Synergistic Fe-Sn-Ni ternary metal oxide nanocomposite for Congo red adsorption: Synthesis, characterization, and Box-Behnken optimization

A Fe-Sn-Ni ternary metal oxide nanocomposite (FSN-MONC) was synthesized via co-precipitation for the efficient adsorption of Congo Red (CR), an azo dye micropollutant known for persistence and toxicity. Structural and morphological analyses confirmed the irregular porous architecture and nanoscale particle aggregation, offering high surface area and abundant adsorption sites. Elemental mapping verified the homogeneous distribution of Fe, Sn, and Ni, while TEM and SAED confirmed highly crystalline nanoparticles (2–20 nm) with polycrystalline multi-phase structure. FTIR and XRD analyses identified metal–oxygen bonds and the coexistence of individual oxide phases (Fe 2 O 3 , SnO 2 , NiO) and mixed phases (NiFe 2 O 4 spinel). BET analysis revealed mesoporosity with a surface area of 243.78 m²/g. Adsorption studies achieved 87.92 % CR removal under optimized conditions, fitting pseudo-second-order kinetics and Langmuir isotherm, consistent with chemisorption and monolayer coverage. Comparative analysis with literature data shows that FSN-MONC exhibits competitive performance (76.87 mg/g). Box–Behnken Design systematically evaluated the effects of pH, adsorbent dosage, concentration, contact time, and temperature. The Fe-Sn-Ni combination imparted synergistic stability, surface activity, and adsorption capacity. FSN-MONC maintained excellent reusability over five cycles, underscoring its promise as a cost-effective, sustainable adsorbent for CR dye removal in wastewater treatment. • Fe-Sn-Ni ternary metal oxide nanocomposite synthesized for Congo Red removal. • Porous morphology: 2–20 nm particles, 243.783 m²/g surface area (FE-SEM/TEM/BET). • XRD shows Fe₂O₃, SnO₂, NiO, and NiFe₂O₄ spinel phase formation. • Pseudo-second order kinetics, Langmuir isotherm confirm chemisorption. • Statistical model: R² = 83.78 %, p < 0.0001, F = 6.46; 5-cycle reusability.