Theoretical Foundations of Chemical Engineering最新文献

Phase transformations were examined using X-ray microanalysis and X-ray diffraction phase analysis in samples of waste material from the nickel plant in Punta Gorda operated by the Cuban state-owned company Commercial Caribbean Nickel S.A. during gas-phase treatment in an HNO₃(vapor)–air atmosphere and subsequent treatment of the phase transformation products with water.

This work focuses on the photoluminescence of porous silicon (PS) structures modified with zinc oxide. The PS samples were prepared by electrochemical etching of single-crystal silicon wafers in a hydrofluoric acid solution. Zinc oxide was introduced into the pores using a solution-based pyrolysis method. An enhancement of photoluminescence in the visible range was observed in PS samples containing zinc oxide, along with differences in the photoluminescence spectra depending on the annealing conditions. The results show that visible photoluminescence can be generated and intensified by introducing zinc oxide into PS via a solution-based approach followed by annealing in air. Variation of the annealing temperature and duration in PS–ZnO heterostructures leads to the appearance of photoluminescence in the ultraviolet, blue, and green regions of the spectrum.

The growth of metal-containing waste raises public concern due to its impact on the environment, human health, and the accelerated depletion of natural resources. In the context of a circular economy, metal recovery from secondary resources is attracting increasing research interest. Liquid–liquid extraction and leaching are the main processes used for separating and recovering metals from such sources. The extractants and solvents typically used in these processes often possess aggressive properties that can cause not only environmental problems but also damage to industrial equipment. Therefore, there is a need to make these processes safer and cleaner by using environmentally friendly solvents. In recent years, deep eutectic solvents have attracted attention due to their ease of preparation, biodegradability, low toxicity, and the ability to finely tune their physicochemical properties. Recently, studies have emerged on their use for metal recovery from electronic waste, minerals, biological materials, and other sources. This review provides an overview of hydrophobic deep eutectic solvents and their application in the recovery and separation of a wide range of metals, including those from lithium-ion batteries.

A statistical model of open porosity formation in flat basalt–plastic composite materials under climatic degradation is proposed. The distribution of the porous structure is considered as a two-dimensional cluster structure on a square lattice. To describe the formation of open porosity, coinciding elements of two-dimensional porosity clusters of several (two, three, or more) flat layers of basalt–plastic composite materials are identified.

The effect of firing temperature on the properties of ceramic samples produced from clay-based mixtures with arsenic-containing waste from the Tuvacobalt plant was examined. An increase in the moisture content of the mixture from 10 to 15% resulted in a significant increase in the strength of the ceramic samples. At 850°C, the compressive strength of the samples increased from 14 to 21 MPa. New phases (andradite and wollastonite) were identified in the ceramic samples and likely contributed to the increase in strength. Arsenic was shown to be incorporated into silicate structures during firing in the form of stable arsenates.

Expanded perlites were obtained from raw materials classified by density and particle size fractions. The bulk densities, thermal conductivity coefficients, fineness moduli, and settlement degree of the expanded perlite were determined. To ensure the stability of the properties of the expanded aggregate, selective mining of perlite in thin extraction layers uniform in average density and narrow fractionation were proposed. For more reliable insulation, two-layer insulation of isothermal tanks was suggested depending on the settlement degree of the expanded perlites.

A novel approach to the surface modification of complex polypropylene fibers and films with metal-containing nanoparticles has been developed and experimentally validated. The process is implemented during melt extrusion of fibers and films. The proposed approach is based on the strong fixation of stabilized nanosized metal-containing particles on the surface of the material through the incorporation of a stable ultrathin polytetrafluoroethylene coating, formed using a previously developed technique. It has been shown that incorporating 0.001–0.2% of stabilized iron-, copper-, and silver-containing nanoparticles into the polytetrafluoroethylene coating increases its density without adversely affecting adhesion to the polypropylene substrate.

The effect of mechanical energy input (2.16, 3.60, and 5.04 kJ/g) on the thermal stability, physical properties, and sorption characteristics of sorbents based on clinoptilolite-bearing rocks and 5 wt % poly(diethylene glycol) sebacate was examined. Dehydration of the samples in the temperature range of 75–150°C was identified as a diffusion-controlled process. It was found that a mechanical energy dose of 5.04 kJ/g significantly increased the oil sorption capacity of the powdery organomineral sorbents in an aqueous medium compared to the untreated rocks.