Adsorption Behavior Research Articles

Evaluation of the efficiency of shell powder as a natural adsorbent for the adsorption of chromium in aqueous solutions: kinetic and thermodynamic approach and modeling of adsorption isotherms

Water pollution by heavy metals such as chromium is a major environmental issue requiring effective remediation solutions. In this study, shellfish powder was used as a natural material to adsorb chromium (III) from aqueous solutions. The results show that shellfish have a significant adsorption capacity, indicating their effectiveness under a variety of conditions. Adsorption kinetics tests showed that the adsorption mechanism followed a pseudo-second-order kinetic model. In addition, thermodynamic parameters show that the adsorption process is a beneficial, spontaneous and endothermic phenomenon. Isotherm models such as Langmuir, Freundlich and Temkin were applied to analyze adsorption behavior. This research could contribute to the development of more sustainable wastewater treatment methods, incorporating natural materials into remediation strategies.

Flaxseed gum nano-microcapsules loaded with secoisolariciresinol diglucoside: Preparation and characterization.

Flaxseed gum (FSG) has promising applications in the field of nano/microencapsulation for its biocompatibility and excellent physicochemical properties. In this study, FSG-based nano-microcapsules (FSG NPs) were prepared using high-speed shear homogenization combined with ultrasound for efficient encapsulation of secoisolariciresinol diglucoside (SDG). The particle size of FSG stands for nano-microcapsules (NP) was determined to be 336.96nm, with a polydispersity index of 0.261. Adsorption kinetics, isotherms, antioxidant activity, surface morphology, rheological properties, and thermal stability were analyzed for FSG NP loaded with SDG. The results of adsorption kinetics analysis indicated that a pseudo-second-order kinetic model could effectively predict the adsorption behavior, with a predicted adsorption capacity of 9.140mgg-1. The Freundlich isotherm fit well with the isothermal model, indicating a non-uniform adsorption process of SDG. According to morphometric analysis, the surface of the nano-microcapsules was smooth without obvious breakage. SDG-loaded FSG NP exhibited low viscosity, high antioxidant activity, and good thermal stability. In vitro release results showed that FSG-SDG NP has a lower release rate in gastric fluid compared to intestinal fluid, which helps to achieve targeted release of SDG in the intestine. These findings provide a way to valorize FSG: As a hydrophilic food colloid, it can be used to produce microcapsules that can be loaded with bioactive compounds.

Protein adsorption to poly(ethylenimine)-modified Sepharose FF: IX. Further studies on counterion effects and behavior in therapeutic protein separation.

Our previous studies on protein adsorption onto anion-exchangers of poly(ethylenimine) (PEI)-grafted Sepharose FF (PEI-Sepharose) proved their significantly improved performance over the commercial nongrafting anion-exchangers such as Q Sepharose FF, and it was found the protein adsorption behavior on PEI-Sepharose was more sensitive to counterions (Cl-, SCN-, HPO42- and SO42-). However, the complicated role of counterions has not been well interpreted due to their distinct chemical and physical characteristics. Thus, we have further studied the counterion effects by adding two halide ions (F- and Br-) to explore the effects of the three halide ions on bovine serum albumin adsorption and the results were compared with previous data. Furthermore, separation of recombinant human serum albumin (rHSA) from fermentation broth was studied. It was found that the counterion preference for PEI-Sepharose increased with the charge density of the counterions, demonstrating the favorable elution by choosing a proper counterion. Moreover, uptake kinetics onto PEI-Sepharose was very sensitive to counterions, even the three halide ions. In contrast, there is little difference among the halide ions for dynamic binding capacity of PEI-Sepharose, presenting a high value (104 ± 3 mg/mL) for the three halide ions. Furthermore, PEI-Sepharose exhibited much higher rHSA separation performance over Q Sepharose FF, characterized by sharper and more symmetrical elution peaks, higher recovery, enriched eluates, and reduced use of elution salt. The high recovery (>90 %) of rHSA from the Pichia pastoris culture supernatant proved the superiority of PEI-Sepharose column in downstream processing of therapeutic proteins.

First-principles investigations of As-doped tetragonal boron nitride nanosheets for toxic gas sensing applications.

