Sorption Properties of the Filter Material MS in Relation to Copper(II) Ions

The sorption of copper(II) ions by the mineral filter material MS was studied. The study was carried out on a model solution of copper(II) sulfate containing an additional 400 mg/dm3 of sodium sulfate. It demonstrates that the sorption properties of MS are due to the simultaneous action of two factors. The first is associated with an increase in the pH of the solution being purified when the MS material is introduced into it, which leads to the precipitation of copper(II) ions from the solution in the form of the corresponding hydroxide. The second is the ability of the MS to remove copper(II) ions from the solution by the mechanism of adsorption described by the Langmuir equation. It was found that with an increase in the pH of the solution from 4 to 6.7, the adsorption of copper(II) ions on the surface of the MS increases (ranges of pH<4 and pH>6.7 have not been studied). The found values of the MS monolayer capacity with respect to copper(II) ions turned out to be comparable in magnitude with similar values for some other mineral sorbents. Keywords: copper(II) ions, sorption, Langmuir equation, adsorption capacity

Aerobic oxidation of 5-hydroxymethylfurfural to 2,5-diformylfuran on supported vanadium oxide catalysts: Structural effect and reaction mechanism

The structure–activity relationship and reaction mechanism for selective oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF) in toluene were studied on vanadium oxide domains on TiO2, Al2O3, Nb2O5, ZrO2, and MgO and with a wide range of VOx surface densities. The structures of these catalysts were characterized by X-ray diffraction (XRD), diffuse reflectance UV–vis spectroscopy (UV–vis DRS), and Raman spectroscopy, and their reducibility was probed by H2-temperature programmed reduction. The structures of the VOx domains evolved from monovanadate to polyvanadate structures with increasing the VOx surface densities, and finally to crystalline V2O5 clusters at surface densities above one-monolayer capacity. Within one-monolayer capacity, higher VOx surface densities and more reducible supports led to higher reducibility and reactivity of the VOx domains. The support surfaces covered with polyvanadates and V2O5 clusters and the supports with acidity favored the formation of DFF. The correlation between the reducibility and reactivity, together with the kinetic studies, suggests that the HMF oxidation to DFF proceeds via the redox mechanism involving the V5+/V4+ redox cycles and the reoxidation of V4+ to V5+ by O2 as the rate-determining step. These results may provide guidance for the design of more efficient catalysts for the HMF oxidation to synthesize DFF.

Study of the Molecular Hydrogen- Zeolites Interaction

An expression of monolayer capacity for hydrogen adsorption was derived on the basis of Ono-Kondo lattice theory. And then, the interaction energies between hydrogen molecules and pore surface atoms in the zeolite were calculated by using Lennard-Jones (12-6) potential model for spherical pores. The results show that the monolayer capacity is dependent on adsorbate–adsorbent and adsorbate–adsorbate interaction energies, and that the interaction energies of hydrogen-zeolite agree with the previously reported isosteric heat of hydrogen on zeolites.

The Influence of Binding Material on Porous Structure of Shaped Hopcalite

The authors have investigated the equilibrated adsorption of water vapors on GFG hopcalite, which was obtained using the extrusion shaping method, with bentonite clay as the binding compound. In the frames of the BET model, the values of the monolayer capacity and the size of medium area occupied by the water molecule in the filled monolayer have been determined. The distribution of pores according to their sizes has been evaluated. It has been established that the modification of the bentonitic clay allows directed construction of the hopcalite porous structure,i.e. the formation of the mesoporous structure with a narrow distribution of the pores capacities by sizes, which was achieved varying the sizes of binding compound particles.