Desorption Isotherms Research Articles

Surfactant-assisted synthesis of NiCo alloy with specific nanopore architecture as a bifunctional electrocatalyst for rechargeable zinc-air batteries

Designing the effective active sites and reaction areas of catalytic materials is important for the development of bifunctional electrocatalysts for zinc-air batteries (ZABs). In this paper, a catalyst with a uniform nanopore structure (noted as NiCo-PS) was one-pot synthesized by using transition metals nickel and cobalt as catalytic active components, sucrose as a carbon source, and triblock copolymers as a soft template. The N2 absorption and desorption isotherms curves show that the pore size distribution of NiCo-PS modified by surfactant is mainly in 3.6 nm range. NiCo-PS exhibits exceptional bifunctional electrocatalysis due to its effective triple-phase reaction interface from its mesoporous structure, with a positive half-wave potential of 0.758 V for ORR and a low overpotential of 390 mV at 10 mA ⋅ [Formula: see text] for OER. Furthermore, the rechargeable ZABs with the NiCo-PS catalyst exhibit a high open-circuit voltage of 1.31 V, a significant peak power density of 105 mA ⋅ [Formula: see text] at 0.56 V, and good stability throughout 270 h testing. This result offers valuable insights for designing catalysts that enhance the active region of the reaction within the cathodes of ZABs and hold significant promise for practical applications.

Simple and rapid determination of tartrazine in fake saffron using the metal organic framework (Fe SA MOF@CNF) by HPLC/PDA

The present study of a novel metal–organic framework containing Fe single atoms doped on electrospun carbon nanofibers (Fe SA-MOF@CNF) based on dispersive micro solid phase extraction (D-μ-SPE) using HPLC–PDA for detection tartrazine in fake saffron samples was designed. The Fe SA-MOF@CNF sorbent was extensively characterized through various techniques including N2 adsorption–desorption isotherms, X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The specific area of surface of the sorbent was 577.384 m2/g. The study variables were optimized via the central composite design (CCD), which included a sorbent mass of 15 mg, a contact time of 6 min, a pH of 7.56, and a tartrazine concentration of 300 ng/ml. Under the optimum condition, the calibration curve of this method was linear in the range of 5–1000 ng/mL, with a correlation coefficient of 0.992. The LOD and LOQ values were ranged 0.38–0.74 and 1.34–2.42 ng/ml, respectively. This approach revealed significant improvements, including high extraction recovery (98.64), recovery rates (98.43–102.72%), and accuracy (RSDs < 0.75 to 3.6%). the enrichment factors were obtained in the range of 80.6–86.4 with preconcentration factor of 22.3. Consequently, the D-μ-SPE method based on synthesized Fe SA-MOF@CNF could be recommended as a sustainable sorbent for detecting tartrazine in saffron samples.

CuMOF@Faujasite nanocomposite as a novel catalyst for hydrogen production

Energy production is one of the most crucial issues presently attracting global attention. In this work, a CuMOF@Faujasite nanocomposite was synthesized and utilized as a novel efficient catalyst for hydrogen production. The produced composite was first characterized using X‐ray diffraction (XRD), Fourier‐ transform infrared (FT‐IR), thermogravimetric analysis (TGA), and differential scanning calorimetry. Surface properties were analyzed via nitrogen adsorption–desorption isotherms. All characterization results revealed the formation of a pure and well‐defined crystalline phase, with a high specific surface area (SBET) of 286 m2/g (SBET of Faujasite is 35 m2/g). Moreover, the morphology and compositional analysis of the nanocomposite were assured through the scanning (SEM) and transmission (TEM) electron microscope and X‐ray photospectroscopy (XPS). SEM and TEM images revealed sponge‐like spheres that are related to Faujasite besides small spherical particles related to CuBDC MOF. XPS analysis revealed a low content of CuMOF in the nanocomposite. The catalytic activity of the nanocomposite was tested for the dehydrogenation of NaBH4. The impact of NaBH4 concentration, weight of the catalyst, and the reaction temperature on NaBH4 hydrolysis was investigated. A hydrogen generation rate (HGR) of 484 mLmin−1 g−1 at 30 °C was achieved using 50 mg of the catalyst and 0.05 mol/l of NaBH4 owing to the high specific area and the selective active sites for such hydrolytic reaction. The kinetic analysis of the activity data indicates the first‐order behavior at low concentrations of NaBH4. Furthermore, at concentrations ≥0.065 mol L−1, zero‐order kinetics was predominant. The time needed for completion of the hydrolysis reaction was found to be decreased (~20 min) by increasing the catalyst mass as well as NaBH4 concentration or even by elevating the reaction temperature (~4 min at 60 °C). The activation energy was estimated; it was found to be 70.5 KJ mol−1. Ultimately, our catalyst showed a reasonable rate of hydrogen production, as compared to others reported earlier.