Pristine and arsenic-doped tetragonal boron nitride nanosheets (BNNS and As-BNNS) have been reported as potential candidates for toxic gas sensing applications. We have investigated the adsorption behavior of BNNS and As-BNNS for CO2, H2S, and SO3 gas molecules using first-principles density functional theory (DFT). Both BNNS and As-BNNS possess negative cohesive energies of -8.47 and -8.22 eV, respectively, which indicates that both sheets are energetically stable. Successful adsorption is inferred from the negative adsorption energy and structural deformation in the vicinity of the adsorbent and adsorbate. As-doping results in a significant increase in adsorption energies from -0.094, -0.175, and -0.462 eV to -2.748, -2.637, and 3.057 eV for CO2, H2S and SO3 gases, respectively. Due to gas adsorption, the electronic bandgap in As-BNNS varies by approximately 32% compared to a maximum of 24% in BNNS. A notable fluctuation in the energy gap and electrical conductivity is seen, with ambient temperature being the point of maximal sensitivity. For SO3, the maximum charge transfer during adsorption in BNNS and As-BNNS is determined to be 0.08|e| and 0.25|e|, respectively. Due to the interaction with gases, all structures exhibit an extremely high absorption coefficient on the order of 104 cm-1 with minimal peak shifting. Additionally, doping an As atom on BNNS' surface remarkably improved its ability to sense CO2, H2S, and SO3 gasses.

Stable nanobubbles on ordered water monolayer near ionic model surfaces

Abstract The stable nanobubbles adhered to mineral surfaces may facilitate their efficient separation via flotation in the mining industry. However, the state of nanobubbles on mineral solid surfaces is still elusive. In this study, molecular dynamics (MD) simulations are employed to examine mineral-like model surfaces with varying degrees of hydrophobicity, modulated by surface charges, to elucidate the adsorption behavior of nanobubbles at the interface. Our findings not only contribute to the fundamental understanding of nanobubbles but also have potential applications in the mining industry. We observed that as the surface charge increases, the contact angle of the nanobubbles increases accordingly with shape transformation from a pancake-like gas film to a cap-like shape, and ultimately forming a stable nanobubble upon an ordered water monolayer. When the solid–water interactions are weak with a small partial charge, the hydrophobic gas (N2) molecules accumulate near the solid surfaces. However, we have found, for the first time, that gas molecules assemble a nanobubble on the water monolayer adjacent to the solid surfaces with large partial charges. Such phenomena are attributed to the formation of a hydrophobic water monolayer with a hydrogen bond network structure near the surface.

Introducing halogen-bonded gates into zeolitic frameworks for efficient benzene/cyclohexene/cyclohexane separation.

The separation of C6 cyclic hydrocarbons (benzene, cyclohexene, and cyclohexane) is one of the most challenging chemical processes in the petrochemical industry. Herein, we design and synthesize a new SOD-topology metal azolate framework (MAF) with aperture gating behaviour controlled by C-Br⋯N halogen bonds, which exhibits distinct temperature- and guest-dependent adsorption behaviours for benzene/cyclohexene/cyclohexane. More importantly, the MAF enables the efficient purification of benzene from its binary and ternary mixtures (selectivity up to 113 ± 2; purity up to 98% +), which is the highest record for benzene/cyclohexane/cyclohexene separation to date. Single-crystal diffraction analyses and computational simulations revealed that halogen bonds play a critical role in the gating and diffusion process, which is the first example of halogen-bonding controlled gating for highly effective adsorptive separation.

COMPREHENSIVE ANALYSIS OF ANTIOXIDANT, PHENOLIC THERMAL STABILITY, MINERAL PROFILE AND HYGROSCOPIC PROPERTIES IN GERMINATED FABA BEAN FLOURS

