Calcined and acid-leached kaolin impregnated with Fe(NO₃)₃·9H₂O (6.6 wt. % Fe₂O₃) was developed as an inexpensive bifunctional catalyst for the slow fixed-bed pyrolysis of polypropylene (PP) and low-density polyethylene (LDPE). Experiments were run with catalyst-to-plastic mass ratios of 1:4, 1:2, and 1:1 in a quartz tube reactor heated from 25 to 800 °C. For PP, increasing the Fe/kaolin loading progressively raised non-condensable gas from 26 wt. % to 44 wt. % and drove liquid aromatics from 27.9% to 72.3%, while combined paraffins olefins fell to 2.5% and wax exhibited a 46 → 24 → 36 wt. % trend. In contrast, LDPE at a 1:4 ratio already yielded 56 wt. % oil and only 22 wt. % wax; further catalyst addition mainly enhanced CH₄/CO-rich pyrolysis gas (PyGas) and char without substantially boosting aromatics. Gas analysis confirmed that Fe₂O₃ reduction and kaolin de-hydroxylation generated in situ H₂O, CO, and H₂. Given the catalyst’s low cost, regenerability, and ability to valorize the two most abundant waste polyolefins within the same reactor, the process offers a scalable route to flexible fuel and gas production from mixed plastic streams.

This study examined the effect of partially replacing semi-reinforcing carbon black grade N550 (up to 10 pts. wt.) and fully replacing industrial chalk with natural shungite mineral in industrial formulations of elastomer compositions intended for manufacturing various rubber technical products. It has been shown that due to the high content of carbon and silicon components in the composition of shungite mineral micropowders, their use as a filler in elastomer formulations significantly improves the physical and mechanical properties of rubber technical products (RTPs) manufactured using such compositions. It was determined that the use of SM as a partial replacement for carbon black in rubbers intended for molded rubber technical products contributes to a reduction in Mooney viscosity (up to 26.8%) and optimal vulcanization time (up to 23.7%), achieving rubbers with the required set of physical–mechanical properties and with an enhancing sealing capability (up to 19.7%). It has been established that the use of shungite mineral micropowders as a complete replacement for industrial chalk increases the strength of rubber products (RTPs) by up to 18.5% and enhances their resistance to liquid aggressive environments.

The disposal of agro-industrial waste is a pressing environmental issue. At the same time, due to the high silica content in specific agricultural residues, their processed products can be utilised in various industrial sectors as substitutes for commercial materials. This study investigates the key technological, physico-mechanical, and viscoelastic properties of industrial elastomeric compounds based on synthetic styrene–butadiene rubber, intended for the tread of summer passenger car tyres, when replacing the commercially used highly reinforcing silica filler (SF), Extrasil 150VD brand (white carbon black), with a carbon–silica filler (CSF). The CSF is produced by carbonising a finely ground mixture of rice production waste (rice husks and stems) in a pyrolysis furnace at 550–600 °C without oxygen. It was found that replacing 20 wt.pts. of silica filler with CSF in industrial tread formulations improves processing parameters (Mooney viscosity increases by up to 5.3%, optimal vulcanisation time by up to 9.2%), resistance to plastic deformation (by up to 7.7%), and tackiness of the rubber compounds (by 31.3–34.4%). Viscoelastic properties also improved: the loss modulus and mechanical loss tangent decreased by up to 24.0% and 14.3%, respectively; the rebound elasticity increased by up to 6.3% and fatigue resistance by up to 2.7 thousand cycles; and the internal temperature of samples decreased by 7 °C. However, a decrease in tensile strength (by 10.7–27.0%) and an increase in wear rate (up to 43.3% before and up to 22.5% after thermal ageing) were observed. Nevertheless, the overall results of this study indicate that the CSF derived from the carbonisation of rice production waste—containing both silica and carbon components—can effectively be used as a partial replacement for the commercially utilised reinforcing silica filler in the production of tread rubber for summer passenger car tyres.

