Multistage Adsorption Research Articles

Efficient phosphorus removal using the La-based perovskite oxides: Role of B-site metal for modulating the surface electronic structure

Highly efficient removal of phosphate from water bodies is of great importance to controlling eutrophication. Herein, the lanthanum-based perovskites (i.e., LaMnO3, LaFeO3) were synthesized and employed for phosphorus adsorption. Adsorption experiments showed that the phosphate removal by LaMnO3 was well fitted with the pseudo second-order kinetic model, with a multi-stage adsorption process. The LaMnO3 exhibited a maximum adsorption capacity of 51.3 mg/g for phosphate calculated using the Langmuir model, which was 2.1 times higher than that of LaFeO3 under neutral conditions. Characterization and DFT calculation results further revealed that the La element on the surface of perovskite was the main adsorption site via inner-sphere complex and/or electrostatic interactions, whereas the B-site metal (i.e. Mn element) could trigger the surface electronic structure modulation such as the reduction of surface bonding barrier, for further improving the phosphate adsorption. Additionally, the LaMnO3 adsorbent exhibited commendable performance in treating natural water with low phosphorus concentration and good regenerative capability. This work provides insight into the development of novel perovskite-type adsorbents for efficiently removing phosphorus in environmental remediation.

Eco-friendly closed-loop recycling of nickel, cobalt, manganese, and lithium from spent ternary lithium-ion battery cathodes

Recycling technology is essential for managing waste and addressing environmental issues related to scrapping power lithium batteries. A closed-loop recycling technique was proposed in this work for maximizing usage of lithium (Li), manganese (Mn), cobalt (Co), and nickel (Ni) resources in spent ternary lithium battery (SNCMB) cathodes. A green and sustainable leaching process utilizes citric acid (CA) and hydrogen peroxide (HP) to efficiently extract Ni, Co, Mn, and Li from SNCMB cathodes. Maximizing leaching rates for Ni (96.69 %), Co (95.38 %), Mn (97.64 %), and Li (98.72 %) under optimal conditions (80 ℃, 4 mol/L CA, 20 g/L solid to liquid (S/L) ratio, 2 vol% HP, 70 min). The Avrami equation models leaching kinetics, requiring a temperature of 80 ℃ to accelerate the process. Hydrogen-type strong acidic cation exchange resin (HR) effectively adsorbs Ni, Co, Mn, and Li ions from leachates through ion exchange under optimal conditions, reducing costs and eliminating the need for separating metals with similar chemical properties. This multi-stage adsorption recycling process renders leachates both economical and eco-friendly. The metal-enriched HR composite (HRC) from the ion-exchange process prepares ternary lithium battery (NCMB) cathodes to maximize metal usage. Microwave heating achieves excellent structure and electrochemical performance of regenerated ternary lithium battery (RNCM) cathodes, with 153.81 mAh/g discharge capacity at 0.1C rate and 90.92 % capacity retention after 50 cycles at 900 ℃ for 4 h. This innovative, efficient, and eco-friendly technique allows for closed-loop recycling of Ni, Co, Mn, and Li from SCNMB cathodes, providing new avenues for lithium battery recycling.

Oxalate modification enabled advanced phosphate removal of nZVI: In Situ formed surface ternary complex and altered multi-stage adsorption process

Nano zero-valent iron (nZVI) is a promising phosphate adsorbent for advanced phosphate removal. However, the rapid passivation of nZVI and the low activity of adsorption sites seriously limit its phosphate removal performance, accounting for its inapplicability to meet the emission criteria of 0.1 mg P/L phosphate. In this study, we report that the oxalate modification can inhibit the passivation of nZVI and alter the multi-stage phosphate adsorption mechanism by changing the adsorption sites. As expected, the stronger anti-passivation ability of oxalate modified nZVI (OX-nZVI) strongly favored its phosphate adsorption. Interestingly, the oxalate modification endowed the surface Fe(III) sites with the lowest chemisorption energy and the fastest phosphate adsorption ability than the other adsorption sites, by in situ forming a Fe(III)-phosphate-oxalate ternary complex, therefore enabling an advanced phosphate removal process. At an initial phosphate concentration of 1.00 mg P/L, pH of 6.0 and a dosage of 0.3 g/L of adsorbents, OX-nZVI exhibited faster phosphate removal rate (0.11 g/mg/min) and lower residual phosphate level (0.02 mg P/L) than nZVI (0.055 g/mg/min and 0.19 mg P/L). This study sheds light on the importance of site manipulation in the development of high-performance adsorbents, and offers a facile surface modification strategy to prepare superior iron-based materials for advanced phosphate removal.