The study aimed to evaluate the phenolic compounds, antioxidant properties, chemical compounds through FTIR analysis, thermal stability of phenolic compounds (at 15, 25, and 35 °C), hygroscopic properties, and minerals in flours made from germinated beans of the White (FBA) and Black Grandmother's Ear (FBB) varieties. To obtain the flours, the seeds were germinated for 96 hours (FBA) and 72 hours (FBB), followed by convective drying at 80 °C. The results indicated that both flours are rich in total phenolic compounds, with caffeic acid, chlorogenic acid, procyanidin B2, and kaempferol-3-glucoside also being identified. Among the methods used for determining antioxidant activity, the FRAP assay showed the highest values of 14.38 mmol Fe2⁺/kg dry basis (FBA) and 14.90 mmol Fe2⁺/kg dry basis (FBB). The FTIR analysis corroborated the findings from the other analyses. Regarding the thermal stability of phenolic compounds, the zero-order model was found to be the most suitable, indicating that higher temperatures, such as 35 °C, accelerate the degradation of these compounds. The adsorption isotherms analysis showed that the GAB (Guggenheim-Anderson-de Boer) model is highly effective in describing the water adsorption behavior of the flours at different temperatures. Finally, the mineral analysis revealed that the flours are particularly rich in potassium and phosphorus. The presence of beneficial minerals, combined with the bioactive functionality of the flours, as well as findings on their hygroscopic behavior and thermal stability, make these flours valuable for the food industry, providing essential insights for product development based on these raw materials.

Transition‐ and Lanthanide‐Metal‐Based Coordination Polymers Offer Efficient Methylene Blue Adsorption

AbstractThis study presents a novel approach toward wastewater remediation via the synthesis of a series of coordination polymers that combine benzene‐1,4‐dicarboxylic acid, benzene‐1,4‐dihydroxamic acid, and 5‐nitroisophthalic acid linkers with Cu, Cr, Ce, and La metal salts to target efficient methylene blue removal. Through a detailed characterization process using techniques like ¹H NMR, PXRD, FTIR, TGA, SEM‐EDX, ICP‐OES, and BET, the structural and surface properties of these CPs were optimized for stability and enhanced adsorption performance. Notably, the CPs exhibited rapid MB adsorption within 10 min and followed pseudo‐second‐order kinetics, indicating a chemisorption‐driven process. This work advances the field by demonstrating that increased pH significantly improves adsorption capacity and that the Sips model best describes the heterogeneous adsorptive behavior, highlighting a mixed Langmuir–Freundlich mechanism. Furthermore, stability and reusability studies revealed minimal metal leaching in the best‐performing CPs, addressing critical environmental concerns around long‐term CP use. This integrated approach not only fills vital knowledge gaps in CP‐based dye adsorption kinetics but also underscores the potential of these materials as sustainable, scalable, and effective solutions for real‐world water treatment applications.

Experimental and computational validation on the adsorption behaviour of quercetin and rutin on ion exchange resins

Experimental and computational validation on the adsorption behaviour of quercetin and rutin on ion exchange resins

Investigation of the adsorption behavior of Cl and O2 on Al (111) surface based on density functional theory

This study systematically investigates the adsorption behavior of Cl and O2 on the Al surface using first-principle calculations based on density functional theory. The calculation results show that the surface energy of Al on (111) surface is 0.8539J / m2, which is the smallest, indicating that the lowest energy is required for crystal formation on the surface of Al (111). For Cl, the adsorption at the Top site is the most stable, and the adsorption energy is 4.71eV, while the adsorption of O2 at the FCC site is the most stable, and the adsorption energy is 9.92eV. The electronic structure and charge density distribution of Cl and O2 adsorbed on Al (111) surface are also studied. Compared with Cl, the adsorption energy of O2 on Al (111) surface is larger (1.84Å), the length of covalent bond formed is shorter, the number of electron transfer in the adsorption process is more (about 1.79 e), the width of hybrid orbital overlap is wider, and the combination with Al surface is closer. Therefore, the strong adsorption characteristics of O2 in the corrosion process lead to a greater impact on the Al alloy.

Mechanistic study of the adsorption capabilities of heavy metals on the surface of ferrihydrite: batch sorption, modeling, and density functional theory.

