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The rising concentration of CO2 in the atmosphere is approaching critical levels, posing a significant threat to life on Earth. Porous carbons derived from biobased materials, particularly waste byproducts, offer a viable solution for selective CO2 adsorption from large-scale industrial sources, potentially mitigating atmospheric CO2 emissions. In this study, we developed highly porous carbons from lemon peel waste through a two-step process, consisting of temperature pretreatment (500 °C) followed by chemical activation by KOH at 850 °C. The largest specific surface area (2821 m2/g), total pore volume (1.39 cm3/g), and micropore volume (0.70 cm3/g) were obtained at the highest KOH-to-carbon ratio of 4. In contrast, the sample activated with a KOH-to-carbon ratio of 2 demonstrated the greatest micropore distribution. This activated biocarbon exhibited superior CO2 adsorption capacity, reaching 5.69 mmol/g at 0 °C and 100 kPa. The remarkable adsorption performance can be attributed to the significant volume of micropores with diameters smaller than 0.859 nm. The Radke–Prausnitz equation, traditionally employed to model the adsorption equilibrium of organic compounds from liquid solutions, has been shown to be equally applicable for describing the gas–solid adsorption equilibrium. Furthermore, equations describing the temperature dependence of the Radke–Prausnitz equation’s parameters have been developed.

Since the last decade, the half-Heusler (HH) compounds have taken an important place in the field of the condensed matter physics research. The multiplicity of substitutions of transition elements at the crystallographic sites X, Y and (III-V) elements at the Z sites, gives to the HH alloys a multitudes of remarkable properties. In the present study, we examined the structural, electronic and thermoelectric properties of ZrCoBi0.75Z0.25 (Z = P, As, Sb) using density functional theory (DFT). The computations have been done parallel to the full potential linearized augmented plane wave (FP-LAPW) method as implemented in the WIEN2k code. The thermoelectrically properties were predicted via the semi-classical Boltzmann transport theory, as performed in Boltztrap code. The obtained results for the band structure and densities of states confirm the semiconductor (SC) nature of the three compounds with an indirect band gap, which is around 1eV. The main thermoelectric parameters such as Seebeck coefficient, thermal conductivity, electrical conductivity and figure of merit were estimated for temperatures ranging from zero to 1200K. The positive values of Seebeck coefficient (S) confirm that the ZrCoBi0.75Z0.25 (x = 0 and 0.25) are a p-type SC. At the ambient temperature, ZrCoBi0.75P0.25 exhibit the large S value of 289 µV/K, which constitutes an improvement of 22% than the undoped ZrCoBi, and show also a reduction of 54% in thermal conductivity (κ/τ). The undoped ZrCoBi has the lowest ZT value at all temperatures and by substituting bismuth atom by one of the sp elements (P, As, Sb), a simultaneous improvement in κ/τ and S have led to maximum figure of merit (ZT) values of about 0.84 obtained at 1200 K for the three-doped compounds.

The half-Heusler alloy NiVSi is investigated theoretically by using first-principles calculations based on the density functional theory (DFT). For a better description of the electronic properties, the TB-mBJ potential is used for exchange-correlation potential. The structural, electronic, magnetic, optical and thermoelectric properties was calculated by WIEN2k software. The negative cohesive and formation energies found reveal that the NiVSi is thermodynamically stable. Electronically, the NiVSi is a half-metal with an indirect band gap of 0.73 eV in the spin-down channel whereas the spin up channel is metallic. The total magnetic moment is of 1. Optically, the obtained high absorption coefficient in ultraviolet wavelength range, make the NiVSi useful as effective ultraviolet absorber. Thermoelectrically, a high figure of merit in the p- and n-type region was obtained, what makes this compound very functional for thermoelectric applications. The generation of a fully spin-polarized current make this compound unsuitable for spintronic applications at room temperature, a doping may be a satisfactory solution to improve this property.

Being an abundant product in Algeria, pulp of carob pods (PCP) was used in this study as a biosorbent for Methylene blue (MB) and Congo red (CR) removal from aqueous media in batch mode in two successive steps. Once the first dye is adsorbed, the biosorbent is used as is to adsorb the second dye in order to study the interactions between them. Characterization of PCP by FTIR spectroscopy, Scanning Electron Microscopy (SEM), EDX, and point of zero charge showed that the principal functional groups present at the surface are oxygenated with a pHpzc value of the 7.2. Contact time of 60 min was amply sufficient to reach equilibrium for both dyes onto PCP and recuperated biosorbents. pH effect on the biosorption onto PCP shows a behavioral divergence between both dyes. Maximum biosorption uptake of CR was observed at pH value of 6.38 while pH variation has no remarkable influence on MB biosorption and the initial pH solution of 5.75 was taken for subsequent biosorption experiments. The adsorption isotherms obtained are in good agreement with the models of Langmuir and Freundlich and the kinetics are well described by the pseudo-second-order model. [ABSTRACT FROM AUTHOR]