Insights into simultaneous efficient removal of cationic and anionic dyes by nitrogen-rich seaweed carbon adsorbent

Textile dyes, including methylene blue (MB) and methyl orange (MO), pose a significant threat to water quality. This study delves into the competitive adsorption mechanisms pivotal for the concurrent removel of cationic MB and anionic MO dyes using nitrogen-rich seaweed-based carbon adsorbents. Synthesized through the pyrolysis and NaOH activation of Enteromorpha seaweed biomass, the preparation method is both uncomplicated and cost-effective, holding promising applications in industry. Characterization unveiled a commendable specific surface area of 911 m2/g, accompanied by abundant nitrogen- and oxygen-containing functional groups. Batch adsorption experiments showcased exceptional removal efficiencies surpassing 99.8% for both dyes. Molecular dynamics simulations offered valuable insights into the dynamic multi-stage adsorption behavior, while density functional theory calculations clarified the chemisorption-based interaction mechanism. Notably, MB displayed superior adsorption affinity compared to MO. An integrated adsorption mechanism was proposed, encompassing electrostatic attraction, migration, and enhanced chemisorptive binding of dye aggregates at active sites on the adsorbent surface. The innovative adsorption mechanism adopted by this carbon-based adsorbent prepared from nitrogen-rich seaweed can effectively remove cationic and anionic dyes, laying a solid foundation for future research on real water bodies with complex compositions.

Developing a mini pilot resin in solution Process for adsorption of uranium in Pachuca reactors (case study: Saghand uranium ore of the Central Iran)

Resin in pulp, as the most frequently employed process for extraction of uranium from low-grade ores, encounters difficulties when the pulp contains dense or abrasive minerals, e.g., Saghand ores in central Iran. To overcome these complications, it was suggested to remove solid content of the pulp at first, and inject the clear solution into a cascade of Pachuca reactors, where uranium is adsorbed by an anion exchanger such as Varion-AP. We made two mini pilot cascades, each comprising ten Pachuca reactors, to check both co-current and countercurrent resin in solution processes on the Saghand leach liquor. The countercurrent scheme, having a higher efficiency, was able to adsorb 99% of uranium from a 238 mg/L solution, with 7 stages, at optimum pH = 1.8. Kinetics of adsorption was controlled by intra-particle diffusion, and a generalized Glueckauf model, fairly well described multistage adsorption. The most significant process variable was found to be flow rate of the resin, whose precise adjustment, results in the optimum process design, where the net present value (NPV) becomes minimum.

Multi-stage adsorption of methyl orange on the nitrogen-rich biomass-derived carbon adsorbent: DFT and MD evaluation

Dyes that are released into the environment may have negative effects on living organisms. To address this issue, a biomass-derived carbon adsorbent made from Enteromorpha was tested for its ability to remove methyl orange (MO) from wastewater. The adsorbent was found to be effective in removing MO, with a 1:4 impregnation ratio producing an adsorbent that could remove 96.34% of MO from a 200 mg/L solution using only 0.1 g of adsorbent. At higher concentrations, the adsorption capacity increased up to 269.58 mg/g. Through molecular dynamics simulations, it was discovered that after mono-layer adsorption reached saturation, the remaining MO molecules in solution formed hydrogen bonds with the adsorbed MO, which led to further aggregation on the adsorbent surface and increased adsorption capacity. Additionally, theoretical investigations revealed that the adsorption energy of anionic dyes increased with Nitrogen-doped carbon materials, with the pyrrolic-N site having the highest adsorption energy for MO. The carbon material derived from Enteromorpha showed promise in treating wastewater containing anionic dyes, thanks to its high adsorption capacity and strong electrostatic interaction with the sulfonic acid groups of MO.