Ferrihydrite (Fh), a widely distributed mineral in the environment, plays a crucial role in the geochemical cycling of elements. This study used experimental and computational approaches to investigate the adsorption behavior of seven heavy metal ions on Fh. The pH edge analysis revealed that the adsorption capacity followed the order: Pb2+ > Cu2+ > Zn2+ > Cd2+ > Ni2+ > Co2+ > Mn2+, with Pb2+ showed the highest adsorption. Competitive adsorption was observed in multi-metal systems, and adsorption isotherms confirmed that Pb2+ and Cu2+ exhibited significantly higher equilibrium adsorption capacities than the other ions. Diffuse Layer Model (DLM) analysis indicated that for most heavy metals (HMs), [triple bond, length as m-dash]FesOM and [triple bond, length as m-dash]FewOM were the predominant adsorption species, while for Pb2+, [triple bond, length as m-dash]FesOPb dominated. Density Functional Theory (DFT) calculations were employed further to investigate the molecular interactions between HMs and Fh. The DFT results revealed that the distribution of surface iron sites on Fh strongly influences the adsorption process. Larger metal ions, such as Pb2+, form stronger coordination bonds with hydroxyl groups on the Fh surface, leading to distinct adsorption mechanisms compared to smaller ions. These findings, combining experimental and computational data, emphasize the critical role of surface iron site distribution and ion size in governing the adsorption behavior of HMs on Fh.

New imidazole-Schiff base compounds for environmentally friendly anticorrosion protection in industrial pickling of mild steel

As part of the development of a new organic entity, we synthesized a new series of Schiff bases belonging to the imidazo[1,2-a]pyridine (IMP) family, named: (E)-2-methoxy-4-(((2-phenylimidazo[1,2-a]pyridin-3-yl)imino)methyl)phenol(IM1) and (E)-4-(((2-phenylimidazo[1,2-a]pyridine-3-yl)imino)methyl)phenol (IM2). Molecular structures were confirmed through chemical analyses, including nuclear magnetic resonance (NMR) and mass spectroscopy. In order to develop new organic ligands to inhibit mild steel corrosion in 1M HCl solution, various weight loss and electrochemical methods, such as electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP), along with surface visualization through scanning electron microscopy (SEM) and atomic force microscopy (AFM), were employed. EIS results revealed excellent inhibition by compounds IM1 and IM2 (98% and 92%, respectively) at a concentration of 1 mM. These findings were supported by the observation of a protective layer formation during prolonged immersion of mild steel in a corrosive solution, with or without inhibitors. Finally, theoretical studies such as density functional theory (DFT) and molecular dynamics simulations were conducted to explore the adsorption behaviour of inhibitors IM1 and IM2 on the iron surface, providing insight into the inhibitor-metal interaction during the adsorption process.

Biosorption of Basic Yellow 28 dye onto watermelon seeds. Part II: modeling and optimization by response surface methodology

ABSTRACT The powder of treated watermelon seeds (WST), obtained through hexane extraction, has proven to be a promising adsorbent for the environmentally friendly and cost-effective removal of Basic Yellow 28 (BY28) using adsorption techniques. By optimizing conditions through Central Composite Design (CCD), focusing on key factors such as temperature, adsorbent weight, and dye concentration, we aimed to enhance the efficiency of the adsorption process. Our study assessed the accuracy of the model and regression coefficients through analysis of variance (ANOVA). The results revealed a strong agreement between the predicted values derived from the model and the experimental values for BY28, with a coefficient of determination (R 2) equal to 0.92, indicating a high level of reliability and effectiveness of the developed model in predicting the adsorption behavior of BY28 on WST. Under optimal conditions, including a temperature of 35°C, an adsorbent weight of 2.45 g/L, and a dye concentration of 50 mg/L, the adsorption process demonstrated exceptional efficiency. This study highlights the remarkable potential of treated watermelon seeds for the removal of organic pollutants, emphasizing the importance of using sustainable and readily available agricultural materials for environmental remediation, thus contributing to both environmental conservation and cost-effectiveness in wastewater treatment processes.