Phosphorus adsorbed by HCl desorption–activated red mud adsorbents: a molecular dynamics studys

In this study, modified red mud after phosphorus adsorption was used as the adsorbent, and HCl and deionized water were used as desorbents to desorb phosphorus. The components in the adsorbent were optimized based on density functional theory, and adsorbent and desorbent models were established. Molecular dynamics simulation was performed to determine the phosphorus concentration before and after desorption, interaction energies, radial distribution function(RDF), mean-square displacement(MSD), and diffusion coefficient. The Monte Carlo method was used to simulate the desorption isotherm, desorption site, heat of desorption, and desorption energy. Simulation results showed that deionized water could only desorb phosphorus on the adsorbent surface, and the stability of the system deteriorated upon adding HCl. HCl destroyed the ionic and hydrogen bonding between the O atoms in H2PO4 − and reactive metal and oxygen atoms in the activated red mud particles. Moreover, the van der Waals force decreased considerably. The ionic and hydrogen bonds between H2PO4 − and the surface of activated red mud particles were broken by HCl, which accelerated the desorption of phosphorus from the adsorbent surface. The interaction between HCl and phosphorus accelerated the diffusion, which decreased the adsorption capacity. Moreover, the desorption capacity increased with increasing temperature.

Hybrid exchange methods regulate Cu+ location on Cu-Y zeolites and improve CO adsorption capacity and selectivity

This work systematically examines the influence of preparation methods on the active Cu+ anchoring sites over FAU zeolites and their CO storage capacity and selectivity. The involved preparation methods here include individual liquid ion exchange method with CuCl2 solution, individual solid ion exchange method with CuCl powder and the hybrid exchange method. For the obtained Cu-Y samples, XRD, Ar adsorption/desorption at 87 K, TEM and NMR were used to characterize their skeleton structure, meanwhile, XPS and H2-TPR were utilized to identify the Cu+, Cu2+ and CuCl distribution. The CO storage capacity was implemented through CO adsorption–desorption isotherms. The correlation between various Cu species and CO storage capacity was analyzed and DFT calculation was employed to further elucidate the optimal Cu+ location induced by preparation methods. Finally, it is found that the isolated Cu+ is the dominating CO adsorption sites and Cu+ on site III present higher bonding energy with CO molecules. The hybrid preparation method seems the optimal choice for Cu-Y synthesis since the initial liquid ion exchange operation could prevent the framework corrosion from the subsequent solid ion exchange process, which benefits the optimal CO storage capacity and CO/N2 selectivity.

Effect of Heat Treatment on Hygroscopicity of Chinese Fir (Cunninghamia lanceolata [Lamb.] Hook.) Wood

Chinese fir (Cunninghamia lanceolata [Lamb.] Hook.) is a widely planted species of plantation forest in China, and heat treatment can improve its dimensional stability defects and improve its performance. The wood samples were heat-treated at various temperatures (160, 180, 200, and 220 °C) for 2 h. To clarify the effect of heat treatment on wood hygroscopicity, the equilibrium moisture content (EMC) was measured, the moisture adsorption and desorption rates were determined, the hygroscopic hysteresis was examined, and the Guggenheim, Anderson, and de Boer (GAB) model was fitted to the experimental data. The moisture absorption isotherms of all samples belonged to the Type II adsorption isotherm, but the shape of the desorption isotherm was more linear for heat-treated wood samples, especially when the heat treatment temperature was higher. According to the results analyzed with ANOVA, there were significant differences in equilibrium moisture content between the control samples and the heat-treated samples under the conditions of 30%, 60%, and 95% relative humidity (RH, p &lt; 0.05), and the results of multiple comparisons were similar. The decrease in hygroscopicity was more pronounced in wood treated at higher temperatures. The EMC of the 160–220 °C heat-treated samples of the control samples was 14.00%, 22.37%, 28.95%, and 39.63% lower than that of the control sample at 95% RH. Under low RH conditions (30%), water is taken up mainly via monolayer sorption, and multilayer sorption gradually predominates over monolayer sorption with the increase in RH. The dynamic vapor sorption (DVS) analysis indicated that the heat-treated wood revealed an increase in isotherm hysteresis, which was due to the change in cell wall chemical components and microstructure caused by heat treatment. In addition, the effective specific surface area of wood samples decreased significantly after heat treatment, and the change trend was similar to that of equilibrium moisture content.

