Adsorption最新文献

Understanding water adsorption/desorption process through nanowindows provides new insights into membrane applications, supercapacitors and elucidation of biological ion separation mechanism. This study evidenced a new stochastic desorption mechanism of water molecules adsorbed inside highly pure single-wall carbon nanotube (SWCNT) through nanowindows, which evidently differs from conventional water desorption mechanism from carbon micropores. This new mechanism was clarified by the comparative analysis of water adsorption/desorption behaviors on endcap-closed SWCNT having nanowindows and endcap-open SWCNT without nanowindows. The water desorption for both open SWCNT samples was deeply associated with unique adsorbed water structures consisting of an ice-like adlayer akin to the graphene wall of SWCNT and core liquid-like water. Nanowindows destabilize the ice-like adlayer, leading to stochastic desorption of water molecules, followed by single-step desorption of adsorbed water through nanowindows of endcap-closed SWCNT having nanowindows. In contrast, water molecules are desorbed from ice-like adlayer and core liquid-like water separately for the endcap-open SWCNT without nanowindows.

Heavy metal pollution poses a considerable environmental threat as toxic substances accumulate in ecosystems, causing prevailing ecological damage and generating risks to human health. We characterized physicochemically unmodified cellulose samples extracted from Ecuadorian biodiversity and used them as potential decontaminants of heavy metal ions in water. The isolated materials underwent characterization using Fourier Transform Infrared Spectroscopy-Attenuated Total Reflectance (FTIR-ATR), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and X-ray Photoelectron Spectroscopy (XPS). Initial testing of heavy metal adsorption involved 2.0 mmol/L and 10.0 mmol/L copper (Cu²⁺) solutions as models. The results demonstrated a removal percentage of Cu²⁺ ions by non-modified cellulose, reaching up to 88.75 ± 2.49% and 54.96 ± 2.51%, respectively using material F25. Additionally, natural (F25, F27, F28, and OP) and control (C1, C, and Af) celluloses were selected to study the removal of Cu²⁺, Cd²⁺, and Pb²⁺ ions from control isolated metal ion solutions ranging from 1 to 100 mg/L. The findings revealed that samples C, OP, and F25 effectively removed Cu²⁺, Cd²⁺, and Pb²⁺ ions when they were present isolated in solutions at concentrations as high as 30 mg/L. Furthermore, assays with mixed metal ion solutions exhibited promising removal of heavy metal ions using OP + F25. Overall, the results suggest that non-modified cellulose derived from biomass holds potential as a material for effectively removing toxic heavy metal ions from water.

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One promising approach to addressing global warming involves capturing storing and reusing greenhouse gas emissions. Following separation, usually via adsorption, potential CO₂ emissions capture rates can reach up to 90%. Hence, It is crucial to enhance efficiency and reduce costs associated with CO₂ capture and utilization processes. This study explores the synthesis of geopolymer/zeolite composites based on phosphate amine tailings for CO₂ capture applications. These materials offer benign environmental advantages and demonstrate reversible adsorption and desorption of carbon dioxide. The research compares the adsorption capacities of the synthesized materials with the geopolymer and the commercial Zeolite 13X, assessing their performance for the CO₂, H₂, and CO adsorption at various temperatures (30, 50, and 100 °C). Furthermore, the samples underwent thorough characterization by XRF, XRD, FTIR, SEM, EDS, XPS, NMR, micro-CT, density, BET surface area, and porosity. The high surface area and low porosity of the materials influence directly in the adsorption capacity, which increases with the addition of more zeolite on the composite. The incorporation of 30% (w/w) of zeolite to the composite yielded notable adsorption capacities at 30 ºC and 1 bar (~ 2.6 mmol·g^− 1).

The cashew nut shell is an agricultural residue generated in the production of cashew nuts. This residue is a hard-management biomass that can be efficiently transformed using pyrolysis, into a biochar. Conversely, potable water security requires the development of efficient adsorbents using novel and renewable materials. Then, in this work, a pyrolysis-derived carbon was chemically activated with KOH to remove phenol from an aqueous solution at 200 ppm that could represent health risk for life. The activated carbon was characterized rigorously, whereas adsorption kinetics and adsorption isotherms were evaluated to determine the suitability of this material to remove phenol. The activated carbon presented a chemical composition of 64.4 wt%; 33.2 wt%, and 1.98 wt% of carbon, oxygen, and hydrogen, respectively. Also, it presented a surface adsorption area of 863 m²/g, with a pore volume of 0.476 cm³/g. The surface chemistry presented -OH groups and the morphology revealed an organized material with the occurrence of porosity. The pseudo-second-order adequately described the kinetics of adsorption (80.93 mg/g and 0.0044 g/mg min, for equilibrium concentration (q_e), and adsorption rate constant (k_PSO), respectively). Additionally, the Toth isotherm model described reasonably the adsorption mechanism suggesting that a monolayer chemisorption that is independent of concentration of phenol took place for activated carbon. The efficiency of phenol uptake in the present work was about 79%, indicating that activated carbon derived from cashew nut shells has the potential for water remediation.

