A high-performance and affordable peanut shell-derived biochar was employed for the efficient removal of Rhodamine B (RhB) from aqueous solutions. The properties of peanut shell biochar (PSB) were ...investigated through Fourier transform infrared (FTIR) spectroscopy and Brunauer–Emmett–Teller surface area measurements. The FTIR analysis revealed numerous active sites and functional groups for the binding of dye molecules, while the BET surface area was determined to be 351.11 m2g-1. Four different isotherms and kinetic models were applied to determine the equilibrium adsorption of RhB, and the results indicated that the Freundlich isotherm was the most appropriate model. A maximum dye removal rate of 94.0% occurred at a pH of 3 with an adsorbent dose of 0.325 g L-1. The prepared adsorbent showed excellent sorbent behaviour and can be reused multiple times after regeneration, with the surface area decreasing from 351.11 m2g-1 to 140.13 m2g-1 after the third cycle. The negative Gibbs free energy ΔGo at all applied temperatures suggested that spontaneous adsorption occurred and RhB adsorption on the PSB was found exothermic, as evidenced by the negative value of ΔHo. The regenerated PSB can be utilized as an efficient, environmentally friendly, and cost-effective sorbent for the removal of dyes at temperatures lower than ambient temperature, providing both technical and financial advantages for sustainable environmental management.
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•Peanut shell biochar efficiently removes the dye in aqueous solutions•Adsorption of active sites is critical to the uptake of the dyes•Adsorbents can be regenerated and reused to reduce the cost of treatment•The peanut shell biochar is an economically viable sorbent option
Defective molybdenum disulfide (MoSsub.2) monolayers (MLs) modified with coinage metal atoms (Cu, Ag and Au) embedded in sulfur vacancies are studied at a dispersion-corrected density functional ...level. Atmospheric constituents (Hsub.2, Osub.2 and Nsub.2) and air pollutants (CO and NO), known as secondary greenhouse gases, are adsorbed on up to two atoms embedded into sulfur vacancies in MoSsub.2 MLs. The adsorption energies suggest that the NO (1.44 eV) and CO (1.24 eV) are chemisorbed more strongly than Osub.2 (1.07 eV) and Nsub.2 (0.66 eV) on the ML with a cooper atom substituting for a sulfur atom. Therefore, the adsorption of Nsub.2 and Osub.2 does not compete with NO or CO adsorption. Besides, NO adsorbed on embedded Cu creates a new level in the band gap. In addition, it was found that the CO molecule could directly react with the pre-adsorbed Osub.2 molecule on a Cu atom, forming the complex OOCO, via the Eley–Rideal reaction mechanism. The adsorption energies of CO, NO and Osub.2 on Au2S2, Cu2S2 and Ag2S2 embedded into two sulfur vacancies were competitive. Charge transference occurs from the defective MoSsub.2 ML to the adsorbed molecules, oxidizing the later ones (NO, CO and Osub.2) since they act as acceptors. The total and projected density of states reveal that a MoSsub.2 ML modified with copper, gold and silver dimers could be used to design electronic or magnetic devices for sensing applications in the adsorption of NO, CO and Osub.2 molecules. Moreover, NO and Osub.2 molecules adsorbed on MoSsub.2-Au2s2 and MoSsub.2-Cu2s2 introduce a transition from metallic to half-metallic behavior for applications in spintronics. These modified monolayers are expected to exhibit chemiresistive behavior, meaning their electrical resistance changes in response to the presence of NO molecules. This property makes them suitable for detecting and measuring NO concentrations. Also, modified materials with half-metal behavior could be beneficial for spintronic devices, particularly those that require spin-polarized currents.