Insights into the role of VOCs properties on thermal desorption behaviors of two porous polymeric resins

Desorption is a critical process in the recovery or post-treatment of adsorbents saturated with volatile organic compounds (VOCs). In this study, the thermal desorption behaviors for eight VOCs on hypercrosslinked polymeric resin (HPR) and macroporous polymeric resin (MPR) were investigated through isothermal desorption and temperature programmed desorption (TPD). Compared with MPR, HPR with more micropores exhibited a lower desorption rate constant, lower desorption efficiency and higher desorption activation energy due to the strong binding energy generated between VOCs molecules and narrow micropores. As the polarizability of VOCs increased, the desorption rate constants on two porous polymeric resins decreased, while the desorption activation energy showed an incremental trend. Excellent linear correlations were observed between VOC polarizability and desorption rate constants (R2 = 0.957 for HPR and R2 = 0.940 for MPR) as well as between VOC polarizability and desorption activation energy (R2 = 0.981 for HPR and R2 = 0.969 for MPR). Furthermore, a polyparameter linear free energy relationship (PP-LFER) was developed to explore the influences of intermolecular interactions on desorption behaviors of VOCs on porous polymeric resins. The results indicated that the dispersive interaction, which is directly related to polarizability of VOCs, was the primary factor influencing the desorption activation energy of VOCs on porous polymeric resins. The find from this study helps evaluate fleetly and availably the desorption properties of VOCs based on their polarizability.

Controlled Synthesis of Mg-MOF-74 and Its CO2 Adsorption in Flue Gas

Yellow nanorod Mg-MOF-74 was obtained through a solvothermal synthesis method. The XRD, N2 adsorption–desorption isotherms, SEM, and TGA results suggest that the particle size of Mg-MOF-74 reaches 400 nm after the introduction of sodium acetate in the precursor of Mg-MOF-74. Furthermore, the morphology of Mg-MOF-74 changed from cauliflower- to rod-shaped particles. At the same time, the BET specific surface area and pore volume of Mg-MOF-74 also increased a lot. Then, the CO2 dynamic adsorption capacity of Mg-MOF-74 was measured with a self-made fixed bed at 30 °C and a 0.1 bar CO2 partial pressure. The results show that the CO2 adsorption capacity of Mg-MOF-74-N2 reaches 3.67 mmol/g, and its CO2 adsorption capacity remains unchanged after 10 CO2 adsorption–desorption cycles.

Efficient mesoporous cross-linkable hybrid poly Schiff-base based on polyimide as a promising molecular sieve for sustainable CO2 capturing and separation

ABSTRACT A cross-linked hybrid poly Schiff-base (PSB) was synthesized and characterized through spectroscopic, morphological, and structural approaches. The BET surface area (SBET) of the PSB is 20.33 m2/g, the pore volume (Vp) is 0.024 cm3/g, and the pore diameter (Dp) is 4.13 nm. The current study elucidates PSB’s strong chemical and thermal stability, as well as the remarkable capacity to adsorb CO2 with perfect selectivity. This property is accomplished by the synergistic interaction of the polymer’s physicochemical and structural features when exposed to CO2, N2 and CH4 molecules. This mesoporous polymer exhibits a CO2/N2 = 60 and CO2/CH4 = 10.5 selectivity, and can adsorb 3.22 mmol/g CO2 (at 298 K/1 bar). Furthermore, the isotherms of CO2 gas adsorption and desorption in the porous polymer are reversible. The use of PSB having effective imide, imine, and meta-hydroxyl functional groups in the adsorption and selectivity of CO2 gas produced excellent results, which make it a suitable candidate for CO2 storage and separation applications.

