Anion exchange resins are widely used to remove phosphates from water; however, they are expensive and cannot be efficiently reused. We have increased the quaternary nitrogen (N-Q) content in activated carbon by impregnating pinecones with urea and zinc chloride and activating it at 600 °C to improve its phosphate-ion adsorption capacity. The sample containing pinecone, urea, and zinc chloride in a 1 : 4 : 1 weight ratio (Ur4-1) adsorbed the largest amount of phosphate ions (0.29 mmol/g). As the weight ratio of urea increased, the N-Q content increased and the specific surface area of samples decreased. These findings indicated that the N-Q content has a larger effect on the phosphate-ion adsorption capacity of samples than on the specific surface area, which is often used as an indicator of the adsorption capacity of activated carbon. Ur4-1, with the largest N-Q content of 1.81 wt%, had the best phosphate-ion adsorption, and the amount it adsorbed at equilibrium pH (pH_e) 2–10 was investigated. Results indicated that Ur4-1 adsorbed higher amounts of phosphate ions (0.051 mmol/g) than the commercial anion exchange resin, IMAC HP555, at pH_e 3.

Carbon powders were prepared from HyperCoals (HPCs), which are ash-free coals produced by Kobe Steel, by precipitating carbon precursors, followed by stabilization and carbonization. The carbon powders are denoted SB-xx or B-xx depending on whether the original coal is sub-bituminous (SB) or bituminous (B), where xx is the carbonization temperature (°C). The specific surface area of SB-900, obtained from a coal primarily used as boiler fuel, is 737 m² g⁻¹, whereas that of B-900, obtained from a coal primarily used as a coke precursor, is 400 m² g⁻¹. SB-900 has a large micropore volume and when used as an. electrode material for electric double-layer capacitors (EDLCs), it had a higher capacitance than a B-900 electrode and commercially available activated carbon (YP-50F). Based on the chemical composition of the starting materials and the number of oxygen-containing functional groups they contain, determined by temperature-programmed desorption, it was clear that factors other than oxygen-containing functional groups significantly influenced the properties of the powders. A detailed examination of the pore characteristics using Ar adsorption measurements based on the Horváth–Kawazoe method showed that the pore size distribution of the HPC-derived carbon powder samples had a peak at 0.46 nm. The differential pore volume increased in the vicinity of this peak. The similarity between the pore size and the size of the ions in the sulfuric acid electrolyte used to evaluate the EDLC characteristics indicates that the powder samples have a higher capacitance than commercially available activated carbon and are suitable for use in EDLCs with aqueous electrolytes. In addition, higher adsorption in SB-900 was observed for pore sizes of 0.6 nm or less than in B-900. It is suggested that SB-900 contains a higher volume of ultra-micropores (0.7 nm or less) than B-900.

The addition of biochar to soil can effectively increase the efficiency of nitrogen (N) use and reduce N losses in agricultural systems. This study evaluates the effects of adding non-labeled ammonium sulfate and ¹⁵N-labeled ammonium sulfate with rice husk-derived biochars produced at 400 °C, 600 °C, and 700 °C on ¹⁵N uptake in tall fescue (Festuca arundinaceous) during a 90-day greenhouse experiment. The uptake and retention of ¹⁵N ammonium sulfate were significantly increased after treatment with 400 °C biochar plus ammonium sulfate fertilizer. This treatment maximized the percentage of N derived from the fertilizer and the cumulative recovery of ¹⁵N in plants (77.7%), while minimizing the potential N losses (22.1%), while treatment with the 600 °C or 700 °C biochar moderately improved the uptake. In contrast, the treatment with ammonium sulfate alone (without biochar), ¹⁵N recovery was only 47.9% and the N losses were the highest (51.9%) among the treatments. The superior performance of the 400 °C biochar treatment is likely explained by its high cation exchange capacity and the presence of oxygen-containing functional groups, which favor ammonium adsorption. The biochars produced at higher temperatures were more aromatic with larger specific surface areas and higher degrees of crystallinity but had lower cation exchange capacities than 400 °C biochar, possibly because their fewer polar functional groups reduced their nutrient retention. Mechanistic interpretations inferred from comparable literature highlight the need for direct characterization by X-ray diffraction and N₂ adsorption analysis. The research indicates that biochar formed at an appropriate carbonization temperature can optimize nitrogen retention and improve the efficiency use of fertilizers in pasture production systems.

