Surface Adsorption Properties Research Articles

Synergistic engineering of shell thickness and core ordering to boost the oxygen reduction performance.

When benchmarked against the extended Pt(111), slightly weaker adsorption and stronger cohesion properties of surface Pt are required to improve activity and durability for the oxygen reduction reaction, respectively, making it challenging to meet both requirements on one surface. Here, using Pt(111) over-layers stressed and modified by Pt-TM (TM = Fe, Co, Ni, V, Cu, Ag, and Pd) intermetallics as examples, we theoretically identified ten promising catalysts by synergistically tailoring the skin thickness and substrate chemical ordering to simultaneously achieve weak adsorption and strong cohesion. More specifically, compared with Pt(111), all candidates exhibit 10-fold enhanced activity, half of which show improved durability, such as mono-layer skin on L12-Pt3Co or Pt3Fe, double-layer Pt on L13-Pt3Ni or Pt3Cu, and triple-layer skin on L11-PtCu, while double- or triple-layer skin on L10-PtCo or PtNi and double-layer skin on L12-PtFe3 show slightly poor durability. Although L10 and L12 based nanocrystals have been demonstrated extensively as outstanding catalysts, L11 and L13 ones hold great application potential. The coexistence of high activity and durability on the same surface is because of the different responses of surface adsorption and cohesion properties to the strain effects and ligand effects. When intermetallic-core@Pt-shell nanocrystals are constructed using this slab model, the necessity of protecting or eliminating low-coordinated Pt and the possibility of maximizing Pt(111) facets and core ordering by morphology engineering were highlighted. The current discovery provides a new paradigm toward the rational design of promising cathodic catalysts.

Process-Oriented Smart Adsorbents: Tailoring the Properties Dynamically as Demanded by Adsorption/Desorption.

Adsorptive separation plays a critical role in chemical, food, pharmaceutical, and environmental industries, as well as in many other industrial areas. Adsorbents are most important for adsorptive separation and undergo adsorption and desorption processes to accomplish the specific tasks of separation. In the process of adsorption, adsorbates diffuse into the pore spaces of adsorbents through pore openings, adsorb on active sites via physical or chemical interactions, and subsequently are regenerated by temperature or pressure swings during desorption. In the process of adsorption and desorption, however, the requirements for pore structures and surface properties of adsorbents are different. In general, adsorbents with small pore openings can realize selective adsorption and do not favor desorption; on the other hand, adsorbents with large pore openings are efficient in desorption but at the expense of adsorption selectivity. Remarkably, active sites possessing strong interactions with adsorbates contribute to high selectivity for adsorption, while desorption becomes difficult. The trade-off between adsorption and desorption presents an enormous challenge to develop high-efficiency adsorbents. Restricted by their fixed structures and surface properties, conventional adsorbents are unable to meet the demands of adsorption and desorption processes simultaneously.To confront the obstacles, the development of advanced adsorbents to meet the demand of adsorptive separation are urgent. A key strategy to address such issues lies in dynamically adjusting the pore structures or the surface properties of adsorbents with controllability according to the demands of adsorption/desorption. For instance, pursuant to the requirements of varying pore structures during adsorption/desorption, the pore openings of adsorbents can be customized through dynamic structural change of the decorated stimuli-sensitive motifs by suitable external intervention. In addition, the active sites within the adsorbents can be exposed to enhance the adsorption selectivity or sheltered to accelerate the desorption through stimuli-triggered adsorbent-adsorbate interactions. Hence, we proposed a concept of process-oriented smart adsorbents (POSAs) on the basis of the requirements of the adsorption/desorption processes. The design and development of such POSAs are based on three aspects, namely, pore openings, pore spaces, and adsorption sites of adsorbents.In this Account, we present the progress in the development of POSAs according to the demands of adsorption/desorption processes. A series of POSAs with incorporated stimuli-sensitive motifs were successfully achieved. The versatility of incorporated motifs allows them to tune the pore structures and surface properties of adsorbents dynamically and further to enhance the adsorption and desorption efficiency simultaneously. Based on the concept of POSAs, we hope that this Account could contribute to the development of high-efficiency adsorbents and ultimately promote their applications in practical industrial separation. Moreover, we present an outlook on future trends and challenges on the road toward the development and applications of POSAs.