Sonochemical fabrication of S-scheme Bi2O2CO3/g-C3N4 heterojunction for enhanced photocatalytic destruction of rhodamine B and tetracycline pollutants under natural solar radiations

Photocatalysis is a promising low cost green technology to efficiently mineralize refractory contaminants from wastewater. In this novel research, S-scheme Bi2O2CO3/g-C3N4 heterojunctions containing (0-25) wt % Bi2O2CO3 were sonochemically fabricated for mitigation of hazardous rhodamine B dye and tetracycline antibiotic under sunlight radiations of 900 W power. The physicochemical properties of the solid specimen were explored by photoluminescence [PL], diffuse reflectance spectrum [DRS], X-ray diffraction [XRD], Mapping, high resolution transmission electron microscope [HRTEM], selected area electron diffraction [SAED], N2–adsorption–desorption isotherms and X–ray photoelectron spectroscopy [XPS] techniques. As elucidated by HRTEM analysis, 15 wt% of spherical Bi2O2CO3 nanoparticles of 12 nm size were deposited on g-C3N4 of 40 m2/g surface area at nearly equidistant from each other. The point of zero charge of g-C3N4 sheets was shifted from pHPZC 6.2 to pHPZC 4.8 with incorporation of 15 wt % Bi2O2CO3 revealing the production of negatively charged surface that strongly destructed cationic rhodamine B dye. The rate of photocatalytic degradation of rhodamine B dye for heterojunction containing 15 wt% Bi2O2CO3 was 0.0168 min−1 which is three fold higher than that of pristine g-C3N4 nanosheets. The radical scavengers experimental results revealed that superoxide radicals and positive holes are the main reactive species in the degradation process. The exceptional photocatalytic reactivity emerged from construction of S-scheme heterojunction with auspicious electron-hole pair separation and transportation electron-hole pairs and significant redox power.

Boosting catalytic activity of Ni/ZrO2 by introducing MoO3 on selective hydrogenolysis of lignin

Conversion of renewable lignin to value-added aromatic chemicals presents a broad prospect to achieve the goals of “carbon neutrality”. In this work, an efficient approach is proposed for selective hydrogenolysis of lignin to valuable 4-propyl syringol in the presence of cost-effective catalyst of yNi/ZrO2-xMoO3. When the lignin hydrogenolysis is performed with 15Ni/ZrO2-10MoO3, 15.4% yield of monophenols is achieved, which is approximately twice as that from the 15Ni/ZrO2 catalytic system (7.8%). Importantly, 33.1% of these monophenols are identified as 4-propyl syringol (4-PS), a versatile fine chemical. An extensive characterization of the modified catalysts by means of XRD, nitrogen adsorption–desorption isotherm, SEM, TEM, XPS, NH3-TPD, CO2-TPD, and H2-TPR, confirms that the introduction of MoO3 changes the primary phase of ZrO2 and the acidity/basicity properties of catalyst. As a result, an enhanced cleavage of the C-O linkage between S-lignin and other units is demonstrated, which consequently contributes to the good selectivity of 4-propyl syringol. Therefore, this work provides a new insight for producing bulk aromatic chemicals via a sustainable route.

Poly(O‐Toluidine)‐polyvinylpyrrolidone copolymer submerged MgFe2O4/CS‐OXSWCNTs nanocomposite for removal of acid red dye from aqueous solutions

