Negative Enthalpy Research Articles

First Report on the Complexation of Uranyl Ion with Two Diglycolamide Ligands in a Room Temperature Ionic Liquid: Optical Spectroscopy and Calorimetric Studies

AbstractThe complexation of UO22+ with N,N,N′,N′‐tetraoctyl diglycolamide (TODGA) and N,N,N′,N′‐tetra‐2‐ethylhexyl diglycolamide (T2EHDGA) was investigated in ionic liquid using UV−vis absorption spectrophotometry and isothermal titration calorimetry. Spectrophotometric titration suggested the formation of two successive complexes, [UO2L]2+ and [UO2L2]2+ where L=TODGA or T2EHDGA. The formation constant values obtained in ionic liquid medium were several orders of magnitude higher than those observed with the analogous DGA ligands in aqueous medium. The stability constant (logβ) for UO22+/TODGA complex was at least an order of magnitude higher than those observed for UO22+/T2EHDGA complex. The speciation of UO22+/DGA complex obtained by spectrophotometric titration was in conformity with those observed in biphasic solvent extraction. Energetically the UO22+/DGA complexation was mainly driven by negative enthalpy and large positive entropy changes as a result of the release of entire water molecules from the solvation sphere of the hydrated UO22+ ions. The results from this work gave an insight understanding of the complexation behaviour of UO22+ ions with DGA ligands in ionic liquid. It is anticipated that such understanding will give valuable information for understanding the extraction behavior of uranyl ions by DGA ligands in ionic liquid.

The thermodynamic study of p-methoxycinnamic acid inclusion complex formation, using β-cyclodextrin and hydroxypropyl-β-cyclodextrin.

Cyclodextrin's ability to form an inclusion complex with a guest molecule is a function of two factors. The first is steric and depends on the relative size of cyclodextrin cavity to the guest molecule, while the second is the thermodynamic interaction between the different system components. This study therefore aims to determine the effect of β-cyclodextrin and hydroxypropyl-β-cyclodextrin as complex formers, on thermodynamic parameter values (ΔH, ΔG, and ΔS) in the formation of inclusion complex with p-methoxycinnamic acid (pMCA). The pMCA complex formation with β-cyclodextrin or hydroxypropyl-β-cyclodextrin was determined in 0.02 pH 4.0M acetate buffer and 0.02M pH 7.0 phosphate buffer, with a 0.2 µ value at 32, 37, and 42±0.5°C. This experiment was carried out in a waterbath shaker until a saturated solution was obtained. Subsequently, pMCA concentration was determined using UV spectrophotometer at the maximum pMCA wavelength, at each pH. The result showed pMCA formed inclusion complex with β-cyclodextrin or hydroxypropyl-β-cyclodextrin and exhibited increased solubility with increase in β-cyclodextrin or hydroxypropyl-β-cyclodextrin concentration. This temperature rise led to a decrease in the complex's constant stability (K). Furthermore, the interaction showed a negative enthalpy (∆H<0) and is a spontaneous processes (∆G<0). At pH 4.0, an increase in the system's entropy occurred (∆S>0), however, at pH 7.0, the system's entropy decreased (∆S<0). The rise in pMCA solubility with increase in cyclodextrin solution concentration indicates an inclusion complex has been formed, and is supported by thermodynamic data.

The supramolecularly complexes of calix[4]arene derivatives toward favipiravir antiviral drug (used to treatment of COVID-19): a DFT study on the geometry optimization, electronic structure and infrared spectroscopy of adsorption and sensing.