Due to their significant disposal problem during oil extraction and biofuel production, Eucalyptus camaldulensis leaves as an abundant forestry waste in the Mediterranean region, was investigated in this study as a precursor for the preparation of a low-cost adsorbents for the treatment of water laden with ascorbic acid (AA) as contaminant. A single step involving activation and carbonization in which the raw material was impregnated with chemical agent (KOH 20% and 40%) and then thermally decomposed at 600°C to produce K-Eucal-20 and K-Eucal-40 adsorbents, respectively. Prior to adsorption tests, Fourier-transform infrared analysis, pHzpc determination, scanning electron microscopy, X-ray diffraction, Brunauer-Emmett-Teller surface area, iodine number and methylene blue index were performed for structural and surface characterization. Important parameters affecting AA uptake including equilibrium time, adsorbent dose, solution pH and temperature were also evaluated. Adsorption isotherms were better described by the Langmuir model than those of Freundlich and Temkin. The maximum adsorption capacities achieved for AA were 190.80 and 305.78 mg/g, by K-Eucal-20 and K-Eucal-40, respectively. Kinetics was found to obey the pseudo-second-order model. Thermodynamic analysis confirms the spontaneity and endothermicity of AA adsorption process. This study shows that activated Eucalyptus camaldulensis leaves can be successfully used as an alternative to the commercially available adsorbents for the removal of such pollutant from liquid media. [ABSTRACT FROM AUTHOR]

Context and results: As an inorganic halide perovskite material, AgCaCl3, characterized by its high stability and environmental friendliness, is considered a potential candidate for major applications in optoelectronics and lens manufacturing. This work aimed to determine the electronic properties such as density of state (DOS) and band structure (BS) of AgCaCl3. The results showed that the material has an indirect band gap almost invariably at 1.5 eV in the pressure range studied. The dielectric function ε ω , absorption coefficient α (ω) , optical conductivity σ (ω) , reflectivity R (ω) , and the refractive index n (ω) showed clearly that the perovskite AgCaCl3 preserved its optical characteristics within the chosen pressure range investigated. The calculated elastic constants C11, C12, and C14 as dynamic stability criteria for the elastic moduli such as bulk modulus (B), shear modulus (G), Young's modulus (Y), Poisson's ratio (υ ), and anisotropy factor (A) showed that the material is a ductile plastic. Debye temperature (θ ), isobaric and isochoric heat capacities (CP, CV), coefficient of the thermal expansion (α), Gibbs free energy (G), and entropy (S) were also studied. The results obtained provide a theoretical basis for experimental work and offer the possibility of future industrial applications of AgCaCl3. Computational and theoretical techniques: Density functional theory (DFT) calculations as implemented in the Wien2K code were used to study the mechanical and thermal properties of AgCaCl3 perovskite over a pressure range. Lattice parameters, electronic, and optical properties are optimized with the approximation of the generalized gradient of the Perdew-Burke-Ernzerhof function (PBE-GGA) function. The mechanical and thermodynamic properties were calculated using ElaStic and Gibbs2 codes, and the properties of AgCaCl3 over the pressure range investigated were predicted. [ABSTRACT FROM AUTHOR]

This study was devoted to the valorization of a plant waste (olive stones): that is widely available in Mediterranean countries in order to remove mercury from natural gas. The raw material from olive stones was prepared by pyrolysis, chemical activation with phosphoric acid, and physical activation under steam. Two olive stone-based granular activated carbons were prepared: one with the virgin stones, while the other was impregnated with sulphur. After treatment, the adsorbents obtained were characterized by determining the iodine number, the methylene blue index, and by estimating the porous properties by N2 adsorption at 77 K. Thermogravimetric analysis and infrared spectroscopy analysis were carried out to determine the functional groups before and after mercury adsorption. An experimental study of vapour-phase mercury adsorption by the activated carbons (virgin and sulphur-impregnated) and a comparison with a commercial material (HGR) were performed. The comparison, made by analyzing the adsorption in a continuous mode, showed that the proportion of sulphur and the porosity were important for the removal of mercury. In the conditions used, the mercury adsorption on the ACs studied follows a physisorption mechanism. The results showed that granular activated carbon-based olive stones (sulphur-impregnated) are very efficient to remove mercury (with 2864 μg/g) and also less expensive than commercial activated carbon due to their local availability. [ABSTRACT FROM AUTHOR]

This study attempts to identify the characteristics of obtained biosorbents to assess their suitability for water treatment. The adsorption tests were conducted in a continuous mode. The prepared biosorbent exhibits excellent adsorption capacities in the liquid phase vis-à-vis red nylosane. Indeed, the ultimate capacities of adsorption (qe) were calculated using the Langmuir linearization, which is 83.33 mg g–1 for the two biosorbents, Cynara cardunculus (CARD) and Eucalyptus globulus (EUCA), and 76.92 mg g–1 for Prunus cerasifera (PRUN). The adsorption equilibrium constants, 0.008 for CARD, 0.0058 for EUCA and 0.0052 for PRUN, present a strong affinity of these biosorbents for red nylosane, which has an acidic pH. A characterization of materials by determining accessible surface to methylene blue, the microporosity by the iodine and surface area by Brunauer–Emmett–Teller method. The determination of acid and base chemical functions that are present in the three biosorbents is by FTIR analysis and pHPZC. The spontaneous and endothermic process with all materials is used. The results prove that the three biosorbents studied are very useful in the treatment of contaminated water with micropollutants such as red nylosane dye. [ABSTRACT FROM AUTHOR]