Trends in the use of bentonite clays

The paper gives a general description of the areas of application of bentonite clays. A number of deposits were evaluated in terms of their use in various technological processes. Analysis of directions of application of bentonite clays in foundry was carried out.Using the methods of X-ray and gas chromatographic analysis, scanning electron microscopy, thermogravimetry and direct adsorption-structural measurements, it is shown that materials obtained from montmorillonite and heteronuclear hydroxo complexes Cr-Cu have greater thermal stability and better sorption characteristics compared to montmorillonite fixed by mononuclear hydroxo complexesUsing montmorillonite modified with heteronuclear hydroxo complexes Cr-Cu with the best adsorption-structural parameters and zeolite NCVM, a laboratory batch of mixed adsorbent catalysts has been developed.This material has been studied in deep vapor oxidation processes of low concentrated organic substances such as acetone, toluene, ethyl acetate, ethanol, butanol and butyl acetate.The conversion rate on the mixed adsorbent catalysts for the studied adsorbates was found to be 94.9–97.7 (average 96.2 %).

Application of the Enzymatic Electrochemical Biosensors for Monitoring Non-Competitive Inhibition of Enzyme Activity by Heavy Metals

The inhibition effect of the selected heavy metals (Ag+, Cd2+, Cu2+, and Hg2+) on glucose oxidase (GOx) enzyme from Aspergillus niger (EC 1.1.3.4.) was studied using a new amperometric biosensor with an electrochemical transducer based on a glassy carbon electrode (GCE) covered with a thin layer of multi-wall carbon nanotubes (MWCNTs) incorporated with ruthenium(IV) oxide as a redox mediator. Direct adsorption of multi-wall carbon nanotubes (MWCNTs) and subsequent covering with Nafion® layer was used for immobilization of GOx. The analytical figures of merit of the developed glucose (Glc) biosensor are sufficient for determination of Glc in body fluids in clinical analysis. From all tested heavy metals, mercury(II) has the highest inhibition effect. However, it is necessary to remember that cadmium and silver ions also significantly inhibit the catalytic activity of GOx. Therefore, the development of GOx biosensors for selective indirect determination of each heavy metal still represents a challenge in the field of bioelectroanalysis. It can be concluded that amperometric biosensors, differing in the utilized enzyme, could find their application in the toxicity studies of various poisons.

Fabrication and Application of Polyethylenimine/Ca-Alginate Blended Hydrogel Fibers as High-Capacity Adsorbents for Recovery of Gold from Acidic Solutions

High-capacity polyethylenimine (PEI)/Ca-alginate blended hydrogel fibers were fabricated via three steps, viz. electrostatic blending of PEI and alginate, ionotropic gelation of alginate and CaCl2, and fixing of PEI into the Ca-alginate matrix, using glutaraldehyde (GA) as a crosslinker. Two crosslinking approaches resulted in different stabilities and gold uptake capacities of the prepared sorbents. Post-crosslinking approach was more efficient than pre-crosslinking likely owing to the better crosslinking efficiency, leading to better stability and sorption capacity. Furthermore, X-ray diffraction (XRD) study revealed the reduction of Au (III) to metallic gold, Au (0) in the crosslinked fibers. The Au (0) predominancy was confirmed with a metal desorption study. The present study thus demonstrates the possibility of recovering metallic gold from aqueous solutions by direct adsorption-coupled-reduction approach using GA-crosslinked PEI/Ca-alginate fibers.