While the world is in search of a vaccine that can cure COVID-19 disease, favipiravir is the most commonly used antiviral drug in the treatment of patients during the pandemic process. In this study, we investigated the host–guest interaction between the popular supramolecule calix[4]arene derivatives and the favipiravir drug by using the DFT (Density Functional Theory) method. The B3LYP hybrid method and 6-31G (d,p) basis set were utilized to determine the optimized structures of the host and guest molecules and their complexes. The negative adsorption energy (∆E) and adsorption enthalpy (∆H) calculated for the complexes formed between calix[4]arene compounds and favipiravir drug molecule mentioned that adsorption of favipiravir molecule was an exothermic process on calix[4]arene structures. On the other hand, among the calixarene derivatives in the study, Gibbs free energy change (∆G) value for the adsorption was only negative on calix[4]arene4 molecule. The infrared spectroscopy (IR) calculations were performed by examining the C=O, O–H and NH2 vibrational frequencies to see the adsorption behavior in the favipiravir-calix[4]arene complex. After adsorption of the favipiravir molecule, HOMO–LUMO gap values decreased significantly for the structures and therefore electrical conductivity increased proportionally. In addition, sensor response factors, Fermi energy levels and workfunction changes of calix[4]arene derivatives were calculated and examined. Charge transfer between the four calix[4]arene compounds and the favipiravir molecule has occurred after adsorption. This attributes that calix[4]arene derivatives can be used as a well-suited favipiravir sensor (electronic and workfunction) and adsorbent at room temperature. Based on the calculations made to see the solvent effect on the adsorption of favipiravir it was determined that it did not affect the interaction between the drug molecule and the calix[4]arene compound too much and the adsorption energy turned into a slightly less negative value.

(Invited) A First-Principles Study on the Structure and Properties of Na-Se Alloys for Sodium Ion Battery

While selenium (Se) is recognized as a promising cathode material for sodium-ion battery (NIB), fundamental understanding of the Na-Se electrochemical reactions upon sodiation is in its infancy. On the basis of density functional theory and ab initio molecular dynamics simulations, we evaluate single Na incorporation in the crystalline Se and investigate the formation of Na-Se alloys in terms of structural evolution and energetics, along with their mechanical and diffusion properties. Our calculations clearly evidence that the inserted Na atom energetically prefers a heptagonal interstitial site, while cleaving the Se network bonds. We also found that the inserted Na atoms undergo migration with low energy barrier of 0.16 (0.045) eV by jumping to adjacent heptagonal sites through intrachain (interchain) paths. When the Na content is sufficiently high, alloying between Na and Se becomes energetically favorable as evidenced by the negative mixing enthalpy, with the most stable state obtained at 66 at.% of Na. Our calculations also show that the increasing degree of sodiation leads to disintegration of the chain-like bonded Se network into small chain. Lastly, we will discuss the influence of alloy composition on the diffusivity of Na and Se and mechanical properties in amorphous NanSe.

Studies of the potential of a native natural biosorbent for the elimination of an anionic textile dye Cibacron Blue in aqueous solution

This work is devoted to the adsorption of Cibacron Blue (CB) an anionic textile dye, on bean peel (BP) an agricultural waste with neither activation nor carbonization. The adsorption was realized in batch configuration at ambient temperature in acidic medium. The adsorbent was characterized by FTIR, SEM and BET analyses; the equilibrium isotherms and kinetics were also studied. It has been found that this waste could be used as a low-cost biosorbent for CB elimination under optimal working conditions. The rate of CB elimination reaches 95% on bean bark (3.6 g/L) at pH 2.2 and a reject concentration of 25 mg/L. The pseudo-second-order describes suitably the experimental data and the external diffusion is the rate-determining step. The Freundlich isotherm fits better the CB adsorption with a correlation coefficient (R2) of 0.94 and an RMSE = 1.5115. The negative enthalpy (ΔH) and free enthalpy (ΔG°) indicate a physical and spontaneous nature of the CB biosorption onto the biomaterial.

Tuning the degree of chemical ordering in the solid solution of a complex concentrated alloy and its impact on mechanical properties

Using the binary enthalpies of mixing in a Co-Cr-Fe-Ni base alloy system, a high entropy alloy (HEA) or complex concentrated alloy (CCA), the equiatomic CoFeNi has been identified, which should form a random solid solution. Subsequent experimental validation established that this alloy is indeed a near-ideal, random face centered cubic (FCC) solid solution. The same thermodynamic basis has been employed to systematically engineer the degree of chemical ordering within the random CoFeNi alloy, from localized domains of short-range ordering (SRO), also referred to as clustered ordering, to well-defined long-range ordered (LRO) domains, by adding controlled amounts of Al and Ti, since these elements have a strong ordering tendency (negative enthalpy of mixing) with Co, Fe, and Ni. A series of seven alloys were designed in this study, based on enthalpies of mixing among 3d transition metals. This change in the degree of chemical ordering has a strong influence on the tensile yield strength of the alloy, for the same nominal grain size, ranging from ~181 MPa in case of CoFeNi to ~793 MPa in case of the Al0.3Ti0.2Co0.7FeNi1.7 CCA. These experimentally measured yield strengths of the candidate CCAs are in close agreement with predicted values afforded by simple strengthening models.

