The Mechanics of Forming Ideal Polymer–Solvent Combinations for Open-Loop Chemical Recycling of Solvents and Plastics

The inherent value and use of hydrocarbons from waste plastics and solvents can be extended through open-loop chemical recycling, as this process converts plastic to a range of non-plastic materials. This process is enhanced by first creating plastic–solvent combinations from multiple sources, which then are streamlined through a single process stream. We report on the relevant mechanics for streamlining industrially relevant polymers such as polystyrene (PS), polypropylene (PP), high-density polyethylene (HDPE), and acrylonitrile butadiene styrene (ABS) into chemical slurries mixed with various organic solvents such as toluene, xylene, and cyclohexane. The miscibility of the polymer feedstock within the solvent was evaluated using the Relative Energy Difference method, and the dissolution process was evaluated using the “Molecular theories in a continuum framework” model. These models were used to design a batch process yielding 1 tonne/h slurry by setting appropriate assumptions including constant viscosity of solvents, disentanglement-controlled dissolution mechanism, and linear increase in the dissolved polymer’s mass fraction over time. Solvent selection was found to be the most critical parameter for the dissolution process. The characteristics of the ideal solvent are high affinity to the desired polymer and low viscosity. This work serves as a universal technical guideline for the open-loop chemical recycling of plastics, avoiding the growth of waste plastic by utilising them as a carbon feedstock towards a circular economy framework.

Effect of the Initial Texture, Recrystallization and Re-Dissolution Process on the Evolution of Texture during Solution Treatment of the 7A65 Hot Rolled Plate

The evolution of textures, the degree of recrystallization and the mechanical properties of 7A65 hot rolled plates during re-dissolution were studied with different thicknesses (25 mm, 65 mm, 120 mm) and different degrees of deformation. It was found that different plates exhibited different trends of re-dissolution because the degrees of deformation increased and the degrees of recrystallization were different during the solution treatment. With the increase of deformation and static recrystallization degrees, texture types changed from Cube, R-Cube to Brass, R, Cube and Copper during the re-dissolution process. The value of the Schmid factor (µ(-)) was calculated and the value along the rolling direction was significantly larger than along the transverse direction, which led to a lower yield strength along the rolling direction. In terms of the average contribution of the yield strength, the strengthening of the grain boundary including LAGBs (low-angle grain boundaries) was found to play a more significant role than the effect of solid atoms and dislocation densities. Therefore, the 25 mm plate exhibits the best mechanical properties, with a yield strength of 565.7 MPa along the rolling direction.

Modelling of the Erosive Dissolution of Metal Oxides in a Deep Eutectic Solvent—Choline Chloride/Sulfosalicylic Acid—Assisted by Ultrasonic Cavitation

Here we report on the results concerning the influence of ultrasound on the dissolution process of metal oxides CoO, Ni2O3 and Mn2O3 in choline chloride/sulfosalicylic acid as a deep eutectic solvent. The mechanism of dissolution under cavitation conditions with ultrasonic assistance is described. Theoretical research resulted in equations describing the dissolution process kinetics and linking its basic parameters. Optimal conditions for the most effective ultrasound application were found. Experimental data on dissolution kinetics of metal oxides in deep eutectic solvents was also obtained. It was discovered that experimental data correlates well with theoretical calculations, which confirms the correctness of developing a picture about the physicochemical nature of the process under study.

The Mechanics of Forming Ideal Polymer Solvent Combinations for Open-Loop Chemical Recycling of Plastics and Solvents

The inherent value and use of hydrocarbon from waste plastics and solvents can be extended through open-loop chemical recycling as this process converts plastic to range of non-plastic materials. This process is enhanced by first creating plastic-solvent-combinations from multiple sources which are then streamlined through single process stream. We report on the relevant mechanics for streamlining industrially relevant polymers such as polystyrene (PS), polypropylene (PP), high-density polyethylene (HDPE) and acrylonitrile butadiene styrene (ABS) into chemical slurries mixed with various organic solvents such as toluene, xylene and cyclohexane. The miscibility of the polymer feedstock within the solvent was evaluated using the Relative Energy Difference method, and the dissolution process was evaluated using the “Molecular theories in a continuum framework” model. These models were used to design a batch process yielding 1 tonne/h slurry by setting appropriate assumptions including constant viscosity of solvents, disentanglement-controlled dissolution mechanism and linear increase of the dissolved polymer’s mass fraction over time. Solvent selection was found to be the most critical parameter for the dissolution process. The characteristics of the ideal solvent are high affinity to the desired polymer and low viscosity. This work serves as a universal technical guideline for open-loop chemical recycling of plastics avoiding the growth of waste plastic in a circular economy framework.

