International Journal of Molecular Sciences

Research

Jump to: Review

15 pages, 5583 KiB

Open AccessArticle

Molecular Simulation of SO₂ Separation and Storage Using a Cryptophane-Based Porous Liquid

by Pablo Collado, Manuel M. Piñeiro and Martín Pérez-Rodríguez

Int. J. Mol. Sci. 2024, 25(5), 2718; https://doi.org/10.3390/ijms25052718 - 27 Feb 2024

Viewed by 527

Abstract

A theoretical molecular simulation study of the encapsulation of gaseous SO₂ at different temperature conditions in a type II porous liquid is presented here. The system is composed of cage cryptophane-111 molecules that are dispersed in dichloromethane, and it is described using [...] Read more.

A theoretical molecular simulation study of the encapsulation of gaseous SO₂ at different temperature conditions in a type II porous liquid is presented here. The system is composed of cage cryptophane-111 molecules that are dispersed in dichloromethane, and it is described using an atomistic modelling of molecular dynamics. Gaseous SO₂ tended to almost fully occupy cryptophane-111 cavities throughout the simulation. Calculations were performed at 300 K and 283 K, and some insights into the different adsorption found in each case were obtained. Simulations with different system sizes were also studied. An experimental-like approach was also employed by inserting a SO₂ bubble in the simulation box. Finally, an evaluation of the radial distribution function of cryptophane-111 and gaseous SO₂ was also performed. From the results obtained, the feasibility of a renewable separation and storage method for SO₂ using porous liquids is mentioned. Full article

(This article belongs to the Special Issue Adsorption Materials and Adsorption Behavior 2.0)

► Show Figures

Figure 1

17 pages, 9890 KiB

Open AccessArticle

Thermodynamic Characteristics and Selectivity of the Liquid-Phase Adsorption of Aromatic Compounds on Hypercrosslinked Polystyrene Networks with Ultimate-High Crosslinking Densities by Data of Liquid Chromatography

by Bulat R. Saifutdinov and Aleksey K. Buryak

Int. J. Mol. Sci. 2024, 25(3), 1551; https://doi.org/10.3390/ijms25031551 - 26 Jan 2024

Viewed by 760

Abstract

This study delves into the thermodynamics of liquid-phase adsorption on hypercrosslinked polystyrene networks (HPSNs), widely recognized for their distinct structure and properties. Despite the considerable progress in HPSN synthesis and characterization, gaps persist regarding the chromatographic retention mechanism, thermodynamics of adsorption, and their [...] Read more.

This study delves into the thermodynamics of liquid-phase adsorption on hypercrosslinked polystyrene networks (HPSNs), widely recognized for their distinct structure and properties. Despite the considerable progress in HPSN synthesis and characterization, gaps persist regarding the chromatographic retention mechanism, thermodynamics of adsorption, and their impact on the adsorption selectivity, especially in the case of networks with ultra-high crosslinking densities (up to 500%). Utilizing high-performance liquid chromatography (HPLC), we have explored, for the first time, the thermodynamic intricacies of liquid-phase adsorption onto HPSNs crosslinked in the entire range of the crosslinking degree from 100 to 500%. Our findings reveal the dependences of thermodynamic characteristics and selectivity of adsorption on the crosslinking degree, textural features, and liquid-phase composition in the region of extremely low adsorbent surface coverages (Henry’s range). We have detected that, in the case of HPSNs, the dependence of the thermodynamic characteristics of adsorption on the liquid-phase composition is different than for classical HPLC stationary phases. Moreover, we scrutinize the impact of the molecular structure of the studied aromatic compounds on the thermodynamic characteristics and selectivity of the liquid-phase adsorption on HPSNs. Investigating liquid-phase adsorption selectivity, we demonstrate the pivotal role of π-π interactions in separating aromatic compounds on HPSNs. Eventually, we unveil that the thermodynamic characteristics of adsorption peculiarly depend on the crosslinking degree due to the profound impact of the crosslinking on the electronic density in benzene rings in HPSNs, whereas the separation throughput peaks for the polymer with a 500% crosslinking degree, attributed to its exceptionally rigid network structure, moderate swelling and micropore volume, and minimum specific surface area. Full article

(This article belongs to the Special Issue Adsorption Materials and Adsorption Behavior 2.0)

► Show Figures

Figure 1

22 pages, 8728 KiB

Open AccessArticle

Comprehensive Investigation of Cu²⁺ Adsorption from Wastewater Using Olive-Waste-Derived Adsorbents: Experimental and Molecular Insights

by Noureddine Elboughdiri, Hana Ferkous, Karima Rouibah, Abir Boublia, Amel Delimi, Krishna Kumar Yadav, Alessandro Erto, Djamel Ghernaout, Alsamani A. M. Salih, Mhamed Benaissa and Yacine Benguerba

Int. J. Mol. Sci. 2024, 25(2), 1028; https://doi.org/10.3390/ijms25021028 - 14 Jan 2024

Cited by 9 | Viewed by 1181

Abstract

This study investigates the efficacy of adsorbents from locally sourced olive waste—encompassing olive skins, leaves, and pits, recovered from the initial centrifugation of olives (OWP)—and a composite with sodium alginate (OWPSA) for the removal of Cu²⁺ ions from synthetic wastewater. Experimental analyses [...] Read more.

