Interphase distribution of a number of polybasic carboxylic acids in aqueous two-phase systems based on polyethylene glycol-1500

In this work, we studied the interphase distribution of a number of polybasic carboxylic acids, in particular, malic, succinic, glutaric, citric, ascorbic and tartaric in two-phase aqueous systems polyethylene glycol-1500 (PEG-1500) - sodium sulfate - water and PEG-1500 - ammonium sulfate - water. Using the spectrophotometric method of analysis, quantitative characteristics (interfacial distribution and degree of recovery) of the extraction of carboxylic acids were determined. In conclusion, it was found that the considered two-phase aqueous systems are promising in the process of extraction of polybasic carboxylic acids. In particular, the system polyethylene glycol 1500 - sodium sulfate - water has effective extraction properties for succinic malic and ascorbic acids. On the other hand, depending on the composition of the extraction systems, the quantitative characteristics for citric, glutaric and tartaric acids practically do not differ.

Theoretical and Experimental Studies of Sulfur and Boron Distribution between the Slag of the CaO-SiO2-B2O3-MgO-Al2O3 System and the Metal

The equilibrium interfacial distribution of sulfur and boron was estimated using the HSC 6.1 Chemistry software package (Outokumpu) and the simplex-lattice planning method. Adequate mathematical models have been constructed in the form of III degree polynomial, which describe the effect of the composition of the studied oxide system on the equilibrium distribution of sulfur and boron between the slag and the metal. Generalization of the results of experimental studies and thermodynamic modeling made it possible to obtain new data on the influence of the basicity and content of B2O3 in the slag of the CaO-SiO2-B2O3-MgO-Al2O3 system on the interphase distribution of sulfur and boron. It was found that in the range of boron oxide concentration of 1.0-10%, an increase in slag basicity from 2 to 5 at 1600°C leads to an increase in the sulfur distribution coefficient from 1 to 20 and, as a consequence, a decrease in the sulfur content in the metal from 0.02 to 0.0014 %, i.e. an increase in slag basicity favorably affects the development of the metal desulfurization process. An increase in the B2O3 content from 2.0 to 10.0% in slags formed in the region of moderate basicity, not exceeding 2-3, is accompanied at 1600°C by a decrease in the boron interphase distribution coefficient from 450 to 150 and an increase in the boron concentration in the metal from 0.006 to 0.021 %, which indicates the progress of boron reduction from slag to metal. The shift of the formed slags to the area of ​​increased basicity up to 5.0 shows a high degree of boron reduction from slag to metal. The results of the laboratory experiment confirmed the results of thermodynamic modeling.

Effect of Basicity and Boron Oxide in Slags of the AOD Process on the Equilibrium Interphase Distribution of Sulfur and Boron

The use of fluorspar in modern metallurgical slags, incl. slags of the argon-oxygen decarburization (AOD) process, as a fluxing agent, is associated with many disadvantages. Those disadvantages can be solved by using boron oxide as an alternative, which also provides conditions for direct microalloying of steel with boron. The paper presents the results of thermodynamic modeling of the effect of basicity and boron oxide content in slags of the CaO–SiO2–B2O3–Cr2O3–Al2O3–MgO system on the equilibrium interphase distribution of sulfur and boron, and their equilibrium content in the metal. Modeling was carried out using the HSC 8.03 Chemistry software package (Outokumpu). Slag from the desulfurization period of the AOD-process was used as the oxide phase. As a result, it was shown that, in the range of basicities 2.0-2.5 and a content of 2-4% B2O3, it is possible to carry out desulfurization of the metal, providing a sulfur content of 0.001-0.007%, and simultaneous microalloying of steel with boron in an amount of up to 0.0103%.

