Enhanced adsorption removal of aflatoxin B1, zearalenone and deoxynivalenol from dairy cow rumen fluid by modified nano-montmorillonite and evaluation of its mechanism

Animal feed supplementation with non-nutritive mycotoxin adsorbents is by far the most practical and effective method for mitigating the adverse effects of mycotoxin contamination. In current research, the nano-montmorillonite (NMMT) was modified by cationic surfactant to improve the adsorption capacity for mycotoxins. The structure and surface properties of raw NMMT and modified nano-montmorillonite (NMMT-STAB) were characterized by scanning electron microscopy, N2 adsorption-desorption isotherms, X-ray diffraction, Fourier transform infrared, elemental content analysis and thermogravimetric analysis. Adsorption properties and mechanism were studied among polar aflatoxin B1, weak polar zearalenone and nonpolar deoxynivalenol. And in vitro adsorption experiments were performed by a batch mode in dairy cow rumen fluid media. The adsorption kinetics and equilibrium isotherms were evaluated. The as-prepared NMMT-STAB exhibited irregular layered structure with abundant pores and excellent surface performance. The N2 adsorption-desorption curves could be classified as type IV and the hysteresis loop of type H3 was visible, which no limiting adsorption was observed at high P/P0. After modification, the change of diffraction angle 2 j could be observed obviously, layer spacing expanded to 21.9 Å, indicating that alkyl chains had been intercalated into the interlayer of NMMT-STAB, which was further confirmed by the results of Fourier transform infrared and elemental content analysis. The equilibrium adsorption capacity of NMMT-STAB to aflatoxin B1, zearalenone and deoxynivalenol reached to 9.23, 9.33 and 2.13 mg/g, which increased by 1.36, 4.81 and 1.92 times than raw NMMT, respectively. Compared to the recently reported mycotoxin adsorbents, the adsorption capacity of NMMT-STAB was also higher. The adsorption kinetic process of NMMT-STAB could be better fitted by pseudo-second-order model. The intra-particle diffusion model showed that the adsorption process could be partitioned to three phases, which appeared as contact time progresses. The Freundlich isotherm model was more appropriate for describing the adsorption behaviors to aflatoxin B1 and zearalenone, but the Langmuir isotherm model was more appropriate for deoxynivalenol. These results stated that the modified NMMT-STAB would be a promising material for decontamination of weak polar and nonpolar mycotoxins in animal feeds due to its features of fast adsorption and high capacity.