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Cemented gangue backfill bodies (CGBBs) are characterized by high brittleness and poor toughness in backfill mining technology. According to different types of waste tires corresponding to different processing and crushing means, waste tire steel fiber (WTSF) was divided into S-WTSF, P-WTSF, and H-WTSF. The influence of CGBBs with different types and amounts of WTSF on the early mechanical properties of the modified samples was studied. Uniaxial compressive strength (UCS) and scanning electron microscopy (SEM) tests on the modified CGBB samples were carried out. The results show that as the WTSF content increased from 0% to 1.5%, the UCS of CGBB samples modified with S-WTSF, P-WTSF, and H-WTSF at a curing time of 3 d first increased and then decreased; the turning point for S-WTSF and P-WTSF was 1%, and the turning point for H-WTSF was 0.5%, whereas the UCS of these modified CGBB samples at a curing time of 7 d decreased continuously with the increasing addition of WTSF content. The addition of WTSF made CGBB samples change from brittleness to ductility. With the increasing content of S-WTSF and P-WTSF, the toughness of the modified CGBB samples at a curing time of 3 d first increased and then decreased (the turning point was 1%), and that at the curing time of 7 d continued to increase. The toughness of CGBB modified with H-WTSF first increased and then decreased (the turning point was 0.5%) with the increase of the H-WTSF content. The toughness enhancement mechanism of CGBB modified by WTSF can be illustrated from a microscopic perspective as follows: WTSF is wrapped by hydration products, and the inlaying and bridging effects of WTSF are formed in the CGBB matrix. This research provides a basis for the improvement of mechanical properties of CGBB modified by WTSF and a new method for the reuse of discarded tires. [ABSTRACT FROM AUTHOR]

Foam concrete is a porous cement-based material that could accommodate a high-volume particle addition at the mid- to high-density range (0.8 to 1.6 g/cm3). However, with low-density foam concrete (0.4 to 0.8 g/cm3), conventional particle inclusion (e.g., sand) tends to degrade the cellular microstructure and mechanical performance. Therefore, to improve low-density foam concrete, the novel use of crumb rubber (the rubber particles recycled from waste tires) in foam concrete is studied, as its unique attributes can potentially allow for the retention of structure and improved performance in foam concrete. The influence of no inclusion, sand, and crumb rubber on the microstructure and mechanical performance in foam concrete with the density of cellularized cement paste as 0.40 and 0.60 g/cm3 was studied. Computed tomography indicates that the inclusion of crumb rubber can mitigate the foam degradation concern associated with particle inclusion in low-density mixtures. A notable improvement was also observed in the mechanical properties of 0.40 g/cm3 rubberized foam concrete mixtures—compressive strength, plateau strength, and impact resistance—when referenced to the sand inclusion counterpart. [ABSTRACT FROM AUTHOR]

[Display omitted] • Desulfurization in waste tire pyrolysis oil and gas was achieved by metal oxides. • Fe 2 O 3 shows the best removal efficiency of 87.7% for sulfur-containing gas. • The desulfurization mechanism was revealed by ReaxFF-MD and experiments analysis. • The removal of S involved Fe-S bonding, C-S breakage, dehydrogenation, O migration. • Fe 2 O 3 promotes cyclization and dehydrogenation to produce monoaromatics (57.4%). Pyrolysis can effectively convert waste tires into high-value products. However, the sulfur-containing compounds in pyrolysis oil and gas would significantly reduce the environmental and economic feasibility of this technology. Here, the desulfurization and upgrade of waste tire pyrolysis oil and gas were performed by adding different metal oxides (Fe 2 O 3 , CuO, and CaO). Results showed that Fe 2 O 3 exhibited the highest removal efficiency of 87.7 % for the sulfur-containing gas at 600 °C with an outstanding removal efficiency of 99.5 % for H 2 S. CuO and CaO were slightly inferior to Fe 2 O 3 , with desulfurization efficiencies of 75.9 % and 45.2 % in the gas when added at 5 %. Fe 2 O 3 also demonstrated a notable efficacy in eliminating benzothiophene, the most abundant sulfur compound in pyrolysis oil, with a removal efficiency of 78.1 %. Molecular dynamics simulations and experiments showed that the desulfurization mechanism of Fe 2 O 3 involved the bonding of Fe-S, the breakage of C-S, dehydrogenation and oxygen migration process, which promoted the conversion of Fe 2 O 3 to FeO, FeS and Fe 2 (SO 4) 3. Meanwhile, Fe 2 O 3 enhanced the cyclization and dehydrogenation reaction, facilitating the upgrade of oil and gas (monocyclic aromatics to 57.4 % and H 2 to 22.3 %). This study may be helpful for the clean and high-value conversion of waste tires. [ABSTRACT FROM AUTHOR]

Polymer waste is currently a big and challenging issue throughout the world. Waste tires represent an important source of polymer waste. Therefore, it is highly desirable to recycle functional fillers from waste tires to develop composite materials for advanced applications. The primary theme of this review involves an overview of developing polystyrene (PS) composites using materials from recycled tires as fillers; waste tire recycling in terms of ground tire rubbers, carbon black, and textile fibers; surface treatments of the fillers to optimize various composite properties; and the mechanical, fire retarding, acoustic, and electromagnetic field (EMI) shielding performances of PS composite materials. The development of composite materials from polystyrene and recycled waste tires provides a novel avenue to achieve reductions in carbon emission goals and closed-loop plastic recycling, which is of significance in the development of circular economics and an environmentally friendly society. [ABSTRACT FROM AUTHOR]

Based on the efficient resource utilization of scrap tires, pyrolysis carbon black (PCB), and pyrolysis oil of waste tire (TPO), scrap tires' products were treated using dry styrene-butadiene-styrene (SBS) polymer modification of asphalt. The products of scrap tires, PCB and TPO, were handled using dry SBS polymer modification of asphalt based on the effective resource use of scrap tires. The consequences of scrap tires, PCB and TPO, were taken using dry SBS polymer modification of asphalt based on the effective resource use of scrap tires. PCB and TPO composite effect seriously degraded. Based on this, the impact of dry SBS polymer modification on the functionality of PCB-TPO-modified asphalt and the mechanism of modification was examined. According to the investigation, the SBS polymer was evenly distributed and fully developed in the asphalt mixture, which significantly enhanced the qualities of asphalt and the asphalt mixture and performed a positive role in the internal structure of the asphalt mixture. [ABSTRACT FROM AUTHOR]