Plastic waste and sewage sludge (SS) are abundant, heterogeneous waste streams whose utilization and recycling are constrained by contamination, variable composition, and limited resource recovery. This review evaluates their integrated thermochemical conversion, focusing on co-incineration, co-pyrolysis, co-gasification, hydrothermal co-carbonization, hydrothermal co-liquefaction, and the use of SS-derived char (SSC) and sewage sludge ash (SSA) as catalytic materials. Co-processing benefits arise from complementary feedstock properties: plastics provide high carbon, hydrogen, volatile matter (VM), and heating value, whereas SS contributes oxygenated intermediates and mineral phases containing Si, Al, Fe, Ca, Mg, and P. Among the reviewed routes, co-pyrolysis shows the strongest evidence of non-additive interactions, including hydrogen transfer, altered decomposition kinetics, and changes in liquid composition. Co-gasification can enhance H₂ formation and tar conversion, while hydrothermal routes are especially attractive for wet SS but remain comparatively underexplored. The review further distinguishes SSA, dominated by mineral acid–base and redox functionality, from SSC, which combines these mineral effects with adsorption and surface reactions on a porous carbon matrix. Key barriers include catalyst deactivation, chlorine and sulfur poisoning, heavy-metal migration, feedstock variability, and limited pilot-scale validation. Future development requires mechanistic controls, catalyst stability testing, techno-economic analysis, life-cycle assessment, and integrated nutrient recovery to establish practical circular waste-management systems.

In 2025, the oil and fat industry of the Republic of Kazakhstan showed steady growth, strengthening the country’s position as a major producer and exporter of vegetable oils. However, the production process generates large amounts of waste (up to 100 tons per day), and its recycling is an important part of the oil and fat industry’s economy. High-temperature processing of plant waste has proven to be a promising method for creating new materials for various industries. The aim of this study was to determine the influence of various technical parameters of carbonization (processing temperature and process environment) on the physical and chemical characteristics of materials obtained by carbonizing sunflower seed husks from the East Kazakhstan region at temperatures of 300, 400, 500, 600, 700 and 800 °C in an inert argon environment, as well as by processing the husks in an oxidizing environment at a temperature of 650 °C, for further use in elastomer compositions as new ingredients. Increasing the carbonization temperature in an inert environment led to an increase in the amorphous carbon content, surface porosity, and pH of the studied materials. Another parameter that showed a tendency to increase with increasing temperature in an inert environment was the BET specific surface area. In the case of using an oxidizing environment, the highest pH value was observed, and the formation of crystalline mineral phases was also observed. The differences in the phase states of the studied materials may play an important role in shaping the spatial stack of the polymer matrix when used in rubber compound formulations.

The integration of biological and renewable resources as fillers or novel components in thermoplastics and rubbers has gained attention due to their potential to mitigate the environmental impact of petroleum- and natural gas-derived fillers. This study explored using a carbon-mineral filler, derived from coal shale processing by-products, as a partial or complete substitute for standard industrial fillers in rubber formulations for sealing materials. Six rubber compositions were produced, varying in the proportion of carbon-mineral filler replacing N550 semi-reinforcing carbon black, and were evaluated for viscoelastic, kinetic, physical-mechanical, structural, and operational properties. Fully substituting technical carbon with the carbon-mineral filler improved technological characteristics, reducing Mooney viscosity by 40.5% and increasing resistance to premature vulcanization by 53.6%. When up to 10 wt.% of N550 was replaced, the materials retained required strength and hardness. Moreover, the elasticity of rubbers increased by up to 1.5 times with higher filler content. Even at elevated substitution levels, sealing performance remained stable, while resistance to aggressive liquid media nearly doubled (up to 1.9 times). These findings suggest that the carbon-mineral filler can extend the service life of rubber sealing products while reducing reliance on conventional fillers.