Physical Sorption Research Articles

Enhancing carbon dioxide adsorption in a hybrid fixed bed via structuring and thermal management: a numerical study

Systems based on physical sorption are an attractive solution for CO2 capture from flue gases, biogas upgrading or gas storage. Besides the sorbent choice, one of the most important factors related to the design of such systems is proper heat management. Commonly used sorbents typically have low thermal conductivity. Nevertheless, catalyst particles characterized by high conductivity are inherently present in adsorptive (hybrid) reactors. Thus, appropriate structuring of hybrid beds can be used for controlling temperature profiles and improving the bed performance. In this study, the behaviour of a nonadiabatic adsorptive reactor described by a two-dimensional model was analysed for the adsorption step. The effect on the CO2 adsorption performance of different spatial distributions of functionalities in the bed was investigated. The optimality problem for nonuniform radial distribution of sorbent and catalyst in the bed was solved, indicating that such a configuration is a potentially important direction for structuring hybrid beds. Results demonstrate that the optimal configuration of radially distributed functionalities significantly increases the amount of CO2 absorbed under identical boundary and initial conditions for the bed. It appears that precise control of the heat generated and removed from the bed is achievable. Such control could be advantageous for the regeneration phase.

Engineering of the High‐Power Laser‐Induced Synthesis of Ni‐Based Metal‐Organic Framework: Investigation of its Optical Properties, Computational Methodology, Electrocatalytic Performances, and Glucose‐Sensing Ability

AbstractMetal‐organic frameworks (MOFs) are porous materials with numerous chemical and structural possibilities. Due to their ease of modification, well‐organized structure, and diverse guest molecule chemistry, MOFs are ideal platforms for uncovering improved functional material design characteristics. Quantitative analysis of glucose is crucial, especially in some food products, for quality control as well as evaluation of the glucose levels helps diagnose and treat diabetes. Recent glucose sensing devices have relied heavily on MOFs and other nanomaterials to enable user‐friendly and safe non‐invasive sensing methods. Nevertheless, the conventional synthesis methods involve multi‐day reactions, cooling, and depressurization processes. This study demonstrates the unprecedented high‐power laser‐induced rapid synthesis (LIRS) of Ni‐based MOF nanospheres with interconnected nano‐rods and noncentrosymmetric primitive triclinic crystalline structure, highlighting their multifunctional usage in sensing and gas sorption applications. Ab initio simulations show excellent agreement with the experimental physical and gas sorption properties. Furthermore, the Ni‐MOF‐based biosensor accurately measures glucose real‐life beverage samples, yielding promising glucose detection biosensor results with a low limit of the detection (LOD) of 13.96 µM and high sensitivity of 120.606 µA mM−1 cm−2.

Effect of carbonaceous materials on phosphorus removal in flow-through packed column systems.

Phosphorus (P) overloading in aquatic environments has long-been recognized as the leading cause of water quality deterioration, harmful algal bloom, and eutrophication. This study investigated P removal performance by five cost-effective carbonaceous materials (CMs) in flow-through packed column systems. These CMs include biochars pyrolyzed from feedstocks of Eucalyptus (E-biochar) and Douglas fir (D-biochar), commercial biochar (C-biochar), iron oxide-coated biochar (Fe-biochar), and commercial activated carbon (AC). The physicochemical properties of CMs, such as specific surface area (SSA), pore volume, pore diameter, elemental composition, and surface charge, were characterized. The packed column experimental results showed that P removal performance followed the order: E-biochar < D-biochar < C-biochar < Fe-biochar < AC. Specifically, the sorption capacity of 1mg/L of P in packed columns was 0.0036mg P/g E-biochar, 0.0111mg P/g D-biochar, 0.0369mg P/g D-biochar, 0.077mg P/g Fe-biochar, and 0.088mg P/g AC, respectively. The largest SSA (1012 m2/g) and pore volume (0.57 cm3/g) of AC accounted for the most outstanding P removal efficiency mainly by physical sorption, while electrostatic interaction explained the high P removal by Fe-biochar (SSA as low as 32.4 m2/g). Our findings provide direct practical implications for effectively removing P in water by cost-effective CMs.

