Elimination of patulin in apple juice using cysteine capped Fe₃O₄ nanoadsorbent

The present study evaluated the preparation of L-cysteine capped Fe₃O₄ (magnetite) nanoparticles (LCys-Fe₃O₄ NPs), with a particular focus on their potential as an adsorbent and also the efficiency of these NPs in the removal of patulin from apple juice. The methods employed, including Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray powder diffraction analysis (XRD), X-ray Photoelectron Spectroscopy (XPS), and Fourier Transform Infrared Spectroscopy (FT-IR), effectively showed the synthesis of LCys-Fe₃O₄ NPs. The proposed method was not only used for patulin removal; rather, it significantly enhanced the sensitivity of patulin measurement. The efficiency of patulin elimination was affected by many factors, including contact time (5-140 min), patulin initial concentration (50-150 µg/L), and amount of NPs (1-5 mg). The synthesized adsorbent achieved a removal efficiency of 98.6% for patulin adsorption at pH = 3.8. This was accomplished by employing 3 mg LCys-Fe₃O₄ NPs over a 100-min duration, resulting in a maximum adsorption capacity of 454 µg/g for the initial concentration of patulin 50 µg/L. This high removal efficiency can be attributed to active surface sites (-NH₂ and -COOH groups). The removal information obtained from an HPLC method, using the prepared adsorbent, exhibited a good fit with the Freundlich isotherm, indicating a multi-layer adsorption process on the adsorbent. The experimental findings were analyzed using an adsorption kinetic model, revealing that the adsorption kinetics of patulin onto LCys-Fe₃O₄ NPs conformed to the pseudo-second-order model. In conclusion, the proposed method demonstrated remarkable efficacy in decreasing patulin concentrations in contaminated apple juice by approximately 81.5%. Moreover, the adsorption process had no impact on the quality of the apple juice.