The ordered mesoporous silica MCM-48 with cubic Ia3d structure was synthesized using the cationic surfactant hexadecyltrimethylammonium bromide (CTAB) as a template agent and tetraethylorthosilicate ...(TEOS) as a silica source. The obtained material was first functionalized with (3-glycidyloxypropyl)trimethoxysilane (KH560); further, two types of amination reagents were used: ethylene diamine (N2) and diethylene triamine (N3). The modified amino-functionalized materials were characterized by powder X-ray diffraction (XRD) at low angles, infrared spectroscopy (FT-IR) and nitrogen adsorption–desorption experiments at 77 K. Characterization from a structural point of view reveals that the ordered MCM-48 mesoporous silica has a highly ordered structure and a large surface area (1466.059 msup.2/g) and pore volume (0.802 cmsup.3/g). The amino-functionalized MCM-48 molecular sieves were tested for COsub.2 adsorption–desorption properties at different temperatures using thermal program desorption (TPD). Promising results for COsub.2 adsorption capacities were achieved for MCM-48 sil KH560-N3 at 30 °C. At 30 °C, the MCM-48 sil KH560-N3 sample has an adsorption capacity of 3.17 mmol COsub.2/g SiOsub.2, and an efficiency of amino groups of 0.58 mmol COsub.2/mmolNHsub.2. After nine adsorption–desorption cycles, the results suggest that the performance of the MCM-48 sil KH N2 and MCM-48 sil KH N3 adsorbents is relatively stable, presenting a low decrease in the adsorption capacity. The results reported in this paper for the investigated amino-functionalized molecular sieves as absorbents for COsub.2 can be considered as promising.
Oxygen surface exchange kinetics of La.sub.0.7A.sub.0.3MnO.sub.3±delta has been studied by the isotope exchange method with gas phase equilibration using a static circulation experimental rig at the ...temperature of 850 °C and oxygen pressure of 1 kPa. Oxides of La.sub.0.7A.sub.0.3MnO.sub.3±delta with different dopant at one level of doping were considered. Rates of elementary acts of the oxygen exchange were found to change differently. So, the oxygen dissociative adsorption rate increased, the oxygen incorporation rate decreased, and the increase in the cation radius did not influence the interphase exchange rate. These trends are associated with the AO segregation processes at the surface and the appropriate mechanism of oxygen reduction is considered. Graphical The oxygen dissociative adsorption rate increased, the incorporation rate decreased, and the increase in the cation radius did not influence the interphase exchange rate. These trends are associated with the AO segregation processes at the surface.
Oxygen surface exchange kinetics of La.sub.0.7A.sub.0.3MnO.sub.3±delta has been studied by the isotope exchange method with gas phase equilibration using a static circulation experimental rig at the ...temperature of 850 °C and oxygen pressure of 1 kPa. Oxides of La.sub.0.7A.sub.0.3MnO.sub.3±delta with different dopant at one level of doping were considered. Rates of elementary acts of the oxygen exchange were found to change differently. So, the oxygen dissociative adsorption rate increased, the oxygen incorporation rate decreased, and the increase in the cation radius did not influence the interphase exchange rate. These trends are associated with the AO segregation processes at the surface and the appropriate mechanism of oxygen reduction is considered.
Adsorption of methane on three samples of metal-organic framework structures (MOF), which contain copper, aluminum or zinc atoms, was measured at temperatures ranging from 303 to 333 K and pressures ...up to 40 MPa using a precise volumetric-gravimetric unit. The determined values of adsorption volumes and characteristic energies served to evaluate the average heats of adsorption, which were compared to the average isosteric heats of adsorption.
Metal organic frameworks (MOFs) have been considered as one of the most exciting porous materials discovered in the last decade. Large surface areas, high pore volumes, and tailorable pore sizes make ...MOFs highly promising in a variety of applications, mainly in gas separations. The number of MOFs has been increasing very rapidly, and experimental identification of materials exhibiting high gas separation potential is simply impractical. High-throughput computational screening studies in which thousands of MOFs are evaluated to identify the best candidates for target gas separation is crucial in directing experimental efforts to the most useful materials. In this work, we used molecular simulations to screen the most complete and recent collection of MOFs from the Cambridge Structural Database to unlock their CH4/H2 separation performances. This is the first study in the literature, which examines the potential of all existing MOFs for adsorption-based CH4/H2 separation. MOFs (4350) were ranked based on several adsorbent evaluation metrics including selectivity, working capacity, adsorbent performance score, sorbent selection parameter, and regenerability. A large number of MOFs were identified to have extraordinarily large CH4/H2 selectivities compared to traditional adsorbents such as zeolites and activated carbons. We examined the relations between structural properties of MOFs such as pore sizes, porosities, and surface areas and their selectivities. Correlations between the heat of adsorption, adsorbility, metal type of MOFs, and selectivities were also studied. On the basis of these relations, a simple mathematical model that can predict the CH4/H2 selectivity of MOFs was suggested, which will be very useful in guiding the design and development of new MOFs with extraordinarily high CH4/H2 separation performances.