The chronic exposure to particulate matter (PM) pollution causes societal and environmental issues, in particular in urban areas where most citizen are regularly exposed to vehicular traffic. Since almost two decades, environmental magnetic monitoring has demonstrated its efficiency to successfully map relative concentrations of airborne particle deposition on accumulative surfaces. A better understanding of the magnetic results requires discriminating the main traffic-related sources of the observed signal on particle collectors. To meet this objective, we investigated a sample set of exhaust and non-exhaust sources with respect to their magnetic fingerprints inferred from hysteresis loops, first-order reversal curve (FORC) diagrams, temperature dependency of initial susceptibility and unmixing of isothermal remanent magnetization acquisition curves. The source sample set comprises 14 diesel and gasoline exhaust smoke residues, 12 abrasive-fatigue wear test pieces from worn brake-pads, brake powders, worn tire-tread and three resuspension products: asphalt concrete, street dust and Saharan mineral dust deposited by precipitation after long-range eolian transport. Magnetic properties of the source samples were compared to those from various accumulative surfaces exposed to urban traffic (passive collectors, filters of facemasks for cycling, plant leaves and tree barks). We found some fingerprints of exhaust pipes and brake wear products on these collectors. The findings highlight the relevance of environmental magnetism tools to characterize different traffic-related source signals in accumulative surfaces in urban environment. [ABSTRACT FROM AUTHOR]

Alternative, renewable and carbon-neutral fuels are an urgent requirement. Pyrolysis has received the most attention in the conversion of biomass into fuel. The main disadvantages of chemical and physical properties of pyrolysis crude bio-oil include its high oxygen content and acidity. Catalytic fast pyrolysis can overcome this problem. Rice straw is an abundant biomass residual that can be of environmental negative impact and is not of proper use. Therefore, this research work introduces the use of this residual in the production of fuel sources by one-step catalytic pyrolysis with the reusability of the employed catalyst. A waste extraction catalyst modified with acidic and nickel sites has been prepared and was utilised for the proposed target in this study. The removal of silica, lignin and minerals by treatment of the rice straw with KOH and then HNO3 in a green terminated process improved the catalytic biomass conversion from 83% to 96% at a catalyst dose of 5%, at 250°C. The pre-treatment of the rice straw enables the reusability of the catalyst in direct catalytic pyrolysis where the employed catalyst exhibits good stability in four consecutive runs. The used KOH and HNO3 were neutralised by mixing to produce KNO3 as a valuable fertiliser. [ABSTRACT FROM AUTHOR]

The oil bitumen BND 90/130, produced at the "LLP SP Caspi Bitum" with the modifier, which consists of copolymer of ethylene with butyl acrylate and glycidyl methacrylate taken in an amount of 0.5-1.6 wt%, and the tire reclaim (4-20 wt%), which is the destructate of mesh elastomers of different chemical nature, was modified; possibility of using the developed bitumen-elastomer binders in road asphalt concrete was justified. Modification of bitumen with a copolymer of ethylene with butyl acrylate and glycidyl methacrylate leads to an improvement in the properties of road bitumen: the softening point, hardness, deformability at low temperatures, elasticity, and adhesion to metal and mineral filler increase. It was shown that ethylene with butyl acrylate and glycidyl methacrylate chemically interacts with the functional groups of bitumen asphaltenes through the epoxy group of glycidyl methacrylate. Analysis of the spectra and group composition indicates an increased content of high molecular weight asphaltenes in the modified bitumen with a slight increase in structuring resins. It has been established that bitumen modified with rubber crumbs of 0.6-1.0mm in size has high elasticity. The most effective composition of a bitumen-regenerated composite material based on tire reclaim has been determined. In terms of the totality of physicochemical and operational characteristics and comparative cost, the most acceptable is the bitumen-regenerated composition (with a regenerate content of 20%) and is superior in the complex of properties to bitumen modified with an optimal content of ethylene with butyl acrylate and glycidyl methacrylate (1.6%). The technology for modifying bitumen with tire reclaim is less time-consuming, more economically profitable, and environmentally effective, since it utilizes large-tonnage waste of worn-out tires. The resulting bitumen-polymer compositions have a high positive set of properties: softening point, hardness, elasticity, frost resistance, and low-temperature characteristics. [ABSTRACT FROM AUTHOR]

The reasonable and effective application of waste tires and discarded concrete in concrete is an important branch of green concrete development. This paper investigates the effects of the inorganic modification mode on the basic mechanical properties of rubber recycled concrete based on indoor tests. Inorganic modification, such as water washing, acid washing, and alkaline washing modification, was mainly used to treat and modify rubber particles. The factors affecting the compressive strength, the splitting tensile strength, the flexural strength, the axial compressive strength, and the modulus of elasticity of modified rubber recycled concrete were analyzed. The study results show that the incorporation of recycled aggregates and rubber reduced the mechanical properties of concrete, with the compressive and splitting tensile strengths showing the greatest reductions of 27.36% and 27.24%, respectively. Three modification methods significantly improved the mechanical properties of rubber recycled concrete. The alkali washing modification method was the most effective, maximally improving the mechanical properties of rubber recycled concrete by 7.53–15.51%. The effects of the three modifications on the mechanical properties of concrete were ranked as follows: alkali washing > acid washing > water washing. This study provides a data basis for the practical application of rubber recycled concrete in engineering and a test basis for the development of green concrete. [ABSTRACT FROM AUTHOR]

In this study, waste tires (WTs) were carbonized under an N2 atmosphere. Subsequently, KOH/WTs‐char with KOH‐assisted CO2 activation was used to prepare activated carbon (AC) as a highly porous carbon material for the removal of Cr(VI) and Cd(II) from water. Various techniques such as elemental analysis, Fourier‐transform infrared spectroscopy, scanning electron microscopy, and N2 adsorption/desorption were employed to investigate the physical and chemical characteristics of the prepared carbons. The WTs‐char activated with KOH under CO2 exhibited a microstructure with a high BET surface area and pore volume of 1841 m2/g and 0.869 cm3/g, respectively, demonstrating excellent adsorbent performance. The maximum removal efficiencies of 99.91 % for Cd(II) and 99.81 % for Cr(VI) were achieved using AC2 carbon under the following conditions: pH 2 for Cr(VI) and pH 5 for Cd(II), contact time of 120 min, adsorbent dose of 0.4 g/100 mL, and temperature of 298 K. The adsorption kinetics followed the pseudo‐second‐order equation, and the equilibrium data fit well with the Redlich–Peterson isotherm equation. The positive values of ▵G indicated that the uptake process for both ions was nonspontaneous and nonfeasible over the temperature studied. Both ions showed negative values of ΔH and ΔS on carbon, suggesting exothermic adsorption and a decrease in disorder. Regeneration studies showed that NaOH was a better desorbing agent than HCl. Cr(VI) desorption resulted in over 90 % removal recovery by AC2 using 1.0 M NaOH even after the fifth cycle. However, the low activation energy indicated that the adsorption was favorable kinetically. Overall, this study demonstrated the effective preparation of highly porous carbon and its successful performance in removing Cr(VI) and Cd(II) ions. [ABSTRACT FROM AUTHOR]