Composition Stability and Cr-Rich Phase Formation in W-Cr-Y and W-Cr-Ti Smart Alloys

W-Cr-Y smart alloys are potential material candidates for plasma facing components due to their protective behaviour during the loss-of-coolant accident (LOCA), while maintaining beneficial properties of W during the normal operation of the fusion power plant. During plasma exposure, the lighter alloying elements are preferentially sputtered at the surface, but in case of a LOCA, the plasma quenches and sputtering stops and diffusion of the alloying elements to the surface becomes intensive. The diffusion of Cr to the surface due to alloying elements (Y, Ti) yields a protective oxide layer stopping the sublimation of WO3. The phase stability and short-range ordering of ternary alloys in W-Cr-Y(Ti) systems has been investigated, using combination of Density Functional Theory (DFT) and Cluster Expansion (CE) methods with Monte-Carlo (MC) simulations. It has been found out from the DFT calculations, that all pairs in the W-Cr-Y system have positive values of the enthalpy of mixing, while most of the Cr-Ti and Ti-W binary structures have negative enthalpies of mixing. The shift in the short-range order as a function of temperature between Cr and W has been predicted as a result of Y addition in W-Cr-Y alloys compared to W70Cr30, by around 400 K towards lower temperatures. A strong tendency towards clustering of Y has been observed even at elevated temperatures (1800 K). The decrease of the order–disorder transition temperature (ODTT) as a result of the Y addition has been observed, while the addition of Ti has not shown any significant changes in the ordering of W-Cr-Ti alloys compared to W-Cr alloy. Our MC simulations showed that for the W70Cr29Y1 alloy the enthalpy of mixing (Hmix) value is positive in the whole analysed temperature range. Free energy of mixing above 1000 K has been calculated from the first nearest neighbours approximation for W70Cr29Y1 and W70Cr29Ti1 alloys. The results of the present investigations provide an insight enabling for optimizing chemical composition of materials for future plasma facing components.

Effect of Al addition on the microstructure, mechanical and wear properties of TiZrNbHf refractory high entropy alloys

A series of AlxTiZrNbHf refractory high entropy alloys (RHEAs) were prepared to investigate the mechanical and wear properties. Despite the different crystal structures of each constituent, the RHEAs exhibited body centered cubic (BCC) phase structures as revealed by X-ray diffraction and transmission electron microscopy. Along with the primary BCC phase, another ordered BCC phase appeared in AlTiZrNbHf, being supported by a high negative mixing enthalpy (<−16.28 kJ-mol−1) and a low valence electron concentration (< 4.04). The improved mechanical properties and wear resistance by the Al addition are ascribed to severe lattice distortion and second phase strengthening. These findings highlight significant alterations in the microstructure, mechanical and wear properties with the Al addition, which are beneficial to the design of alloys for wear applications.

Via resistance increase accelerated by thermal stress

The resistance between an aluminum (Al) metal line and a tungsten (W) via increased after thermal stress. In the wafer processing, the post W chemical mechanical planarization (WCMP) cleaning left residual WO3 on the W plug. Since the resistivity of WO3 is low, the interfacial resistance was low and escaped the first electrical detection. However, the WO3 was spontaneously reduced by the Ti of the overlaying metal line, through which TiO2 formed. The reduction was accelerated by a thermal stress. Compared with WO3, TiO2 has a more negative formation enthalpy, and the valence electrons of Ti are more tightly bound to the O ion cores. As a result, the resistivity of TiO2 is higher than that of WO3. In addition, there was Al diffusing through TiN to reduce the oxides of both Ti and W. The product Al2O3 is thermodynamically the most stable, and the most resistive amongst the oxides of the three metals. Meanwhile, due to its superhydrophilicity, the residual WO3 had retained liquid that contained hydrofluoric acid (HF) used for the post WCMP cleaning. The HF corroded the Ti glue layers of both the via sidewall and the overlaying metal line. The dry etch of the metal line exposed the Ti-corroded volume of the metal line to the deionized (DI) water for the post metal-etch cleaning. The DI water oxidized the Ti on the W plug. The W/TiN interface on the W plug was also subjected to enhanced mechanical stress which led to voids along the interface. All these factors had caused an increase of the via resistance which eventually became high enough to be detected. The fix employed was to increase the NH4OH concentration to more effectively remove the residual WO3. The thermal stress implemented in the fab therefore had prevented the residual WO3 from developing into a costly field failure.

