Yurii Volfkovich

Polymer Ion-Exchangers Modified with Zirconium Hydrophosphate for Removal of Cd2+ Ions from Diluted Solutions

Hybrid ion-exchangers have been synthesized by modification of strongly acidic cation-exchange resin with zirconium hydrophosphate. The samples were investigated with scanning and transmission electron microscopy and standard contact porosimetry. Single nanoparticles and their aggregates have been found in the polymer. The nanoparticles in transport pores increase the electrical conductivity of ion-exchanger from 0.21 to 0.65 Ohm−1 m−1. The diffusion coefficient of Cd2+ ions reaches 2.43 × 10−11 m2 s−1 for initial resin and (2.50–4.34) × 10−11 m2 s−1 for nanocomposites. The inorganic constituent improves Cd2+ recovery from a solution, which contains also Ca2+ and Mg2+. The degree of Cd2+ removal is 18% for non-modified resin and 99% for the sample containing 38 mass% zirconium phosphate.

Effect of Incorporated Inorganic Nanoparticles on Porous Structure and Functional Properties of Strongly and Weakly Acidic Ion Exchangers

Weakly and strongly acidic cation exchange resins were modified with nanoparticles of zirconium hydrophosphate. The materials were investigated with methods of standard contact porosimetry and transmission electron microscopy. Both non-aggregated nanoparticles (4–20 nm) and larger formations (from 250 nm to several microns) have been found. The modifier particles occupy both hydrophilic and hydrophobic pores of the polymers. This provides transformation of porous structure of the resins due to additional swelling pressure. As a result, some regions of the polymer become unavailable for sorbate. The transformation affects sorption of Brilliant Green and Ni2+ ions. It was found that sorption rate is described by the model of chemical reaction of pseudo-second order. Depending on the interaction of polymer matrix with species being sorbed, the inorganic modifier is able to accelerate or slow down sorption. The composites were found to show breakthrough capacity toward the dye that is higher two to ten times compared with the pristine resins. However, lower breakthrough capacity toward Ni2+ is attributed to the composite based on strongly acidic resin.

Electrodes Based on Carbon Nanomaterials: Structure, Properties, and Application to Capacitive Deionization in Static Cells

Both fibrous- and corpuscular-like materials based on activated carbon, which are considered as electrodes for capacitive deionization, were investigated with a method of standard contact porosimetry. Nanosized pores as well as micro- and macropores have been recognized for the investigated materials. It was found that the hydrophilic specific surface area that is provided by the smallest mesopores and micropores has been found to reach 520–850 m2 g−1; total surface area is 940–1520 m2 g−1. Galvanostatic measurements of dependences of cell voltage on time were performed in a static cell; capacitance of the electrodes was determined from the plateau of the curves. The capacitance of electric double layer was calculated. For the CH900 material, which is characterized by the highest volume of hydrophilic micropores and nanosized voids, this value achieves 63 F g−1. The model for capacitive deionization in a static cell has been developed; the approach allows one to calculate the process using only experimental parameters (surface conductivity and capacitance of electric double layer).

Hierarchical Structure of the Derma Affected by Chemical Treatment and Filling with Bentonite: Diagnostics with a Method of Standard Contact Porosimetry

The evolution of derma porosity during pre-tanning, tanning, retanning, and modifications with inorganic particles was investigated with techniques of standard contact porosimetry, transmission, and scanning electron microscopy. The method, which allows us to perform quantitative analysis of pore size distribution of the hierarchical structure, has been proposed. The interrelation between porosity due to different elements of the structure (helices, microfibrils, fibrils, fibril bundles, and fibers) and the total porosity was found to be described by a linear polynomial function. Ordering-disordering, loosing-compaction, and shrinkage-swelling at each structure level, which are affected by chemical treatment of the derma, tanning, retanning, and filling with bentonite, are analyzed.