To improve the in situ soil stabilization, different chemical additives are used (ion exchange compounds, additives based on H2SO4 or vinyl polymers, and organic additives using lignosulfonates). One interesting alternative is the production of additives from various waste materials. The extensive testing of waste-based blends with soil was performed; the mechanical (unconfined compressive strength (UCS)) and hydraulic (capillary rise, water absorption, and frost resistance (FR)) soil properties were measured. The optimization process led to obtaining additive compositions ensuring high strength and sealing properties: by-pass ash from the ceramics industry, waste H2SO4, pyrolytic waxes/oils from waste mixed plastics, waste tires and HDPE, and emulsion from chewing gum waste. For sandy soil, the following additives were the most promising: emulsion from pyrolytic wax (EPW) from waste PE foil (WPEF) with the addition of waste H2SO4, pyrolytic-oil emulsion from waste tires, EPW from waste mixed plastics with the addition of "by-pass" waste ash and NaOH, EPW from WPEF with the addition of NaOH, and EPW from WPEF reaching up to 93% FR, a 79.6% 7-day UCS increase, and a 27.6% of 28-day UCS increase. For clay: EPW from WPEF with the addition of NaOH, EPW from WPEF with the addition of waste H2SO4, and solely EPW from WPEF reaching up to 7.5% FR, an 80.7% 7-day UCS increase, and a 119.1% 28-day UCS increase. [ABSTRACT FROM AUTHOR]

The pyrolytic oil reside (POR) is produced during vacuum pyrolysis of waste tire powder (WTP) at 600 °C. Then, the pyrolytic oil residue is considered as a rheology modifier for bitumen at low temperatures. Characterization of POR showed lower viscosity and flash point with same elemental analysis to neat bitumen. Interestingly, the POR provides high-content resin (~ 20%) and similar C/H to resin part of neat bitumen which caused the increase in ductility. By blending POR with bitumen, penetration increased and softening point decreased. Short-term aging properties (compatibility, retained penetration) displayed improvement in aging resistance. Stiffness curves of bending beam rheometer (BBR) at − 12 °C proposed a winter-flexible binder by adding POR. Also, rotational viscometry (RV) indicated shear-thinning behavior of modified bitumen. The validity of this assumption was confirmed during dynamic shear rheometer (DSR) study. Damping factor considered an enhancement in soft viscous performance of modified bitumen at low temperatures in comparison to neat bitumen. [ABSTRACT FROM AUTHOR]

Millions of used or worn-out tyres are disposed of by many countries annually. These tyres can be put to good use when recycled. Used tyres are among the most problematic and challenging sources of solid waste, especially in landfills. Therefore, the use of waste tyres for composite materials having desired performance properties can be used as a means of disposing of the tyres. Fibrous material-reinforced composites with enhanced physical and mechanical performance and incorporating sisal fibres were produced using waste tyre material, sisal, and polyester resin. The physical and mechanical properties of hybrid composite board panels, including flexural strength, compression strength, tensile strength, and water absorption, were determined according to ASTM Standards. The rubber tyre particles used in the study had a size of 1.00 mm, and the sisal used had an average length of 6mm. A systematic experimental design was formulated and worked accordingly in the fabrication of the composite. The hybrid composite produced has adequate mechanical properties to perform as a substitute for solid wood in several applications such as tabletops, general purpose, load-bearing boards, ceiling boards, furniture, door panels and partitioning boards. [ABSTRACT FROM AUTHOR]

As a potential long-life pavement material, the high brittleness of epoxy asphalt prevents its application. Recycled from waste tires, crumb rubber (CR) can be used with styrene-butadiene-styrene (SBS) to prepare SBS/CR composite modified asphalt. The main objective of this paper is to conduct the material design of epoxy asphalt with SBS, CR, and core-shell rubber (CSR) to toughen the epoxy asphalt and enhance its performance. First, SBS modified epoxy asphalt and SBS/CR composite modified epoxy asphalt (CMEA) were prepared to optimize the toughening materials based on tensile tests. Subsequently, based on the optimized material, the optimal proportion was determined through the response surface method by the Design-Expert software. Third, the microscopic morphology of different epoxy asphalt was observed by laser scanning confocal microscopy (LSCM), and the changes in functional groups were tracked using Fourier transform infrared spectroscopy to reveal the toughening mechanism. Finally, the viscosity test was carried out on the optimal SBS/CR-CSR CMEA at different temperatures to determine its mixing temperature and allowable time. The results show that the SBS/CR-CSR CMEA is the best toughening method, and the optimal epoxy and CSR proportion is 37% and 12%, respectively. Its tensile strength increases by 467.11% and elongation at break increases by 68.73% compared with unmodified epoxy asphalt. The formation of interpenetrating polymer network structure between the SBS/CR network and epoxy resin network, as well as the change in the benzene ring that determines the softness and toughness, may be the main strengthening and toughening mechanisms. The suitable mixing temperature is 160°C for the optimal SBS/CR-CSR CMEA in this paper, which reduces about 20°C compared with conventional CR or SBS/CR composite modified asphalt, providing better environmental benefits. Overall, the SBS/CR-CSR CMEA presents a new solution for the promotion and application of epoxy asphalt. [ABSTRACT FROM AUTHOR]

Today, one of the most important problems for humans is disease and mortality due to air pollutants, especially in large and industrial cities. This research is to evaluate the health risk of children and adults' exposure to heavy metals and PAHs in the air of cities of Arak, Isfahan, Ahvaz, Tabriz, Shiraz, Karaj and Mashhad and identifying the factors affecting pollution, based on sampling data from 120 stations, was done during 2019–2020. ICP OES and GC/MS were used to determine the amount of heavy metals and PAHs, respectively. US-EPA models were used for carcinogenic and non-carcinogenic risk assessment and Factor analysis models, PCA, CFA with SPSS and LISREL software were used to identify factors affecting contamination. The risk index for children and adults, except in the cities of Arak and Isfahan, was obtained within the allowable range and the carcinogenicity and non-carcinogenicity risk of all metals, except Mn in Arak and Isfahan for children and adults was seen below the threshold. The carcinogenic risk of all PAHs was also obtained to an acceptable extent. During the statistical analysis, combustion of fuels, vehicle exhaust, tyre wear and industrial activities were identified as the most important factors in causing pollution. [ABSTRACT FROM AUTHOR]