Tunable zirconium-based metal organic frameworks synthesis for dibutyl phthalate efficient removal: An investigation of adsorption mechanism on macro and micro scale

The tunable porous structure of metal organic frameworks (MOFs) plays a crucial role in determining their adsorption performance. In this study, we developed and employed a strategy involving monocarboxylic acid assistance to synthesize a series of zirconium-based MOFs (UiO-66-F4) for the removal of aqueous phthalic acid esters (PAEs). The adsorption mechanisms were investigated by combining batch experiments, characterization and theoretical simulation. By adjusting the affecting factors (i.e., initial concentration, pH values, temperature, contact time and interfering substance), the adsorption behavior was confirmed as a spontaneous and exothermic chemisorption process. The Langmuir model provided a good fit, and the maximum expected adsorption capacity of di-n-butyl phthalate (DnBP) on UiO-66-F4(PA) was calculated to be 530.42 mg·g−1. Besides, through carrying out the molecular dynamics (MD) simulation, the multistage adsorption process in the form of DnBP clusters was revealed on a microcosmic scale. The independent gradient model (IGM) method showed the types of weak interactions of inter-fragments or between DnBP and UiO-66-F4. Furthermore, the synthesized UiO-66-F4 displayed excellent removal efficiency (>96 % after 5 cycles), satisfactory chemical stability and reusability in the regeneration process. Hence, the modulated UiO-66-F4 will be regarded as a promising adsorbent for PAEs separation. This work will provide referential significance in tunable MOFs development and actual applications of PAEs removal.

Study on the influence mechanism of mineral components in biochar on the adsorption of Cr(VI)

Cr(VI) is extremely harmful to the ecological environment. The secondary purification method of treating low concentrations is not satisfactory currently. In this paper, wheat straw were pyrolyzed at 800 °C to obtain biochar, which were used to explore the effect of minerals on adsorption effect as a precursor at different pH and 25 °C. The biochar was gradually eluted with HCl and HF to remove the ash, soon loaded with K+, Ca2+, Mg2+ and Fe3+, respectively. The results show that under the action of H+, the CO bonds left after mineral removal have lower potential energy than the original surface functional groups in terms of conversion to –OH and binding to Cr. The order of promotion of Cr(VI) adsorption by the four elements is Fe3+> Mg2+＞ Ca2+> K+. As the radius of metal ions decreases, so does the electronegativity of biochar and the surfactive site increases. The adsorption mechanisms of alkali metals, alkaline earth metals and transition metals to Cr(VI) are mainly based on ion exchange, precipitation and complexation, respectively. The adsorption of Cr(VI) by wheat straw biochar was consistent with the quasi-secondary kinetic model. Combined with the results of intraparticle diffusion model fitting, it shows that this process is a multi-stage adsorption process with the combined effect of physical and chemical adsorption.

Achieving win-win outcomes with cerium-loaded porous aluminum sludge hydrogel microspheres for enhanced phosphate removal

Breaking the technical bottleneck of traditional powdered adsorbent in phosphate adsorption application treatment, a macroscopic high adsorption performance aluminum sludge-based composite hydrogel material was constructed to synergistically solve the problems of water eutrophication and aluminum sludge resourcization. In this study, porous Ce-modified aluminum sludge hydrogel microspheres (Ce-AlS-SA) were prepared to improve the surface chemical structure and microscopic morphology of the macroscopic adsorbent material to enhance the adsorption capacity and achieve effective solid-liquid separation. The best adsorption performance of the material (Ce-AlS12-SA1) was obtained when the Ce-AlS: SA: Na2CO3 was 12:1:1, and obtained the optimal adsorption conditions by Response Surface Method (RSM) with 1.5 mg/L of the dosage, 4 of pH and 50 mg/L of Cphosphate. The maximum adsorption of 20.36 mg P/g was obtained by the Langmuir model at 303 K, which was 2.92 times more than raw sludge. According to the Freundlich and pseudo-second-order kinetic model, the adsorption process is chemisorption; the multi-stage adsorption process is reflected in the intraparticle diffusion and film diffusion models. The main mechanisms combined with the characterization analysis are electrostatic gravity, ligand exchange, and inner-sphere complexation. Meanwhile, Ce-AlS12-SA1 shows good resistance to interference in the coexistence of multiple ions. Therefore, this material can be recognized as a new material with in-depth, diversified and practical needs for resourceful utilization, which is expected to achieve extensive engineering applications in the future.

