Almagul R. Kerimkulova

This review critically examines physical and chemical strategies used to enhance the adsorption of CO₂, volatile organic compounds (VOCs), SO₂ and H₂S by biochar-based sorbents. The literature indicates that adsorption performance is governed by the combined effects of feedstock properties, thermochemical conversion conditions, pore structure, surface area and surface chemistry. Physical activation, particularly with steam or CO₂, primarily promotes pore development and increases accessible surface area, whereas chemical treatments with KOH, H₃PO₄, H₂SO₄, amine-based compounds, and biopolymers can additionally modify surface functionality and gas–surface interactions. Across the reviewed studies, KOH activation and nitrogen functionalization are frequently associated with enhanced CO₂ uptake, while acidic surface modification can improve interactions with selected polar VOCs. For sulfur-containing gases, pore development together with appropriate surface functional groups can facilitate both physical adsorption and surface reactions. Rather than identifying a universally optimal modification route, the available evidence shows that sorbent design should be tailored to the physicochemical properties of the target gas. The review also examines biomass residues as precursors and key technical factors affecting the scalability of biochar-based gas purification systems. Overall, the literature highlights biochar’s potential for gas adsorption and the need for evaluation of modification strategies and validation under realistic conditions.

The article describes the synthesis of an activated carbon-carbon/ash composite based on carbonized rice husk (CRH) and Ca-lignosulfonate. The obtained adsorbents were characterized by modern physicochemical research methods: scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS analysis), X-ray photoelectron spectroscopy (XPS), and low-temperature nitrogen adsorption. It was established that despite the presence of residual mineral impurities in an amount of about 15 wt. %, the synthesized CRH-lignosulf@850 composite exhibits a high specific surface area and a well-developed pore volume. These impurities are represented by the phases CaSiO3, MgSiO3, CaSO4 and SiO2, which proved to be resistant to alkaline leaching. The morphology of the obtained composites features a well-developed structure with both micro- and mesoporosity. According to calculations based on the Quenched solid density functional theory (QSDFT), the specific surface area of the obtained СRH-lignosulf@850 sample is 1144 m²/g, and the total pore volume is 0.947 cm³/g. Studies of methylene blue (MB) sorption under static conditions showed that the CRH-lignosulf@850 composite demonstrates high adsorption performance. According to the adsorption isotherms, the Toth model effectively describe the process, with the maximum sorption capacity of the material reaching 283.4 mg/g. The results obtained indicate the potential for using CRH-lignosulf@850 blocks to capture toxic compounds in emissions from enterprises producing organic products.

The occurrence of microplastics in natural and process waters presents a significant challenge for the design and operation of engineering water treatment and water supply systems in buildings and structures. This study experimentally evaluated the efficiency of a ULP21-4040 reverse osmosis membrane in removing polyethylene terephthalate (PET), polyethylene (PE), and polypropylene (PP) particles of different sizes from artificially contaminated water (hereafter, model water). Experiments were conducted using a pilot-scale HAIAO RO-250 unit operated at 1.3 MPa with a nominal capacity of 250 L/h. Model water was prepared by adding 1 g of each polymer with nominal particle sizes of 0.20 or 0.45mm to 100 L of distilled water. Each polymer–size combination was tested in triplicate. Microplastic particles in the permeate (treated water) and concentrate (water with increased concentrations of retained contaminants) were recovered using Sefar filter cloth with a 100 μm mesh size and quantified gravimetrically. Particle presence was confirmed by digital microscopy. Mean removal efficiency exceeded 97%, ranging from 97.81 ± 0.24% for 0.20mm PP to 99.87 ± 0.07% for 0.45mm PET. Retention efficiency depended on polymer type and particle size. Mass-balance calculations showed that an average of 0.81% of the initial microplastic mass accumulated inside the membrane module. The results support the potential application of the ULP21-4040 membrane as a final treatment stage in compact engineering water treatment systems. Further research should investigate membrane fouling, pressure losses, energy consumption, cleaning regimes, and long-term performance under actual operating conditions to support integration into building water supply systems and water reuse.