Preparation and Characterization of Pyramids/Particles NiO/SnO2 Composite for Sorption and Separation of Molybdenum and Zirconium Ions from Some Synthetic Fission Products

AbstractPyramids/particles of NiO/SnO2 composite (NS7) was produced by applying the sol–gel autocombustion method. The produced composite was investigated using different techniques, X-ray diffraction, Fourier-transform infrared, Raman spectroscopy, scanning electron microscope, dynamic light scattering, ultraviolet–visible absorbance spectroscopy, and BET surface area then was applied for the adsorption and separation of molybdenum and zirconium ions from lanthanum, strontium, and cesium. 3D pyramids of NiO and particles of SnO2 are confirmed in the composite with a homogeneous mesoporous structure. The composite has good affinity for zirconium and molybdenum ions with fast kinetics and Qmax of 27.1 and 33.3 mg/g, respectively, low affinity for lanthanum, and negligible affinity for strontium and cesium. The sorption mechanism is physical sorption and endothermic in nature. The adsorbed Zr(IV), Mo(VI), and La(III) ions were separated using the desorption process as the following sequence: First, 95 ± 2% (14.3 ppm) of the loaded La was desorbed by washing with double distilled water. Then 96 ± 2% (41.3 ppm) of the loaded Zr was recovered by 1 M potassium chloride without interfering ions. Finally, 98 ± 2% (42.88 ppm) of Mo is desorbed by 1 M sodium acetate solution. The NS7 composite can be reused five times successfully.

Zinc Oxide/Moringa Oleifera Gum-Grafted L-Methionine-Functionalized Polyaniline Bionanocomposites for Water Purification

This study evaluates the preparation of novel ternary functional adsorbents based on polyaniline, zinc oxide nanoparticles, and moringa oleifera gum to produce zinc oxide/Moringa oleifera gum-grafted L-methionine-functionalized polyaniline bionanocomposites (ZM-g-Pani) and employed to sequestrate divalent metal ions (Cd2+, Hg2+ and Pb2+) from wastewater samples. The morphological and structural properties of ZM-g-Pani were exploited using FT-IR, FE-SEM/EDS, TEM, and XRD. FT-IR and FE-SEM studies show that the as prepared nanocomposite has an abundant number of reactive groups and a porous structure, thus demonstrating outstanding divalent metal cation removal. FT-IR study confirms that the attachment of L-methionine to polyaniline is facilitated by the C-S linkage. Both TEM and FE-SEM techniques confirmed the clustered granules of ZnO over the surface of polyaniline, which ultimately provided more surface area to adsorb metal ions. The study demonstrated that Cd2+, Hg2+ and Pb2+ ions could undergo physical sorption and chemisorption simultaneously during the adsorption process. The maximum adsorption capacity was 840.33, 497.51, and 497.51 mg/g for Cd2+, Hg2+, and Pb2+, respectively. The impact of co-existing ions, including NO3−, PO43−, SO42−, Cl−, Na+, Cu2+, and Al3+, showed that there were no notable alterations in the adsorption of the selected metal ions with ZM-g-Pani. ZM-g-Pani showed eight successive regeneration cycles for Cd2+, Hg2+, and Pb2+ with more than 85% removal efficiency.