Competitive Adsorption Studies of Cd(II) and As(III) by Poly (Butylene Succinate) Microplastics: Based on Experimental and Theoretical Calculation

Microplastics (MPs) can serve as vectors for heavy metals in aquatic environments; however, the adsorption behavior of MPs on multiple heavy metal systems is still unclear. This study investigated the adsorption characteristics of biodegradable poly (butylene succinate) (PBS) for cadmium (Cd(II)) and arsenic (As(III)) in both single and binary systems. Adsorption isotherms were studied using the Linear, Langmuir, and Freundlich models, and further analysis of MPs adsorption characteristics was conducted using site energy distribution theory and density functional theory. The results indicate that the maximum adsorption capacities of PBS for Cd(II) and As(III) are 2.997 mg/g and 2.606 mg/g, respectively, with the Freundlich model providing the best fit, suggesting multilayer adsorption on heterogeneous sites. As(III) has a higher adsorption affinity for PBS than Cd(II), with a binding energy of −11.219 kcal/mol. Additionally, the adsorption mechanisms of Cd(II) and As(III) on PBS include electrostatic interactions and surface complexation, with the primary adsorption sites at the C=O of the carboxyl group and the hydroxyl group. The comprehension of interfacial interactions between biodegradable plastics and heavy metals is facilitated by a combination of theoretical calculations and experimental investigations.

Elimination of organic compounds by a material (Magadiite-NA)

This underscores the need for developing effective techniques to treat polluted water and improve its quality.In this study, we investigated the adsorption behavior of Magadiite-Na, a material, as an adsorbent for removing organic pollutants Betadine and Salicylic Acid were selected as model compounds to evaluate the material's efficiency. The adsorption process was analyzed using isotherm models and kinetic models to understand the mechanism and identify the optimal conditions for maximum efficiency. The results demonstrated high adsorption capacities, with a maximum extraction rate of approximately 99.7% for Betadine and 93.3% for Salicylic Acid under optimal conditions. These findings highlight the effectiveness of Magadiite-Na as an environmentally friendly and cost-efficient solution for treating water polluted with organic compounds, contributing to sustainable water treatment practices and environmental protection.

PtRu Intra‐Cluster Electron Modulation Accelerates Multi‐Scenario Hydrogen Evolution Reaction

AbstractThe development of advanced nanomaterial manufacturing technology and the in‐depth analysis of the structure‐activity relationship are conducive to the sustainable development of platinum‐based catalysts in terms of low cost and high performance. The in situ conversion of Pt4+ and Ru3+ is creatively achieved into highly dispersed, small‐sized heterojunction clusters in the confined space by reductant preset framework materials, and these clusters benefited from the hollow carbon spheres gap supramolecular self‐assembly strategy to achieve high exposure. The intra‐cluster Ru→Pt electron transfer and induced electronic structure modulation enhance the adsorption and activation of H2O molecules at the interface, accelerating the desorption coupling of [H] at the Pt or Ru site. As a catalyst, PtRu/BNHCSs have achieved significant hydrogen production from electrolyzed water in multiple scenarios, exceeding the performance of the commercial Pt/C catalyst. These scenarios include high‐current water splitting to hydrogen in both pH‐neutral and simulated seawater, direct seawater hydrogen production, and anion‐exchange membrane integrated continuous and efficient electrolytic hydrogen production. In situ Fourier transform infrared and in situ Raman interface monitoring techniques reveal the interfacial adsorption behavior of H2O, providing important experimental and theoretical insights for understanding and revealing the synergistic effect and the interfacial reaction behavior of intra‐cluster atoms of PtRu heterojunction.

Amino-functionalized manganese oxide for effective hexavalent chromium adsorption.

This study explores the use of functionalized manganese oxide (K-MnO2-NH2) for the removal of hexavalent chromium (Cr(VI)) ions, a highly toxic heavy metal contaminant, from wastewater. The synthesis of K-MnO2-NH2 was achieved through a two-step process, followed by comprehensive characterization using various analytical techniques, which confirmed the material's formation as a pure phase. The K-MnO2-NH2 exhibited exceptional chromium removal efficiency, achieving up to 90% (4.53mg/g) of Cr(VI) removal at pH 2. This high efficiency is attributed to the incorporation of amine groups via functionalization with 3-aminopropyltriethoxysilane (APTES), which introduces active sites with a strong affinity for Cr(VI) ions. Kinetics studies indicated that a chemical reaction governs the adsorption process, while thermodynamic data suggested it to be exothermic, and thermodynamic data reveal the process to be exothermic. The Freundlich isotherm best described the adsorption behavior. The Cr(VI) adsorption capacity of K-MnO2-NH2 was determined to be 45.17mg/g. K-MnO2-NH2 effectively removed Cr(VI) from industrial wastewater, achieving a removal efficiency of around 41% (25.5mg/g) and visible discoloration showing excellent reusability, maintaining over 80% removal efficiency after five cycles without requiring regeneration. This innovative approach highlights the potential of K-MnO2-NH2 as a sustainable and effective solution for Cr(VI) removal in environmental remediation and water purification.