This study investigates the efficacy of adsorbents from locally sourced olive waste—encompassing olive skins, leaves, and pits, recovered from the initial centrifugation of olives (OWP)—and a composite with sodium alginate (OWPSA) for the removal of Cu²⁺ ions from synthetic wastewater. Experimental analyses conducted at room temperature, with an initial Cu²⁺ concentration of 50 mg/L and a solid/liquid ratio of 1 g/L, showed that the removal efficiencies were approximately 79.54% and 94.54% for OWP and OWPSA, respectively, highlighting the positive impact of alginate on adsorption capacity. Utilizing statistical physics isotherm models, particularly the single-layer model coupled to real gas (SLMRG), allowed us to robustly fit the experimental data, providing insights into the adsorption mechanisms. Thermodynamic parameters affirmed the spontaneity and endothermic nature of the processes. Adsorption kinetics were interpreted effectively using the pseudo-second-order (PSO) model. Molecular modeling investigations, including the conductor-like screening model for real solvents (COSMO-RS), density functional theory (DFT), and atom-in-molecule (AIM) analysis, unveiled intricate molecular interactions among the adsorbent components—cellulose, hemicellulose, lignin, and alginate—and the pollutant Cu²⁺, confirming their physically interactive nature. These findings emphasize the synergistic application of experimental and theoretical approaches, providing a comprehensive understanding of copper adsorption dynamics at the molecular level. This methodology holds promise for unraveling intricate processes across various adsorbent materials in wastewater treatment applications. Full article

(This article belongs to the Special Issue Adsorption Materials and Adsorption Behavior 2.0)

► Show Figures

Figure 1

15 pages, 7237 KiB

Open AccessArticle

Substitutional Coinage Metals as Promising Defects for Adsorption and Detection of Gases on MoS₂ Monolayers: A Computational Approach

by Josue Gutierrez-Rodriguez, Miguel Castro, Jose Manuel Nieto-Jalil, Dora Iliana Medina, Saul Montes de Oca, José Andrés García-González, Eduardo Rangel-Cortes and Alan Miralrio

Int. J. Mol. Sci. 2023, 24(12), 10284; https://doi.org/10.3390/ijms241210284 - 17 Jun 2023

Cited by 1 | Viewed by 1356

Abstract

Defective molybdenum disulfide (MoS₂) monolayers (MLs) modified with coinage metal atoms (Cu, Ag and Au) embedded in sulfur vacancies are studied at a dispersion-corrected density functional level. Atmospheric constituents (H₂, O₂ and N₂) and air pollutants [...] Read more.

Defective molybdenum disulfide (MoS₂) monolayers (MLs) modified with coinage metal atoms (Cu, Ag and Au) embedded in sulfur vacancies are studied at a dispersion-corrected density functional level. Atmospheric constituents (H₂, O₂ and N₂) and air pollutants (CO and NO), known as secondary greenhouse gases, are adsorbed on up to two atoms embedded into sulfur vacancies in MoS₂ MLs. The adsorption energies suggest that the NO (1.44 eV) and CO (1.24 eV) are chemisorbed more strongly than O₂ (1.07 eV) and N₂ (0.66 eV) on the ML with a cooper atom substituting for a sulfur atom. Therefore, the adsorption of N₂ and O₂ does not compete with NO or CO adsorption. Besides, NO adsorbed on embedded Cu creates a new level in the band gap. In addition, it was found that the CO molecule could directly react with the pre-adsorbed O₂ molecule on a Cu atom, forming the complex OOCO, via the Eley–Rideal reaction mechanism. The adsorption energies of CO, NO and O₂ on Au_2S2, Cu_2S2 and Ag_2S2 embedded into two sulfur vacancies were competitive. Charge transference occurs from the defective MoS₂ ML to the adsorbed molecules, oxidizing the later ones (NO, CO and O₂) since they act as acceptors. The total and projected density of states reveal that a MoS₂ ML modified with copper, gold and silver dimers could be used to design electronic or magnetic devices for sensing applications in the adsorption of NO, CO and O₂ molecules. Moreover, NO and O₂ molecules adsorbed on MoS₂-Au₂s₂ and MoS₂-Cu₂s₂ introduce a transition from metallic to half-metallic behavior for applications in spintronics. These modified monolayers are expected to exhibit chemiresistive behavior, meaning their electrical resistance changes in response to the presence of NO molecules. This property makes them suitable for detecting and measuring NO concentrations. Also, modified materials with half-metal behavior could be beneficial for spintronic devices, particularly those that require spin-polarized currents. Full article