AbstractIn this study, a new hybrid material was created that exhibits excellent adsorption performance and high stability. POT‐PVP/MgF/CS‐OXSWCNTs NCs were synthesized using a three‐step approach. The process involved the chemical polymerization of poly(o‐toluidine)‐polyvinylpyrrolidone (POT‐PVP) with MgFe2O4 nanoparticles (MgF NPs) and chitosan‐oxidized single‐wall carbon nanotubes (CS‐OXSWCNTs). The synthesis process involved the use of an egg white method to synthesize MgF NPs and cross‐linking chitosan with OXSWCNTs using glutaraldehyde (GA) to obtain CS‐OXSWCNTs. The POT‐PVP copolymer was then used to coat MgF NPs and CS‐OXSWCNTs NCs. The successful synthesis of the NCs with strong component interaction was confirmed by several characterization techniques, including X‐ray diffraction spectroscopy (XRD), Fourier‐transform infrared spectroscopy (FTIR), and Raman spectroscopy. Microscopy analysis using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) verified that the POT‐PVP copolymer had properly coated the MgF NPs and CS‐OXSWCNTs NCs. The N2 adsorption–desorption isotherm verified that the specific surface area of NCs had increased with the addition of MgF NPs and CS‐OXSWCNTs NCs. Furthermore, the composite structure greatly improved the thermal stability of POT‐PVP/MgF/CS‐OXSWCNTs NCs. To evaluate how well the nanocomposites (NCs) eliminated pollutants, an artificially produced toxic effluent that contained acid red dye (A.R) was applied. To investigate their impact on dye removal, several parameters were changed, including pH, adsorbent dosage, time, temperature, and ionic strength. The POT‐PVP/MgF/CS‐OXSWCNTs NCs showed a higher removal rate based on a greater surface area, stability, and conducting power than MgF NPs and POT‐PVP. It was found that 25 mg L−1 and 7.5 mg were the optimal dye concentration and adsorbent dosage, respectively. The POT‐PVP/MgF/CS‐OXSWCNTs NCs achieved 99.46% removal efficiency at an acidic pH of 2. The NCs were found to have a maximum dye adsorption capacity of 107.4 mg g−1, and the adsorption process followed the pseudo‐second‐order kinetics. Thermodynamic analyses revealed that the dye adsorption onto POT‐PVP/MgF/CS‐OXSWCNTs NCs was endothermic, implying a spontaneous and physical adsorption mechanism. It can be inferred from these results that POT‐PVP/MgF/CS‐OXSWCNTs NCs are useful for eliminating dye pollutants from water.

Reuse of polymeric waste for the treatment of marine water polluted by diesel

Accidental diesel spills can occur in marine environments such as harbors, leading to adverse effects on the environmental compartment and humans. This study proposes the surgical mask as an affordable and sustainable adsorbent for the remediation of diesel–contaminated seawater to cope with the polymeric waste generated monthly in hospital facilities. This approach can also be helpful considering a possible future pandemic, alleviating the pressure on the waste management system by avoiding improper mask incineration and landfilling, as instead occurred during the previous COVID–19. Batch adsorption–desorption experiments revealed a complete diesel removal from seawater after 120 min with the intact laceless mask, which showed an adsorption capacity of up to 3.43 g/g. The adsorption curve was better predicted via Weber and Morris's kinetic (R2 = 0.876) and, in general, with Temkin isotherm (R2 = 0.965–0.996) probably due to the occurrence of chemisorption with intraparticle diffusion as one of the rates–determining steps. A hysteresis index of 0.23–0.36 was obtained from the desorption isotherms, suggesting that diesel adsorption onto surgical masks was faster than the desorption mechanism. Also, the effect of pH, ionic strength and temperature on diesel adsorption was examined. The results from the reusability tests indicated that the surgical mask can be regenerated for 5 consecutive cycles while decreasing the adsorption capacity by only approximately 11%.

Perovskite-Derivative Ni-Based Catalysts for Hydrogen Production via Steam Reforming of Long-Chain Hydrocarbon Fuel

Large-scale hydrogen production by the steam reforming of long-chain hydrocarbon fuel is highly desirable for fuel-cell application. In this work, LaNiO3 perovskite materials doped with different rare earth elements (Ce, Pr, Tb and Sm) were prepared by a sol-gel method, and the derivatives supported Ni-based catalysts which were successfully synthesized by hydrogen reduction. The physicochemical properties of the as-prepared catalysts were characterized by powder X-ray diffraction, high-resolution transmission electron microscopy, N2 adsorption–desorption isotherms, H2 temperature-programmed reduction, and X-ray photoelectron spectroscopy. The catalytic performance of the as-prepared catalysts for hydrogen production was investigated via the steam reforming of n-dodecane. The results showed that the catalyst forms perovskite oxides after calcination with abundant mesopores and macropores. After reduction, Ni particles were uniformly distributed on perovskite derivatives, and can effectively reduce the particles’ sizes by doping with rare earth elements (Ce, Pr, Tb and Sm). Compared with the un-doped catalyst, the activity and hydrogen-production rate of the catalysts are greatly improved with rare earth element (Ce, Pr, Tb and Sm)-doped catalysts, as well as the anti-carbon deposition performance. This is due to the strong interaction between the uniformly distributed Ni particles and the support, as well as the abundant oxygen defects on the catalyst surface.