Autogenetic Carbon Oxyanions Enable Interfacial OH− Deconfinement for Reinforced Biomass Electrooxidation over Wide Potential Window

AbstractThe preferential adsorption toward OH− on the anode most likely blocks the accessibility of organic molecules and triggers competitive oxygen evolution reaction (OER), typically precipitating a narrow potential window. Here, an OH− deconfinement strategy enabled by CO32− self‐transformed from C2O42− on metallic nickel oxalate (NiC2O4) for efficient synthesis of bioplastic monomer 2,5‐furanedicarboxylic acid (FDCA) with faradaic efficiency of >95% via electrocatalytic 5‐hydroxymethylfurfural (HMF) oxidation reaction (e‐HMFOR) at a wider potential window of 1.38–1.56 VRHE, outperforming state‐of‐the‐art Ni‐based electrocatalysts is presented. In situ, tests corroborate that the construction of NiOOH with surface‐adsorbed CO32− (NiOOH‐CO32−) from NiC2O4 can be facilitated by self‐liberating CO32−. The CO32− ions serving as an electric field engine can effectively weaken OH− coverage through electrostatic repulsion and enhance HMF adsorption at the NiOOH‐CO32− surface, thereby heightening e‐HMFOR while inhibiting OER. Computational results further indicate that the CO32− on NiOOH hoists the energy barrier of oxygen intermediate conversion (O* → OOH*) to suppress OER but promotes the e‐HMFOR kinetics. The precise modulation of OH− adsorption behavior on the electrocatalyst offers a powerful kit for boosting the oxidative upgrading process while circumventing the competing reaction OER.

60Coγ activation of Cladophora rupestris biomass functional groups and its effect on Pb2+ adsorption.

To investigate the modification of Pb2+ adsorption of the functional groups of Cladophora rupestris (C. rupestris) biomass by gamma radiation (60Coγ-ray), the interface structure, chemical properties, adsorption behaviors, and Pb2+ adsorption mechanisms of C. rupestris biomass were investigated after irradiation with varying doses of 60Coγ-ray. The results indicate that 60Coγ-ray significantly changed the surface characteristics and interfacial chemistry of the C. rupestris biomass.This led to fracturing and fragmentation that produced a larger specific surface area and more abundant pore structure, increasing the electronegativity in the C. rupestris biomass. The theoretical Pb2+ adsorption capacity increased significantly (2.6-2.9 times) after 60Coγ-ray irradiation. 60Coγ-ray caused preferential degradation of protein components in the dissolved organic matter of the C. rupestris biomass, and protein deamination increased the absorption sites of cations. In the C. rupestris biomass, 60Coγ-ray altered the elemental composition and functional groups, particularly the carbon- and oxygen-containing functional groups, to improve Pb2+ adsorption. In conclusion, 60Coγ-ray can activate the functional groups of C. rupestris biomass and improve their Pb2+ adsorption sites. This study provides new insight into modification of biomass materials for enhanced removal of heavy metals from waterbodies.

Irradiated Gao Miao Zi Bentonite for Uranium Retention: Performance and Mechanism

Bentonite has been considered as backfill material in the long-term deep geological disposal sites for radioactive waste. The performance of raw and irradiated bentonite based on the retention of radioactive nuclides, such as U(VI), is a critical factor for its application. Herein, the intrinsic features and adsorption behavior of Gao Miao Zi (GMZ) bentonite based on uranyl ions was investigated. In aqueous solutions, bentonite can achieve an adsorption rate of up to 100% for U(VI). The primary mechanism of U(VI) adsorption by GMZ bentonite is ion exchange, supplemented by surface complexation. Strong irradiation can introduce slight structural changes and framework fractures in bentonite, reducing its adsorption capacity for U(VI). This study provides an in-depth analysis of the adverse effects of high doses of radiation (100 kGy) on the microstructure and adsorption properties of bentonite, offering important insights for the safe storage of radioactive waste.