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High mercury levels from industrial and natural sources necessitate effective water mercury removal methods owing to human and ecosystem toxicity risks. This study addresses the adsorption of Hg ions onto mixed-valent magnetite nanoparticles (MNPs) owing to their high surface area, reactivity, and magnetic recovery ability. The adsorption capacity of MNPs is influenced by the morphological characteristics. The influence of the vegetable fiber surface charge in magnetite, along with the change in pH, on the Hg ion adsorption process by MNPs remains an open question. The adsorption capacities of the synthesized MNPs and Cabuya fibers (Agave Americana L. ASPARAGACEAE) impregnated with magnetite nanoparticles (FC-MNPs) were compared. The synthesis and impregnation of MNps were performed using the chemical coprecipitation method with ferrous and ferric chloride as precursor solutions. The composition, surface properties, and morphology of the synthesized adsorbents were investigated by scanning electron microscopy (SEM) coupled with an energy dispersive X-ray spectrometer (EDS), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and Raman spectroscopy (RS), which provided evidence that MNps reached an approximate diameter of 19 nm. Both adsorbents were used for the removal of Hg (II) at different initial pH values, times, temperatures, adsorbent dosages, and analyte concentrations. FC-MNPs and MNPs were able to achieve approximately 93% and 83% Hg (II) removal, respectively, under the following experimental conditions: the adsorbent dose 0.5 g, Hg (II) 10 mg/L, pH 5.0, stirring speed of 150 rpm, temperature of 25 °C, and equilibrium time of 4 h. Equilibrium data were evaluated by fitting the Langmuir and Freundlich isotherm models to the experimental conditions. Additionally, kinetic studies of pseudo-first and pseudo-second order were conducted to understand the mechanism of interaction between the adsorbent and the metal ions. The results show that FC-MNPs has a maximum adsorption capacity of Hg(II) of 4.95 mg/g of adsorbent, and that the reaction system follows pseudo-second order kinetics and the Freundlich isotherm model. Finally, the experimental results reported in this work show that cabuya fibers impregnated with MNPs have an important impact on the immobilization of aqueous contaminants. This offers a new method for developing novel nanocomposite adsorbents for the removal of metallic ions from wastewater.

Investigation of NaI adsorption on Porous Silica Nanoparticles (PSN-blank) and functionalized PSN (PSN-NH₂) was conducted to study the possibility of PSN radiolabeling using adsorption techniques. This research aims to study the radiolabeling of ¹³¹I compounds with porous material nanoparticles using the adsorption method. The study began with the adsorption study of NaI (non-radioactive) to understand the initial adsorption behavior on two types of nanoparticles: PSN-Blank and PSN-NH₂. Adsorption parameters such as temperature, time, pH, initial concentration of adsorbate, and functional groups were studied to predict the most influential parameters in the radiolabeling process. The adsorption kinetics were evaluated to determine whether they tended to be pseudo-first or pseudo-second order. The NaI adsorption isotherms on PSN-Blank and PSN-NH₂ at different temperatures were also tested using the Langmuir and Freundlich models. The investigation results showed that the adsorption of NaI on PSN-Blank and PSN-NH₂ was spontaneous, endothermic, tended to obey pseudo-second-order adsorption kinetics, and the adsorption isotherm of the Langmuir model. The activation energy of NaI adsorption on PSN-NH₂ was higher than that on PSN-Blank. After the adsorption characteristics of NaI by PSN and PSN-NH₂ were comprehended, actual radiolabeling experiments using the ¹³¹INaI adsorption were carried out. The radiolabeling results showed, the presence of amine groups increases the adsorption rate of PSN and makes the PSN bond with the labeled compound more stable. The presence of amine groups increases the radiochemical yield and stability of ¹³¹I-labeled PSN compounds.

The composite adsorbent derived from titanate nanotubes (TNTs), layered double hydroxides (LDHs) and oyster shell (OS) were used to removal cationic and anionic dyes. Scanning electron microscopy confirmed the successful integration of TNTs, LDHs, and OS, displaying distinct rod-like and hexagonal structures, as well as a rough surface. Energy dispersive spectroscopy identified essential elements such as calcium, sodium, oxygen, titanium, and aluminum, critical for the composite’s functionality. X-ray diffraction revealed characteristic peaks corresponding to anatase-phase titanium dioxide, LDHs, and calcium carbonate, validating TLO’s structural integrity. Fourier-transform infrared spectroscopy detected functional groups vital for adsorption, including OH-, Ti-O, and Ca-O bonds. BET surface area analysis (BET) showed a significantly larger surface area of 82.11 m²/g for TLO compared to its individual components, enhancing its adsorption capacity. Zeta potential analysis demonstrated a variable surface charge across a range of pH values, enabling TLO to effectively adsorb both cationic and anionic pollutants. Methylene blue, acid red 1, and congo red, in pH 3 to 9 solutions, showed high capacities, with maximum values of 1111 mg/g for methylene blue, 357 mg/g for acid red 1, and 192 mg/g for congo red. These results highlight TLO’s strong electrostatic attraction and ion exchange for cationic dyes, and surface precipitation for anionic dyes, particularly in neutral to alkaline environments. TLO is regarded as an effective material for advanced wastewater treatment.

