Adsorption最新文献

Cadmium is a threat to human health and the environment. Therefore, there is a need for efficient and sustainable adsorbents to remediate cadmium-contaminated water. This study explores the effectiveness of Rhassoul clay/alginate composite beads in adsorbing cadmium from aqueous solutions, a simple, efficient, and cost-effective water treatment method. Various physicochemical factors influencing the adsorption capacity of the Rhassoul/alginate hybrid composite beads were examined, including adsorbent dosage (0.5–4.0 g/L suspension), contact time (30–360 min), pH (2–7), initial Cd²⁺ concentration (20–200 mg/L), and temperature (25–40 °C). The results revealed an adsorption capacity of 20 mg/g for non-modified Rhassoul clay, while the Rhassoul/alginate composite beads exhibited a significantly higher maximum adsorption capacity of 105 mg/g. Thermodynamic parameters (∆G°, ∆H°, and ∆S°) indicated the process was spontaneous and endothermic.

Graphical abstract

Paraben contamination in aquatic systems, primarily from personal care products, pharmaceuticals and industrial effluents, is an increasing environmental concern due to their widespread use as preservatives. The removal of parabens through conventional wastewater treatment processes is challenging and requires the development of innovative water treatment methods. In this study, graphene oxide nanoflakes were produced by Improved Hummers’ method and their adsorption characteristics were investigated for simultaneous removal of five parabens. Fourier transform infrared spectroscopy, Raman Spectroscopy, X-Ray Powder Diffraction, Scanning Electron Microscope and Transmission Electron Microscope were used and the nanoflakes were successfully characterized. A chromatographic method was developed for the simultaneous quantification of parabens. Process optimization for overall removal efficiency of parabens was achieved using Response Surface Methodology by a multiple response function. Nonlinear regression was used to fit the equilibrium data and the Freundlich model described the adsorption isotherm data accurately with R² values between 0.9807 and 0.9957. Factors such as mass of adsorbent, pH of solution and their interaction have the most significant impact on the adsorption process, while contact time shows low significance on the response. The adsorption behaviors of parabens were closely correlated with their hydrophobicity. Along with hydrophobic interactions, other mechanisms such as π–π stacking, hydrogen bonding and electrostatic forces, likely played significant role in the strong adsorption of parabens onto the GO surface. The reusability experiment showed that graphene oxide nanoflakes had a high potential present as a reusable adsorbent for the removal of parabens.

The increasing presence of pesticide contaminants in water bodies poses significant environmental and health challenges. This study introduces a novel enzyme-based photocatalytic technology composed of reduced graphene oxide (rGO), zinc oxide (ZnO), and chitosan (CS) designed to enhance the degradation efficiency of diazinon pesticides in polluted water. The nanozymes were characterized by XRD, SEM-EDX, and FTIR to ensure homogeneous structure and distribution of the materials, and the adsorbed pesticide content was measured using a UV-Vis spectrophotometer. Adsorption studies showed that the diazinon removal efficiency increased with higher pH, longer contact time, and initial concentration, reaching maximum adsorption efficiency at neutral pH. Isotherm analysis showed that diazinon adsorption on rGO/ZnO/CS nanozymes followed the Freundlich model, exhibiting heterogeneous adsorption characteristics with moderate adsorption capacity. These findings highlight the potential of rGO/ZnO/CS nanozymes as effective adsorbents for removing diazinon pesticides from contaminated water, offering promising applications in environmental remediation.

In the modern era, there is a pressing need to develop potential gas adsorbents to reduce the toxic gases produced by modern technology in the environment. In this project, we have investigated 2D graphene and double-doped (B, N) nanosheets for adsorption of N₂O₄ gas. We used density functional theory calculations to examine how N₂O₄ gas interacts with pure graphene, doubly boron, nitrogen, and boron-nitrogen-doped graphene sheets. We study the geometrical structure changes, cohesive energy, electronic property, and optical property to assess the stability of the sheets and complex structures, as well as their adsorption ability. Upon analyzing the adsorption energy, we observe an increase in adsorption energies for all the doped nanosheets undergoing N₂O₄ gas adsorption. The band structure analysis reveals a change in the band gap due to doping and gas adsorption, suggesting an interaction between the gas and the nanosheets. The optical properties analysis primarily reveals the highest values in the X-ray region; however, the analysis of the change in intensity peaks and shifting in the UV region for all structures confirms the interaction between the N₂O₄ gas and the adsorbent.

Mass transport in nanoporous materials is a key property that allows to improve the performance of many gas separation processes and design more efficient heterogeneous catalytic reactors. In many instances a combination of surface resistance and internal diffusion are present. The combined model for surface barrier and diffusion in a ZLC system is discussed in detail and the analytical solutions valid for the traditional and the partial loading experiments have been derived for the spherical and slab geometries. The model reduces to the limiting forms of pure diffusion when (frac{k{R}_{p}}{D}>100), and pure surface barrier when (frac{k{R}_{p}}{D}<1). This study has shown that most literature studies have analysed ZLC responses incorrectly based on an effective combined dimensionless parameter. Two methods are described to obtain the parameters from the long-time asymptotic behaviour of the response curves. Both approaches have been demonstrated on curves generated from the full model solution and experimental data on an etched sample of Y zeolite. Both the analysis of the model and of the experimental results confirm that to characterize combined surface barriers and diffusion one should perform at least experiments at two different flowrates where the system is kinetically controlled, and crucially a partial loading experiment with a time to the switch which should be at least an order of magnitude smaller than the smallest of the diffusion and surface barrier times.

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.

Graphical abstract

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.

Graphical abstract

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.