Optimized safranin adsorption onto poly(vinylidene fluoride)-based nanofiber via response surface methodology

This study is a comparative work on the surface interactions and adsorptive properties of poly(vinylidene fluoride) nano-fibers (PVDF NFs) and UiO-66/PVDF NFs prepared by using the electro-spinning method. X-ray diffraction (XRD), fourier transform infrared (FT-IR), scanning electron microscope (SEM), thermogravimetric analysis (TGA), and energy-dispersive X-ray (EDX) have been applied to confirm and determine physicochemical changes during preparing and to modify PVDF NFs. The results of XRD, FT-IR, SEM, TGA, and EDX show significant changes in porosity that happened on the surface of adsorbents. The PVDF NFs and UiO-66/PVDF NFs have been applied to remove safranin O (SO) dye in aqueous solution as a cationic azo dye. Three essential factors of the initial concentration of SO, contact time, and pH were optimized by using the Box-Behnken response surface methodology (BBRSM). By using PVDF NFs, the maximum equilibrium adsorption capacity of 28.201 mg g−1 is obtained at optimal adsorption parameters of a contact time of 117.972 min, initial concentration of dye 34.896 mg L−1and pH of 9.975. And also by applying UiO-66/PVDF NFs, the maximum equilibrium adsorption capacity of 25.896 mg g−1 is achieved at optimal parameters of a contact time of 58.47 min, initial concentration of 34.83 mg L−1 and pH of 7.2, which clearly shows that the addition of metal-organic frameworks (MOFs) to the PVDF NFs is reduced the contacted time by half. The adsorptive experimental data were correlated by the famous isotherm and kinetic models. The extrapolated data showed that the SO dye adsorption on the PVDF NFs and UiO-66/PVDF NFs follow better the Langmuir isotherm and the pseudo-second-order kinetic model. Moreover, the thermodynamics result of the nano-fibers shows that, the adsorption process is exothermic and spontaneous. The high efficiency and adequate adsorption ability in the SO removal suggest that the UiO-66/PVDF NFs could be effectively applied as a good applicant in the water filtration of azo dyes.

Experimental study and molecular simulation on aggregation behavior of surface‐active ionic liquids containing saturated nitrogen heterocycles in aqueous solution

AbstractThe aggregation behavior of N‐decyl‐N‐methylmorpholinium bromide (DMMB) in aqueous solutions was systematically investigated by experimental measurements and molecular simulation, including surface tension, electrical conductivity, fluorescence measurement, 1H NMR and dissipative particle dynamic (DPD) simulation. The critical micelle concentration (cmc) of DMMB which was obtained by different techniques showed a pretty good agreement. From the surface tension measurements, a series of surface adsorption properties such as surface tension at the cmc (γcmc), effectiveness of surface tension reduction (∏cmc), maximum surface excess concentration (Γmax), minimum surface area per molecule (Amin), were determined. The cmc values and a variety of thermodynamic parameters (, and ) of micellization in the temperature range of 25–45°C were obtained via electrical conductivity experiments. In the investigated temperature range, the thermodynamic parameters reveal that micelle formation is entropy‐driven. Furthermore, micelle aggregation number (Nagg) of DMMB was calculated through the fluorescence measurement. Analysis of the 1H NMR spectrum indicates the micelle formation mechanism. The DPD simulation reflects the process of micro‐phase separation. From the simulation results, at concentrations higher than cmc, spherical micelles can be formed. The investigation of DMMB micelles may help us gain a better understanding about surfactant micellization process and expand the range of potential application in materials science.