(This article belongs to the Special Issue Adsorption Materials and Adsorption Behavior 2.0)

► Show Figures

Graphical abstract

35 pages, 10629 KiB

Open AccessArticle

Faujasite-Type Zeolite Obtained from Ecuadorian Clay as a Support of ZnTiO₃/TiO₂ NPs for Cyanide Removal in Aqueous Solutions

by Ximena Jaramillo-Fierro, Hipatia Alvarado, Fernando Montesdeoca and Eduardo Valarezo

Int. J. Mol. Sci. 2023, 24(11), 9281; https://doi.org/10.3390/ijms24119281 - 25 May 2023

Cited by 5 | Viewed by 1653

Abstract

In this study, zeolites prepared by the hydrothermal method from Ecuadorian clay were combined with the precursor clay and with the semiconductor ZnTiO₃/TiO₂ prepared by the sol-gel method to adsorb and photodegrade cyanide species from aqueous solutions. These compounds were [...] Read more.

In this study, zeolites prepared by the hydrothermal method from Ecuadorian clay were combined with the precursor clay and with the semiconductor ZnTiO₃/TiO₂ prepared by the sol-gel method to adsorb and photodegrade cyanide species from aqueous solutions. These compounds were characterized by X-ray powder diffraction, X-ray fluorescence, scanning electron microscopy, energy-dispersive X-rays, point of zero charge, and specific surface area. The adsorption characteristics of the compounds were measured using batch adsorption experiments as a function of pH, initial concentration, temperature, and contact time. The Langmuir isotherm model and the pseudo-second-order model fit the adsorption process better. The equilibrium state in the reaction systems at pH = 7 was reached around 130 and 60 min in the adsorption and photodegradation experiments, respectively. The maximum cyanide adsorption value (73.37 mg g⁻¹) was obtained with the ZC compound (zeolite + clay), and the maximum cyanide photodegradation capacity (90.7%) under UV light was obtained with the TC compound (ZnTiO₃/TiO₂ + clay). Finally, the reuse of the compounds in five consecutive treatment cycles was determined. The results reflect that the compounds synthesized and adapted to the extruded form could potentially be used for the removal of cyanide from wastewater. Full article

(This article belongs to the Special Issue Adsorption Materials and Adsorption Behavior 2.0)

► Show Figures

Figure 1

16 pages, 4465 KiB

Open AccessArticle

Characterization and Co-Adsorption Mechanism of Magnetic Clay-Biochar Composite for De-Risking Cd(II) and Methyl Orange Contaminated Water

by Fengxiao Zhao, Rui Shan, Shuang Li, Haoran Yuan and Yong Chen

Int. J. Mol. Sci. 2023, 24(6), 5755; https://doi.org/10.3390/ijms24065755 - 17 Mar 2023

Cited by 7 | Viewed by 1650

Abstract

The application of the adsorption method in sewage treatment has recently become a hot spot. A novel magnetic clay-biochar composite (BNT-MBC) was fabricated by co-pyrolysis of bentonite and biomass after being impregnated with Fe (NO₃)₃·9H₂O. Its adsorption [...] Read more.

The application of the adsorption method in sewage treatment has recently become a hot spot. A novel magnetic clay-biochar composite (BNT-MBC) was fabricated by co-pyrolysis of bentonite and biomass after being impregnated with Fe (NO₃)₃·9H₂O. Its adsorption capacity for Cd(II) and methyl orange was approximately doubled, reaching a maximum of 26.22 and 63.34 mg/g, and could be easily separated from the solution by using external magnets with its saturation magnetization of 9.71 emu/g. A series of characterizations including surface morphology and pore structure, elemental analysis, functional group analysis and graphitization were carried out, showing that the specific surface area was increased 50 times by loading 20 wt.% bentonite, while its graphitization and oxygen-containing functional groups were also enhanced. The isotherm fitting indicated that Cd(II) was adsorbed in multiple layers, while methyl orange was in both monolayer and multilayer adsorptions. The kinetic fitting indicated that chemisorption was the rate-limiting step of both, and it was also a complex process controlled by two steps with the fitting of intra-particle diffusion. In the binary system of Cd(II) and methyl orange, the co-existing pollutants facilitated the adsorption of the original one, and there was no competition between adsorption sites of Cd(II) and methyl orange. BNT-MBC also exhibited good reusability and can be magnetically recovered for recycling. Thus, the magnetic clay-biochar composite BNT-MBC is a cost-effective and promising adsorbent for simultaneous removing Cd(II) and methyl orange from wastewater. Full article

