Electroplating sludge valorization into ceramic pigments: Directed transformation of chromium species

Abstract Electroplating sludge (ES), a hazardous waste containing heavy metals, poses significant environmental challenges. This study presents a sustainable strategy for transforming chromium‐rich ES into high‐value uvarovite (Ca 3 Cr 2 (SiO 4 ) 3 ) green pigments via an optimized solid‐state synthesis route. Guided by thermodynamic analysis using FactSage software, the Ca/Si and Ca/Cr molar ratios were optimized to 1.6 and 1.2, respectively, to compensate for the variability in sludge composition. Borax was identified as the optimal mineralizer, enhancing crystallinity while suppressing secondary phase formation. The introduction of carbon effectively reduced the hexavalent chromium content. The synthesized pigments exhibited excellent green coloration and maintained structural stability up to 1200°C. Leaching tests confirmed Cr(VI) concentrations below 0.1 mg/L, complying with regulatory standards. When incorporated into commercial glazes at 3–6 wt.%, the pigments demonstrated coloration performance comparable to conventional Cr 2 O 3 ‐based alternatives. This work establishes a technically viable pathway for the valorization of ES, addressing both waste management and circular economy objectives.