STUDY THE INTERPHASE DISTRIBUTION OF NICOTINIC ACID IN EXTRACTION SYSTEMS BASED ON POLY-N-VINYLFORMAMIDE

Разработан способ извлечения никотиновой кислоты из водных растворов с применением водорастворимого полимера в качестве экстрагента. Исследовано комплексообразование в экстракционных системах с применением жидкостной экстракции. В качестве экстрагента синтезирован поли-N-винилформамид молекулярной массой 25 ∙ 103 г/моль. Для экстракции никотиновой кислоты применены высаливатели сульфат и хлорид аммония. Рассчитаны коэффициенты распределения – от 36 до 215 и степень извлечения аналита – от 87,8 до 98,8%. Эксперимент проводили при рН 6–7, в этих условиях никотиновая кислота находится в растворе в виде биполярного иона. Методом ИК спектроскопии изучено комплексообразование в экстракционных системах. Установлено, что цвиттер-ионы никотиновой кислоты образуют прочные комплексы с водой. На основании результатов ИК спектроскопии предложен механизм взаимодействия никотиновой кислоты с водой и поли-N-винилформамидом, позволяющий объяснить результаты межфазного распределения витамина в экстракционных системах. Установлены условия, при которых достигается практически полное извлечение никотиновой кислоты: рН водно-солевого раствора 6–7, концентрация полимера 0,2 г/см3 и высаливателя 20% масс. Проведено сравнение экстракционных характеристик, полученных с поли-N-винилформамидом и другими полимерами. Установлено, что применение в качестве экстрагента поли-N-винилформамида обеспечивает практически 99%-е извлечение никотиновой кислоты, что превышает этот показатель по сравнению с другими полимерами до 96% и органическими растворителями до 45%. Определение никотиновой кислоты в водном растворе проведено методами УФ спектрофотометрии по собственному поглощению при 262 нм или капиллярного электрофореза. A method for extracting nicotinic acid from aqueous solutions using a water-soluble polymer as an extractant has been developed. Complex formation in extraction systems using liquid extraction is investigated. Poly-N-vinylformamide with a molecular weight of 25 ∙ 103 g/mol was synthesized as an extractant. For the extraction of nicotinic acid, salting agents (ammonium sulfate and chloride) were used, distribution coefficients and the degree of analyte extraction were calculated. The distribution coefficients – from 36 to 215 and the degree of analyte extraction – from 87,8 to 98,8% were calculated. The experiment was performed at pH 6–7, under these conditions, nicotinic acid is in solution as a bipolar ion. Complex formation in extraction systems has been studied by IR spectroscopy. It was found that the zwitterions of nicotinic acid form strong complexes with water. Based on the results of IR spectroscopy, a mechanism for the interaction of nicotinic acid with water and poly-N-vinylformamide is proposed, which allows us to explain the results of interphase distribution of vitamin in extraction systems. The conditions under which almost complete extraction of nicotinic acid is achieved (the 6–7 pH of the water-salt solution, the polymer concentration are 0,2 g/cm3and the salting agent is 20% by weight) are established. The extraction characteristics obtained with poly-N-vinylformamide and other polymers were compared. It was found that the use of poly-N-vinylformamide as an extractant provides almost 99% recovery of nicotinic acid, which exceeds this indicator in comparison with other polymers by up to 96% and organic solvents by up to 45%. Determination of nicotinic acid in an aqueous solution was performed by UV spectrophotometry based on self-absorption at 262 nm and capillary electrophoresis.

Distribution of heavy metals in water and bottom sediments in reservoirs of the Dnipro cascade (Ukraine).

<p>The Dnipro river is the main catchment in Ukraine. Within its territory the river flow is regulated and  represents a cascade of six reservoirs in direction from upper to down: Kyiv,  Kanevsky, Kremenchug, Kamensky, Dniprovsky, and Kakhovsky.  Reservoirs have a total water mirror area of 6950 km² and a total water volume of 44 km³. These figures make 95% and 91% of the total number of all large reservoirs in Ukraine, respectively. Their location in various natural and climatic zones, the difference in morphometric and hydrodynamic characteristics, hydrobiological, physicochemical, and sedimentation processes, as well as levels of anthropogenic load make them a unique object for studying intra-water processes, including processes of transformation, interphase exchange and accumulation of heavy metals in bottom sediments.</p><p>The study presents long-term data on the dynamics of the content and patterns of distribution of heavy metals (Fe, Mn, Cu, Zn, Pb, Ni, Co, Cd) in water, as well as in suspended solids, and bottom sediments of these reservoirs.</p><p>The influence of hydrological factors, physicochemical and hydrobiological processes on the nature of the transformation and interphase distribution of the heavy metals in the system “water – suspended substances – bottom sediments” has been shown. The contribution of mineral particles, Fe hydroxides and Mn oxides, and high molecular weight fractions of humic substances (humic and fulvic acids) on sorption processes and the removal of heavy metals from the solution phase were studied.</p><p>It has been found that the shift of the equilibrium of the calcium-carbonate system towards the formation of the CaCO<sub>3</sub> solid phase, which is associated with intensive hydrobiological processes in the Kremenchug and Kakhovsky reservoirs, leads to the additional removal of heavy metals from the solution due to deposition.</p><p>The study reveals the special aspects of the interphase distribution of heavy metals between the liquid and solid phases, due to the physicochemical conditions of the aquatic environment, as well as the morphometric characteristics of the reservoirs, flow rate, water temperature, duration of the ice cover during winter, and the content of organic substances.</p><p>The results of the distribution of heavy metals among various types of bottom sediments and their different particle size fractions are presented.</p><p> It has been shown that a specific feature of the first in the cascade Kyiv Reservoir is the high content of dissolved humic substances, which play an important role in the migration of heavy metals.</p><p>The co-existing forms of metals in the solution phase are investigated with the thermodynamic modeling approach. This method was also used to evaluate the flow of metals from pore solutions of bottom sediments into the aquatic environment. Differences in the rate of molecular diffusion of metals from bottom sediments have been shown. They are caused by both the water chemistry and pore solutions, and the concentrations of metals and binding ligands.</p><p>The levels of anthropogenic load with heavy metals on the reservoir ecosystems have been evaluated over the past 30 years.</p>