•Adsorption of N2O, O2, N2, and CO2 on silica gel was studied up to 1000 kPa.•Adsorption equilibria and kinetics of silica gel and activated carbon were compared.•CO2 was adsorbed more strongly than ...N2O on silica gel, opposite to activated carbon.•Adsorption rates were estimated by a non-isothermal model with parameter consistency.•Macropore diffusion contributed highly to the adsorption kinetics in silica gel.
To gain insights into N2O recovery from industrial effluent, adsorption equilibria and kinetics of N2O, O2, N2, and CO2 on silica gels were evaluated at 293, 308, and 323 K under pressures of up to 1000 kPa using a volumetric method. Adsorption characteristics of the adsorbates on silica gel were compared with those on activated carbon. Adsorption isotherms indicated lower adsorption amounts for all of the adsorbates on silica gel, compared to those on activated carbon; both materials adsorbed higher amounts of N2O and CO2 than O2 and N2. In the case of silica gel, CO2 was adsorbed more strongly than N2O, while activated carbon exhibited the opposite. The experimental uptake on silica gel was well fitted by the non-isothermal diffusion model. The adsorption rate on silica gel was slower than that on activated carbon for all the adsorbates, while the order of adsorption rate was the same: N2 > O2 ≫ N2O ≥ CO2. The uptake results of N2O on varying sizes of silica gel indicated that macropore diffusion significantly affected adsorption on silica gel, which was not the case for activated carbon. The adsorption characteristics of N2O and CO2 on silica gel were distinct from those on activated carbon, due to the inherent electrical properties and molecular structural interactions of the adsorbent and adsorbates.
•High surface area activated carbon-alginate beads were synthesized.•The process of adsorption was carried out under different adsorption conditions.•The adsorption kinetics, isotherms and ...thermodynamic were studied.•The maximum adsorption capacity of 230mg/g was achieved for 100mg/L of MB solution.
High surface area mesoporous activated carbon-alginate (AC-alginate) beads were successfully synthesized by entrapping activated carbon powder derived from Mangosteen fruit peel into calcium-alginate beads for methylene blue (MB) removal from aqueous solution. The structure and surface characteristics of AC-alginate beads were analyzed using Fourier transform infra-red (FTIR) spectroscopy, scanning electron microscopy (SEM) and surface area analysis (SBET), while thermal properties were tested using thermogravimetric analysis (TGA). The effect of AC-alginate dose, pH of solution, contact time, initial concentration of MB solution and temperature on MB removal was elucidated. The results showed that the maximum adsorption capacity of 230mg/g was achieved for 100mg/L of MB solution at pH 9.5 and temperature 25°C. Furthermore, the adsorption of MB on AC-alginate beads followed well pseudo-second order equation and equilibrium adsorption data were better fitted by the Freundlich isotherm model. The findings reveal the feasibility of AC-alginate beads composite to be used as a potential and low cost adsorbent for removal of cationic dyes.
The crosslinked chitosans synthesized by the homogeneous reaction of chitosan in aqueous acetic acid solution with epichlorohydrin were used to investigate the adsorptions of three metals of Cu(II), ...Zn(II), and Pb(II) ions in an aqueous solution. The crosslinked chitosan characterized by
13CNMR, SEM, and elemental analysis, and the effects of pH and anion on the adsorption capacity were carried out. The dynamical study demonstrated that the adsorption process was followed the second-order kinetic equation. The results obtained from the equilibrium isotherms adsorption studies of three metals of Cu(II), Zn(II), and Pb(II) ions by being analyzed in three adsorption models, namely, Langmuir, Freundlich, and Dubinnin-Radushkevich isotherm equations, indicated to be well fitted to the Langmuir isotherm equation under the concentration range studied, by comparing the linear correlation coefficients. The order of the adsorption capacity (
Q
m) for three metal ions was as follows: Cu
2+
>
Pb
2+
>
Zn
2+. This technique for syntheses of the crosslinked chitosans with epichlorohydrin via the homogeneous reaction in aqueous acetic acid solution showed that the adsorptions of three metal ions in aqueous solution were followed the monolayer coverage of the adsorbents through physical adsorption phenomena.
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