(This article belongs to the Special Issue Adsorption Materials and Adsorption Behavior 2.0)

► Show Figures

Figure 1

26 pages, 4471 KiB

Open AccessArticle

Comparative Study of the Effect of Doping ZnTiO₃ with Rare Earths (La and Ce) on the Adsorption and Photodegradation of Cyanide in Aqueous Systems

by Ximena Jaramillo-Fierro, Guisella Cuenca and John Ramón

Int. J. Mol. Sci. 2023, 24(4), 3780; https://doi.org/10.3390/ijms24043780 - 14 Feb 2023

Cited by 4 | Viewed by 1840

Abstract

Cyanide is a highly toxic compound that can pose serious health problems to both humans and aquatic organisms. Therefore, the present comparative study focuses on the removal of total cyanide from aqueous solutions by photocatalytic adsorption and degradation methods using ZnTiO₃ (ZTO), [...] Read more.

Cyanide is a highly toxic compound that can pose serious health problems to both humans and aquatic organisms. Therefore, the present comparative study focuses on the removal of total cyanide from aqueous solutions by photocatalytic adsorption and degradation methods using ZnTiO₃ (ZTO), La/ZnTiO₃ (La/ZTO), and Ce/ZnTiO₃ (Ce/ZTO). The nanoparticles were synthesized by the sol-gel method and characterized by X-ray powder diffractometry (XRD), Scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS), Diffuse reflectance spectroscopy (DRS), and Specific surface area (SSA). The adsorption equilibrium data were fitted to the Langmuir and Freundlich isotherm models. Adsorption kinetics were also evaluated using the pseudo-first-order and pseudo-second-order models and the intraparticle diffusion model. Likewise, the photodegradation of cyanide under simulated sunlight was investigated and the reusability of the synthesized nanoparticles for cyanide removal in aqueous systems was determined. The results demonstrated the effectiveness of doping with lanthanum (La) and cerium (Ce) to improve the adsorbent and photocatalytic properties of ZTO. In general, La/ZTO showed the maximum percentage of total cyanide removal (99.0%) followed by Ce/ZTO (97.0%) and ZTO (93.6%). Finally, based on the evidence of this study, a mechanism for the removal of total cyanide from aqueous solutions using the synthesized nanoparticles was proposed. Full article

(This article belongs to the Special Issue Adsorption Materials and Adsorption Behavior 2.0)

► Show Figures

Figure 1

Review

Jump to: Research

27 pages, 2244 KiB

Open AccessReview

Innovative Strategy for Truly Reversible Capture of Polluting Gases—Application to Carbon Dioxide

by Abdelkrim Azzouz and René Roy

Int. J. Mol. Sci. 2023, 24(22), 16463; https://doi.org/10.3390/ijms242216463 - 17 Nov 2023

Cited by 1 | Viewed by 934

Abstract

This paper consists of a deep analysis and data comparison of the main strategies undertaken for achieving truly reversible capture of carbon dioxide involving optimized gas uptakes while affording weakest retention strength. So far, most strategies failed because the estimated amount of CO [...] Read more.

This paper consists of a deep analysis and data comparison of the main strategies undertaken for achieving truly reversible capture of carbon dioxide involving optimized gas uptakes while affording weakest retention strength. So far, most strategies failed because the estimated amount of CO₂ produced by equivalent energy was higher than that captured. A more viable and sustainable approach in the present context of a persistent fossil fuel-dependent economy should be based on a judicious compromise between effective CO₂ capture with lowest energy for adsorbent regeneration. The most relevant example is that of so-called promising technologies based on amino adsorbents which unavoidably require thermal regeneration. In contrast, OH-functionalized adsorbents barely reach satisfactory CO₂ uptakes but act as breathing surfaces affording easy gas release even under ambient conditions or in CO₂-free atmospheres. Between these two opposite approaches, there should exist smart approaches to tailor CO₂ retention strength even at the expense of the gas uptake. Among these, incorporation of zero-valent metal and/or OH-enriched amines or amine-enriched polyol species are probably the most promising. The main findings provided by the literature are herein deeply and systematically analysed for highlighting the main criteria that allow for designing ideal CO₂ adsorbent properties. Full article

(This article belongs to the Special Issue Adsorption Materials and Adsorption Behavior 2.0)

► Show Figures

Scheme 1

Journal Menu

Journal Browser

Adsorption Materials and Adsorption Behavior 2.0

Share This Special Issue

Special Issue Editor

Special Issue Information

Keywords

Related Special Issue

Published Papers (8 papers)

Research

Review

Further Information

Guidelines

MDPI Initiatives

Follow MDPI