As an adsorbent, biomass activated carbon is effective at the removal of a wide range of organic and inorganic pollutants; however, its synthesis remains complex. Although spent coffee grounds (SCG) could be an effective material for the production of activated carbon, achieving a sufficient surface area has proven to be difficult. Here, this study presents a preliminary investigation into the optimal manufacturing conditions of activated-carbon adsorbents derived from SCG. SCG samples were characterized according to proximate analysis, elementary analysis, surface area, and pore volumes, then subjected to various processes (i.e., drying, carbonization, and chemical activation) with different operating parameters (temperature and time). The samples were optimized as follows: (1) Stable drying of SCG with a high moisture content of approximately 65% required consumption energy of 49 kWh/kg and drying at 105 °C for 20 h. (2) By comparing changes in the consumption energy and product yield with an increasing amount of carbon fraction, it was found that drying carbonization was more suitable than hydrothermal carbonization for SCG. The optimum drying carbonization temperature for achieving attractive biochar was 500 °C for 1 h. (3) Activated carbon with the optimum surface area (3687 m²/g) and mesopore volume fraction (approximately 70%) was achieved with a chemical activator agent ratio of approximately 3 and heating at 850 °C for 1 h. Furthermore, the butane working capacity of the activated carbon was related to the mesopore volume/surface area and reached 74.5% at a mesopore volume/surface area of 0.0004, indicating its suitability for activated carbon canisters. These findings can be used to optimize the synthesis of industrial-grade activated carbon from SCG.

Biomass waste, generated globally in vast quantities, represents an underutilized yet highly valuable resource for advanced material production. This study highlights a novel valorization pathway for waste tangerine peels, sourced from Jeju Island, South Korea, by converting them into high-performance activated carbon (T-AC) with exceptional pore characteristics, specifically designed for volatile organic compound (VOC) removal. Utilizing a unique combination of hydrothermal carbonization (HTC) and dry carbonization (DC) processes, the structural properties of the biomass were optimized, significantly enhancing the fixed carbon content. Subsequent chemical activation with an alkaline agent yielded T-AC with an outstanding specific surface area (1530–3375 m²/g) and total pore volume (0.73–2.00 cm³/g), with a tailored pore distribution favoring the sub-mesopore range (2.0–4.0 nm). The T-AC demonstrated remarkable performance in removing methylene chloride (MC), a hazardous VOC, with methylene chloride activity (MA) increasing from 44.7% to 76.3% as the activation agent ratio increased, while methylene chloride working capacity (MWC) improved significantly from 17.1% to 55.9%. These results underscore the transformative potential of tangerine peel-derived AC as a sustainable solution for VOC remediation, combining environmental waste management with advanced adsorption technology. The findings not only advance the field of biomass utilization but also offer a scalable approach for tackling pressing environmental and industrial challenges.

Lithium–oxygen batteries (LOBs) offer the highest theoretical specific energy among metal–air chemistries, but their practical deployment is limited by the sluggish reversibility of Li₂O₂ formation/decomposition on the cathode, which requires a porous, electronically conductive carbon combining mesoporous transport with graphitic domains. Here, we report a two-step, KOH-assisted thermal treatment route for producing graphite-like porous carbon that converts spent mushroom substrate (SMS)—a lignin-rich agro-industrial waste generated at >5 million tonnes per year in East Asia—into a graphite-like porous carbon (G-SMS) for LOB cathodes. SMS derived from Pleurotus ostreatus cultivated on an oak–sawdust substrate was carbonized at 800 °C (1 h, 3 °C min⁻¹), followed by KOH-assisted heat treatment at 1200–1800 °C. A KOH/C ratio of 0.5 was selected for the detailed graphitization series for its reagent economy and carbon yield: the 1.0 ratio gave ~10 wt% lower production yield and, at 1800 °C, lower carbon content (97.6 wt%) with residual ash (1.7 wt%), for no compensating benefit. Within the KOH/C = 0.5 series, G-SMS-1800/0.5 combined the smallest interlayer spacing (d₀₀₂ = 0.347 nm), the lowest Raman I_D/I_G (0.69), the largest mesopore fraction (96.9%) and mesopore volume (0.31 cm³ g⁻¹), and the highest powder conductivity (8607 S m⁻¹ at 2000 kgf), giving the highest mesopore-volume-weighted conductivity descriptor of the matrix, V_Meso × σ = 2668 cm³ g⁻¹ S m⁻¹. This sample was identified as the most robust host, and its cycling stability was benchmarked against Super P in a modified CR2032 LOB cell (1 M LiTFSI in N,N-dimethylacetamide, 2.0 atm O₂): G-SMS-1800/0.5 sustained 330 cycles, whereas Super P reached only 200 cycles under identical conditions, a ~1.65-fold improvement. KOH-mediated catalytic graphitization thus lowers the thermal budget of biomass graphitization while providing a conductive, mesopore-dominated host for Li₂O₂ deposition, providing a potential route for the valorization of spent mushroom substrate into graphite-like porous carbon for LOB cathodes.

This study investigates the key material properties governing the long-term stability of ceramic heat-storage media exposed to severe high-temperature and high-humidity conditions (up to 950 °C under high-steam partial pressure). Candidate ceramics, including high-purity alumina, mullite, and cordierite compositions, were evaluated through physical property measurements, chemical composition analysis, SEM–EDX microstructural characterization, and hydrothermal corrosion simulations. Ceramics containing significant SiO₂ exhibited chemical weakening due to steam-induced silica dissolution and the formation of hydroxyl-rich surface layers. However, the overall mechanical integrity was predominantly limited by thermal shock failure occurring during rapid heating–cooling cycles and repeated steam condensation and evaporation. The results demonstrate that ceramics with a low coefficient of thermal expansion (CTE ≈ 2–4 × 10⁻⁶/K) show markedly enhanced resistance to thermal shock, leading to improved operational durability. In addition, low open porosity (<10 vol%) effectively restricted internal steam penetration and reduced the rate of hydrothermal degradation, particularly in SiO₂-based systems where pore-connected pathways accelerate corrosion. These findings indicate that thermal shock resistance, enabled by intrinsically low CTE, together with reduced porosity, constitutes the primary design criterion for ensuring the structural reliability of ceramic heat-storage components operating in high-humidity thermal environments.