[Display omitted] • Zinc leached in higher concentration than other metals in all asphalt mixtures. • The main source of zinc may be the aggregates. • All metal concentrations would not exceed the drinking water limit. There are concerns about the potential toxicity of bitumen and recycled materials such as reclaimed asphalt pavements from end-of-life roads and crumb rubber from scrap tires used in asphalt mixtures because they contain metals that may be released into the groundwater. This study investigated the potential metal leaching of laboratory-prepared asphalt mixtures modified with polymer coated rubber (PCR) with wet and dry technology, devulcanized rubber (DVR), compared to an unmodified control mixture and a blend modified with a synthetic polymer (SBS). The objectives were to i) quantify concentrations of metals released, ii) calculate the flux rate, the cumulative mass release, and the assessment ratio for each metal, iii) verify if the metals exceeded the EPA drinking water limit, and, finally, iv) assess the source of metals release. Zinc had the highest concentration among all metals and was present in eluates from all mixtures. The cumulative zinc concentration from DVR mixture was 41% and 34% higher than the control and SBS mixtures, respectively. For PCR wet, the cumulative zinc concentration was 9% higher than the control blend and 1% lower than the SBS mix. The assessment ratio indicated that all metal concentrations would not exceed the drinking water limit, except for zinc, for which further evaluations were required. The main source of zinc may derive from aggregates. This work showed that crumb rubber might not be the only source of metal leaching, and its use in asphalt pavements does not cause a metal leaching higher than other materials. [ABSTRACT FROM AUTHOR]

The technological properties of composite materials (thermal, strength, rheology, electrical and morphology) are very important parameters for high-performance applications. In this study, we aimed to improve the properties of PVA by using carbon materials obtained by the pyrolysis of waste tires, with the aim of recycling them instead of disposing of them. For this purpose, PVA biocomposite films containing carbonized waste rubber at different rates were prepared. The thermal properties of the prepared biocomposite films were examined via thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) methods. While rheological measurements were carried out with a rheometer, bulk conductivities were measured with a pico-ammeter. In addition, the morphology of biocomposite films was determined via field emission scanning electron microscopy. The nanomechanical properties of biocomposite film was investigated via XPM analyses. According to the rheological measurements and nanoindentation hardness results, it is understood that as the amount of carbonized waste rubber increases, flexibility decreases and harder and brittle structures are observed in biocomposite films. The electrical measurement results showed that electrical conductivity increased as the amount of carbonized waste rubber increased. When all the results obtained were evaluated, it could be concluded that biocomposite films obtained by increasing the electrical conductivity and hardness of PVA can be used in the electronics industry. [ABSTRACT FROM AUTHOR]

The primary objective of this research is to assess the mechanical properties of shotcrete or sprayed concrete reinforced with waste tire textile fibers (WTTFs). Shotcrete is extensively employed in civil and mining engineering projects for support systems. This study examines the physical and mechanical characteristics of shotcrete samples, both without fibers and reinforced with WTTFs, including density, water absorption, volume of permeable voids, ultrasonic pulse velocity, uniaxial compressive strength, and splitting tensile strength. The reinforced samples consist of WTTF fibers at 0.5%, 1%, and 1.5% concentrations. Test results demonstrate that the inclusion of waste tire textile fibers enhances the mechanical properties of shotcrete, particularly its deformability and energy absorption capacity. Based on the test outcomes, a 1% fiber concentration is recommended as the most suitable ratio for utilizing waste tire textile fibers in shotcrete. Furthermore, these flexible fibers do not impede shotcrete pumping or spraying capabilities. [ABSTRACT FROM AUTHOR]

Crumb rubber concrete (CRC) is a cementitious composite produced by incorporating rubber crumbs into normal concrete (NC), characterized by large deformation, high damping, high energy absorption, and lower Young's modulus than normal concrete. This article presents a study on the seismic performance of frame structures under four scenarios: one normal concrete frame and three CRC frames. The total lateral stiffness, fundamental period, lateral earthquake loading, and interstory lateral displacements are calculated and compared based on the standardized design procedure. The results indicate that CRC frame structures increase the fundamental period and reduce the lateral earthquake loadings. The fundamental period of the CRC columns and beams (S3) is increased by 5.48% against normal concrete beams and columns (S0). However, decrease in the total lateral stiffness and increase the interstory lateral displacements was observed. The lateral earthquake loading is reduced by more than 4% against S0. These two competing factors determine the plausibility and benefit of CRC in structural application regarding earthquake design. The inter-story lateral displacements of CRC structures are still within the permissible design limits, confirming CRC's plausibility in structural application. This study also lays the technical ground for further exploring CRC in concrete structural applications that may recycle large quantities of scrap automobile tires. [ABSTRACT FROM AUTHOR]

The reuse of scrap tires to save storage space and lower traditional disposal risks is an environmental challenge. Currently, recycled tires are considered low-cost, lightweight materials that can be used to improve soil, retaining walls, backfills and roadbeds. The present study investigated the effect of the tire-shred aspect ratio and weight percentage on the bearing capacity and displacement of a stabilized mechanical retaining wall with multi-plate anchors under static loading. To this end, sandy soil containing tire shreds with widths of 1 and 2 cm, aspect ratios of 1, 2, 3, 4 and 5 at 5%, 10%, 15% and 20% contents (weight percentage of soil) was examined. Direct shear tests were conducted to determine the shear strength parameters of the mixtures. It was found that an increase in the tire-shred content in the mixture at a fixed aspect ratio, the bearing capacity of the mixture increased. Also at a fixed aspect ratio, the horizontal wall displacement increased with an increase in the tire-shred content. The wall bearing capacity was determined to increase at a fixed tire-shred content with an increase in the aspect ratio of the tire shreds. The results of the particle image velocimetry showed that an increase in the tire-shred aspect ratio increased the strain on the particle slip surface. [ABSTRACT FROM AUTHOR]

The recycling of scrap tire rubber requires high levels of energy, which poses challenges to its proper valorization. The application of rubber in construction requires significant mechanical and/or chemical treatment of scrap rubber to compatiblize it with the surrounding matrix. These methods are energy-consuming and costly and may lead to environmental concerns associated with chemical leachates. Furthermore, recent methods usually call for single-size rubber particles or a narrow rubber particle size distribution; this, in turn, adds to the pre-processing cost. Here, we used microbial etching (e.g., microbial metabolism) to modify the surface of rubber particles of varying sizes. Specifically, we subjected rubber particles with diameters of 1.18 mm and 0.6 mm to incubation in flask bioreactors containing a mineral medium with thiosulfate and acetate and inoculated them with a microbial culture from waste-activated sludge. The near-stoichiometric oxidation of thiosulfate to sulfate was observed in the bioreactors. Most notably, two of the most potent rubber-degrading bacteria (Gordonia and Nocardia) were found to be significantly enriched in the medium. In the absence of added thiosulfate in the medium, sulfate production, likely from the desulfurization of the rubber, was also observed. Microbial etching increased the surface polarity of rubber particles, enhancing their interactions with bitumen. This was evidenced by an 82% reduction in rubber–bitumen separation when 1.18 mm microbially etched rubber was used. The study outcomes provide supporting evidence for a rubber recycling method that is environmentally friendly and has a low cost, promoting pavement sustainability and resource conservation. [ABSTRACT FROM AUTHOR]