Sorption interactions and behavior of bentonite-lignite based composite toward immobilization of dyes, pharmaceuticals and surfactants

The presence of dyes, pharmaceuticals, and surfactants in the environment results from extensive industrial and societal progress, prompting the need to explore efficient and safe techniques for their removal. Common concentrations in wastewater can range from micrograms to milligrams per liter, which is concerning due to their persistence and potential health impacts. The sustainable approach of using a nonconventional, eco-friendly mineral-organic composite might address this environmental issue. This study focuses on utilizing a composite of bentonite (BEN) and lignite (LIG) as a sorbent for dyes: Rhodamine b (RB), Remazol brilliant blue r (RBBR), pharmaceuticals: ibuprofen (IB), sulfamethoxazole (STX), and surfactant: sodium dodecylbenzenesulfonate (SDBS) from both synthetic solutions and real wastewater. BEN was chosen for its high cation exchange capacity, while LIG was selected for its ability to adsorb both anionic and cationic formsdiverse functional groups. The composite with BEN to LIG ratio of 20:80 (BL 20:80) demonstrated superior sorption capacity. The adsorption performance is quantified, showing removal efficiencies of up to 18.9 mg RBBR/g, 22.8 mg RB/g, 1.77 mg IB/g, 1.47 mg STX/g, and 4.7 mg SDBS/g. Sorption efficiency is influenced by factors such as the initial sorbate concentration, the pH of the solution, the form of sorbates, and the adsorbents textural, physicochemical (point of zero charge pHZPC), ion-exchange capacity, hydrophobicity/hydrophilicity) properties. Generally, STX and RB is favored by slightly acidic conditions (pH 4–7), while RBBR and IB are favored by alkaline conditions (pH > 7). The complex physical sorption mechanism includes hydrogen bonding, electrostatic and dispersion forces, as well as π-π interactions. Nuclear magnetic resonance spectroscopy (NMR) suggests that a significant portion of the hydrogen bonding interactions contributes to RB adsorption. The sorption results indicate that the specially-designed mineral composite can effectively remove various chemically distinct organic compounds from real wastewater. Subsequent investigations will focus on the granulated BL 20:80 composite and its applicability in dynamic column systems. This aligns with the ongoing development of purification technologies.

Thermodynamic functions and parameters of sorption from flue gases (CO2,SOx,NOx) by Khekordzula clinoptilolite

Generation during the production process and emissions into the atmosphere with flue gases (CO2,SOx,NOx) cause the “greenhouse effect” and the problem of global warming. Despite the existing practice of using zeolite as an adsorbent for a number of gases in projects such as Carbon Capture, Utilization and Storage to prevent climate change, the thermodynamic functions and parameters of the zeolite tuff containing the mineral Khekordzula clinophtholite in the inner Kartli region of Georgia are unknown and have not been studied. According to the research data, the corresponding thermodynamic parameters were determined, namely the enthalpy of formation of the mineral clinophthylolite in the Khekordzula zeolite tuff ΔfH2980=−39,825.838kj·mol−1, Gibbs energy ΔfG2980=−36,734.784kj·mol−1, entropy S2980=−10.373j·K·mol−1; Dehydration and as well as physical sorption (CO2, SOx, NOx) start parameters: temperature T=352.90K, pressure P=6.84mmHg. The thermodynamic parameters of the Khekordzula natural clinoptilolite tuff, taking into account its basic mineralogical composition, were determined: ΔfH2980=−30,403.76kj·mol−1; ΔfG2980=−29,963.01kj·mol−1; S2980=−1.48j·K·mol−1; T=374.22K, P=0.0003mmHg. It has been confirmed that chemisorption (CO2, SOx, NOx) by Khekordzula clinophthylolite should begin at temperatures above 2000 K. The results of the conducted studies make it possible to evaluate the prospects of using Khekordzula and natural zeolites of similar composition as an adsorbent for harmful industrial gases, which will help plan and implement effective solutions to environmental problems.

