Corrosion remains a significant challenge in the oil and gas industry, adversely impacting all stages of the production cycle, including exploration, extraction, transportation, and refining. This review provides a comprehensive analysis of corrosion mechanisms, classification systems, and the practical application of corrosion inhibitors, with particular emphasis on their effectiveness in protecting oilfield and refinery equipment. Special attention is given to organic corrosion inhibitors, specifically those based on imidazolines, phosphonates, and urotropine. These compounds are known for their ability to form protective films that reduce corrosion rates in harsh environments characterized by high concentrations of H₂S, CO₂, and other aggressive agents. Imidazoline-based inhibitors are recognized for their capacity to establish hydrophobic barriers on metal surfaces, while phosphonates are particularly effective under high-temperature conditions. Urotropine, in turn, demonstrates considerable efficiency in acidizing operations commonly employed in well stimulation. The review also explores the synergistic effects achieved through the combined use of different corrosion inhibitors, resulting in improved overall protection. In addition, it addresses critical challenges such as the environmental impact and toxicity of certain conventional inhibitors, underscoring the urgent need for the development of sustainable and environmentally friendly alternatives. This analysis aims to support the optimization of corrosion control strategies, thereby enhancing operational reliability and extending the service life of vital infrastructure in the oil and gas sector.

Solid waste management is one of the main problems in large cities. The determination of the quantitative and qualitative composition of municipal solid waste is necessary for proper planning in the processing of such waste. This article presents the results of studies of the morphological composition, physico-chemical parameters and energetical potential of municipal solid waste (MSW) from the landfill of the city of Shymkent. Waste samples were taken from 10 different points of the landfill. The volume–mass parameters of the samples and their average density were determined. The combined waste samples mainly consisted of food waste, paper and cardboard, polymers and plastic, glass, metal, textiles, wood, leather, bones and rubber. Most of the waste, more than 30%, contains plastic products. The moisture of the combustible fraction of the samples is low and varies from 0.3% to 2.3%. The average ash content of the combustible fraction of the samples was determined and its average value is 18.4%. The yield of the volatile substances was determined and the average value per dry state is 78.7%. To determine the energetical potential of municipal solid waste, the gross calorific value was determined and the net calorific value was calculated, the average value of which is 24.15 MJ/kg. This shows the possibility of using solid waste as an energy source.

Kazakhstan’s asbestos industry produces over 3 million tons of waste annually. The primary component of asbestos ore waste (AOW) is magnesium rich minerals. In this study, the extraction of magnesium from AOW with nitric acid (HNO₃) was for the first time systematically studied. A series of experiments were conducted to optimize acid concentration (300–600 g/L), leaching temperature (55–95 °C), leaching time (60–180 min), solid-to-liquid ratio (1:3–1:7), and particle size, with the overall goal of maximizing magnesium extraction and cost efficiency. Our results provide dependence of magnesium extraction in the order of acid concentration > temperature > time > solid-to-liquid ratio, while particle size was found to be negligible. The cost-efficiency optimization demonstrated the positive impact of the relatively low acid concentrations (< 450 g/L) and temperatures between 65 and 85 °C, while the Protodyakonov model validated a linear dependence of the extraction rate on temperature and acid concentration. Our model demonstrates that extraction efficiencies of up to 90% can be achieved while reducing reagent use and lowering the overall cost of magnesium production. Leaching of magnesium by HNO₃ also opens a pathway to a closed-cycle process, due to the formation of magnesium nitrate. The thermal decomposition of Mg(NO₃)₂ provides valuable products such as MgO and NO₂ reused in HNO₃ regeneration for subsequent cycles. The proposed model predicts magnesium extraction from asbestos ore depending on leaching parameters with reasonable accuracy.