In this article, waste fibres from the recycling tire process with a different percentage of addition (0, 2.5, 5, 7.5, 10, 12.5) were mixed to increase their tensile strength, tear resistance, and bending resistance with natural rubber NR. The effect of short fiber on composite mechanical properties was investigated. Despite substantial research on the mechanical characteristics of rubber products reinforced with fiber waste, the experimental work focused on identifying precursory physical mechanisms that are responsible for fracture behavior during tests and structural monitoring. The findings reveal that milling and vulcanization conditions have a significant role in enhancing mechanical characteristics. The waste fibres and natural rubber provide strong interfacial adhesion during two rolls of milling and vulcanization at 140°C. Waste fiber may boost the tensile strength of a composite material by up to 7.5% of waste fiber, with a slight decrease at 10% and 12.5%. The flexing test findings showed that adding fiber to the recipe improved it by up to 7.5% before gradually degrading, and it is obvious that the recipes' tear resistance improves in comparison to the basic recipe. The discoveries have the potential to increase the tensile strength, tear resistance, and flexing resistance of industrially manufactured rubber conveyor belts, which are important physical properties in engineering applications. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study on how crumb rubber particles from waste tires and corrugated round steel fibers affect the mechanical behavior of concrete. In addition to the standard plain mix and five combinations of mixes composed of 0.5%, 1.0%, and 1.5% ratios, three steel fiber and crumb rubber mixes, 0.5%, 1.0%, and 2.0% weight of sand, coarse aggregate, cement, and silica fume were evaluated. The percentage of silica fume that replaced the weight of the cement in this study was 8%. The fresh properties of the 12 mixtures in terms of slump and density were studied. After 28 days of curing 36 cubes, 36 cylinders, and 12 prisms, the hardened properties were determined by evaluating the mean compressive, split, and flexural strengths. The results indicate that a synergetic effect is observed for the combination of crumb rubber and corrugated round steel fibers to improve the fresh and hardened properties of concrete. Adding fiber reinforcement to concrete can mitigate the negative impacts of rubber, and vice versa. According to the combination content, increases in compressive strength, tensile strength, and flexural strength of up to 49.04%, 38.60%, and 75.76%, respectively, were achieved compared with the control combination. This validates the applicability of the proposed mathematical prediction formulation to evaluate the compressive strength, split tensile strength, and modulus of rupture of rubberized fibrous concrete in terms of fiber and rubber ratios. Based on these results, a promising solution for tire disposal is to recycle waste rubber for fibrous concrete applications. [ABSTRACT FROM AUTHOR]

The objective of this work is the energy characterisation and evaluation of the energy efficiency potential of the rubber manufacturing industry in Italy, exploiting the detailed data included in energy audits by large and energy-intensive companies. This sector is divided into two sub-activities: the manufacture of rubber products and the production of tyres. Existing studies are focused mainly on tyre production, and there is a lack of quantitative evaluation of energy indicators that can provide guidance for improving process efficiency. In this work, updated global and specific energy performance indicators (EnPIs) related to the production process and to the auxiliary and general services are defined and evaluated. At the same time, targeted actions and interventions to improve the energy efficiency of the sector are analysed, showing the role of different intervention areas and their cost-effectiveness. The analysis is based on 100 Italian mandatory energy audits of the sector collected according to Art.8 EU Directive 27/2012. The applied methodology made it possible to calculate specific energy performance indicators by considering the overall and sub-process energy consumption of different production sites. Based on a detailed database containing real data from recent energy audits, this study provides an up-to-date and reliable benchmark for the rubber industry sector. In addition, the analysis of energy audits allows the identification of the most effective energy efficiency interventions for the rubber industry in terms of cost-effectiveness and payback time. [ABSTRACT FROM AUTHOR]

The environmental impact of non-biodegradable rubber waste can be severe if they are buried in moist landfill soils or remain unused forever. This study deals with a sustainable approach for reusing discarded tires in construction materials. Replacing ordinary Portland cement (OPC) with an environmentally friendly geopolymer binder and integrating crumb rubber into pre-treated or non-treated geopolymer concrete as a partial replacement of natural aggregate is a great alternative to utilise tire waste and reduce CO2 emissions. Considering this, two sets of geopolymer concrete (GPC) mixes were manufactured, referred to as core mixes. Fine aggregates of the core geopolymer mixes were partially replaced with pre-treated and non-treated rubber crumbs to produce crumb rubber geopolymer concrete (CRGPC). The mechanical properties, such as compressive strength, stress–strain relationship, and elastic modulus of a rubberised geopolymer concrete of the reference GPC mix and the CRGPC were examined thoroughly to determine the performance of the products. Also, the mechanical properties of the CRGPC were compared with the existing material models. The result shows that the compressive strength and modulus of elasticity of CRGPC decrease with the increase of rubber content; for instance, a 33% reduction of the compressive strength is observed when 25% natural fine aggregate is replaced with crumb rubber. However, the strength and elasticity reduction can be minimised using pre-treated rubber particles. Based on the experimental results, stress–strain models for GPC and CRGPC are developed and proposed. The proposed models can accurately predict the properties of GPC and CRGPC. [ABSTRACT FROM AUTHOR]

This research focuses on valorising waste burnt tires (BTs) through a two-phase oxidation process, leading to the production of onion-like carbon-based nanostructures. The initial carbonization of BTs yielded activated carbon (AC), denoted as "BTSA", followed by further oxidation using the modified Hummer's method to produce onion-like carbon designated as "BTHM". Brunauer–Emmett–Teller (BET) surface area measurements showed 5.49 m2/g, 19.88 m2/g, and 71.08 m2/g for raw BT, BTSA, and BTHM, respectively. Additional surface functionalization oxidations were observed through Fourier-Transform Infrared (FTIR), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM) analyses. Raman spectroscopy indicated an increased graphitic nature during each oxidation stage. BTHM was assessed in batch adsorption studies for cupric wastewater remediation, revealing a two-phase pseudo-first-order behaviour dominated by mass transfer to BTHM. The maximum adsorption capacity for Cu2+ on BTHM was determined as 136.1 mg/g at 25 °C. Langmuir adsorption isotherm best described BTHM at a solution pH of 6, while kinetics studies suggested pseudo-second-order kinetics. Furthermore, BTHM, laden with Cu2+, served as a catalyst in a model coupling reaction of para-idoanisole and phenol, successfully yielding the desired product. This study highlights the promising potential of BTHM for both environmental remediation and catalytic reuse applications to avoid the generation of secondary environmental waste by the spent adsorbent. [ABSTRACT FROM AUTHOR]