The Kinetic Aspects of the Dissolution of Slightly Soluble Lanthanoid Carbonates

The problem of the complex use of mineral raw materials is significant in the context of many industries. In the rare earth industry, in the context of limited traditional domestic reserves and dependence on imports of lanthanides, an unambiguous and comprehensive solution has not yet been developed. Promising areas include the involvement of technogenic raw materials in the industrial turnover. The present study examines the kinetics of the dissolution process of poorly soluble lanthanide compounds when changing the parameters of the system. The results obtained reflect the dependence of the degree of extraction of lanthanide on the following variable parameters of the system: temperature, concentration of the complexing agent, and intensity of mixing. On the basis of the experiment, the values of the activation energy and the reaction orders were calculated. The activation energy of the carbonate dissolution process, in kJ/mol, was as follows: 61.6 for cerium, 39.9 for neodymium, 45.4 for ytterbium. The apparent reaction orders of the carbonates are equal to one. The prospect of using the research results lies in the potential to create a mathematical model of the process of extracting a rare earth metal by the carbonate alkaline method.

Influence of the textural and structural functions of the Urals carnallite rocks on the kinetics of dissolution processes

В статье показана необходимость исследования кинетики процессов растворения карналлитовых пород Приуралья. Описана методика подготовки образцов и лабораторного изучения скорости растворения. Представлены данные о химическом составе образцов 4-х цветовых разностей карналлитовых пород, текстурно-структурных особенностей, результатов по определению скорости растворения и вещественного состава нерастворимого в воде остатка. Цель исследования заключалась в изучении скорости и процессов растворения в воде при температуре 500С в режиме вынужденной конвекции и оценке влияния текстурно-структурных особенностей карналлитовых пород. Задачами исследования являлись: определение солевого и минерального составов, изучениеструктуры и микровключений в шлифах, проведение экспериментов по кинетикерастворения. При решении поставленных задач использовались следующие методы: АЭС-спектрометрия, петрографический анализ, гидростатический метод, РКФА. Проанализирован фактический материал исследования, сделаны соответствующие выводы. Проведенными исследованиями было показано, что важными факторами, влияющими на кинетику процессов растворения, являются вещественный состав и текстурно-структурные свойства. В работе определена суммарная (массовая) скорость растворения образцов. Железооксидная пленка, оконтуривающая зерна карналлитовых пород, экранирует поверхность растворения, замедляя процесс диффузии. Наличие галита и неравномерное его содержание вызывает колебания скорости растворения изамедляет процесс растворения во времени. Микровключения газов положительно влияют на динамику процесса растворения, усиливая конвекцию и массоперенос. С увеличением гидродинамических параметров растворителя (плотности и вязкости) скорость растворения понижается. Установленные закономерности могут оказывать существенное влияние на процессы, происходящие при скважинной добыче (подземное растворение) и галургической переработке карналлитовых руд. The article shows the need to study the kinetics of the dissolution processes of carnallite rocks of the Permian deposits of the Urals. The technique of preparation of samples, laboratory study of the rate of dissolution in water is described. The data on the chemical composition of samples of 4-color differences of carnallite rocks, textural and structural features, the results of determining the rate of dissolution and the material composition of the water-insoluble residue are presented. The purpose of the study was to study the rate and processes of dissolution in water at a temperature of 500C in the forced convection mode and to assess the influence of the textural and structural features of the carnallite rocks of the Urals. The objectives of the study were: determination of salt and mineral compositions, study of textural and structural features and assessment of the effect of microinclusions on the kinetics of the dissolution process. When solving the tasks, the following methods were used: study of the textural and structural features of carnallite rocks - by the petrographic method; determination of the rate of dissolution and density of samples - by the gravimetric method; determination of the density of brines - pycnometric method; the chemical composition of the initial samples and solutions (brines) was analyzed by AES-spectrometry; the mineral composition of the water-insoluble residue - by X-ray quantitative phase analysis. The factual material of the research is analyzed, the corresponding conclusions are drawn. Studies have shown that important factors affecting the kinetics of dissolution processes are the material composition and textural-structural properties. In this work, the total (mass) rate of dissolution of samples was determined, including the vertical and horizontal components. The iron oxide film outlining the grains of carnallite rocks screens the dissolution surface, slowing down the diffusion process. The presence of halite and its uneven content causes fluctuations during dissolution, slowing down the dissolution process over time. Microinclusions of gases have a positive effect on the dynamics of the dissolution process, enhancing convection and mass transfer. With an increase in the hydrodynamic parameters of the solvent (density and viscosity), the dissolution rate decreases. The research results can be suitable for the organization of mining by underground dissolution and for the processing of carnallite rocks of the Permian deposits of the Urals by the halurgical method.