Adsorption behavior of carboxy- and amine-terminated magnetic beads for patulin: Batch experiments in aqueous solution and apple juice

Patulin (PAT) is a highly water soluble, heat resistant and toxic fungal metabolite mostly contaminating apple juice. Due to its serious health effects, its removal from foodstuffs is required to ensure food safety. In this study, carboxy- and amine-terminated iron oxide spheres (Fe3O4-COOH and Fe3O4-NH2) were investigated for their adsorbing capacity of PAT in both aqueous solution and apple juice, and evaluated for being an effective detoxifying agent for PAT. The physical and chemical properties of adsorbents were characterized by X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR) and Scanning Electron Microscopy (SEM). The maximum adsorption capacities Fe3O4-COOH and Fe3O4-NH2 for PAT obtained at 25 °C, pH 6 for 5 h were 0.206 mg/g and 0.104 mg/g, respectively. Best fitting adsorption isotherm and kinetics models of PAT adsorption process were Hill isotherm (Radj2 = 0.985) and pseudo-second kinetic models (Radj2 > 0.99) for carboxy groups and Langmuir isotherm (Radj2 = 0.974) and pseudo-second kinetic models (Radj2 > 0.99) for amine groups on the surface of adsorbents. These models with the experimental results confirmed the physical adsorption process, while thermodynamic analysis indicated that adsorption process was spontaneous and endothermic between PAT and both adsorbents. Reusability study showed the effective removal of PAT at four cycles by both adsorbents. This study indicated that carboxy- and amine-terminated magnetic spheres have promising potentials in PAT removal from both aqueous solution and apple juice without affecting quality parameters of juice.