Tyrosol removal by photo–Fenton–like process using CaAlFe mixed oxides synthesized via hydrocalumite from aluminum salt cake

Solids with potential application in tyrosol (Ty) removal by photo–Fenton processes have been synthesized using aluminum salt cake as a source. Two series of hydrocalumite layered double hydroxides (LDH) were synthesized: one containing structural Fe3+ (occupying octahedral positions in the LDH) and another containing surface impregnated Fe3+; all solids were calcined in air at 750 °C. The solids were characterized by powder X–ray diffraction, FT–infrared spectroscopy, thermal analysis, N2 adsorption–desorption isotherms at –196 °C, particle size distribution and electron microscopy. One of the main differences between the two series was that Fe3+ impregnation by the incipient wetness method and subsequent calcination at 750 °C did not lead to the formation of CaAlFe mixed oxides. The calcined solids were evaluated as photocatalysts in the photo–Fenton process for Ty removal (a typical compound found in olive oil mill wastewater), the samples containing surface Fe3+ showing better results. The solid prepared by impregnation of hydrocalumite with 20% iron and subsequently calcined at 750°C, under the optimum reaction conditions (catalyst dose = 0.5 g/L, [H2O2] = 0.468 g/L and [Ty]0 = 100 mg/L, in the presence of UV light), reached complete Ty removal with contaminant mineralization of 95% after only 60 min reaction. The cyclic study showed that this sample maintained its stability after 3 cycles of reuse without iron leaching, and a better performance than other materials reported in the literature.

Immobilization of Schiff base-Pd complex in mesoporous silica KIT-6 channels: A novel, green, recyclable, and highly versatile mesoporous catalyst for the carbon-carbon cross-coupling reaction

In this study, we developed an efficient and novel nanocatalyst by immobilizing Schiff base-Pd complex inside mesoporous silica KIT-6 channels, which were successfully synthesized by using a simple procedure. The catalytic activity of KIT-6@Schiff base-Pd was investigated in the synthesis of a wide variety of biphenyl derivatives. The N2 adsorption–desorption isotherms indicated the excellent Brunauer–Emmett–Teller surface area for KIT-6@Schiff base-Pd of 121.65 m2/g. The chemical and physical properties of raw and modified samples (KIT-6@Schiff base-Pd) were characterized based on Fourier transform-infrared spectra, thermogravimetric analysis, energy-dispersive X-ray spectroscopy, N2 adsorption–desorption, scanning electron microscopy, X-ray elemental mapping, and X-ray diffraction analyses. We found that the synthesized catalyst could be recovered and reused up to four times.

Application of a Bio-waste Einkorn (Triticum monococcum L.) Husks Adsorbent for Removal of Metanil Yellow and Methylene Blue from Aqueous Media with Equilibrium, Kinetic, and Thermodynamic Studies

In this study, the activated carbon (TmAC) with a high surface area and appropriate pore distribution was produced from einkorn (Triticum monococcum L.) husks by using ZnCl2 with chemical activation method. The efficiency of the obtained activated carbon on the adsorption of anionic (metanil yellow) and cationic (methylene blue) dyestuffs from aqueous solutions was investigated in more detail. In addition, the surface characterization of activated carbon was performed using thermogravimetric analysis-differential thermal analysis (TGA-DTA), elemental analysis, scanning electron microscopy (SEM) images, Brunauer–Emmett–Teller (BET) specific surface areas, N2 adsorption–desorption isotherms, pore volumes, pore size distributions, and Fourier-transform infrared spectroscopy-attenuated total reflection (FTIR-ATR) spectra. The highest surface area of activated carbon was measured as 1321 m2 g−1 at the carbonization temperature of 500 °C by using impregnation ratio (w/w = 2.0). Batch method was used in adsorption experiments. The parameters affecting the adsorption studies such as adsorbent concentration, initial dye concentration, adsorption time, temperature, and pH were investigated. The adsorption mechanisms of metanil yellow (MY) and methylene blue (MB) on activated carbon were explained by using isotherms (Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich), kinetic models (pseudo-first-order and pseudo-second-order), and the thermodynamic parameters (Gibbs free energy, enthalpy, and entropy).Graphical