Electrocatalysis for CO2 and CO Reduction

Renewable energy-driven electroreduction of CO2 represents a promising approach toward artificial carbon recycling. Electrolytes of high alkalinity are known to favor C-C coupling, a key step toward value-added C2+ hydrocarbon products such as ethylene, ethanol, acetate and n-propanol. However, the undesired side reaction with CO2 has limited the practical implementation of alkaline electrolytes in CO2 electrolyzers. This challenge can be circumvented by sequential electroreduction of CO2 to CO and then CO to C2+. This presentation aims to introduce our efforts on the development of advanced electrocatalysts for CO2 and CO reduction. Topics to be covered include i) highly dense Cu nanowires with abundant grain boundaries and undercoordinated surfaces, ii) Cu nanocrystals of well-controlled shapes and iii) bimetallic electrocatalysts with controlled atomic ensembles. Atomic structures of these nanostructures are characterized by using state-of-the-art electron microscopy and X-ray spectroscopy techniques. Surface structures and adsorption properties of the electrocatalysts are probed by measuring temperature- or potential-programed chemisorption of small molecules (e.g., COad and OHad). Kinetic analysis was performed to discern the rate-determining factors and reaction pathways. The established structure-property-performance correlations are further subjected to computational simulations to develop fundamental understanding of the catalytic mechanisms. Our work highlights the great potential of electrosynthesis with CO2 as the feedstock toward renewable hydrocarbons.

Artificial solid-electrolyte interface facilitating uniform Zn deposition by promoting chemical adsorption

Zn-air batteries are promising energy storage and conversion systems to replace the conventional lithium-based ones. However, their applications have been greatly hindered by the formation of Zn dendrites and ZnO passivation layer on the Zn anodes. Herein, we report the fabrication of an artificial protective layer comprised of N-doped threedi-mensional hollow porous multi-nanochannel carbon fiber with well-dispersed TiO2 nanoparticles (HMCNF). The incorporated TiO2 nanoparticles and N dopants improve the ion flux distribution and promote the surface adsorption, facilitating the interfacial pseudocapacitive behaviors during Zn deposition. The hierarchical architecture also induces homogenous electric field distribution at the anode/electrolyte interface. Accordingly, the deposition behavior of Zn is regulated, giving rise to enhanced utilization and rechargeability of Zn. When integrated in alkaline Zn-air batteries, the HMCNF-coated Zn anodes exhibit improved electrochemical performances relative to those with the bare Zn anodes, demonstrating a versatile strategy to boost energy storage of metal anodes through optimizing surface adsorption properties.

Adsorption of azo dye Congo red on the Sn-doped TiO2 surface

In this paper, the effect of SnO2 impurity on the surface charge and adsorption properties of TiO2 samples is investigated. The experimental value of the zero charge point for TiO2 with 3%, 6% and 12% of SnO2 equals 3.53, 3.97 and 3.2, respectively. The adsorption activity of the samples was studied on model solutions of the anionic dye – Congo red. The maximum adsorption capacity (qexp) equals 24.6 mg/g for 3Sn/TiO2, 25.0 mg/g for 6Sn/TiO2 and 39.1 mg/g for 12Sn/TiO2. Langmuir, Freundlich, and Dubinin-Radushkevich models were used to describe the adsorption mechanism of Congo red dye on the surface of Sn/TiO2 samples. Based on the results of the studies of Congo red adsorption by the surface of titanium dioxide doped with Sn, all samples agree best with the Langmuir model. The correlation coefficients for the Langmuir isotherms are in the range of 0.9927 - 0.9996, while the values ​​of R2 for the Freundlich and Dubinin-Radushkevich isotherms are in the range of 0.721 - 0.8329 and 0.8283 - 0.9433, respectively. Experimental data obtained from adsorption isotherms show that the TiO2 sample containing 12% SnO2 is the most active. The best result of Congo red removal occurred at a concentration of Co = 5 mg/l (% of removed dye ≈ 83% for 12Sn/TiO2; 81% for 6Sn/TiO2 and 71% for 3Sn/TiO2). Therefore, the studied samples of TiO2 doped with SnO2 can be used as effective adsorbents of Congo red from aqueous solutions.