Synthesis of azole-functionalized microspheres and their adsorption properties for gold(I) thiosulfate complex.

Gold is an essential precious metal with exceptional properties. Thus, azole-functionalized microspheres (PS-3-AT) were prepared by grafting 3-amino-1,2,4-triazole (3-AT) into chloromethyl polystyrene beans (PS-Cl) and used as a novel adsorbent for the gold(I)-thiosulfate complex. The effects of initial gold concentration, thiosulfate concentration, temperature, and pH on the Au(S2O3)23- adsorption process over PS-3-AT were investigated. In this study, PS-3-AT was considered an effective adsorbent for Au(I) recovery from a thiosulfate solution, demonstrating that PS-3-AT completely adsorbed Au(S2O3)23- with an adsorption capacity of 39.8 kg t-1 achieved during multistage adsorption testing. Through adsorption kinetics and isotherm studies, the pseudo-second-order and Freundlich models well describe the adsorption process of PS-3-AT for Au(I), also suggesting the exothermic nature. Furthermore, SEM, FT-IR spectroscopy, BET, and XPS techniques were used to characterize the surface and structural properties of the samples. Notably, a reliable adsorption mechanism was developed that proposed the formation of the -NH+Cl- group during the grafting process and Cl- exchange with Au(S2O3)23- to achieve Au(I) capture. Moreover, quantum chemistry calculations and the independent gradient model (IGM) were adopted to visualize the interaction between PS-3-AT and Au(S2O3)23- at an atomic level. The desorption ratio was 97.9% while 2 M NaCl was used as the desorbent, and regeneration with PS-3-AT was achieved after five cycles. Therefore, the facile synthetic method and adsorption properties of PS-3-AT for the gold(I)-thiosulfate complex are satisfactory, which is valuable for the development of thiosulfate gold leaching technologies.

High-performance Fe3O4-terephthalaldehyde magnetic-nanocomposite for removal phenanthrene and 9-phenanthrol: A comprehensive experimental and theoretical analysis

Ascribing to the serious environmental and health risks caused by phenanthrene (PENE) and its dangerous degradation intermediate, 9-phenanthrol (9-PENE), solving their contamination problem was extremely urgent. In this work, a novel Fe3O4-terephthalaldehyde (Fe3O4-TERE) magnetic nanomaterial was fabricated by introducing aromatic rings onto Fe3O4 nanoparticles through encapsulation and grafting technique. The Fe3O4 core provided convenience for the subsequent recycling and regeneration. The grafted aromatic carbons could act as adsorption active sites to form π–π interaction with PENE/9-PENE’s aromatic rings, thus improving the capture performance. The properties of the prepared magnetic nanomaterials were investigated via multiple characterization techniques. As expected, the Fe3O4-TERE could be utilized for effectively reducing the contamination risk of PENE and 9-PENE. Furthermore, the Fe3O4-TERE possessed with excellent regeneration performance. The abundant homogeneous reaction sites of Fe3O4-TERE provided possibility for the monolayer adsorption of PENE and 9-PENE. There were multiple microscopic interactions and driving forces jointly or individually participated the multi-stage adsorption reaction. Moreover, density functional theory calculations not only analyzed the validity and existence form of the π–π interaction under different adsorption configuration modes, but also provided deeply perspectives related to the microscopic bonding mechanism. This work proposed a promising fabrication strategy for magnetic nanomaterials used for removing and remediation of polycyclic aromatic hydrocarbons contamination, as well as provided profound theoretical perspectives for analyzing the adsorption mechanism.