In this work, efficient black carbon nanoparticles were prepared rubber under O₂ and Ar atmosphere for the removal of methylene blue (MB). The nanomaterials obtained were characterized using SEM, N₂ adsorption isotherms, XRD, EDS, TGA, DLS, RAMAN, FTIR, UV-Vis and cytotoxic test. Batch experiments were carried out to study the impact of the MB contact on adsorbates varying the contact time an MB initial concentration. The optimal fit was by pseudo-second-order model of the experimental data of the adsorption kinetics in both adsorbents. The BCNPO presents a greater rate of adsorption of 30 mg/L of MB at 9 min can be due to the greater surface area with respect to the 7.5 mg/L of MB on BCNPA. The isotherms adsorption of MB in adsorbents was fit at Langmuir and Freundlich models. The data demonstrated that physisorption mechanisms predominantly dictated both the rate and interaction adsorbate-adsorbent of the adsorption process. The results showed that both physisorption mechanisms controlled the adsorption rate and capacity. All the samples showed selectivity toward MB. The maximum efficiency of adsorption of MB was found to be 130 and 28 mg/g in BCNPO and BCNPA, respectively. The adsorbed amounts of MB on the BCNPO are greater than those on BCNPA; this result can be due to a larger surface area, pore diameter and the presence of the OH groups on the surface of the BCNPA sample rather than interaction with cationic of MB. Additionally, the viability of cells exposed toward BCNPO and BCNPA showed low toxicity that were important result for potential water remediation applications. The adsorption of MB dye on BCNPA and BCNPO is a spontaneous and exothermic process.

Surface area and porosity are the main factors that affect hydrogen storage at room temperature. However, there are several external factors such as pressure of gas, reaction time and the amount of sample used during the process that might affect the performance of the hybrid nanocomposites towards hydrogen storage. In this study, central composite design (CCD) for response surface methodology (RSM) was used in determining the optimum conditions namely mass of sample (A), pressure of hydrogen gas (B) and reaction time (C) towards the hydrogen storage at room temperature. Rice husk derived graphene-like material (GRHC) was added into zeolitic imidazolate frameworks-8 (ZIF-8) to form a hybrid nanocomposite of ZIF-8/GRHC (ZGK) via in-situ synthesis. Due to synergistic effect, the surface area of ZGK (1065.51 m²/g) shows a great enhancement as 0.04 g GRHC was introduced as compared to pristine ZIF-8 (687.32 m²/g). On the other hand, the thermal stability of ZGK improved significantly as it can withstand up to 1000 ºC as compared to pristine GRHC and ZIF-8 respectively. Due to superior physicochemical properties of ZGK, it was chosen to undergo optimization of hydrogen storage at room temperature. From the confirmatory test which was run for three times, the optimum hydrogen storage at room temperature in ZGK was 1.95 wt.% when 0.50 g of ZGK was used; 15 bar of hydrogen gas was applied and the reaction time was 60 min as per suggested from the CCD.

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Most hydrogels for dye treatment only have the adsorption ability for anionic or cationic dyes, while a few zwitterionic hydrogels that can adsorb both anionic and cationic dyes need a complicated regeneration process when they are reused. To prepare reusable zwitterionic adsorbent hydrogels, in this paper, a zwitterionic composite hydrogel with Ag@g-C₃N₄ was prepared, which not only can adsorb both anionic and cationic dyes but also has photocatalytic degradation ability. The scanning electron microscopy images show that the optimum hydrogel has a large number of micro pores for dye adsorption. The adsorption capacity of the hydrogel achieves the highest in mixed dye concentration of 50 mg·L^-1 with pH value of 7–9. Benefiting from the synergistic effect of adsorption and photocatalytic degradation, the removal efficiency of methyl orange and methylene blue in mixed dyes was up to 93.86% and 91.80%, respectively. The photocatalytic activity trapping experiments showed that superoxide radicals as well as hydroxyl radicals played a major role in photocatalytic degradation. After 5 consecutive photocatalytic degradations, the removal ratio of the hydrogel for dyes was still above 80%, indicating good photocatalytic degradation and reusability properties. This research suggested the zwitterionic composite hydrogel has a promising prospect in removing dyes from wastewater treatment.