Adsorption properties of magnetic carbon nanotubes for patulin removal from aqueous solution systems

Abstract

Patulin (PAT) is a type of mycotoxin produced by the P. expansum, Aspergillus, Penicillium, and Paecilomyces fungal species and constitutes serious food-related and environmental health threats to consumers. In this study, a novel magnetic multi-walled carbon nanotube (MWCNT) adsorbent was successfully synthesized, and its adsorption properties for the efficient removal of PAT from aqueous solution were investigated. The effects of adsorption parameters, such as pH, initial PAT concentration, adsorption time and temperature, were investigated for optimization of the adsorption process. The kinetic and isotherm studies revealed that PAT adsorption was well described by a pseudo-second order model and the Freundlich model, respectively. The maximum adsorption capacity of the as-prepared magnetic MWCNTs reached 640.2 μg/g, which was much higher than that of biological material-based absorbents (p < 0.05), and the adsorption equilibrium time was significantly shortened to 1 h (p < 0.05). Thermodynamic studies revealed that the adsorption process was exothermic. The adsorption activation energy determined from the Arrhenius equation was found to be approximately −27.31 kJ mol−1, suggesting that the adsorption of PAT on magnetic MWCNTs was random and spontaneous in nature within the experimental temperatures. Moreover, the recycling, separation and regeneration of the spent magnetic MWCNTs were evaluated, and the results demonstrated that the spent magnetic MWCNTs could be separated magnetically and regenerated by sodium hydroxide solution for recycling uses up to four cycles without significantly losing adsorption efficiency. Therefore, this novel magnetic MWCNT-based adsorbent could be a potential adsorbent to be applied for PAT removal from many aqueous systems.