The study was aimed at analyzing the efficiency of thermal esterification of soybean husk polysaccharides with citric acid and its effect on the mechanical characteristics of compressed husks. The thermal treatment of a mixture of husks and citric acid was studied within the temperature range of 110–170 °С without the use of solvents and catalysts. The duration of thermal treatment varied from 30 to 180 min. This process was found to be accompanied by the hydrolysis of husk polysaccharides and their esterification within the analyzed temperature range. The main products of thermal treatment are modified husks and bio-oils. The bio-oils contain predominantly the products of citric acid transformation (55 to 82%). The low-molecular-weight transformation products of husk polysaccharides are represented by furan compounds. The process of esterification was confirmed by the results of studying modified husks via infrared spectroscopy and conductometric titration. The accumulation dynamics of ester linkages in husk biomass were also analyzed in relation to temperature and thermal treatment duration. The cross-linking degree of cellulose polymer chains was found to increase with increasing temperature and thermal treatment duration. Comparative tests of the original compressed husk samples and the modified husks revealed an improvement in their mechanical properties following thermal treatment in the presence of citric acid. A 1.2-fold strength increase and a 2.5-fold stiffness increase were observed. The presented results experimentally confirm the potential of esterification of soybean husks with citric acid, with their use as a filler in the production of composite materials.

Paving bitumens intended for use in the construction of road, bridge, and airfield pavements do not meet the requirements for crack resistance, heat resistance, elasticity, and adhesion to the surface of mineral materials. Pavement performance can be improved by the addition of thermoplastic elastomers to paving bitumens. These factors determine the relevance of research in this area. This study focused on obtaining polymer bitumen compositions by the addition of styrene/butadiene block copolymers and a plasticizer to paving bitumen, as well as studying some of its properties. Industrial oil I-40 produced by Angarsk Petrochemical Company was used as the plasticizer. BND 100/130 bitumen and styrene/butadiene block copolymers produced in Russia and China were tested. The infrared spectrum of the copolymers exhibits styrene-related absorption bands at 3061, 3024, 1640, 1601, 1450, 1493, 756, 730, and 659 cm^-1; butadiene segments are recorded around 994, 964, and 911 cm^-1. The elemental analysis shows that the content of butadiene segments is 3.1 times higher in the Chinese copolymer than in the copolymer produced in Russia. It was found that with the increasing percentage of copolymer content in the paving bitumens, the dynamic viscosity and extensibility of the composition increase, and its brittleness temperature decreases. With the growing content of butadiene units in the copolymer, dynamic viscosity, softening and brittleness temperatures, penetration, and extensibility increase; for the Chinese copolymer, these parameters are higher than those of the copolymer produced in Russia.

In this work, we investigate the electrochemical and electrokinetic characteristics of electrodeionization extraction of cobalt, copper, and cadmium ions from process solutions of electroplating plants for subsequent recycling. The research objects were selected following a review of publications on the possibility of using electromembrane methods for purification and concentration of industrial wastes. The current–voltage characteristics of the electrodeionization process were studied experimentally. The I–V curves showed the presence of a minimal linear ohmic section at voltages from 1 to 3 V and a plateau with a slight upward slope at the section from 3 to 5 V. Under a further increase in voltage, a region of supercritical current is observed, which is related to the formation of H⁺ and OH^- ions at the membrane–ion-exchange resin interfaces. The kinetic dependencies of the concentrations of retained substances on the residence time in the desalting and concentration chambers of the electrodeionization unit at different current densities and flow rates were analyzed. At a low current density of 5 A/m², three main sections were observed: (1) in the range from 0 to 900 s, where ion accumulation on ion-exchange membranes in desalting and concentration chambers occurs; (2) in the range from 900 to 2700 s, where intensive ion transfer is observed; (3) in the range from 2700 to 3600 s, where electrochemical regeneration of ions in purification chambers takes place. The results obtained were used to develop a technological scheme for wastewater treatment from heavy metal ions.