A facile fabrication of highly dispersed CeO2/SiO2 aerogel composites with high adsorption desulfurization performance

A simple, low energy consumption and environment-friendly strategy was used to prepare highly dispersed CeO2/SiO2 aerogel composites with different molar ratio of Si/Ce via sol-gel method and subsequently drying under the ambient pressure, in which the oxidation of Ce3+ species into Ce4+ species could be achieved by adding H2O2. The structural and surface properties of adsorbents were analyzed by XPS, XRD, FT-IR, Py-IR, SEM, XRF and N2 adsorption-desorption isotherm. The adsorption desulfurization performances of CeO2/SiO2 for thiophenic compounds from simulated gasoline and model aromatic products were investigated and compared by the breakthrough and batch adsorption experiments. As a result, the weak Lewis acid centers appeared on the surface of CeO2/SiO2. Among them, CeO2/SiO2 with a Si/Ce of 25 performed best, the adsd by Duanpacity for TP from simulated gasoline (n-heptane) was 10.9 mg-S/gads, followed by model aromatic products (benzene, 10.6 mg-S/gads; p-xylene, 10.1 mg-S/gads), however, the difference between them was slight, attributed to the formation of S-Ce bonding instead of C-Ce bonding. The very weak competitive adsorption of benzene and p-xylene with thiophene originated from the weak Lewis acid-base interaction. After the fourth solvent washing regeneration, the breakthrough adsorption capacity of regenerated CeO2/SiO2-25 still remained 60% of the fresh one. The equilibrium adsorption data of CeO2/SiO2-25 for thiophene were well fitted by Langmuir and Freundlich model, and the adsorption for TP was more favorable at the higher temperature. The adsorption process of CeO2/SiO2-25 was well fitted by pseudo-second-order kinetic model, which was spontaneous, endothermic and the freedom degree increased. The solvent (n-heptane, benzene, p-xylene) hardly influence the adsorption behavior of TP on CeO2/SiO2.

Foaming behavior of sugar-based surfactants: influence of molecular structure and anticipation from surface properties

Sugar-based surfactants are a class of environmentally-friendly surface-active molecules well known for their functional performances, good biodegradability and reduced ecological footprint. Many previous studies have explored the surface properties of these surfactants. However, very little research has investigated their foaming properties. The present study examines the foaming behavior of 17 nonionic sugar-based surfactants with gradual structure variation. Foaming properties such as foamability, foam stability and maximum foam density were measured using the gas-sparging method. The influence of surfactant structure and concentration on foaming properties was evaluated. The data on surface adsorption properties, determined in the previous study, and foaming properties were then analyzed using a Principal Component Analysis. It was shown that the foaming behavior of glycolipids can be correlated to concentration and interfacial properties. Predictive models are proposed to anticipate the foaming behavior and provide a useful guide for screening the foamability of bio-based surfactants in various technological applications.

Composition of Surface Groups and Adsorption Properties of Activated Carbons Derived from Different Bio-precursors

Activated carbons (AC) are widely used in a variety of applications because of their controllable porosity and surface functionalities. In this work, AC were prepared from different hard woods through one- and two-step pyrolysis/activation for the adsorption of organic pollutants in water. Water vapor was used as the activating agent. The influence of the precursor and preparation methods on the properties of the resulting AC was evaluated through multiple techniques. Temperature-programmed oxidation (TPO) measured the reactivity toward oxygen of chars and AC, while temperature-programmed desorption coupled with mass spectrometry (TPD/MS) revealed functional groups on AC surface. Methylene blue adsorption tests evaluated the adsorption capacity of the prepared AC and the presence of mesopores. Depending on the oxidation reactivity of the char produced by pyrolysis, the resulting AC show different surface composition and adsorption performance. With the increasing char oxidation reactivity, the AC has higher degree of surface functionalization and enhanced adsorption toward methylene blue. In particular, Red Maple char is the more reactive one, followed by Birch and Ironwood. Thus, Red Maple AC prepared through the two-step process, exhibits lower activation yield, higher concentration of surface functionalities and improved methylene blue adsorption. TPO technique could predict the degree of surface functionalization and adsorption properties of the final AC.

