This study investigated the macro- and microelement profiles and bioactive substances (BAS) in the herbaceous species of the genus Rheum collected from two villages near Almaty, Kazakhstan, and the accumulation of heavy metals (HMs) in wild plants of Eastern Kazakhstan. Representative zonal species from the steppes and desert–steppes (Eastern Kazakhstan) were analyzed—totaling one hundred samples across 18 species from six families. According to the research, different plant species have a selective ability to accumulate heavy metals, even when growing in the same type of soil. Long-term observations reveal dominant patterns of HM (Cu, Zn, Mn, Co, Pb, Cd) occurrence in dry-steppe vegetation. It was found that Cu and Co demonstrate moderate bioadsorption with minimal accumulation, while Zn, Mn, and Pb show strong biological enrichment. Cadmium falls under elements with pronounced biological retention. Copper and cobalt are classified as moderately absorbed with limited buildup. Native plants in this region contain substantially greater amounts of lead relative to cobalt, and reflect cadmium–zinc geochemical specificity: Cd 3.85, Zn 0.15, Mn 0.10, Pb 0.09, Co 0.07, Cu 0.04, per Clark’s concentration index. Samples of collected Rheum tataricum L. in the village of Miyaly were found to have higher levels of flavonoids, phenolic compounds, and organic acids, while raw materials from the village of Bakbakty showed increased accumulation of anthracene derivatives and tannins. Flavonoids constituted the largest proportion of the studied groups of biologically active substances in both samples, confirming the high biological and pharmacological value of the plant material studied. The results obtained during the research can be successfully applied to the development of a strategy for the conservation of plant biodiversity in the studied areas and the sustainable management of plant resources.

Iron-based catalysts for direct CO₂ hydrogenation to hydrocarbons (CO₂-FTS) have attracted rapidly growing research interest as a Power-to-X route, yet we did not identify a prior systematic review with descriptive quantitative synthesis focused specifically on this catalyst class. To the best of the authors’ knowledge, this work provides a systematic descriptive quantitative synthesis, covering 60 coded reports published between January 2017 and July 2026 and identified by structured searches of Scopus, Web of Science Core Collection, and ScienceDirect. After PRISMA-adapted eligibility reconciliation, 49 primary studies were included; 42 reported extractable numerical CO₂ conversion data and contributed to the descriptive quantitative synthesis, while seven were retained for qualitative analysis only. Median CO₂ conversion across the 42 quantitative studies was 38.3% (range 8.5–69.9%; SD = 15.3%), providing a dataset-specific reference for the reviewed literature. Across the predefined subgroups, mean CO₂ conversion varied from 31.6% to 47.1%, with substantial differences in operating conditions and small subgroup sizes limiting direct attribution to catalyst composition. The highest absolute conversion, 69.9%, was achieved by two-stage reactor engineering with interstage H₂O removal, not catalyst reformulation, identifying product-water inhibition as an important single-stage conversion constraint. The highest recorded product selectivities across the dataset were 64.3% to C₅⁺ (Na-FeMgMnOx), 82.6% to light olefins (Y₂O₃/Fe–Co/SAPO-34), and 75.6% to aromatics (ZnFeOx-Na/HZSM-5); maximum demonstrated stability was 205 h (3K/6Cu-Fe₂O₃/C nanosheets). Analysis of the full conversion–selectivity dataset reveals that only approximately 14% of studied systems simultaneously exceeded the conversion median and a 44% target-selectivity threshold. The synthesis further identifies that key physicochemical descriptors (BET surface area, post-reaction Mössbauer phase composition, CO₂-TPD basicity, ASF α, space-time yield normalised to iron mass, and stability data) are absent from 60–85% of primary reports, and proposes recommended reporting elements to facilitate future quantitative synthesis. Because study-level variances and standardised controls were unavailable, no weighted effect-size meta-analysis was performed; the results should be interpreted as a descriptive quantitative synthesis. The review was not prospectively registered.

The development of efficient and recoverable catalysts is essential for advancing carbon dioxide utilization technologies and improving the sustainability of catalytic processes. Magnetic iron oxide-based composites supported on carbon materials are particularly promising due to the combination of catalytic activity, structural stability, and the possibility of magnetic separation from the reaction medium. The aim of this study was to produce potassium-modified magnetic iron oxide composite catalysts based on Fe₃O₄ and CoFe₂O₄ on carbon supports and to study the influence of synthesis conditions and composition on their phase composition and structural characteristics. Based on a comparative analysis of the obtained data, the catalyst composition was optimized and a preliminary assessment of their application in CO₂ hydrogenation was conducted. Potassium-modified magnetic iron-containing composites supported on carbon nanotubes (CNTs) and coconut shell activated carbon (AC) were synthesized via coprecipitation and vortex electromagnetic field (VEF) synthesis followed by thermal treatment and evaluated as promising materials for CO₂ utilization processes. The influence of synthesis parameters, including pH, Fe²⁺/Fe³⁺ molar ratio, coprecipitation temperature, and calcination temperature, on the structural, phase, and magnetic properties of the catalysts was studied. Structural analysis confirmed the formation of Fe₃O₄ and CoFe₂O₄ spinel phases. The optimal calcination temperature of 673 K ensured the formation of a well-crystallized Fe₃O₄ phase with sufficiently high saturation magnetization, whereas a further increase in temperature resulted in partial oxidation of Fe₃O₄ with the formation of Fe₂O₃. Optimal synthesis conditions were determined ensuring uniform deposition of Fe₃O₄ nanoparticles measuring 10–100 nm on carbon supports. It was found that CoFe₂O₄-based composites possess high coercivity but are characterized by lower catalytic activity in the CO₂ hydrogenation reaction: the maximum CO₂ conversion for CoFe₂O₄–K/CNTs was 59% at 600 °C, which is lower than that of the studied iron oxide composites. Synthesis using VEH (vortex electromagnetic homogenizer) improved particle dispersion and catalytic performance, increasing apparent CO₂ conversion from 51% to 54% at 450 °C. Methane formation was more pronounced at intermediate temperatures, whereas at temperatures above 500 °C the product distribution shifted toward CO, indicating the increasing contribution of the reverse water–gas shift (RWGS) reaction. It was shown that optimization of the synthesis parameters made it possible to obtain magnetic composites with controlled structural-phase and magnetic properties, and the combination of high dispersion, structural stability and magnetic activity makes the synthesized composites promising catalysts for carbon dioxide hydrogenation processes.