First-principles study on the structural, electronic and optical properties of vacancy-ordered double perovskites Cs2PtI6 and Rb2PtI6

In this paper, the structural, electronic and optical properties of vacancy-ordered double perovskites Cs2PtI6 and Rb2PtI6 were studied based on first-principles calculations. The stability of studied compounds is ensured by the negative formation enthalpy. The calculated results show that both Cs2PtI6 and Rb2PtI6 are indirect bandgap semiconductors. The bandgap values of Cs2PtI6 and Rb2PtI6 are 1.29 and 1.15 eV, respectively, which are suitable for photosensitive materials of solar cells. For both Cs2PtI6 and Rb2PtI6, the valence band maximum (VBM) is dominated by the I-5p orbitals and the conduction band minimum (CBM) is mainly composed of the I-5p orbitals along with the Pt-5d orbitals. The optical properties of Cs2PtI6 and Rb2PtI6 in the photon energy range from 0 to 12 eV have been comprehensively studied by the HSE06 method. The results show that these two compounds exhibit excellent light absorption, especially in the ultraviolet range. Due to the suitable bandgaps and excellent light absorption, the vacancy-ordered double perovskites Cs2PtI6 and Rb2PtI6 can be effective candidates for lead-free photovoltaic materials.

A physicochemical, thermodynamical, structural and computational evaluation of kynurenic acid/cyclodextrin complexes

In this work, the interaction between Kynurenic acid (KYNA) and several natural and modified cyclodextrins (CDs) is carried out. Among all the CD tested, HPβ-CD showed the strongest complexation constant (KF), with a value of 270.94 ± 29.80 M−1. Between natural (α- and β-) CDs, the complex of KYNA with β-CD was the most efficient. The inclusion complex of KYNA with CDs showed a strong influence of pH and temperature. The KF value decreased at high pH values, when the pKa was passed. Moreover, an increase of the temperature caused a decrease in the KF values. The thermodynamic parameters of the complexation (ΔH°, ΔS° and ΔG°) were studied with negative entropy, enthalpy and spontaneity of the process at 25 °C. Moreover, the inclusion complex was also characterized using FTIR and TGA. Finally, molecular docking calculations provided different interactions and their influence in the complexation constant.

Liquid Structure and Thermophysical Properties of Ternary Ni-Fe-Co Alloys Explored by Molecular Dynamics Simulations and Electrostatic Levitation Experiments

The structure, thermodynamic and dynamic properties of normal and metastable liquid Ni2xFe50−xCo50−x alloys were systematically investigated by combining electrostatic levitation (ESL) experiments and molecular dynamics (MD) simulations. Their composition dependence and mutual interaction were explored in detail. The actual densities of liquid Ni90Fe5Co5, Ni80Fe10Co10, Ni70Fe15Co15 and Ni60Fe20Co20 alloys were measured by ESL experiments in a wide temperature range. The simulated densities of these liquid alloys are in good agreement with the corresponding experimental data. The thermodynamic properties show that all these alloys exhibit a negative excess volume and mixing enthalpy. Meanwhile, their pair distribution functions indicate that Fe and Co atoms easily bond with Ni atoms and have a similar characteristic to each other if compared with Ni atoms. Furthermore, the structure factors validate that there exist icosahedral short-range and medium-range orders of Ni-Ni, Fe-Fe, Fe-Co and Co-Co bonds in these liquid alloys. Additionally, the solute diffusion properties reveal that the correlation between dynamic behavior and alloy composition is determined by the diffusion of Fe and Ni atoms.

Effective removal of arsenate from wastewater using aluminium enriched ferric oxide-hydroxide recovered from authentic acid mine drainage