This article presents the results of the study of the morphological composition of municipal solid waste (MSW) from the landfill of Atyrau city, and the waste’s energy characteristics and presence of microorganisms, including bacteria, fungi and viruses. This study was carried out under a government order to determine the feasibility of recycling accumulated and incoming waste into electricity and its hazard to the environment and the workers involved in handling it. At the moment, there is no MSW recycling in Kazakhstan, which has led to the accumulation of more than 125 million tons of waste with an annual increase of 5 million tons. The research included four major cities (Almaty, Shymkent, Atyrau and Astana), which were selected not only on the basis of population, but also because the cities were located in different climatic zones. Samples were collected at the city landfills: 10 samples with an average distance of 100 m from each other were collected to provide a maximum coverage of both recently received waste and long-time stored waste. The research showed that neither climatic conditions nor the population size had a significant impact on MSW density, the values of which ranged from 120.1 kg/m³ to 145.4 kg/m³, as this indicator directly depends on the quality of life. The mass of the combustible fraction ranged from 39.41% to 54.62% and was mainly represented by plastic, textile and paper waste. The average value for the four cities was 50.30%. The higher calorific value fell in the range of 24.22–30.49 MJ/kg, with an average value of 26.71 MJ/kg. Microbiological studies showed little difference in average composition regardless of climatic conditions. Thus, no sharp differences in MSW composition, its energy characteristics and microbiological composition were found. The results of this study may be useful for optimising MSW recycling and disposal processes, as well as for developing measures to reduce their negative impact on the environment and human health.

Zirconium-based conversion coatings were prepared on unpolished ST20LS mild steel by conventional immersion and cathodic polarization in aqueous H₂ZrF₆ solutions. Five-factor experimental designs were used to examine the effects of pH, temperature, deposition time, H₂ZrF₆ concentration, drying temperature/applied cathodic potential for both methods. The Zr conversion coatings were characterized by SEM/EDS, Raman spectroscopy, and XPS. Their protective properties were evaluated by neutral salt-spray testing, potentiodynamic polarization, and gravimetric testing in an oil–water emulsion. Cracks were observed in the Zr conversion coating prepared by the immersion method. The coating prepared at pH 4.0 decreased the salt-spray corrosion rate from 6.00 to 3.07 mm·year⁻¹. Cathodic polarization promoted coating formation on the rough steel surface, and the results showed that solution pH and applied potential affected the corrosion protection performance. Among the samples selected for detailed electrochemical analysis, the coating deposited at pH 6 and −1.2 V versus Ag/AgCl showed the strongest overall protection. Its polarization resistance reached 1310 Ω·cm², compared with 232 Ω·cm² for uncoated steel, while the corrosion current density decreased from 5.431 to 0.305 μA·cm⁻², corresponding to a protection efficiency of 94.5%. Raman and XPS results supported the formation of a poorly crystalline zirconium oxide/oxyhydroxide-containing layer. The results suggest that cathodically generated OH⁻ promotes interfacial hydrolysis and condensation of zirconium complexes, improving conversion-coating formation on rough mild-steel surfaces.

The presence of iron(II) impurities hinders the leaching and purification of magnesium ores. The most viable technological solution is to oxidise Fe²⁺ to Fe³⁺, which then precipitates as goethite. However, this process requires the development of new catalysts for use in highly acidic media. This study demonstrates that the Pt^0.25/CeO₂⁵/TiO₂ catalyst is highly effective at oxidising Fe²⁺ in 0.3 M HNO₃, outperforming samples supported on pure titanium dioxide or cerium dioxide. The rate constant is 0.304 L/(mol·min) at room temperature. Notably, the activation energy is only 10.7 kJ/mol, which is over five times lower than that of the non-catalytic process. This result was achieved by selectively depositing platinum particles onto highly dispersed cerium dioxide particles (average size ~5 nm), synthesised using the sol–gel method, and then depositing them onto titanium dioxide. Using a hybrid mixed oxide support ensures a high density of oxygen vacancies at the interface between the platinum (Pt) and mixed cerium and titanium dioxide phases. The formation of abundant adsorbed oxygen species enhances the catalytic activity of the Pt^0.25/CeO₂⁵/TiO₂ catalyst. The catalyst Pt^0.25/CeO₂⁵/TiO₂ also reaches a plateau in terms of efficiency after a durability experiment, which is the highest among the other samples.