Multifunctional carboxymethyl cellulose sodium encapsulated phosphorus-enriched biochar composites: Multistage adsorption of heavy metals and controllable release of soil fertilization

Water and soil heavy metal contamination induced by wastewater irrigation endanger human health. To improve the long-term heavy metal removal performance in the complicated aqueous/soil system, a novel carboxymethyl cellulose sodium (CMC-Na) encapsulated phosphorus (P)-enriched biochar (CMC@MBC) was synthesized. The maximum adsorption capacities of the unmodified biochar for Pb(II), Cd(II), and Ni(II) were increased by 822, 464, and 256 mg/g, respectively. The CMC-Na encapsulation introduced abundant carboxymethyl groups and enables CMC@MBC a strong anti-pH interference ability. The sewage treatment result revealed that CMC@MBC functioned admirably with prolonged sewage flushing. The long-term effectiveness of CMC@MBC against heavy metals might be explained by a multistage adsorption process: immediate adsorption by the CMC-Na coating, fast adsorption at the interface of CMC-Na and P-enriched biochar (MBC), and delayed adsorption by the P compound progressively released from MBC. Heavy metal speciation analysis indicates that the contributions of different adsorption mechanisms vary with heavy metals. The macromolecular spatial network structure of CMC-Na could be a good cover for preventing P leaching, making CMC@MBC a great slow-release fertilizer (SRF) with a cumulative P release ratio of 61 % after 28 days of application. This work suggests that CMC@MBC is a low-cost and high-efficiency adsorbent and phosphorus SRF.

Thermodynamics analysis of multi-stage temperature swing adsorption cycle for dilute CO2 capture, enrichment and purification

Direct air capture is a carbon-negative technology that absorbs dilute carbon dioxide from the air directly, which requires a significant amount of energy and the construction of large-scale equipment. The main challenge for direct air carbon dioxide capture is the development of non-fossil energy sources for carbon dioxide compression and purification. In this work, a multi-stage adsorption system based on temperature swing adsorption with adsorption materials that can be driven by thermal energy is designed for direct air capture. The model of adsorption process is built on thermodynamic principles and conservation of mass, and the common tangent plane approach of adsorption is adopted at the end of each step calculation to validate the selected solution. Analysis of the process shows that, the CO2 purity in the storage bed can exceed 90% and the pressure can exceed 14 bar with zeolite 13X at a regeneration temperature of 368 K. Exploration of thermal performance has been investigated regarding specific energy and exergy efficiency of various regeneration temperatures. The influence of mass of adsorbent on the purity and specific energy has also been evaluated. Results show that the specific energy declines from 11.92 MJth/molCO2 to 8.73 MJth/molCO2, and the optimal exergy efficiency increases from 0.205 % to 0.238 % as the regeneration temperature grows from 368 K to 373 K. The values of adsorbent mass in the second and third beds for optimal purity and specific energy are calculated. It means that a thermally-powered carbon separation device can not only meet the requirements of direct air capture but also get the optimal purity of carbon dioxide or specific energy by altering the operation parameters.

Recovery of rare earths, lithium and fluorine from rare earth molten salt electrolytic slag via fluoride sulfate conversion and mineral phase reconstruction

To solve the problem of rare earths (RE) lithium (Li) and fluorine (F) recovery in rare earth molten salt electrolysis slag, a recovery method was developed based on magnetic separation, sulfuric acid leaching, HF recycling, water leaching, fluorination precipitation. First, RE, Li and iron-containing phases in a slag sample were separated using a magnetic separation method. Second, sulfuric acid-leaching was used to reconstruct the phases of RE and Li in the non-magnetic fraction, which were transformed into a rare earth sulfate easily dissolved in water. At the same time, the HF generated in the sulfuric acid leaching process is recovered by multistage adsorption. Finally, qualified fluoride rare earth products were obtained by HF cycle precipitation. The results show that the recovery of iron is 85.30% under the condition that the magnetic separation intensity of 0.668 T, particle size of 58–75 μm, and the main phase in the non-magnetic fraction is the rare earth phase, and the iron content is only 2.90%. Under the conditions of a concentrated acid concentration of 98.00%, a temperature of 633 K, a liquid–solid ratio of 2:1, a particle size of 58–75 μm, a constant stirring speed of 300 r·min−1, and reaction time of 3 h, the removal rate of F is 95.30%, and the transformation rates of Nd, Pr, Dy, and Li reached more than 95.00%. Through water immersion and fluorination precipitation, rare earth fluoride products can be obtained. The purity, particle size, and water content of the products met the standards required for industrial rare earth molten salt electrolysis.

