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Efficacy of Two Texas Bentonites in Binding Aflatoxin B1 and in Reducing Aflatoxicosis in Broilers
- Ana Luisa Barrientos-Velazquez, Radhika Kakani, Justin Fowler, Akram-ul Haq, Christopher A. Bailey, Youjun Deng
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- Journal:
- Clays and Clay Minerals / Volume 70 / Issue 3 / June 2022
- Published online by Cambridge University Press:
- 01 January 2024, pp. 354-369
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The incorporation of bentonites in aflatoxin-contaminated animal feeds to remedy aflatoxicosis has been tested widely in animal trials. Yet, a large variation in efficacy among samples has been observed which has been attributed to variations in the properties of the clay mineral adsorbents. The objectives of the current study were: (1) to evaluate the mineral and chemical composition of two selected bentonites to find minerals or elements which are potentially of concern; (2) to characterize the aflatoxin B1 (AfB1) adsorption (selectivity, capacity, reversibility, and interlayer accessibility) by the bentonites; and (3) to evaluate the safety and efficacy of selected clays as amendments of aflatoxin-contaminated feed for broiler chickens. The mineral, chemical, and exchange cation composition of the clays were analyzed, and they appeared to be safe for use in feed. The bentonites and their fractions showed that adsorption capacities range from 0.48 to 0.97 mol/kg. The interlayer spaces of both montmorillonites were accessible by AfB1, and the adsorption was irreversible. Three-day old broiler chickens were given clean and high-aflatoxin-concentration (1400 mg/kg) diets with and without the presence of the two bentonites. After three weeks the chickens were sacrificed and biomarkers were evaluated. The presence of aflatoxins reduced the body weight by 58% and resulted in a 25% mortality rate. Adding bentonites 1TX and 4TX increased the body weight of the chickens by 14 and 23%, respectively, but did not improve the mortality rates. The results suggested that selected bentonites could effectively sequester aflatoxins in vivo but did not eliminate the total toxicity present in highly contaminated poultry feed.
Effects of Metal-Polycation Pillaring and Exchangeable Cations on Aflatoxin Adsorption by Smectite
- Ahmad Khan, Mohammad Saleem Akhtar, Saba Akbar, Khalid Saifullah Khan, Mazhar Iqbal, Ana Barrientos-Velazquez, Youjun Deng
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- Journal:
- Clays and Clay Minerals / Volume 70 / Issue 2 / April 2022
- Published online by Cambridge University Press:
- 01 January 2024, pp. 155-164
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Natural smectites bind aflatoxins from water effectively, but the complex chemical environment in the guts of mammals and other animals can limit binding of aflatoxins. Many efforts have been made to enhance the adsorption capacity and affinity of smectites for aflatoxins in the presence of biological compounds. The main objective of the present study was to modify smectite structures by pillaring and cation exchange to enhance aflatoxin B1 adsorption capacity and selectivity. Smectite was pillared with Al and Al-Fe polycations or saturated with Ca, Mg, Zn, or Li. Structural changes in smectites with or without heat treatment were determined using X-ray diffraction and Fourier-transform infrared spectroscopy. Equilibrium aflatoxin B1 adsorption to the smectites was measured in aqueous solution and in simulated gastric fluid. Pillaring with the polycations expanded smectites in the z-direction to 18.6 Å and the expansion was stable after heating at 500°C. Changes in the Al–OH–Al infrared bands in the stretching region supported the formation of pillared clays. Migration of Mg, Zn, and Li into the octahedral sites of the smectite was observed as Mg and Zn saturation yielded a d spacing of 15 Å at 200°C which collapsed to 9.6 Å at 400°C. The 14.6 Å peak of the Li-saturated smectite collapsed to 9.6 Å at 200°C while the 15 Å Ca-saturated smectite peak was stable up to 400°C. The unheated Al- and AlFe-pillared smectites adsorbed significantly more aflatoxin B1 from an aqueous suspension than did unpillared clay. In both water and simulated gastric fluid, heat treatment decreased aflatoxin B1 adsorption to pillared smectites, but heat treatment increased aflatoxin B1 adsorption to unpillared smectites. Without heat treatment, smectites saturated with divalent cations (Ca, Mg, Zn) adsorbed more aflatoxin B1 from an aqueous suspension than the smectite saturated with a monovalent cation (Li). Ca-saturated smectite showed the greatest aflatoxin B1 adsorption, 114 g kg–1, from aqueous suspension after 400°C heat treatment. The Zn-, Mg-, and Li-saturated smectites showed maximum aflatoxin adsorption of 107, 93, and 90 g kg–1, respectively, after 200°C heat treatment. From simulated gastric fluid with pepsin, the 200°C heated, Zn-saturated smectite had maximum aflatoxin B1 adsorption of 68 g kg–1. Pillared smectites effectively adsorbed aflatoxin B1 from aqueous suspension, but Ca- and Zn-saturated smectites after heat treatment might improve the selectivity of smectites for aflatoxin B1 over pepsin and enhance the efficacy of smectite as a feed additive.