Hydrogen is a versatile energy vector for a plethora of applications; nevertheless, its production from waste/residues is often overlooked. Gasification and subsequent conversion of the raw synthesis gas to hydrogen are an attractive alternative to produce renewable hydrogen. In this paper, recent developments in R&D on waste gasification (municipal solid waste, tires, plastic waste) are summarised, and an overview about suitable gasification processes is given. A literature survey indicated that a broad span of hydrogen relates to productivity depending on the feedstock, ranging from 15 to 300 g H2/kg of feedstock. Suitable gas treatment (upgrading and separation) is also covered, presenting both direct and indirect (chemical looping) concepts. Hydrogen production via gasification offers a high productivity potential. However, regulations, like frame conditions or subsidies, are necessary to bring the technology into the market. [ABSTRACT FROM AUTHOR]

Waste tires, which are a serious environmental threat due to the ever-increasing number of on-road vehicles, must inevitably be effectively recycled. Many researchers have posited that granular soil and crumbed waste tire mixtures can be used to reduce seismic forces in so-called geotechnical seismic isolation (GSI) systems because of the high-energy absorption capacity of sand and rubber (SR) mixtures. However, there are concerns about the stability of superstructures due to the high compressibility of SR mixtures. Asphalt mixtures have also gained new application areas outside of transportation engineering, such as in hydraulic structures and seismic isolation, due to their ductile, cohesive and viscoelastoplastic properties in recent years. In this study, sand–rubber–bitumen (SRB) mixtures were produced by adding bitumen as a binder to SR mixtures containing crumbed rubber (CR) at different ratios (1%, 2%, 3%, and 4% of the sand weight). The dynamic properties of the SRB mixtures were determined by cyclic simple shear tests, depending on vertical and cyclic stresses. We found that the SRB mixture containing 3% CR had the maximum damping ratio (D) and that an increase in the rubber content of SRB mixtures causes a decrease in the secant shear modulus (Gsec). In addition, it was observed that the Gsec increased with the vertical stress and decreased with the cyclic stress ratio. In comparing the D and Gsec values of the SRB mixtures with those of SR mixtures under similar loading conditions, it was found that the SRB mixtures had both higher D and stiffness. As a result, SRB mixtures are more suitable than SR mixtures in terms of damping, and SRB mixtures can be an alternative material for use in GSI systems. [ABSTRACT FROM AUTHOR]

This study extensively explored the impact of integrating waste tire rubber into high-performance concrete (HPC) by substituting natural sand. Different fractions of rubber particles—5%, 10%, and 15% replacements of the fine aggregate—were rigorously investigated. Properties from fresh to hardened concrete were assessed, including compressive and tensile strength, modulus of elasticity, workability, and damping coefficient. Replacing up to 10% of sand with 0.6 mm rubber particles showed minimal strength compromise compared to standard HPC. However, at a 15% replacement rate, a noticeable decline in strength became evident, highlighting an optimal threshold for inclusion. Additionally, rubber incorporation notably enhanced concrete ductility and damping, marking a substantial improvement in dynamic properties. Efforts to offset strength reduction through increased fines content and mineral admixture could not counteract the decline at the 15% replacement level, suggesting limitations in compensatory measures. Methodological refinements enhanced data accuracy, including capping and surface treatments during compression testing. The study underlined the viability of controlled rubber substitution for bolstering HPC's dynamic attributes. Despite strength reductions at higher replacement rates, controlled waste tire rubber integration proves promising for enhancing HPC's dynamics without compromising structural integrity, advocating its suitability across diverse construction applications. [ABSTRACT FROM AUTHOR]

Nanocomposites based on acrylonitrile butadiene rubber (NBR) and ethylene–proplene diene monomer (EPDM) (50/50) filled with different concentrations of nano-waste magnetic filler (nWMF) up to 120 phr were prepared by two laboratory two roll mill mixer. nWMF was characterized using XRD, TEM and VSM. The prepared nanocomposites were investigated by different techniques: SEM, TGA, and DSC. In addition the rheological, mechanical, dielectric and magnetic properties were studied. However, the miscibility of NBR/EPDM/nWMF nanocomposites is enhanced after the addition of nano-waste magnetic filler (nWMF). Also, it is found that the thermal stability of NBR/EPDM blend is improved by increasing nWMF loadings. The incorporation of nWMF in rubber matrix increased minimum/maximum torque, cure rate index and reinforcing factor but decreased both optimum cure and scorch time. The mechanical properties showed an enhancement up to 40 phr of nWMF. Further, the magnetization shows a continuous increase with nWMF loading. In addition, the values ε′ and ε″ increased upon rising nWMF concentration. The nanocomposite containing 40 phr shows promising mechanical and dielectric properties which validate its use for insulating and antistatic purposes. [ABSTRACT FROM AUTHOR]

The incorporation of rubber recycled aggregates from end-of-life tyres (ELT) in the manufacturing process of sustainable building materials has gained great interest in recent decades as a result of the large volume of this waste being generated annually. In this work, the objective is to make a contribution towards the circularity of construction products by carrying out a physico-mechanical characterisation of new gypsum composites made with the incorporation of these recycled rubber aggregates. To this end, up to 30% by volume of the original raw material has been substituted, analysing the mechanical resistance to bending and compression. Although lower than those of traditional gypsum material, both properties exceed the limits set at 1 and 2 MPa, respectively, by the current regulations. In addition, water absorption by capillarity significantly decreases, and thermal conductivity is reduced by more than 35% with respect to the reference material. Finally, in order to provide the research with a practical application, a prefabricated plate design has been proposed that incorporates the gypsum materials studied and an agglomerated rubber band that increases the thermal resistance and improves the efficiency of the designed construction system. In this way, this research reflects the potential of these novel building materials and explores new avenues for their application in building construction. [ABSTRACT FROM AUTHOR]