Novel magnetically separable tetrahedral Ag3PO4/NrGO/CuFe2O4 photocatalyst for efficient detoxification of 2,4-dichlorophenol

An effective as well as eco-friendly photodegradation methods by atoxic and easily reusable photocatalysts are essential for wastewater treatment. Silver phosphate (Ag3PO4) specifically in tetrahedral shape is one of the superior catalysts under visible light but its photocorrosion, poor electron transfer ability and low surface adsorption properties limits its applications. Combination of Ag3PO4 and nitrogen doped reduced graphene oxide (NrGO) having higher in surface area, ample functional groups and hetero atom doping is expected to get over the problem. Further addition of a spinel ferrite (CuFe2O4) could enhance the visible light response activity and helps in easy separation of catalyst for reuse. Given the merits of Ag3PO4, NrGO and CuFe2O4 we rationally integrated a novel magnetically separable stable Ag3PO4/NrGO/CuFe2O4 photocatalyst for efficient detoxification of 2,4-dichlorophenol (2,4-DCP). About 95.3% degradation efficiency was achieved by Ag3PO4/NrGO/CuFe2O4 (k = 0.01978 min−1) which was ~2.6 times higher than pure Ag3PO4 (k = 0.00747 min−1) in 60 min of visible light irradiation. The Ag3PO4/NrGO/CuFe2O4 heterojunction was able to separate and recycle easily using an external magnetic field due to its strong magnetism, and after 5 recycles it showed 88.6% of degradation efficiency revealed its higher stability and recyclability. The photocatalytic mechanism of Ag3PO4/NrGO/CuFe2O4 was explained by heterojunction energy-band theory. In addition, the plausible intermediate products of 2,4-dichlorophenol were analyzed by ESI/LC-MS and proposed the pathway. Moreover, the phytotoxicity was also studied on V. radiata in which GI (germination index) was found to be 11.97% before degradation, while 80.31% of GI was observed in 60 min of degradation which revealed that more significant reduction in toxicity was attained on this photodegradation.

Adsorption equations of binary gases based on adsorption factor

Gas adsorption equations can reveal the certain relationship between equilibrium adsorption amounts and the concentration of adsorbates, such as Langmuir, BET adsorption equations, which are the classical gas adsorption equations proposed by scientists in a few decades ago. In this work, adsorption equations of binary gases are established based on adsorption factor (χ), which is first proposed in our paper. χ is proven an intrinsic parameter, irrespective of the gas concentration (C), which can reveal the internal relation between the adsorbed gas and the surface of the solid. χ can be deduced by solving the linear equations consisted with adsorption capacity (q) of binary gases and single components. Importantly, χ shows significant meanings for applications, such as explanation of the sensing mechanisms, discrimination of gas species and concentration of mixed gas, deduction of reliable q∼logC equations of binary gases, and prediction of surface properties of adsorbents, which can be profoundly researched in future works.

Oxygen vacancy formation and their role in the CO2 activation on Ca doped ZrO2 surface: An ab-initio DFT study

A detailed investigation regarding modifications that occur in surface properties of zirconium oxide, through the generation of oxygen vacancies and through the doping process with calcium, was carried out within the ab-initio (periodic) density functional theory framework. Vacancy formation energies, geometric parameters, vibrational frequencies, and electronic properties are presented for both pure and doped surfaces. It was demonstrated that oxygen vacancies may alter substantially the surface properties of zirconia. The theoretical calculations show that the energy needed to remove a surface oxygen atom, creating a vacancy, is high, but the presence of calcium greatly facilitates this process. The surface adsorption and activation properties were examined through the interaction between the (−111) face (pure and doped) and the chemically stable CO2 molecule. It was shown that this surface is capable of activating CO2. The adsorption process results in different geometries (CO2−δ and CO3−δ species), which present different interaction strengths depending on the presence of a vacancy and the alignment between the molecule with the electrons localized in the vacancy site. A thermodynamic analysis revealed that the presence of calcium provides an overall energetically more stable environment and therefore the doping process increases the surface capacity of adsorbing CO2.