The Determinative Role of the Exchange Cation and Layer-Charge Density of Smectite on Aflatoxin Adsorption
- Youjun Deng, Lian Liu, Ana Luisa Barrientos Velázquez, Joe B. Dixon
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- Journal:
- Clays and Clay Minerals / Volume 60 / Issue 4 / August 2012
- Published online by Cambridge University Press:
- 01 January 2024, pp. 374-386
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Using bentonites to adsorb aflatoxin is an effective method of minimizing the toxicity of aflatoxin to animals and humans. Early studies indicated a more than 10-fold difference in aflatoxin adsorption capacity among different bentonites. The determining mineralogical and chemical properties of the clays in aflatoxin adsorption are still poorly understood. The objective of this study was to test the hypothesis that a bentonite’s selectivity and adsorption capacity for aflatoxin is mainly determined by the ‘size matching’ requirement, on a nm scale, between the non-polar interlayer surface domains and the aflatoxin molecules. The non-polar surface domain size of smectites was varied by (1) selecting smectites with different charge densities; and (2) changing the valence and the size of exchange cations to control the amount of water in the hydration shells of the cations. Infrared spectroscopy and X-ray diffraction were also used to characterize the aflatoxin-smectite complexes to investigate if layer-charge density would affect the bonding strength between aflatoxin and the minerals. A large aflatoxin adsorption capacity and high selectivity for aflatoxin were achieved by selecting smectites that had low charge density as represented by their <110 meq/100 g cation exchange capacity. An individual smectite’s selectivity and adsorption capacity for aflatoxin could be enhanced or weakened by replacing the exchange cation. When the smectite was saturated with divalent cations that have smaller hydrated radius (e.g. Ba2+), the smectite’s adsorption capacity and affinity for aflatoxin were enhanced. Aflatoxin entered the interlayer of all six smectites tested. The strength of its bonding to the smectites was not affected by the layer-charge density of the smectites. The results confirmed the importance of nm-scale polarity and size match between aflatoxin molecules and the adsorbing sites on smectite. The high selectivity for aflatoxin can be achieved by selecting a smectite with adequate charge density or by replacing the exchange cations with divalent cations that have low hydration energy.
Yttrium and REE Mineralization in Manganese Pods Occurring in Bentonite Deposits of the Eocene Texas Coastal Plain
- Debora Berti, Niall C. Slowey, Youjun Deng, Thomas E. Yancey, Ana L. Barrientos Velazquez
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- Journal:
- Clays and Clay Minerals / Volume 71 / Issue 3 / June 2023
- Published online by Cambridge University Press:
- 01 January 2024, pp. 253-273
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Eocene-aged bentonite deposits in Gonzalez (Texas, USA) carrfy scattered manganese oxide-rich pods where rare earth element (REE) concentrations as high as 7800 ppm have been detected — 10 times greater than in the already enriched bentonite. This study investigated the nature of the association between REEs and Mn oxides as well as REE modes of occurrence in these pods, in order to understand the processes that mobilize and accumulate REEs in the low-temperature depositional environment of the Texas coastal plain. Embedded, polished blocks of Mn pods were analyzed by Scanning Electron Microscopy (SEM); sections were then extracted by the FIB liftout technique from regions bearing REEs for further analysis by Transmission Electron Microscopy (TEM). The SEM and TEM results revealed the presence of abundant yttrium phosphate nanoparticles identified as xenotime, forming large globular aggregates that reach a few microns in diameter; these xenotime aggregates also host trace concentrations of Zr, Dy, Er, Yb, and Ce. Further, rhabdophane nanoparticles were detected that host predominantly light REEs and Y. The relative proportions of REEs in rhabdophane vary between particles and show decoupling of Ce from other light REEs, suggesting oxidation from Ce3+ to Ce4+. The REE enrichment of these Mn pods is due to extensive weathering along fractures cutting through the bentonite deposit that drove their remobilization and transport downward. At the base of the bentonite, where fractures terminate against the boundary with a cemented sandstone, changes in flow regime combined with gradual downward changes in fluid composition, prompted co-precipitation of Mn oxides and REE phosphates (xenotime and rhabdophane).