Aflatoxin Adsorption by Bentonites from Contemporary Mine Sites In Texas.

Smectite clay binders have been effective in diets of diverse animal types to prevent liver cancer and other harmful effects of aflatoxin B₁ (AfB₁). Among 20 smectite clays tested from the USA and Mexico there was a ten-fold range of AfB₁ adsorption. Two of the better performing clays were provided by Southern Clay Products, Gonzales, TX. The abrupt increase in corn production for fuel is likely to increase the fungus production of AfB₁ since the water supply is limited. Thus, five smectite clay samples from SCP mines were collected that differed in color and hardness.

The samples are being characterized by methods recommended for evaluating clay binders of AfB₁*. Samples were dried in air, ground, and analyzed without further treatment. Smectite clay is the dominant mineral as expected (~15 Å) for all the samples.

The FTIR spectra have the AlOH bands at ~915 cm^-1as implied by 060 XRD peaks. The FTIR band at 883 cm^-1 for FeAlOH indicates octahedral Fe in the smectite as observed here and in earlier high-performing bentonite adsorbents. The AlMgOH band is only present for 3 samples (two poor and the intermediate adsorbent). The prominent SiO₂ band at 795 cm^-1 and the strong 4.05 Å peaks in samples 1TX and 3TX indicate dilution of the smectite by opaline silica and cristobalite. Quartz is a diluent in samples 4TX and 5TX.

Both Na-hexametaphosphate and ultrasonic probe treatments were required to disperse the clay for laser diffraction particle size analysis. The better adsorbents have >61% <5 μm particles. The pH range is from 6.5 to 4.2 and the less acid samples are the better adsorbents. The 0.50 to 0.17 mol/kg adsorption capacity range of the five bentonites relates well to their mineralogy and particle size distribution.

 

*Dixon et al. 2008, Applied Clay Science 40:201-208.