The most important goal of this work was to investigate the different physical and mechanical properties of the nanoclay (montmorillonite, MMT)-filled 50/50 wt.% of natural rubber/styrene butadiene rubber (NR/SBR) blend containing 40 phr of waste tire rubber (WTR) in the presence of bio-resin. The MMT was added into the NR/SBR/WTR blends and processed via a two-roll mill to prepare blends at 0, 5, 10, 15, and 20 phr of nanoclay filler and a constant concentration of 10 phr of bio-resin. The morphology, rheological, percent of swelling weight, and mechanical properties of the MMT-reinforced NR/SBR/WTR blends were examined. The cure characteristics of the blends showed that MMT significantly affected the scorch and vulcanization times, torques, and curing rate of NR/SBR/WTR blends at all filler contents. Also, the findings revealed that the MMT was an efficient reinforcing material for the NR/SBR/WTR blend, improving crosslink density, tensile and tear strengths, hardness, compression set, and abrasion resistance. The tensile strength of filled NR/SBR/WTR blends achieved its maximum value (11.2 MPa) when the MMT content was 15 phr. While the elongation percent of the filled blends decreased for all MMT concentrations compared with the pristine blend. The elastic modulus and tear strength of the blends improved as the MMT loading increased. The hardness (Shore A) continued to increase with increasing MMT loading. On the contrary, the rebound resilience gradually decreased leading to improved interaction between the matrix and filler. [ABSTRACT FROM AUTHOR]

[Display omitted] • Less pollutants in pyrolytic gas were emitted at steady stage than other stages. • Heavy metals were mainly concentrated in pyrolytic carbon. • PAHs and PCDD/Fs were mainly concentrated in pyrolytic oil. • The findings contribute to the development of pollutant control technology. Pyrolysis is considered a highly practical, cost-effective, and environment-friendly technology for waste tires disposal. In this study, pyrolysis processes of waste tires were conducted in a pilot scale furnace feeding at 30 kg/h. The properties of pyrolytic products and the distribution patterns of pollutants generated in different operating stages (start-up, steady, and shut-down) were investigated. The pyrolytic gas in the steady state had a high caloric value of 10799 kJ/Nm3, valuable as heating source for pyrolysis. The elements of sulfur and zinc were effectively fixed as ZnS in the pyrolytic carbon. The basic properties of pyrolytic oil were in line with commercial diesel oil except for the lower flash point. Heavy metals were mainly concentrated in the pyrolytic carbon, with slightly higher concentrations in the steady state. Moreover, polycyclic aromatic hydrocarbons (PAHs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were mainly concentrated in the pyrolytic oil, with predominated low-ring PAHs and high chlorinated PCDD/Fs. The concentrations of PAHs and PCDD/Fs in the gas phase were higher during the start-up stage due to the memory effect, whereas were effectively reduced during the steady stage. The concentration of PAHs in the solid phase was highest during the furnace start-up and lowest in the shut-down stage. In contrast to PAHs, the PCDD/Fs in the solid phase reached their highest concentration during the shut-down stage, which was mainly affected by temperature. The results provide guidance for the reducing of pollutant emissions and the recycling of pyrolytic products. [ABSTRACT FROM AUTHOR]

[Display omitted] • The tandem hydrotreatment process was initially proposed to produce p-cymene. • A yield of 79.1% of p-cymene was obtained on the Pd/SBA-15 catalyst. • The intermediate limonene in waste tire pyrolysis was completely converted into p-cymene. • The optimized temperatures: hydropyrolysis at 425 ℃, hydrotreatment at 400 ℃. The resource utilization and valorization of waste tires (WT) are of significant importance in reducing environmental pollution. To produce high-value p-cymene from WT, we propose a catalytic cascade process combining hydropyrolysis and catalytic gas-phase hydrotreating in a two-stage fixed-bed reactor. The effect of catalysts prepared with three different acidic supports on the hydrogenation/dehydrogenation of limonene, a compound derived from the hydropyrolysis of WT, was investigated. The p-cymene formation could be controlled by optimizing process parameters, including hydropyrolysis temperature, hydrogenation temperature, and catalyst-to-feedstock ratio (C/F). Experimental results indicated that, in the absence of a catalyst, limonene was the main product of WT depolymerization. Under optimized conditions (hydropyrolysis temperature of 425 ℃, hydrotreating temperature of 400 ℃, C/F of 10:1, and reaction pressure of 0.15 MPa), the highest relative content of p-cymene (79.1%) was obtained over the Pd/SBA-15 catalyst. This demonstrates that our proposed catalytic cascade process of hydropyrolysis and selective gas-phase hydrogenation/dehydrogenation can convert WT into p-cymene with high added value. [ABSTRACT FROM AUTHOR]

Utilizing natural expansive clays that are available on-site as sewer trench backfill can cause destructive deformations due to volume changes, which are caused by seasonal climatic changes. Such deformations result in manhole structures protruding from the surface, which cause damage to the surrounding infrastructure and generate potential trip hazards. In this study, mixtures of recycled materials with minor sensitivity to moisture variations and superior compactibility were investigated using geomechanics theories associated with granular materials as an alternative backfill material. Blends of recycled glass (RG), plastic (RP), and tire-derived aggregates (TDA) were mixed on-site, wetted to the required moisture content (MC), and used to backfill excavated trenches around two manhole structures and extended to approximately 11 m along the trench. A benchmark trial was constructed by backfilling with natural soils available on-site according to the normal procedure. The full-scale trial sites were instrumented using settlement plates and MC sensors at various locations and depths for performance monitoring. The results of approximately 17 months of field monitoring showed that settlements over both areas that were backfilled with recycled blends were <20% of those over areas backfilled with site-won soils. Approximately 82% of the settlements in the recycled blends occurred during construction. In contrast, trenches that were backfilled with site-won soils continued to exhibit deformation due to consolidation and swell–shrink cycles. The outcome of this study could contribute to the United Nations' Sustainable Development Goals, in particular, Goal 12, by improving the industry's confidence in the reuse of wastes in geotechnical applications. This study investigated the application of mixtures of RG, RP, and recycled tire when backfilling deep excavated trenches in nontrafficable areas. In deep excavated trenches, quality control of the traditional compaction methods that use the excavator's arm is challenging due to safety restrictions that limit the presence of the testing crew in the trench. The blends that were developed in this study are designed to exhibit self-compacting properties, lower the settlement potential of excavated clay and gravel fill materials, and have less sensitivity to moisture variations. Therefore, they are useful in applications, such as backfilling deep (>1.5 m) excavated trenches. The outcomes of this study could promote sustainable construction approaches through the utilization of recycled materials in earthworks and construction projects. In addition, this would mitigate the challenges associated with waste management, because the substitution of virgin materials with recycled materials or wastes could divert waste from landfills. Furthermore, by improving the strength and deformation properties of backfilled trenches, less damage to the surrounding structures at the surface, such as residential houses, sidewalks and fence lines, is expected. [ABSTRACT FROM AUTHOR]

