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.

Bentonites are readily available clays used in the livestock industry as feed additives to reduce aflatoxin (AF) exposure; their potential interaction with nutrients is the main concern limiting their use, however. The objective of the present study was to determine the safety of a dietary sodium-bentonite (Na-bentonite) supplement as a potential AF adsorbent, using juvenile Sprague Dawley (SD) rats as a research model. Animals were fed either a control diet or a diet containing Na-bentonite at 0.25% and 2% (w/w) inclusion rate. Growth, serum, and blood biochemical parameters, including selected serum vitamins (A and E) and elements such as calcium (Ca), potassium (K), iron (Fe), and zinc (Zn) were measured. The mineral characteristics and the aflatoxin B1 sorption capacity of Na-bentonite were also determined. By the end of the study, males gained more weight than females in control and Na-bentonite groups (p ≤ 0.0001); the interaction between treatment and sex was not significant (p = 0.6780), however. Some significant differences between the control group and bentonite treatments were observed in serum biochemistry and vitamin and minerals measurements; however, parameters fell within reference clinical values reported for SD rats and no evidence of dose-dependency was found. Serum Na and Na/K ratios were increased, while K levels were decreased in males and females from Na-bentonite groups. Serum Zn levels were decreased only in males from Na-bentonite treatments. Overall, results showed that inclusion of Na-bentonite at 0.25% and 2% did not cause any observable toxicity in a 3-month rodent study.

Due to the environmental problems derived from the use of common surfactants as modifiers for clay mineral adsorbents to mitigate mycotoxin contamination of animal feeds, finding non-toxic modifiers to prepare safe and efficient adsorbents is necessary. The objective of the present study was, therefore, to modify acidified palygorskite with polyhexamethylene biguanide (PHMB) to obtain antibacterial polyhexamethylene biguanide/palygorskite (PHMB/Plg) composites for the removal of zearalenone, a common mycotoxin. The PHMB/Plg composites were characterized and analyzed by X-ray diffraction, Fourier-transform infrared spectroscopy, field-emission scanning electron microscopy, and isothermal nitrogen adsorption analysis. The adsorption properties of the composites with respect to zearalenone and their antibacterial activity with respect to Escherichia coli and Staphylococcus aureus were studied. The results indicated that the hydrophobicity of palygorskite was enhanced after modification with PHMB, which could effectively improve the adsorption property of palygorskite toward the nonpolar zearalenone molecules. The adsorption capacity of PHMB/Plg increased with increasing amounts of polyhexamethylene biguanide and increasing pH. The adsorption data were described well by pseudo-second order kinetics and by the Langmuir adsorption model. The maximum adsorption capacity was 2777 μg/g. When the amount of PHMB added increased to 15 wt.%, the composites obtained exhibited good antibacterial performance, and the minimum inhibitory concentrations for Escherichia coli and Staphylococcus aureus were both at 2.5 mg/mL.

Aflatoxins in contaminated corn do not degrade in corn fermentation solution (CFS) during biofuel production; rather, they are enriched in the co-product, dried distillers grain. Aflatoxin B1 (AfB1) is the most toxic form of all aflatoxins. Removing AfB1 from CFS is desirable to minimize its toxicity to animals. Smectites can adsorb AfB1 from aqueous solutions and, therefore, inactivate the toxin, but proteins in CFS inhibit the adsorption of AfB1 by smectites. The current study aimed to minimize the interference by CFS in adsorption of AfB1 on smectite by modifying a calcium-smectite (Ca-3MS) with a small nutritive organic compound, e.g. carnitine, choline, arginine, histidine, or tryptophan. The organo-smectites were characterized by X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy, and adsorption of AfB1 in CFS by these composites was examined. Various degrees of intercalation of the organic nutrients into the smectites were observed with XRD and FTIR. After immersing the smectite and organo-smectites in the CFS, the d001 values of Ca-3MS expanded to ~1.82 nm due to protein interaction, but the organo-smectites were confined to ~1.39 nm, which indicated that the protein had limited access to the organo-smectite interlayers. The IR bands at ~1652, 1544, 1538, and 1454 cm–1 from the organo-smectites revealed, however, that complete protein inhibition was not achieved. The organo-smectites were capable of adsorbing AfB1 in simple aqueous solution with maximal adsorption capacity up to 0.55 mol kg–1. Significantly greater (p ≤ 0.05) AfB1 adsorption was achieved by choline- and carnitine-modified smectites compared with the original Ca-3MS in the presence of competing protein (pepsin) in simple aqueous solution. In real CFS, both AfB1 adsorption capacities (Qmax) and affinities (K) by all organo-smectites were greater (Qmax = up to 0.45 mol kg–1 and K = up to 0.165 μM–1) than those by Ca-3MS (Qmax = 0.22 mol kg–1 and K = 0.031 μM–1). The study suggested that using smectites modified with an organic nutritive compound could be an effective, economical, and safe strategy for removing mycotoxins, including aflatoxins, during biofuel production.

