Magnetic adsorptive removal of toxic organic dyes from water by using a polyoxometalate-modified metal-organic framework composite (P2W16Ni2O62/MIL-101(Cr)/CuFe2O4) as a novel fast nano-adsorbent

This study focuses on a magnetic nanoadsorbent, P₂W₁₆Ni₂O₆₂/MIL-101(Cr)/CuFe₂O₄, demonstrating the significant potential for removing cationic dyes. The synthesized nanosorbent was characterized by FT-IR, XRD, BET, SEM-EDX, sorption capacity and VSM. The obtained results revealed that the nanosorbent has a surface area of 1012.2 m²/g, and notable sorption capacity: 342.12 mg/g for MB, 296.80 mg/g for MG, and 496.56 mg/g for CV. The research optimized the adsorption parameters using Response Surface Methodology (RSM) and Box-Behnken Design (BBD). The optimal conditions included a pH of 10, a dye concentration of 50 mg L⁻¹, and a magnetic nanosorbent amount of 0.03 g/L. The kinetic studies showed that the adsorption of dyes aligns with the pseudo-second-order (PSO) kinetic model and the Langmuir isotherm model, indicating a chemisorption mechanism based on the adsorption energy calculations. The thermodynamic analyses confirmed that the adsorption processes were endothermic and spontaneous. According to the stability tests, the adsorbent retains its structural integrity and chemical composition over five reuse cycles, highlighting its potential for practical applications in wastewater dye removal.