Interaction mechanism of lead ions with stibnite surfaces and enhancement of xanthate adsorption

Addition of lead ions can greatly increase the flotation recovery of stibnite, but the surface adsorption properties of lead ions on stibnite have not yet been ascertained. In this work, the mechanism of interaction of lead ions with a stibnite surface and the consequent enhancement of xanthate adsorption was systematically investigated using a range of sophisticated surface-analysis techniques. X-ray photoelectron spectroscopy (XPS) results showed that lead ions could adsorb onto a lead-treated stibnite surface in the form of PbS and PbO species. Time-of-flight secondary-ion mass spectrometry (ToF–SIMS) demonstrated the adsorption of lead ions and its occurrence states on the stibnite surface. Local electrochemical impedance spectroscopy (LEIS) results showed that higher local impedance was measured after the stibnite surface was treated with lead ions. Ultraviolet (UV) and Fourier-transform infrared spectroscopy (FT-IR) confirmed that large amounts of xanthate in the pulp solution were consumed after lead ions were added to modify the stibnite surface, and that more xanthate species were detected on the lead-treated mineral surface than on the untreated surface. Surface modification of stibnite with lead ions increased the number of reactive sites on the mineral surface, thereby facilitating adsorption of the collector and increasing the recovery of stibnite.

Changes in surface characteristics and adsorption properties of 2,4,6-trichlorophenol following Fenton-like aging of biochar

Fenton-like system formed in a natural soil environment deemed to be significant in the aging process of biochar. Aged biochars have distinct physico-chemical and surface properties compared to non-aged biochar. The aged biochar proved to be useful soil amendment due to its improved elements contents and surface properties. The biochar aging process resulted in increased surface area and pore volume, as well as carbon and oxygen-containing functional groups (such as C=O, –COOH, O–C=O etc.) on its surface, which were also associated with the adsorption behavior of 2,4,6-trichlorophenol (2,4,6-TCP). The biochar aging increased the adsorption capacity of 2,4,6-TCP, which was maximum at pH 3.0. The 2,4,6-TCP adsorption capacity of aged-bush biochar (ABB) and aged-peanut shell biochar (APB) was increased by 1.0–11.0% and 7.4–38.8%, respectively compared with bush biochar (BB) and peanut shell biochar (PB) at the same initial concentration of 2,4,6-TCP. All biochars had similar 2,4,6-TCP desorption rates ranging from 33.2 to 73.3% at different sorption temperatures and times. The desorbed components were mainly 2,4,6-TCP and other degraded components, which were low in concentration with small molecule substance. The results indicated that the aged-biochar could be effective for the long-term remediation of naturally organic polluted soils.

A high performance barium-promoted cobalt catalyst supported on magnesium-lanthanum mixed oxide for ammonia synthesis.

Ammonia synthesis was performed over a barium-promoted cobalt catalyst supported on magnesium–lanthanum mixed oxide. The rate of NH3 formation over this catalyst was about 3.5 times higher than that over the unpromoted catalyst at 9 MPa and 400 °C. Furthermore, no sign of thermal deactivation was observed during long-term overheating at 600 °C for 360 h. The results of physicochemical studies, including XRPD, DRIFTS, H2-TPD, CO2-TPD, Nads + H2 TPSR and kinetic analysis, revealed that the addition of Ba promoter increased the surface basicity of the catalyst and modified the adsorption properties of the Co surface towards H2 and NH3. The decreased adsorption strength of the corresponding sites towards hydrogen and ammonia resulted in greater availability of active sites in the Ba-promoted cobalt catalyst. These characteristics are considered to have a profound effect on the performance of this catalyst in NH3 synthesis.