The growing demand for efficient and sustainable materials for air purification has stimulated interest in activated carbons derived from renewable biomass resources. In this study, activated carbons were prepared from Rice Husk, Wheat Straw, Sawdust, and Walnut shells and systematically investigated as sorbents for toxic gases and volatile organic compounds. The materials were characterized using nitrogen and water vapor sorption isotherms, scanning electron microscopy, thermogravimetric analysis, Fourier-transform infrared spectroscopy, energy-dispersive X-ray and XPS analysis to evaluate their textural properties, morphology, thermal stability, and surface chemistry. The results showed that the precursor type strongly influences the pore structure and functional group composition of the activated carbons. Wheat straw and Rice Husk-derived activated carbons exhibited the highest total pore volume and a well-developed porous structure, together with a high content of oxygen- and silicon-containing elements. Gas breakthrough experiments with different probes showed that Wheat Straw-derived activated carbon excels in non-polar VOC—cyclohexane removal due to its highly microporous structure. In contrast, Rice Husk-derived activated carbon displays strong affinity toward inorganic gases such as NH₃ and, after urea modification, achieves enhanced performance for SO₂. These results underscore the versatility and practical applicability of carbon materials obtained from plant residues.

The growing demand for efficient and sustainable materials for air purification has stimulated interest in activated carbons derived from renewable biomass resources. In this study, activated carbons were prepared from rice husk, wheat straw, sawdust, and walnut shells and systematically investigated as sorbents for toxic gases and volatile organic compounds. The materials were characterized using nitrogen and water vapour sorption isotherms, scanning electron microscopy, thermogravimetric analysis, Fourier-transform infrared spectroscopy, and energy-dispersive X-ray analysis to evaluate their textural properties, morphology, thermal stability, and surface chemistry. The results showed that the precursor type strongly influences the pore structure and functional group composition of the activated carbons. Wheat straw and Rice husk–derived activated carbons exhibited the highest total pore volume and a well-developed porous structure, together with a high content of oxygen- and silicon-containing elements. Gas breakthrough experiments with different probes showed that wheat straw–derived activated carbon excels in VOC removal due to its highly microporous structure. In contrast, rice husk–derived activated carbon displays strong affinity toward inorganic gases such as NH₃ and, after urea modification, achieves enhanced performance for SO₂. These results underscore the versatility and practical applicability of carbon materials obtained from plant residues.

This review presents a modern comprehensive analysis of the physicochemical characteristics of carbon materials for the sorption of gases. The main classes of carbon sorbents are considered as follows: nanotubes, activated carbon, graphene, fullerene, composite materials, and organic vapors. Modern methods of modification of carbon materials are systematized. Particular attention is paid to the effect of particle size, morphology, and porous structure on the kinetics and equilibrium characteristics of adsorption. The results of experimental and theoretical studies of the adsorption of the gases (CO₂, SO₂, NO_x, H₂S, NH₃, and CO) are analyzed. A comparative economic analysis of carbon materials is carried out, taking into account the cost of production and estimated costs of modification. Modern areas of application of carbon sorbents are analyzed as follows: industrial gas purification, automotive filters, air conditioning systems, personal protective equipment, and gas sensors. Particular attention is paid to the study of the prospects and future of materials. Prospective development directions are considered, including the creation of hierarchically porous structures, the development of self-healing materials, and integration with artificial intelligence to optimize adsorption processes. The cost of graphene and nanotube production is predicted to decrease by 50–70% by 2030, which will lead to an expansion of their commercial application.

This research work provides for the possibility of cleaning soils contaminated with heavy metals with nanostructured sorbents made from plant residues. As the object of the study, soil samples from Almaty, Semey, Aktau and Ridder were taken, and the process of sorption was carried out with biosorbents made from rice husks, Pine buds and sunflower husks. Physico-chemical studies (Sam, bat, RFA) were carried out on samples prepared by carbonization of sorbents in an argon atmosphere at a temperature of 800°C. The results showed that sorbents have a high porosity and a developed surface area, which increases their adsorption capacity. According to 5-day adsorption experiments, manganese (Mn) and rubidium (Rb) were effectively sorbed with all sorbents (30-70 %). At the same time, it was shown that sunflower husks effectively absorb rubidium, Pine buds-manganese and strontium, and rice husks-iron and rubidium. The results obtained show that carbon nanosorbents from plant residues are capable of effectively cleaning soils contaminated with heavy metals and are suitable for their use as an environmentally safe physico-mechanical method.