Preparation of micron-sized benzamidine-modified magnetic agarose beads for trypsin purification from fish viscera

The effective method for trypsin purification should be established because trypsin has important economic value. In this work, a novel and simple strategy was proposed for fabricating micron-sized magnetic Fe3O4@agarose-benzamidine beads (MABB) with benzamidine as a ligand, which can efficiently and selectively capture trypsin. The micro-sized MABB, with clear spherical core-shell structure and average particle size of 6.6 μm, showed excellent suspension ability and magnetic responsiveness in aqueous solution. The adsorption capacity and selectivity of MABB towards target trypsin were significantly better than those of non-target lysozyme. According to the Langmuir equation, the maximum adsorption capacity of MABB for trypsin was 1946 mg g−1 at 25 °C, and the adsorption should be a physical sorption process. Furthermore, the initial adsorption rate and half equilibrium time of MABB toward trypsin were 787.4 mg g−1 min−1 and 0.71 min, respectively. To prove the practicability, MABB-based magnetic solid-phase extraction (MSPE) was proposed, and the related parameters were optimized in detail to improve the purification efficiency. With Tris-HCl buffer (50 mM, 10 mM CaCl2, pH 8.0) as extraction buffer, Tris-HCl buffer (50 mM, 100 mM CaCl2, pH 8.0) as rinsing buffer, acidic eluent (0.01 M HCl, 0.5 M NaCl, pH 2.0) as eluent buffer and alkaline buffer (1 M Tris-HCl buffer, pH 10.0) as neutralization solution, the MABB-based MSPE was successfully used for trypsin purification from the viscera of grass carp (Ctenopharyngodon idella). The molecular weight of purified trypsin was determined as approximate 23 kDa through sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The purified trypsin was highly active from 30 °C to 60 °C, with an optimum temperature of 50 °C, and was tolerant to pH variation, exhibiting 85 % of maximum enzyme activity from pH 7.0 to 10.0. The results demonstrated that the proposed MABB-based MSPE could effectively purify trypsin and ensure the biological activity of purified trypsin. Therefore, we believe that the novel MABB could be applicable for efficient purification of trypsin from complex biological systems.

Using Zeolite Materials to Remove Pharmaceuticals from Water.

Pharmaceutical drugs, including antibiotics and hormonal agents, pose a significant threat to environmental and public health due to their persistent presence in aquatic environments. Colistin (KOL), fluoxetine (FLUO), amoxicillin (AMO), and 17-alpha-ethinylestradiol (EST) are pharmaceuticals (PhCs) that frequently exceed regulatory limits in water and wastewater. Current removal methods are mainly ineffective, necessitating the development of more efficient techniques. This study investigates the use of synthetic zeolite (NaP1_FA) and zeolite-carbon composites (NaP1_C), both derived from fly ash (FA), for the removal of KOL, FLUO, AMO, and EST from aquatic environments. Batch adsorption experiments assessed the effects of contact time, adsorbent dosage, initial concentration, and pH on the removal efficiency of the pharmaceuticals. The results demonstrated that NaP1_FA and NaP1_C exhibited high removal efficiencies for all tested pharmaceuticals, achieving over 90% removal within 2 min of contact time. The Behnajady-Modirshahla-Ghanbary (BMG) kinetic model best described the adsorption processes. The most effective sorption was observed with a sorbent dose of 1-2 g L-1. Regarding removal efficiency, the substances ranked in this order: EST was the highest, followed by AMO, KOL, and FLUO. Sorption efficiency was influenced by the initial pH of the solutions, with optimal performance observed at pH 2-2.5 for KOL and FLUO. The zeolite-carbon composite NaP1_C, due to its hydrophobic nature, showed superior sorption efficiency for hydrophobic pharmaceuticals like FLUO and EST. The spectral analysis reveals that the primary mechanism for immobilizing the tested PhCs on zeolite sorbents is mainly due to physical sorption. This study underscores the potential of utilizing inexpensive, fly ash-derived zeolites and zeolite-carbon composites to remove pharmaceuticals from water effectively. These findings contribute to developing advanced materials for decentralized wastewater treatment systems, directly addressing pollution sources in various facilities.