The carrier-doping of monolayer graphene induced by molecular adsorption was investigated by changing the interfacial proton activity by chemical modification of the supporting substrate surface with self-assembled monolayers (SAMs) of different acidity. Graphene field-effect transistors were fabricated on SiO₂/Si substrates functionalized with n-octyltriethoxysilane (OTS) and 3-aminopropyltriethoxysilane (APS), which respectively contain neutral alkyl and basic amino terminal groups. Surface characterization through water contact angle measurements and X-ray photoelectron spectroscopy confirmed the formation of a SAM. Electrical transport measurements showed that oxygen exposure induced hole-doping in graphene on OTS, whereas graphene on APS showed electron-doping by both oxygen and water vapor adsorption. The type and density of carriers doped by oxygen/water adsorption were explained by a water-mediated electrochemical doping mechanism, in which the redox potential is changed by the interfacial proton activity governed by the acidity of the SAM. Systematic shifts of the G and G’ bands in the Raman spectra supported the carrier-type variation. These findings indicate that adsorption-induced charge transfer in graphene can be electrochemically changed by changes in the substrate surface chemistry. The ability to tailor oxygen- and water-mediated doping through interfacial proton control provides a versatile platform for the design of graphene-based sensing devices with different carrier characteristics.

Sodium (Na)-ion batteries (NIBs) are attracting increasing attention as next-generation energy storage systems because they do not rely on rare metals. Hard carbon (HC) is considered their most promising anode material. By tailoring the pore structure by templating methods, HC materials with a high energy density have been developed for NIBs. However, further improvements are required to achieve the desired properties without compromising the excellent characteristics already achieved. This study aims to further increase the battery capacity of zinc oxide (ZnO)–templated HC using a simple phosphorus (P)-doping method. We investigated the effects of soaking in phosphoric acid and subsequent heat treatment on the carbon morphology and electrochemical properties. The results showed that P doping increased the battery capacity without altering the ZnO–templated HC morphology. Both the sloping and plateau regions of the capacity increased, suggesting that P doping promotes Na adsorption on the carbon surface and Na storage between the layers and in the pores. Furthermore, the types of P functional groups depended on the synthesis conditions and influence the battery performance. These findings show that surface modification with specific P functional groups can effectively increase the Na storage capability of HCs.

Xenon isotope–nuclear magnetic resonance (¹²⁹Xe–NMR) spectroscopy is a powerful technique for investigating the pore sizes of porous carbon materials, particularly those with narrow pore size distributions. However, the ¹²⁹Xe–NMR spectra of complex and disordered porous materials often exhibit peak broadening and overlapping owing to broad pore size distributions and the presence of differently shaped pores (e.g., slit-shaped and cylindrical). This in turn makes accurate assessment of the pore sizes difficult. To overcome this issue and enable selective and individual evaluations for each pore, this study proposes a combined method based on molecular masking and ¹²⁹Xe–NMR spectroscopy. Fullerene C₆₀ was used as the molecular masking agent. A model porous carbon material, comprised of a mixture of microporous and mesoporous carbons, was vacuum-impregnated with a C₆₀–toluene solution. Subsequently, the toluene was removed, resulting in the selective masking of micropores smaller than 1 nm by the C₆₀ molecules. In addition, ¹²⁹Xe–NMR were spectra measured at −75 °C under a Xe gas pressure of 100 kPa for the model porous carbon material before and after the C₆₀ masking. These spectra showed that C₆₀ masking totally eliminated the spectral contributions from micropores smaller than 1 nm, while leaving the signals from larger mesopores essentially unchanged, enabling an individual evaluation of unmasked mesopores. N₂ adsorption and desorption isotherms confirmed these observations. Taken together, these results demonstrate the potential of the combined method for selectively evaluating the pore sizes of disordered and complex porous carbon materials.

Annually, large amounts of woody prunings from Prunus mume (Japanese apricot) are generated through orchard management. However, despite their renewable and lignocellulosic nature, they remain underutilized. We used pruned Prunus mume branches as a biomass precursor for the production of activated carbon (AC) by chemical activation with potassium hydroxide (KOH). The effect of the impregnation ratio on the pore structure and surface area of the resulting AC samples was investigated. The best material produced had a high Brunauer–Emmett–Teller surface area of 2389.0 m²/g and well-developed microporosity. Phenol was selected as a model pollutant to evaluate the adsorption performance. The best AC sample had a maximum phenol adsorption capacity of 285.9 mg/g, which is approximately 1.7 and 1.2 times higher than that of coal- and coconut shell-based AC samples respectively (171.4 and 232.6 mg/g,). The material achieved adsorption equilibrium within 1 h, indicating superior kinetics. These findings highlight the feasibility of converting fruit tree prunings into high-performance AC.