Functional montmorillonite can be dispersed in polymer coatings and organic species and polymers can be intercalated into the interlayer space or grafted onto the surface of the functional montmorillonite. The addition of functional montmorillonite into polymer-based coatings can significantly improve anti-corrosion, refractory, super-hydrophobicity, antibacterial activity, and absorption of solar radiation by the resulting montmorillonite/polymer coatings. Montmorillonite can be functionalized for this purpose by ion exchange, intercalation, exfoliation, or combinations of these treatments. The rigid montmorillonite layers interspersed within the polymer matrix inhibit the penetration of corrosive substances, minimize the impact of high-temperature airflow, and thereby lead to strong resistance of the coating to corrosion and fire. The combination of polymers and dispersed montmorillonite nanolayers, which are modified by metal ions, metal oxides, and hydrophobic organic species, allows the resulting  composite coating to have quite a rough surface and a much smaller surface free energy so that the montmorillonite/polymer coating possesses superhydrophobicity. The interlayer space of functional montmorillonite can also host or encapsulate antibacterial substances, phase-change materials, and solar energy-absorbing materials. Moreover, it can act as a template to make these guest species exist in a more stable and ordered state. Literature surveys suggest that future work on the functional montmorillonite/polymer coatings should be targeted at the manufacture of functional montmorillonite nanolayers by finding more suitable modifiers and tuning the dispersion and funtionalities of montmorillonite in the coatings.

Calcined clays are used as a supplementary cementitious material (SCM) because, as hydrated aluminosilicates of the phyllosilicate group, they can be activated thermally, promoting dehydroxylation and structural disorder, i.e. making them reactive. The main effect of using calcined clay as an SCM is that CO2 emissions into the atmosphere are reduced by the reduction in the clinker/cement factor due to substitution of a proportion of clinker by calcined clay. Clays rich in kaolinite (1:1) group minerals offer most promise in terms of thermal activation. However, increased costs caused by demand for kaolinite from other industries means that type 2:1 calcined clays and mixtures of them have begun to be investigated as possible pozzolanic materials. The physical, chemical, and mineralogical characteristics that control the performance of these calcined clays as SCMs are still under discussion. Few in-depth studies of the behavior of these characteristics have been reported. The origin and geological history of raw materials, as well as their impact on the thermal activation and performance as SCM, are not well understood or, in some cases, have not been considered. The objective of the current work, therefore, was to study multicomponent clays from metamorphic rocks with low-grade kaolinite (<50%) from a tropical region of Colombia for possible use as SCMs. The clay deposit was identified by geological exploration techniques and classified in depth according to horizons of the weathering profile. The samples were extracted from the first 50 m of the deposit and characterized physically, chemically, and mineralogically; they were calcined at 650, 750, and 850°C; their degree of alteration was estimated by the Chemical Index of Alteration (CIA); and their performance as an SCM was evaluated by the Strength Activity Index (SAI) and Frattini test. As a main result, a relationship was found between the weathering profile of the deposit and the CIA of raw clays, which confirmed the high weathering and degree of alteration of the parent rock in the deposit (weathered rock and residual soil with a CIA > 80%). Furthermore, pozzolanic (physical and chemical) tests demonstrated the potential use of calcined clays from this deposit as SCMs, as well as their thermal activation at low temperature (≤750°C). In addition, the pozzolanic activity increased with the kaolinite/(muscovite+illite+vermiculite) ratio mainly, and, in turn, the thermal activation temperature increased with the mica and type 2:1 clay content.