Mesoporous architectural magnetic halloysite-polymer beads for removing toxic streptomycin from water: A sustainable remediation approach

Streptomycin (STR) is a widely used antibiotic to treat various infectious diseases in humans and animals. Increased STR production and distribution result in harmful residue in soil and water. Consequently, STR exists in biotic- and abiotic-counterpart of the environment and poses potential toxicity and risk due to its bioaccumulation and biomagnification properties. Sustainable remediation of STR from wastewater requires selective, minimal, low-cost, regenerable, and reusable materials as adsorbents. In this study, magnetic-halloysite incorporated polymer composite beads (SPHM) were synthesized and used for the efficient clean-up of toxic STR from wastewater. SPHM has a mesoporous structure with an abundance of oxygen-containing functional groups and exhibits a synergistic STR clean up performance (qm = 235.71 ± 13.98 mg/g). Sorption and interfacial studies revealed that diffusion, hydrophobic and ionic interactions, including electrostatic interaction, are involved in STR remediation. Electrostatic interaction plays a vital role alongside the physical sorption mechanism due to the presence of hydroxyl and carboxyl groups induced from poly (vinyl alcohol) and sodium alginate. Moreover, X-ray photoelectron spectroscopy (XPS) and Time-of-flight secondary ion mass spectrometry (ToF-SIMS) analyses confirm the involvement of opposing charged groups of SPHM and STR in adsorption. SPHM can be magnetically separated in just 20 s and is regenerable and reusable up to 10 times, with outstanding performance and stability. The sorption process requires only a minimal amount of SPHM, i.e., 0.5 g/L for STR clean-up. Even the natural surface water composition did not affect its performance. Hence, natural nanoclay-based, biocompatible and low-cost SPHM has a great potential for the sustainable remediation of streptomycin and other similar antibiotics from wastewater.

Changes in Physical and Water Sorption Characteristics of Three Solid Woods after One-Sided Surface Charring.

One-sided surface charring of wood is a modification process used to lower moisture absorption and improve the resistance to biological degradation for durable surface exterior claddings. Cupressus lusitanica, Gmelina arborea, and Tectona grandis wood samples from fast-growth plantation were charred with a hot plate using three temperatures (300, 350, and 400 °C ± 3 °C) for 10 min. Wood density, surface quality (color and presence of splits), and sorption characteristics (wetting rate and water uptake) were evaluated. Results show that samples charred at 300 °C presented a lower loss of density and thickness than samples charred at 400 °C. Changes in the chemical structure of the wood as a result of the high temperatures caused a decrease of all color parameters (L*, a*, and b*). These values decreased in the samples charred at 400 °C for the three species. Also, the presence of cracks and splits on the surface, or in some cases the presence of detachments from the charring surface, was mostly observed in the samples charred at 350 and 400 °C. One-sided surface charring reduced the liquid water sorption of wood samples in comparison with that of reference samples, especially for C. lusitanica and T. grandis. G. arborea, due to the composition of its anatomical structure and its initial density, chars faster than the other species, causing a greater loss of density, wetting rate values like those of the reference wood, and higher values of water uptake.

Hydrated carboxylate ionic liquids as chemical CO2 sorbents of high capacity and moderate enthalpy of absorption

Tetralkylphosphonium carboxylate ionic liquids are herein presented as efficient carbon dioxide chemisorbents in the presence of water. The ionic liquids tetrabutylphosphonium formate and acetate, tributylmethylphosphonium formate and a series of triethylalkylphosphonium formates and acetates, have been prepared by various synthetic procedures either from hydroxide or methylcarbonate precursors, or via multiple steps starting from the parent triethylphosphine. Their physicochemical properties, namely melting or glass transition temperatures, thermal decomposition behaviour, densities and viscosities have been determined. As dry substances, they are viscous liquids or low-melting solids, whereas they show little tendency to solidify in their hydrated forms. They were used mostly as monohydrates in CO2 solubility measurements, exhibiting highest capacities (3 mol L−1, i.e. ≈ 0.9 molCO2 molIL−1, at 5 bar, 25 °C) at equimolar H2O/ionic liquid ratios, approaching those of commercial aqueous amine sorbents. Carbon dioxide chemisorption into hydrogencarbonate takes place, as demonstrated by infrared spectroscopy with isotopic labelling. CO2 absorption isotherms were recorded at various temperatures and the data used to estimate the heat of absorption according to three different thermodynamic models. Enthalpies of CO2 absorption depended heavily on the model used. Rationalisation of this was done on the grounds of the expected relevance of physical and chemical sorption processes. Average heats of CO2 absorption lie between −40 and −45 kJ mol−1, in accordance with mild chemical absorption albeit significantly lower than those for typical chemical sorbents such as amines. This reinforces the feasibility of hydrated carboxylate ionic liquids for CO2 capture technologies of low regeneration energies.