The catalytic conversion of carbon dioxide (CO2), generated in large quantities at oil and gas production facilities and gas processing plants, into high-value hydrocarbons is regarded as a promising pathway for the development of low-carbon petrochemical technologies. Particular attention has been devoted to iron-based catalysts capable of hydrogenating CO2 into olefins, alcohols, and other C2+ products that can serve as valuable feedstocks for petrochemical applications. This review summarizes recent advances in the understanding of the structural evolution of iron-based catalysts under CO2 hydrogenation conditions. The effects of catalyst composition, promoters, textural characteristics, activation procedures, and reaction conditions on the formation of active phases, the carburization of iron oxides, and the selectivity toward C2+ products are systematically analyzed. In addition, the mechanisms of phase transformations between iron oxides and iron carbides, as well as their roles in the formation of olefins and oxygenated compounds, are discussed. The analysis provides deeper insight into the relationship between the structure of ironbased catalysts and product selectivity. The findings may serve as a practical foundation for the development of efficient catalysts and the optimization of CO2 conversion processes aimed at producing valuable feedstocks for the petrochemical and gas-processing industries.

This study presents the development of magnetic composite nanosorbents based on iron oxide and humic acids (HA) for the removal of heavy metal ions from aqueous media. The nanocomposites were synthesized by chemical co-precipitation followed by surface modification with humic acids in a vortex electromagnetic field. The phase composition, structure, morphology, and physicochemical properties of the synthesized materials were investigated using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and magnetometry. The sorption properties of the obtained materials were assessed using atomic absorption spectrometry based on the degree of extraction of heavy metal ions from model aqueous solutions. It was established that modification of the iron oxide surface with humic acids promotes the formation of a functionalized surface capable of interacting with metal ions. The combination of sorption sites provided by the humic matrix with the magnetic properties of iron oxide enables efficient separation of the sorbent from the treated medium using an external magnetic field. The scientific significance of the study lies in establishing the relationship between the composition and surface characteristics of the magnetic composites and their sorption efficiency. The developed materials can be considered promising sorbents for the treatment of natural and wastewater contaminated with heavy metal ions.

The consumption of vegetable oils is steadily increasing, especially in Asian countries. Once used, the utilized cooking oils are either thrown into landfills or dumped there, endangering both the environment and people. One common method is to convert waste cooking oil (WCO) into biofuel; however, since WCO contains many free radicals, burning it releases large quantities of pollutants, meaning that disposal of WCO poses significant environmental risks. To stabilize the WCO (Cocos nucifera) before converting it into biofuel, this study analyzed the extraction, optimization, and use of antioxidant-rich bio-oil from Anisomeles malabarica leaves as a natural additive. Solvent screening revealed that a hexane–ethanol ratio of 4:2 was optimal for generating 76.7% bio-oil at room temperature. A maximum yield of 77% was attained by temperature and time optimization, which determined that 50 °C and 20 min were ideal. The extraction exhibits zero-order kinetics during the increasing phase, according to kinetic studies, with rate constants ranging from 0.54 to 1.44% min⁻¹ (R² = 0.950–0.997). The Peleg equilibrium model (average R² = 0.806) was used to describe the extraction profile. The regression equation ln(k) = 1799.3 × (1/T) − 10.828 (R² = 0.9748, p = 0.0002) was obtained using Arrhenius analysis. It was found that the compounds responsible for the antioxidant scavenging activity were found to be phytol, hexadecenoic acid, and tocopherol (vitamin E). The DPPH (2,2-diphenyl-1-picrylhydrazyl) test confirmed that 3% (v/v) bio-oil scavenged about 95% of free radicals, whereas the conjugated diene experiment demonstrated that over 90% of lipid oxidation in WCO was prevented. The combustion and emission properties of biofuel (WCB), which was created by transesterifying bio-oil-treated WCO, were compared to those of neat diesel and untreated WCO-derived biofuel (WC). In comparison to both WC50 and neat diesel, WCB50 demonstrated an equivalent in-cylinder pressure and heat release rate, but significantly reduced emissions of NO_x, CO, hydrocarbons, and smoke. These results show that Anisomeles malabarica bio-oil works well as a natural antioxidant addition for clean combustion and biodiesel stabilization.