High temperature and a large salt content weaken the surface hydration ability of clay particles in drilling fluid, reduce zeta potential, agglomerate clay particles, increase particle size, and destroy the stability of drilling mud. A filtrate reducer is required, therefore, to maintain the zeta potential of the clay, prevent the agglomeration of clay particles, and maintain good performance of the drilling mud at high temperature and high salt content. To prepare temperature- and salt-resistant polymer filtrate reducer, a betaine monomer was synthesized and copolymerized with a conventional monomer. A betaine monomer 3-(dimethyl (4-vinyl benzyl) ammonia) propyl sulfonate (DVBAPS) was synthesized and then used to create a copolymer filtrate reducer. The copolymer filtrate reducer, referred to as PAAAND, was prepared by free radical copolymerization with 2-acrylamide-2-methylpropane sulfonic acid, acrylic acid, N-vinyl pyrrolidone, acrylamide, and DVBAPS. The optimum synthesis conditions were determined by single factor evaluation, and the chemical structure of the PAAAND was confirmed by Fourier-transform infrared spectroscopy and 1H nuclear magnetic resonance spectroscopy. Results from particle-size distribution and zeta-potential measurements showed that PAAAND increased the zeta potential of clay particles and the distribution width of particles size, which served to maintain the stability of the drilling mud under high-temperature and high-salt conditions. The results of scanning electron microscopy showed that PAAAND made the filter cake formed by clay particles smoother and denser, which reduced filtration loss. The reduction in filtrate loss continued even after aging at high temperature, and, thus, PAAAND performed better than commercial products.

Clays and clay minerals dissolve over a broad pH range, such as during sediment diagenesis and in a variety of applications, including nuclear waste storage, landfills, and geopolymer binders in the construction industry. The solubility depends on process parameters (pH, temperature, pressure, etc.) and material properties (phase content, clay mineral composition, particle size, etc.). Pretreatments such as calcination or severe grinding change the material properties and could enhance solubility, which is called activation. The aim of the current study was to determine the solubility of three different clay minerals after calcination (metakaolinite, metamontmorillonite, and metaillite) in high molar alkaline solutions (NaOH) up to 10.79 mol/L and pH = 14.73. Furthermore, the solubility of an Al(OH)3 powder in alkaline solution (NaOH) was analyzed, as it can be used to adjust the Si:Al ratio of geopolymer precursors. The residues of the clay minerals after the alkaline treatment were investigated to disclose potential alterations in their phase contents. Based on the results of the thermal and alkaline activation, conclusions about the suitability as geopolymer precursors were made. All clay minerals showed an increase in solubility proportional to the concentration of the alkaline solution. The solubility decreased in the order metakaolinite > metamontmorillonite > metaillite. Thereby, dissolution was incomplete for all three clay minerals (<90%) after 7 days and congruent for metakaolinite and metaillite but incongruent for metamontmorillonite.

Removing trace water from oil is an important industrial process and is commonly accomplished using vacuum filtration. The drawbacks of this method, however, are: poor efficiency, large oil loss, and significant energy consumption. The objective of the current study was to develop a better system to solve these problems using a sodium polyacrylate (PAA-Na)-modified bentonite as the dehydrating agent and, for the first time, to apply it to transformer oil. PAA-Na was prepared by aqueous solution polymerization. A dehydration test was carried out to determine the optimum addition of PAA-Na, and the highest dehydration rate of 76.5% was obtained with the addition of 20 wt.% PAA-Na. The steady dehydration rate of the PAA-Na-modified bentonite was better than that of other adsorbents (calcium chloride, zeolite 5A, unmodified bentonite). The process of adsorbing saturated water vapor on PAA-Na modified bentonite was studied and interpreted from the aspects of adsorption isotherms and thermodynamic properties. The results showed that the adsorption isotherm data followed the Freundlich isotherm model and the thermodynamic parameters indicated that the process was endothermic. Fourier-transform infrared spectroscopy results revealed that PAA-Na was synthesized successfully and it had a huge proportion of hydrophilic groups. According to thermogravimetric analysis, the PAA-Na-modified bentonite was stable up to 200°C, giving a flexible region for pretreatment and regeneration. X-ray diffraction showed no change in the diffraction pattern before and after modification. Moreover, considering the results of scanning electron microscopy and surface-area analyses, one may safely say that PAA-Na was distributed homogeneously on the surface of the bentonite. In addition, PAA-Na-modified bentonite exhibited a high dehydration rate in xylene, naphtha, and diesel, indicating a broad range of applications.