Interaction between radio-oxidized polypropylene and gaseous HCl. Part 2. Kinetics and reaction mechanisms

In Part 1 of this article, evidence of cross-infection effects of polyolefins and halogenated polymers present in the long-lived intermediate-level waste (LL-ILW) packages was shown. We choose to study the interaction between polypropylene and one of the main degradation products of PVC, i.e. HCl. Polyolefins and chlorinated polymers were chosen because they are the two most abundant classes of polymer types found in the LL-ILW packages. We showed that the interaction between HCl and pristine or radio-oxidized PP results in HCl consumption and in CO2, H2O and CO formation. The object of the present article is to further study the reaction mechanisms. Using derivative methods at room temperature, the reaction of HCl with hydroperoxide was documented while alcohols seem stable. A model taking into account HCl diffusion, sorption in PP and reaction with hydroperoxide is insufficient to explain the observed HCl consumption kinetics. We concluded that HCl consumption is not only due to physical sorption and to chemical reaction with a unique oxidized compound, but multiple reactions with different oxidation products should be considered as well.

Cellulose acetate/chitosan composite film loaded with ground cinnamon for active packaging: water vapor sorption kinetic, compounds release, and antimicrobial effect

This study evaluated structural, physical, and water sorption properties of cellulose acetate/chitosan composite film incorporated with ground cinnamon as an antimicrobial. The controlled release of antimicrobial compounds and antimicrobial effects on Escherichia coli and Staphylococcus aureus were also monitored. The composite film formed highly porous and fibrous materials with higher thermal resistance. A higher ratio of chitosan in the film improved the swelling degree and water-vapor absorption capacity but reduced adsorption rates. Consequently, antimicrobial compounds, including eucalyptol, naphthalene, and β-caryophyllene, were more quickly released from the composite film with a larger chitosan ratio, affecting stronger antimicrobial effects. The inclusion of ground cinnamon with residual fat content in the film contributed to an extended inhibition of microbial growth in an indirect packaging system. Understanding the chitosan/cellulose acetate ratio in the film composite formation and the incorporation of ground cinnamon is important to control the compounds' release and generate long-term antimicrobial effects of active packaging materials on fresh food products.

Activation of Zeolite in a Magnetic Fluidized Bed

The influence of the phase composition of zeolite rocks and their modification under the influence of an electromagnetic field in an environment of ferromagnetic particles on the physical properties and sorption of heavy metals has been studied. The results of water purification from heavy metals using activated zeolite in a magnetic fluidized bed are presented.

Impact of pyrolysis process conditions on the structure of biochar obtained from apple waste

Biochar is an eco-friendly carbon material whose properties allow it to be used as a sorbent for wastewater treatment or soil remediation. The paper presents the results of research related to the pyrolysis process of apple waste after supercritical CO2 extraction with the simultaneous use of physical activation. The research assessed the influence of the temperature of the pyrolysis process and steam activation on the structural properties of the obtained biochar, i.e. specific surface, porous structure, and presence of functional groups. The results obtained confirmed that lower temperature pyrolysis produces biochar characterised by the presence of functional groups and ordered structure. On the other hand, high temperature pyrolysis with simultaneous steam activation determines microporosity and high values of the specific surface area. Taking into consideration pollutant sorption mechanisms (physical and chemical sorption), the obtained biochar materials can be used as sorbents in water and wastewater treatment.

