Zearalenone (ZEN) as an estrogenic fungal toxin produced by Fusarium graminearum widely presents in grains, corn, wheat and their by-products. The presence of ZEN seriously endangers the health of animal and humanbeing due to the reproductive toxicity, immunotoxicity, genotoxicity, carcinogenic and teratogenic effects. The adsorption method is the most effective way to remove ZEN, and the commonly used adsorbents are silicate minerals. Attapulgite is an advantageous resource in China, which is used as a feed material to enhance immune function and antioxidant capacity, promote intestinal health, and improve animal production performance and product quality. However, it is difficult to realize the efficient removal of low polarity and hydrophobic ZEN using hydrophilic and negatively charged attapulgite. It is thus indispensable to modify attapulgite with cationic surfactants to enhance their surface hydrophobicity and adsorption property toward ZEN. Imidazole ionic liquid surfactant C_nmimBr has lower critical micelle concentration, higher adsorption efficiency and better surface properties than conventional surfactants with the same carbon chain length. In this paper, attapulgite was modified with ionic liquid surfactant C_nmimBr for the efficient adsorption of ZEN.

APT (25.0 g) was dispersed in 250 mL distilled water at a stirring rate of 540 r/min to form a uniform suspension, and different types of C_nmimBr (i.e., C₁₂mimBr, C₁₄mimBr, C₁₆mimBr, and C₁₈mimBr) were added into the suspension with different concentrations (i.e., 0.5%, 1.0%, 2.5%, 3.0%, and 5.0%), respectively. The mixtures of C_nmimBr and APT were stirred at room temperature for 4 h, and then the solid products labeled as C_nmimBr-APT nanocomposites were centrifuged, washed with deionized water until no bromine ions, dried at 105 ℃ for 4 h, and ground to the fine particles below 75 µm.

The removal ratio of C_nmimBr-APT nanocomposites toward ZEN was determined via batch experiments. The influences of C_nmimBr amounts and carbon chain length on the adsorption performance for ZEN were investigated. 1.0% C₁₆mmBr-APT, 2.5% C₁₆mmBr-APT, and 5.0% C₁₆mmBr-APT were selected as adsorbents to investigate the effect of adsorption condition (i.e., adsorbent dosage, contact time, pH value, initial concentration, and coexisting nutrients) on the adsorption performance of ZEN. The adsorption process was analyzed using kinetic and thermodynamic models.

According to the Fourier transform infrared spectra, the relative intensity of C―H bonds at 2 930 cm^-1 and 2 865 cm^-1, and C=N at 1 630 cm^-1 gradually increases with the increase in the carbon chain length and added amount of C_nmimBr, indicating that C_nmimBr is anchored on the APT surface to realize the organic modification. Meanwhile, the organicization degree also increases with the increase in the carbon chain length and C_nmimBr dosage. Furthermore, the modification process does not change the crystal structure of APT, but the specific surface area reduces with the increase in the hydrophobicity, which is beneficial to the efficient removal of ZEN through hydrophobic interaction.

The in-vitro adsorption experiments indicate that the adsorption performance of C_nmimBr-APT nanocomposites is positively associated with C_nmimBr dosage and carbon chain length. The adsorption process follows the pseudo second order kinetic model and Langmuir isotherm. When the modified amount of C₁₆mimBr is 5.0%, the maximum adsorption capacity of C₁₆minBr-APT nanocomposites to ZEN is 7.45 mg·g^-1. Furthermore, pH value and co-existed nutrients (e.g., amino acids, vitamins and minerals) have little effect on the adsorption performance of ZEN.

The novel ZEN adsorbents were prepared based on the organic modification of APT using C_nmimBr with different carbon chain lengths. The results indicated that C_nmimBr modification did not change the crystal structure of APT, while the surface hydrophobicity increased with the increase in the carbon chain length of C_nmimBr. Meanwhile, the adsorption capacity of C_nmimBr-APT nanocomposites toward ZEN increased with the increase in the C_nmimBr dosage, carbon chain length, adsorbent dosage, and initial solution concentration. The adsorption mechanism was mainly due to the hydrophobic interaction between the long organic carbon chains of C_nmimBr and ZEN molecules, and C_nmimBr-APT nanocomposites presented a considerable application potential for the removal of ZEN adsorbents due to the good selective adsorption in the presence multiple nutrients.