The growing need for sustainable fuel sources and the expanding waste management issue have prompted researchers to investigate waste-to-fuel conversion technologies. By using the potential of 100% tire oil (TO), a profitable and environmentally acceptable alternative to waste tire disposal may be realized. Tire oil utilization addresses waste management difficulties, reducing dependency on traditional fossil fuels, and minimizes environmental impacts. The study examined the pure diesel and diesel-tire oil blended fuel to examine the energy, exergy, economic, and sustainability parameters. Diesel fuel (DF), TO10 (Diesel 90%, TO 10%), TO20, TO30, TO50, TO70, and TO were used as tested fuel. Single-cylinder diesel engines with crankshaft speeds from 1500–3500 rpm in steps of 500 rpm were used for the experiments. The TO10 had the most significant energy efficiency (31.49%) and exergy efficiency (32.51%) at 2500 rpm compared to the other tested fuels. In comparison to the other studied fuels, TO demonstrated the highest sustainability index with a value of 1.48 which was more sustainable than other fuels. Based on these data, it was feasible to conclude that TO10 was the most sustainable fuel and was well-suited for diesel engines with no modification. [Display omitted] • This research examined energy, exergy, economic, and sustainability parameters. • Up to 100% tire pyrolysis oil fuel is tested in the IC engine. • TO10 (TO 10%, Diesel 90%) is the most sustainable fuel compared to other fuels. • TO10 (TO 10%, Diesel 90%) exhibits the highest energy exergy efficiency. • TO10 (TO 10%, Diesel 90%) indicates the lowest economic indicators. [ABSTRACT FROM AUTHOR]

Pyrolysis of waste tyres produces harmful hydrogen sulfide and other mercaptan compounds as by-products. The current study is concerned with the purification of hydrogen-rich pyrolysis gas from hydrogen sulfide gas that is present in a great amount (up to 5.1% mol at 420 °C), and mercaptans that are also problematic impurities. The method proposed is absorption by alkanolamines which is one of the most economical methods applied in natural gas sweetening. However, it has not been adopted in waste tyre pyrolysis gas purification yet. Two organic absorbents were tested, diethanolamine (DEA), N-methyldiethanolamine (MDEA) as well as theirs blends, at various concentrations. The application of 30 wt% DEA in water reduced H 2 S emission by 98%. In turn, 40 wt% MDEA aqueous solutions reduced H 2 S emission by 97%. The best results were produced when 30 wt% DEA was mixed with 40 wt% of MDEA (1:1 vol ratio) which allowed a removal of 99% of H 2 S from the pyrolysis gas. Moreover, the maximum H 2 S emission was 7 ppm, and a level below 5 ppm was kept for 99% of experiments duration. Finally, the application of this mixture also reduced significantly the concentrations of other sulfur-containing compounds such as methyl mercaptan and carbonyl sulfide (a minimum of 98%), ethyl mercaptan (∼90%), and carbon disulphide (by more than 99%). Thus, aqueous solvent mixture of 30 wt% DEA with 40 wt% of MDEA (1:1 v/v) can be recommended as a potential desulfurization method for waste tyres pyrolysis gas. • Pyrolysis gas is a valuable fuel, but it needs pre-treatment focused on desulfurization. • Raw pyrolysis gas contains high concentrations of H 2 S (up to 5.1%) and mercaptans. • Solutions of alkanolamines can be applied in desulfurization of pyrolysis gas. • DEA, MDEA and as their blends are effective in cleaning pyrolytic gas from H 2 S (>97%). • Blends of DEA/MDEA can also remove other sulfur containing compounds. [ABSTRACT FROM AUTHOR]

The article presents research on the purification process of pyrolysis gas from hydrogen sulfide. To our best knowledge, similar studies have not been performed yet on a real pyrolysis gas obtained from waste tyres, which contains huge amounts of hydrogen sulfide - average 3.6% (up to 5.1% at 420 °C). Different sorbents were tested, among them sodium hydroxide, zinc oxide, and manganese oxide. NaOH in concentration 0.05 M appeared to be the most efficient, showing ∼94% H 2 S removal efficiency under the conditions studied. ZnO features a better efficiency of H 2 S removal from hot gas (∼55%) than MnO. Furthermore, the combination of ZnO and a 0.05 M solution of NaOH was studied. The detailed composition of the pyrolysis gas was performed, too. The main components and sulfur-containing compounds, such as methyl mercaptan, carbonyl sulfide, and ethyl mercaptan, concentrations were measured. Predominantly, the gas consists of methane, hydrogen, ethane, ethene, carbon dioxide, iso-butane, and hydrogen sulfide. Aggregated concentrations of the above-mentioned exceed 80% of the gas, which makes it a very promising gaseous fuel. • Pyrolysis gas with a high heating value – approx. 34 MJ/m3 – contains significant amounts of hydrocarbons and hydrogen. • Pyrolysis gas features high concentrations of sulfur-containing compounds, mainly hydrogen sulfide with average conc. 3.6%. • Pyrolysis gas is as a valuable gaseous fuel, but it needs pre-treatment focused on desulfurization. • Tested metal oxides can significantly reduce the concentration of hydrogen sulfide in the gases (∼55% - ZnO; 38% - MnO). • Sodium hydroxide (NaOH) features the best potential for hydrogen sulfide removal, reaching about 94% removal efficiency. [ABSTRACT FROM AUTHOR]

Massive waste tires unrecycled will pose a significant threat to the urban environment. Hydrothermal gasification (HTG) is a promising technology converting polymer wastes into H 2 -rich syngas. The homogeneous catalytic hydrothermal gasification behavior of natural rubber (NR) and styrene-butadiene rubber (SBR) was estimated based on reactive force field molecular dynamics (ReaxFF-MD). KOH had the highest catalytic performance in enhancing the degradation efficiency (22.5 %) and H 2 yield (27.4 %) in HTG of NR, and K 2 CO 3 demonstrated the most optimal alkaline catalyst for SBR to enhance the degradation efficiency (27.2 %) and H 2 yield (37.9 %). K 2 CO 3 loading with 6 wt% manifested the optimum amount for lifting DE and H 2 yield in HTG of SBR, while 10 wt% K 2 CO 3 loading represented the best effect for lifting DE (26.5 %) and H 2 yield (42.6 %) in HTG of NR. The activation energy of SBR in HTG was about 259 kJ/mol, which was about 72 kJ/mol higher than that of NR. With 6 wt% K 2 CO 3 , the activation energy of SBR and NR in HTG decreased to about 143 kJ/mol and 122 kJ/mol, respectively. The present work could provide essential theoretical support and fundamental data for the application of the homogeneous catalysts in HTG recycling of waste rubber materials. • Catalytic HTG of rubber polymeric wastes was examined by ReaxFF-MD. • K 2 CO 3 was the optimum catalyst to improve the H 2 yield of SBR in HTG. • K-based catalyst was better than Na-based one for hydrothermal gasification of NR. • A better catalystic effect was realized by promoting the formation of OH radicals. • The lowest activation energy of SBR was 143 kJ/mol with K 2 CO 3 addition. [ABSTRACT FROM AUTHOR]