Surface electric field and adsorption properties of noble metal modified graphene in methane gas

Based on COMSOL Multiphysics software, the geometric model of graphene structure is set on the two-dimensional plane, and the thickness of graphene layer is set at 400 nm. The real and imaginary parts of the refractive index of graphene are defined. Then, the Ag and Au films are coated on both sides of graphene to form the Ag/G/Ag and Au/G/Au sandwich structures, respectively. In addition, the electric field modes between 300 nm and 600 nm are obtained by parameterized scanning calculation of the incident wavelength λ. At the same time, adsorption, scattering and extinction spectra are plotted. Results indicated that the maximum field strength of both the Ag/G/Ag and Au/G/Au sandwich structures are nearly doubled as compared to the intrinsic graphene. Finally, the adsorption, scattering and extinction properties are discussed. It is concluded that the resonance absorption peaks can be adjusted and improved by Ag/Au modification. The strongest plasma resonance mode shifts towards high energy. Moreover, Ag/G/Ag has stronger surface plasmon resonance effect than that of Au/G/Au structure.

表面脱乙酰魔芋及壳聚糖包埋魔芋吸附性能比较

表面脱乙酰魔芋及壳聚糖包埋魔芋吸附性能比较

Superior adsorption removal of dye and high catalytic activity for transesterification reaction displayed by crystalline CaO nanocubes extracted from mollusc shells

Nano structuring and surface functionalization of industrially important Calcium Oxide (CaO) material has broad spectrum applications in daily civic life. In this context, cubical shape CaO nanoparticles are extracted via an eco-friendly green approach from dead mollusc shells collected from sea beaches. The surface structural morphology of as-prepared catalyst is thoroughly characterized by XRD, DLS particle size, SEM, TEM-EDS, TGA, TPD, BET surface area (80 m2g−1) analysis, adsorption and electro-kinetic (zeta potential/point of zero charge) properties etc. measurement. Practical applications of this cubic nano crystal (lattice constant 12.51 Å and size 60–80 nm) for adsorption removal of toxic neutral red dye and catalytic activity for transesterification are systematically studied relative to commercial CaO particles under similar experimental conditions. Influential factors responsible for optimum dye adsorption isotherms, kinetics/thermodynamics of catalytic activity, stability and reusability/leaching are properly investigated in correlation with its observed crystal structural and physicochemical properties.

Investigation of surface adsorption and thermodynamic properties of 1-tetradecyl-3-methylimidazolium bromide in the absence and presence of tetrabutylammonium bromide in aqueous medium

The aggregation behavior of imidazolium-based long-chain ionic liquid 1-tetradecyl-3-methylimidazolium bromide [C14mim][Br] has been investigated in the absence and presence of (1, 2, and 5) mM tetrabutylammonium bromide (C4H9)4NBr at three temperatures (298.15, 308.15, and 318.15) K. The critical micelle concentration (CMC), surface parameters such as maximum surface excess concentration (), the minimum area surfactant monomer at the air/water interface (), surface tension at CMC () and surface pressure () are determined by employing conductivity and surface tension measurements. Various thermodynamic parameters of micellization such as standard free energy of micellization (), standard enthalpy of micellization (), and standard entropy of micellization () are calculated by utilizing the temperature dependence of CMC observed using conductivity study. Other thermodynamic parameters such as free energy of adsorption (Δ) and surface free energy () are also evaluated. Refractive index measurements and UV–vis spectroscopic studies have been utilized to confirm the values of CMC obtained via conductivity and surface tension measurements. FTIR spectroscopic studies signify the various interactions prevailing in the system constituting long-chain ionic liquid and electrolyte.