Magnetically separable P4VP–Fe₃O₄ nanoadsorbent for efficient diclofenac removal from water: Synthesis, optimization, and mechanistic insights

In this study, we synthesized and applied a novel paramagnetic nanocomposite, P4VP-Fe₃O₄, for the efficient removal of Diclofenac (DF) from aqueous media. The nanoadsorbent was thoroughly characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area analysis, Fourier transform infrared spectroscopy (FTIR), and diffuse reflectance spectroscopy (DRS), which confirmed its morphological, structural, and surface properties. Critical process parameters, including solution pH, contact time, initial DF concentration, and adsorbent dosage, were systematically optimized using response surface methodology (RSM). Under optimal conditions (DF = 10 mg/L, pH = 5, adsorbent dosage = 1 g/L, and contact time = 75 min), a maximum removal efficiency of 93.3 % and an adsorption capacity of 9.33 mg/g (experimentally obtained under optimized batch conditions) were achieved. Adsorption behavior fit well with the Langmuir isotherm model (R² > 0.993), indicating a theoretical maximum adsorption capacity (qm) of 175.44 mg/g based on equilibrium isotherm fitting. Kinetic analysis showed that the process followed a pseudo-second-order model (R² > 0.985), which provided the best statistical fit to the experimental data, although it does not necessarily imply a specific adsorption mechanism. Due to its magnetic separability, high removal performance, reusability, and low cost, the synthesized P4VP-Fe₃O₄ nanoadsorbent represents a promising candidate for the removal of pharmaceutical contaminants from aquatic environments. • P4VP-Fe₃O₄ nanoadsorbent was synthesized for Diclofenac removal from water. • The adsorbent was characterized using TEM, XRD, BET, FTIR, and DRS techniques. • RSM optimized pH, contact time, DF concentration, and adsorbent dosage. • Adsorption followed Langmuir isotherm and pseudo-second-order kinetic models. • The adsorbent showed 93.34 % removal, magnetic separation, and reusability.