Removal of Fluoride from Aqueous Solution using Calcium Peroxide as a Low-cost Adsorbent

Removal of fluorides from water is essential for humans and animals because it causes dental and bone deficiency. The maximum permissible limit of fluoride is 1.5 mg/L, according to the World Health Organization. Recently it became known that countries like Pakistan, India, Sri Lanka, China, Argentina, etc. have high fluoride concentration in groundwater. In the present work, calcium peroxide nanoparticles adsorption behaviour and its fluoride removal efficiency from an aqueous phase was studied. Adsorption technique was used to concentrate fluoride on the adsorbent. The advantage of using adsorption is that it is a technique which is easy to implement and relatively cheap. To characterise the structure, size and morphology of adsorbent nanoparticles, Fourier-transform infrared spectroscopy, X-ray powder diffraction, scanning electron microscopy with energy dispersion X-ray spectroscopy, and Raman spectroscopy were applied. In batch adsorption experiments, the process parameters varied were: pH (2–12); contact time (5–60 min); adsorbent dosage (0.05–1 g); concentration (10–100 mg/L), and temperature (5–60°C). The kinetic study has shown that the experimental data are consistent with pseudo second order model with the regression coefficient of 0.99. The adsorption equilibrium is best describable by Langmuir isotherm model with adsorption capacity of 89.6 mg/g. The process thermodynamic was also studied to confirm the proposed mechanism of fluoride adsorption on the adsorbent. The isothermal multistage adsorption was investigated to understand the mechanism of calcium peroxide nanoparticle adsorption for fluoride removal. The maximum fluoride adsorption capacity calculated for CaO2 was 89 mg/g, with 90% defluoridation efficiency. The results suggested that calcium peroxide nanoparticles can be considered as a promising adsorbent for fluoride removal.

Biosorption of organic micropollutants onto lignocellulosic-based material.

The occurrence of organic micropollutants such as pharmaceutical drugs and hormones in the environment reflects the inefficiency of traditional wastewater treatment technologies. Biosorption is a promising alternative from a technical-economic point of view, so understanding the mechanisms of adsorption in new biosorbents is vital for application and process optimization. Within this context, this study aims to evaluate the mechanisms of adsorption and removal of synthetic and natural hormones by Pinus elliottii bark biosorbent (PS) compared to commercial granular activated carbon (GAC) through kinetic models, isotherm models, and thermodynamic models. The adsorbents were also characterized by morphology, chemical composition, functional groups, and point of zero charge. Characterization of the adsorbents highlights the heterogeneous and fibrous morphology and broader range of functional groups found for PS. Kinetic adjustments showed high accuracy for pseudo-second-order, Elovich, and intraparticle diffusion models, presenting multilinearity and evidencing multi-stage adsorption. The isotherms for PS followed high-affinity models, predominantly chemisorption, while those for GAC followed the Langmuir model, where physisorption predominates. These mechanisms were confirmed by thermodynamic models, which also indicated a higher dependence on temperature in the adsorption process. In the fortified water removal test, PS showed removal values higher than GAC, highlighting the advantages of this adsorbent.

Seawater Desalination Using MOF-Incorporated Cu-Based Alginate Beads without Energy Consumption.

The demand for fresh water is gradually and globally increasing due to the growth of population and water contamination. To meet this global demand, we fabricated metal-organic framework (MOF)-incorporated Cu-based alginate beads (Cu-MOF-Alg beads) for effective removal of water-dissolved salt ions from seawater. Alginic acid formed a matrix for preconfined Cu coordination. In this matrix, the MOFs were successfully in situ synthesized with organic ligands. The as-prepared Cu-MOF-Alg beads exhibited exceptional salt ion adsorption with the extraction of sedimented MOF particles. The adsorption characteristics of the fabricated Cu-MOF-Alg beads exhibited a linear isotherm according to the concentration of Na+ ions. In addition, the beads could be applied over a wide concentration range of target solutions and maintained their ion adsorption capacity after three repeated uses. The beads exhibited rapid adsorption kinetics, and their salt ion removal rate was approximately 94.3% through a multistage adsorption process. The MOF-treated seawater, which was desalinated to a low concentration of 1000 ppm, was filtered by a mangrove-inspired membrane, which yielded a total ion removal rate of 98.1%. Considering the low material cost compared to other adsorption-based desalination techniques and the absence of external energy supply, the proposed hybrid desalination system can produce purified water at an extremely low cost. Thus, this desalination technique could be economically and ecofriendly utilized for practical seawater desalination in a facile manner.