A new iodine–dextrin–lithium complex (IDLC) was synthesized and structurally characterized as a hybrid supramolecular system combining antiseptic, stabilizing, and biocompatible components. The compound integrates iodine as the primary antimicrobial agent, lithium as a coordination and stabilization element, and dextrin as a biodegradable polysaccharide matrix enabling sustained release. Physicochemical analyses confirmed the formation of a uniform, thermally stable complex. Biological evaluation revealed strong bactericidal activity, with minimum bactericidal concentrations (MBCs) ranging from 1.95 to 15.63 µg mL⁻¹ against both Gram-positive and Gram-negative pathogens, including multidrug-resistant Staphylococcus aureus and Acinetobacter baumannii. Cytotoxicity studies revealed moderate, concentration-dependent effects on human peripheral blood mononuclear cells (CC₅₀ = 0.23–0.48 mg/mL; 11.7–24.4 μg I/mL) and low toxicity toward MDCK cells (CC₅₀ = 10–20 mg/mL; 507–1014 μg I/mL), confirming a favorable safety profile. IDLC exhibited cytotoxic effects on tumor cell lines (HepG2, HeLa, AGS, K562, and H9) as well as on the normal MeT-5A cell line; however, the CC₅₀ values are similar, and selectivity indices are close to 1, indicating no selective cytotoxicity toward tumor cells. Thus, IDLC demonstrates non-specific cytotoxicity at high concentrations, consistent with its iodine content. The research confirms that iodine can be effectively stabilized within a dextrin-lithium framework to yield a biologically active, thermally resistant complex, suitable for pharmaceutical use.

The sustainable operation of hydroponic systems depends on maintaining the chemical stability of circulating nutrient solutions and preventing the accumulation of toxic compounds. The accumulation of phytotoxic ammonium, heavy metals, and organic metabolites in recirculating nutrient solutions remains one of the key challenges limiting the efficiency, sustainability, and scalability of hydroponic cultivation. This review provides a comprehensive comparative analysis of zeolites, activated carbons (ACs), and their functionalized and composite forms as key sorbents for nutrient management, contaminant removal, and environmental safety in hydroponic cultivation. Natural zeolites, with their well-defined crystalline structure and high ion-exchange selectivity toward ammonium and heavy metal cations, enable effective NH₄⁺/K⁺ balance regulation and phytotoxicity mitigation. ACs, characterized by high specific surface area and tunable surface chemistry, complement zeolites by offering extensive adsorption capacity for organic compounds, root exudates, and pesticide residues, thereby extending the operational lifespan of nutrient solutions and improving overall system performance. Further advancements include the integration of zeolites and ACs with two-dimensional (graphene, g-C₃N₄) and three-dimensional (MOF, COF) frameworks, yielding multifunctional materials that combine adsorption, ion exchange, photocatalysis, and nutrient regulation. Transition-metal modification, particularly with Fe, Mn, Cu, Ni, and Co, introduces redox-active centers that enhance sorption, catalysis, and phosphate stabilization. The comparative synthesis reveals that the combined application of zeolite- and carbon-based composites offers a synergistic strategy for developing adaptive and low-waste hydroponic systems. From a techno-economic and environmental standpoint, the judicious application of these materials paves the way for more resilient, efficient, and circular hydroponic systems, reducing fertilizer and water consumption, lowering contaminant discharge, and enhancing food security. This systematic review was conducted according to the PRISMA 2020 guidelines. Relevant studies were identified through Scopus, Web of Science, and Google Scholar databases using specific inclusion and exclusion criteria.

A new iodine-dextrin-lithium complex (IDLC) was synthesized and structurally characterized as a hybrid supramolecular system combining antiseptic, stabilizing, and biocompatible components. The compound integrates iodine as the primary antimicrobial agent, lithium as a coordination and stabilization element, and dextrin as a biodegradable polysaccharide matrix enabling sustained release. Physicochemical analyses confirmed the formation of a uniform, thermally stable complex. Biological evaluation revealed strong bactericidal activity, with minimum bactericidal concentrations (MBC) ranging from 1.95 to 15.63 µg ml-1 against both Gram-positive and Gram-negative pathogens, including multidrug-resistant Staphylococcus aureus and Acinetobacter baumannii. The complex also demonstrated inhibitory effects in virus-infected MDCK cell cultures. Cytotoxicity studies showed CC50 = 0.23-0.48 mg ml-1 on human MNCs and more than 10 mg ml-1 on MDCK cells, confirming low toxicity. The results of the study on the cytotoxicity of IDLC suggest a cytotoxic effect on tumor cell lines such as HepG2, HeLa, AGS, K562, and H9, as well as normal cell lines MeT-5A. Therefore, it can be estimated that IDLC has the potential to be a new drug with antitumor activity against these cell lines. The research confirms that iodine can be effectively stabilized within a dextrin-lithium framework to yield a biologically active, thermally resistant complex, suitable for pharmaceutical use.