Statement of Retraction: Synthesis of Nanocrystalline Polycalix[4]amides Containing Mesogenic Triazole Units and Investigations of Their Thermo Physical Properties and Heavy Metal Sorption Behavior

Statement of Retraction: Synthesis of Nanocrystalline Polycalix[4]amides Containing Mesogenic Triazole Units and Investigations of Their Thermo Physical Properties and Heavy Metal Sorption Behavior

Enhancing interfacial synergies for the preparation of high mechanical strength and interconnected porosity of alumina extrudates through pre-wetting method

The forming of catalyst supports is a crucial step in the application of industrial catalysts. Alumina, a widely employed catalyst support, is often shaped using nitric acid as a peptizer to enhance mechanical strength. However, the use of large amounts of nitric acid typically results in a decrease in specific surface area and damage to the pore structure due to chemical corrosion. In this work, we present a more practical approach that is pre-filling the open pores of pseudo-boehmite powder with water instead of directly filling them with nitric acid solution. The binder with a small quantity of nitric acid plays a synergistic role in functioning as a glue on the particle surfaces. And through this method, high-strength (231 N cm−1) alumina support can be prepared more efficiently through extrusion. Besides, the pore structure of the extrudates was characterized by multi-scale methods, including nitrogen physical sorption and XRM (X-ray microscopy), which revealed abundant interconnected hierarchical pores deriving from the pre-wetting shaping process. This proposed approach enables the attainment of high mechanical strength and interconnected porosity for alumina extrudates with less use of acid, which holds a significant practical application value.

Preparation of Ni(II)Fe(III)-layered double oxide and its application for the removal of methyl orange dye: Adsorption isotherm and thermodynamic study

The Ni(II)Fe(III)-LDO has been synthesized by calcination of Ni(II)Fe(III)-LDH at 500 ℃. The prepared LDO is applied in the treatment of Methyl Orange (MO) dye from a synthetic solution. A batch of experiments is conducted to examine the effects of varying adsorption parameters, i.e. initial dye concentrations and temperature. The results indicate that the adsorption of MO increases with rising dye concentration and solution temperature. Temkin, Freundlich, and Langmuir isotherms are analyzed to investigate the adsorption process at different pH levels. Various thermodynamic parameters such as ΔS, ΔH and ΔGº have also been calculated. The adsorption of MO dyes on the Ni(II)Fe(III)-LDO is found endothermic and non-spontaneous in nature. The findings reveal the adsorption process is physical sorption.

Highly efficient capture of iodine vapor by [Mo3S13]2− intercalated layered double hydroxides

From the swollen LDH, bulky [Mo3S13]2− anions are facilely introduced into the LDH interlayers to assemble the Mo3S13-LDH composite, which exhibits excellent iodine capture performance and good irradiation resistance. The positive-charged LDH layers may disperse the [Mo3S13]2− uniformly within the interlayers, providing abundant adsorption sites for effectively trapping iodine. The Mo-S bond serving as a soft Lewis base has strong affinity to I2 with soft Lewis acidic characteristic, which is conducive to improvement of iodine capture via physical sorption. Besides, chemisorption has a significant contribution to the iodine adsorption. The S22−/S2− in [Mo3S13]2− can reduce the I2 to [I3]− ions, which are facilely fixed within the LDH gallery in virtue of electrostatic attraction. Meanwhile, the S22−/S2− themselves are oxidized to S8 and SO42−, while Mo4+ is oxidized (by O2 in air) to Mo6+, which combines with SO42− forming amorphous Mo(SO4)3. With the collective interactions of chemical and physical adsorption, the Mo3S13-LDH demonstrates an extremely large iodine adsorption capacity of 1580 mg/g. Under γ radiation, the structure of Mo3S13-LDH well maintains and iodine adsorption capability does not deteriorate, indicating the good irradiation resistance. This work provides an important reference to tailor cost-effective sorbents for trapping iodine from radioactive nuclear wastes.