipitation parameters (Na2S concentration, temperature, and reaction time), more than 99% of the cadmium was selectively recovered as CdS. The precipitates underwent analysis for mineralogy, chemistry, purity, and particle size. XRD analyses indicated CdS formation in "Greenockite" and "Hawleyite" forms, confirmed by SEM-EDS data, revealing fine powder consisting of micro and nanoparticles (< 0.5 µm) with varied spherical shapes.