Vibrational Spectra of Zeolite Y as a Function of Ion Exchange

Adsorptive stripping voltammetric sensor based on Cd zeolitic imidazole framework-67 for electrochemical detection of sarin simulant

A selective and reliable modified glassy carbon sensor, based on a 1.0% Cd zeolitic imidazole framework-67 modified glassy carbon sensor (GCS2), has been developed for ultrasensitive detection of dimethyl methyl phosphonate (DMMP) in human biological fluid. The synthesis of porous nanoparticles of Cd zeolitic imidazole framework-67 (Cd ZIF-67) was carried out via the hydrothermal method. The resulting Cd ZIF-67 powder emerges with good crystallinity, a rhombic dodecahedral morphology with particle size in the range 300 ~ 500 nm, and a specific surface area of 1780 m2·g-1. Furthermore, the fabricated sensor exhibited superior performance in the detection of DMMP with two linearity ranges of 0.02-2.0 nM and 2.0-9.0 nM and a limit of detection (LOD) of 0.06 pM. The fabricated sensor exhibited good reliability, long-term stability, and repeatability, which are favourable attributes for electroanalytical detection. In addition, the fabricated sensor displayed superior performance without significant interference during the assay of DMMP in a biological fluid (human serum sample) within two linearity ranges of 0.1-1.0 nM and 1.0-6.0 nM and a LOD of 0.03 nM.

Aluminosilicates as a Double-Edged Sword: Adsorption of Aflatoxin B1 and Sequestration of Essential Trace Minerals in an In Vitro Gastrointestinal Poultry Model

Aflatoxins can cause intoxication and poisoning in animals and humans. Among these molecules, aflatoxin B1 (AFB1) is the most dangerous because of its carcinogenic and mutagenic properties. To mitigate these effects, clay adsorbents are commonly included in the diet of animals to adsorb the carcinogens and prevent their absorption in the gastrointestinal tract. In this study, four clays, three smectites (C-1, C-2, and C-3), and one zeolite (C-4), were compared as adsorbents of AFB1 and trace inorganic nutrients using an in vitro gastrointestinal model for poultry. Characterization of the clays using Fourier transform infrared spectroscopy revealed characteristic bands of smectites in C-1, C-2, and C-3 (stretching vibrations of Si-O, Al-O-Si, and Si-O-Si). The C-4 presented bands related to the bending vibration of structural units (Si-O-Si and Al-O-Si). X-ray diffraction analysis showed that C-1 is a montmorillonite, C-2 is a beidellite, C-3 is a beidellite-Ca-montmorillonite, and C-4 is a clinoptilolite. The elemental compositions of the clays showed alumina, silica, iron, calcium, and sodium contents. The cation exchange capacity was higher in C-3 clay (60.2 cmol(+)/kg) in contrast with the other clays. The AFB1 adsorption of C-1 was the highest (98%; p ˂ 0.001), followed by C-2 (94%). However, all the clays also sequestered trace inorganic nutrients (Fe, Mn, Zn, and Se). Both smectites, montmorillonite and beidellite, were the most suitable for use as adsorbents of AFB1.

Tuning the Catalytic Activity of Recyclable Heterogeneous Catalysts for the Direct Etherification Reaction of Glycerol Using Antagonistic Additives

Using zeolite as a heterogeneous catalyst, the reaction conditions were optimized to increase the yield and selectivity of diglycerol (DG) and triglycerol (TG) in the direct etherification reaction of glycerol. By the addition of weakly acidic alkali metal-based inorganic salts (NaHSO4 and KHSO4), the selectivities and yields of DG and TG increased. Although the conversion of glycerol was lowered due to the role of the additive as an inhibitor, the reaction conditions were optimized by controlling the amounts and reaction times of the additives to increase the yields of DG and TG. Under the optimized condition, the glycerol conversion was as high as 85.4%, and the highest yields of DG and TG were observed as 54.1% and 21.3%, respectively. The recyclability of the catalysts was much enhanced by the influence of the additives suppressing the formation of oligomers.

A Short Review on the Utilization of Incense Sticks Ash as an Emerging and Overlooked Material for the Synthesis of Zeolites

The traditional hydrothermal synthesis methods are mainly performed under batch operation, which generally takes few days to weeks to yield a zeolite with the desired properties and structure. The zeolites are the backbone of the petrochemical and wastewater industries due to their importance. The commercial methods for zeolite synthesis are expensive, laborious and energy intensive. Among waste products, incense sticks ash is a compound of aluminosilicates and could act as a potential candidate for the synthesis of zeolites for daily needs in these industries. Incense sticks ash is the byproduct of religious places and houses and is rich in Ca, Mg, Al and Si. As a result, incense sticks ash can be proven to be a potential candidate for the formation of calcium-rich zeolites. The formation of zeolites from incense sticks ash is an economical, reliable and eco-friendly method. The application of incense sticks ash for zeolite synthesis can also minimize the problem related to its disposal in the water bodies, which will also minimize the solid waste in countries where it is considered sacred and generated in tons every day.

Computational Study of the Adsorption of Phosphates as Wastewater Pollutant Molecules on Faujasites

The adsorption of sodium dihydrogen phosphate (NaH2PO4) onto X- and Y-type faujasite zeolites was computationally studied using the Density Functional Theory (DFT) method. The structures were modeled using the Materials Studio software. The Si/Al ratios for the X- and Y-type zeolite models were 1.2 and 2.5, respectively. The central pore of the zeolite provided a more favorable coordination for adsorbing NaH2PO4. Full molecular optimization and adsorption energy calculations were performed using the VASP code. The adsorption was more effective on zeolite Y, with an adsorption energy of 161 kJ/mol, compared to the zeolite X system, with an adsorption energy of 31.64 kJ/mol. This calculated value for X-type faujasite was found in the interval of the adsorption energy of H2PO4− on hydrated Fe oxide (94.4 kJ/mol) and modified polyether sulfone (22.5 kJ/mol), and the calculated adsorption energy of the molecule on Y-type faujasite coincides with the reported value for this adsorbate on Mg/Ca-modified biochar structures. The molecular conformations of the adsorbate on the two studied models are very different, so the difference between the adsorption energy values of each type of zeolite model is comprehensible. On the one hand, the oxygen atoms of the molecule formed a bidentate complex with the hydrogen atoms of the pore in the X-type faujasite model, and the O-H distance was 1.5 Ǻ. On the other hand, an adsorbed oxygen atom of the phosphate was placed on a hydrogen atom at site II of the Y-type faujasite zeolite, and two of the hydrogen atoms of the phosphate were placed on the oxygen atoms. The Bader analysis results indicated that the negative charge of the phosphate anions was delocalized on the zeolites protons. The hydroxy groups of the phosphate form bonds between their hydrogen atoms and the oxygen atoms of the zeolite porous structure; therefore, we concluded that these sites have an alkaline character. The aim of this study was to include a computational analysis of possible phosphate adsorption mechanisms in faujasite zeolites that can be confirmed by experimental tests, and hence contribute to the generation of new technologies for capturing pollutant molecules in wastewater. The results are in agreement with the experimental information concerning the influence of pH on the adsorption activity of phosphate adsorption on zeolites.