Solid Sorbents as a Retrofit Technology for CO2 Removal from Natural Gas Under High Pressure and Temperature Conditions

The capture of CO2 under high pressure and temperature is challenging and is required in a number for industrial applications including natural gas processing. In this work, we examine the use of benchmark hybrid ultraporous materials HUMs for their potential use in CO2 adsorption processes under high-pressure conditions, with three varying temperatures (283, 298 and 318 K). NbOFFOVE-1-Ni and SIFSIX-3-Ni were the selected HUMs given their established superior CO2 capacity under low pressure (0–1 bar). Both are microporous with highly ordered crystalline structures as compared to the mesoporous hexagonal silica (Santa Barbara Anhydrous-15 (SBA-15)). SBA-15 was previously tested for both low and high-pressure applications and can serve as a benchmark in this study. Sorbent characterization using XRD, SEM, FTIR and N2 adsorption were conducted to assure the purity and structure of the sorbents. TGA analysis were conducted to establish the thermal stability of the sorbents under various temperatures. High-pressure CO2 adsorption was conducted from 0–35 bar using magnetic suspension balance (Rubotherm). Although the SBA-15 had the highest surface (527 m3/g) are of the three adsorbents, the CO2 adsorption capacity (0.42 mmol/g) was an order of magnitude less than the studies HUMs with SIFSIX-3-Ni having 2.6 mmol/g, NbOFFIVE-1-Ni achieving 2.5 mmol/g at 298 K. Multistage adsorption isotherms were obtained at different pressures. In addition, results indicate that electrostatics in HUMs are most effective at improving isosteric heat of adsorption Qst and CO2 uptake. Higher temperatures had negative effect on adsorption capacity for the HUMs and SBA-15 at pressures between 7–9 bar. In SAB-15 the effect of temperature is reversed in what is known as a cross over phenomena.

Predicting The Composition Of Qurna Crude Oil Fraction By Ternary Composition Diagram

With a goal to identify, and ultimately removing from the oil fraction, the carcinogenic components, an oil fraction oil has been analyzed into a main three hydrocarbon groups, paraffins, aromatics, and polycyclic saturates. A multi-stage adsorption apparatus has been used. Four units of 300 g alumina each seems to be sufficient for removing the polynuclear aromatics from 75 g of an oil fraction boiling between 365-375 °C from Qurna crude oil. The usefulness of the ternary diagram for analyzing the oil fraction to the three hydrocarbons groups has been studied and verified. An experimentally based linear relationship of density and refractive index was established to enable of identifying the composition of an oil fraction using the values on refractive index alone. Separation of uncontaminated paraffins requires higher adsorbent/ oil ratio and/or more significant number of adsorption units. Ensuring no overloading of the adsorbent was essential for the separation.

Establishment of adsorption isotherms of m- and p-cresols in chromatographic process with aluminum terephthalate metal-organic framework as stationary phase

Close boiling points pose great challenges to the separation of the isomers m-cresol and p-cresol. Metal−organic frameworks (MOFs) material with uniform pore structure, high specific surface area and good chemical stability is a potential adsorbent. In this study, m-cresol and p-cresol were separated by a chromatographic process with aluminum terephthalate metal-organic framework (MIL-53(Al)) as stationary phase and acetonitrile as mobile phase. In view of the unique “breathing” effect of MOFs materials, according to the kinetic process and thermodynamic equilibrium of adsorption and desorption, the hybrid adsorption isotherm equations were established, which can reflect the “breathing” effect by combining the Langmuir adsorption process of narrow pore and the multi-stage adsorption process of large pore. The parameters of adsorption isotherm were determined by inverse method and genetic algorithm, and the adaptability of the equilibrium dispersive chromatography model based on this adsorption isotherm to the single-component adsorption process and two-component competitive adsorption process was proved under different injection concentration, injection time and flow velocity conditions. The separation process of m-cresol and p-cresol was optimized by the chromatographic model and genetic algorithm. Under the optimized conditions, the separated m-cresol and p-cresol were obtained with the purity values of 96.26% and 93.23%, and the recovery values of 96.93% and 96.59%, respectively.