Preparation and characterization of zinc-exchanged montmorillonite and its effectiveness as aflatoxin B1 adsorbent

A zinc-exchanged montmorillonite (Zn-MONT) was prepared from a natural montmorillonite (MONT) and the adsorption of aflatoxin B1 (AFB1) was investigated at pH 3 and 7. Characterization of Zn-MONT was done by determination of chemical composition, the point of the zero charge (pHpzc), thermal (DTA/TGA/DTG) and X-ray powder diffraction (XRPD) analysis.Adsorption of AFB1 (C0 = 4 ppm) by Zn-MONT, at different solid/liquid ratios (10, 1 and 0.5 g L−1), at pH 3 or 7, showed that its adsorption was high (over 96%) and independent of pH, similar to MONT. No desorption of AFB1 from MONT-AFB1 and Zn-MONT-AFB1 complexes occurred at pH 6.5, suggesting strong binding of AFB1 by both adsorbents. Furthermore, AFB1 adsorption by Zn-MONT followed a non-linear (Langmuir) type of isotherm at pH 3 with a calculated maximum capacity of 60.17 mg g−1. The stability of MONT-AFB1 and Zn-MONT-AFB1 complexes was evaluated by calculating the binding energies between AFB1 and metal cations using quantum chemical methods. The evaluated interaction energies of AFB1 with hydrated Zn2+, Mg2+, and Ca2+ cations showed that the strongest interaction was the interaction of the Zn2+ system, −70.2 kcal mol−1, whereas energies for Mg2 and Ca2+ systems were −68.8 and −62.9 kcal mol−1, respectively. The results indicate that Zn-MONT can be suitable for potential practical application as both, an antibacterial and an aflatoxin binding agent.

► Adsorption of aflatoxin B1 (AFB1) by zinc modified montmorillonite (Zn-MONT) was studied at pH 3 and 7.
► Presence of zinc in the interlamellar space of MONT increased adsorption of AFB1.
► The binding energies between AFB1 and metal cations were calculated using quantum chemical methods.
► Known antibacterial activity, and high affinity for AFB1 make Zn-MONT suitable for potential practical application.