Speciation simulation and sorption mechanism of 238Pu in radioactive waste repository lithosphere

Abstract The assessment of the migratory and environmental behavior of radioactive nuclides escaping from waste treatment facilities heavily relies on the use of numerical models capable of simulating and characterizing all significant processes of nuclides in complex geological environments. Adsorption models typically encompass the chemical properties of the nuclides themselves and their chemical reactions with the surrounding environment, as well as processes such as ion exchange or physical adsorption. These processes must be taken into consideration in the long-term safety assessment of radioactive waste repositories. The redox-sensitive nuclide 238Pu, a critical member among transuranic elements, exhibits a diverse range of aqueous forms, and concurrently, it possesses high toxicity. The chemical behavior of 238Pu shows strong spatial variability with changes in environmental conditions. In this study, we constructed a theoretical model for the migration of nuclides in soil and groundwater environments through indoor static batch experiments and hydrogeochemical simulations. Experimental methods were employed to dissect the micro-scale, irreversible adsorption reaction processes of nuclides and identify their primary existing forms. According to field measurements, the pH of groundwater was recorded as 7.48, with an Eh of 125.7 mV. Introducing a solid-to-liquid ratio of 1:10 g/mL in centrifuge tubes, we measured the radioactive nuclide concentration after achieving adsorption and desorption equilibrium, obtaining adsorption and desorption isotherms. The PHREEQC software was employed to investigate the changes in 238Pu forms under varying conditions of pH and redox potential. Field measurements provided groundwater pH and Eh values. The activity concentration of the nuclide was measured after reaching adsorption and desorption equilibrium. The results show that the adsorption isotherms of 238Pu differ from its desorption isotherms, indicating an irreversible adsorption-desorption process. Ion exchange and surface complexation were identified as the main modes of adsorption. PHREEQC simulations revealed that 238Pu primarily existed in forms such as tetravalent Pu(OH)4 and trivalent Pu(SO4)2 −, PuSO4 +. Pu(OH)4 accounted for the largest proportion (97%) in the groundwater solution system, while a minimal amount of pentavalent PuO2 + was present. Environmental factors, such as pH and the presence of ions like SO4 2− and HCO3 −, influenced the forms of 238Pu.

Harnessing bimetallic oxide nanoparticles on ionic liquid functionalized silica for enhanced catalytic performance

The present study reports on harnessing bimetallic (V and Ni) oxide nanoparticles supported on ionic liquid-functionalized silica for enhancing catalytic performance in epoxidation and hydrogenation reactions. The as-synthesized catalyst was ably characterized through various techniques such as FTIR, X-ray diffraction (XRD), N2 adsorption−desorption isotherms, X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). A selective organic transformation of Isophorone to Homalinol via two-steps tandem reaction significantly promoted by synthesized catalyst. During epoxidation and hydrogenation reactions, V-NiNPs@SILP catalyst demonstrated excellent catalytic performance, leading to 98.23 % conversion with 99.06 % selectivity. Moreover, the synthesized catalyst exhibited recyclability for five consecutive cycles with minute loss in activity.

Adsorption and desorption mechanism of toluene gas by iron modified activated carbon fiber

To enhance the adsorption performance of activated carbon fiber (ACF) on volatile organic compounds such as toluene, a series of Fex/ACF adsorption materials were prepared by impregnation and anaerobic atmosphere calcination. The various adsorption effects of Fex/ACF on toluene under different synthesis conditions were discussed, and both the modified and unmodified adsorption materials were characterized by using N2 adsorption–desorption isotherms, XRF, XRD, FT-IR, SEM, and XPS etc methods. The results indicated that iron modified ACF demonstrated the optimal adsorption performance when ACF was loaded with 3 % iron and calcined at 500 °C, and it achieved a saturated toluene adsorption capacity of 218.12 mg/g, which was 24 % higher than that of the unmodified sample. And its adsorption process of toluene followed Yoon-Nelson model. The adsorption capacity was maintained at approximately 70 % when four adsorption/desorption cycle tests. The toluene adsorption performance of Fe0.03/ACF-500 on toluene mainly involved surface adsorption (such as n-π interaction, and π-π interaction), pore filling, and complexation between the loaded metal iron and toluene.