This study explored an eco-friendly approach for the synthesis of novel aluminium enriched ferric oxide-hydroxide (Fe/AlO(OH)) from authentic acid mine drainage (AMD). The synthesized Fe/AlO(OH) was subsequently tested for arsenate removal capabilities. Fe/AlO(OH) was synthesized from bona fide AMD via selective precipitation, thermal activation, and vibratory ball milling. One-factor-at-a-time (OFAAT) method was used to optimize operational parameters, which include adsorbent dosage, concentration, pH, agitation time, and temperature. Optimized conditions were observed to be 150 ppm of As(V), Solid: Liquid ratio – 1 g: 250 mL, contact time of 60 min, and ambient temperature and pH. Limited temperature and pH effects on adsorption were observed. Equilibrium data fits using Langmuir-, Freundlich-, Two surface Langmuir-, Dubinin-Radushkevich-, and Dubinin-Astokov isotherm models showed highly favorable adsorption conditions, the highest known maximum adsorption capacity for As(V) of 102–129 mg g−1, and coupled physisorption/diffusion limited adsorption. Thermodynamic analysis showed positive Gibbs free energy (ΔG°), negative enthalpy change (ΔH°), and positive entropy change (ΔS°) – likely a result of an inner sphere complexation of the As(V) with the Fe/Al surface. Considering the obtained results, valorization of AMD for the synthesis of Fe/AlO(OH) was viable and effective. This initiative could potentially minimize the footprints of AMD and arsenic pollution.

Study on mechanical, electronic and optical properties of Pb-free double halide perovskites In2TiX6 (X = Cl, Br, I) for solar cells based on first-principles

In recent years, perovskite solar cells have attracted the attention of many researchers due to their advantages such as high conversion efficiency, simple manufacturing process and low cost, and have become an important research direction in the field of new energy batteries. At the same time, it is also a very promising new type of solar cells. In this paper, the geometric characteristics, mechanical properties, electronic properties and optical properties of three perovskites In2TiCl6, In2TiBr6 and In2TiI6 were studied by using first-principles. The Poisson and Pugh’s ratios show the ductile characteristics of In2TiX6 (X = Cl, Br, I). The mechanical stability of studied compounds has been confirmed by the Born stability criteria. Moreover, the thermodynamic stability has been proved by the negative formation enthalpy and cohesive energy. In2TiCl6 and In2TiBr6 are indirect band gap semiconductors with band gap values 2.15 and 2.12 eV, respectively, and In2TiI6 is a direct band gap semiconductor with band gap value 1.24 eV. Theoretical calculations showed that In2TiI6 has better absorption capacity than In2TiCl6 and In2TiBr6 in the near ultraviolet and visible light regions. The results demonstrate that the compound In2TiI6 can be a potential candidate for excellent light absorbing material.

Determination of thermodynamic and microscopic origins of the Soret effect in sodium silicate melts: Prediction of sign change of the Soret coefficient.

The Soret effect in silicate melts has attracted attention in earth and material sciences, particularly in glass science and engineering, because a compositional change caused by the Soret effect modifies the material properties of silicate melts. We investigated the Soret effect in an Na2O-SiO2 system, which is the most common representative of silicate melts. Our theoretical approach based on the modified Kempers model and non-equilibrium molecular dynamics simulation was validated for 30Na2O-70SiO2(mol. %). The sign and order of the absolute values of the calculated Soret coefficients were consistent with the experimental values. The positive Soret coefficient of SiO2 in the SiO2-poor composition range was accurately predicted. Previous experimental studies have focused on SiO2-rich compositions, and only the negative sign, indicating SiO2 migration to the hot side, has been observed. In the SiO2-poor composition range, the Q0 structure was dominant and had four Si-O-Na bonds around an SiO4 unit. The Si-O-Na bond had high enthalpic stability and contributed to the large negative enthalpy of SiO2 mixing. According to our model, components with a large negative partial molar enthalpy of mixing will concentrate in the cold region. The microscopic and thermodynamic origins of the sign change in the Soret effect were determined.

Microstructure, wear and oxidation behavior of AlCrFeNiX (X = Cu, Si, Co) high entropy alloys produced by powder metallurgy

AlCrFeNiX (X = Cu, Si, Co) high entropy alloys (HEAs) were produced by mechanical alloying and sintering. The effects of the “X" additive on the microstructure, hardness, wear, and high-temperature oxidation behavior of HEAs were investigated. Different phases occurred in AlCrFeNiX HEAs depending on the “X" element. In addition to the BCC phase in all alloys, there are FCC phases in AlCrFeNiCu and AlCrFeNiCo alloys and two different intermetallic phases AlCrFeNiSi alloy. High negative mixing enthalpy values were found to be effective in phase and microstructure formation. In the alloy containing Si, 750 HV micro-hardness was seen as the highest hardness value. In the alloys containing Co and Cu, 450 and 420 HV micro-hardness values were determined, respectively. The best wear resistance and the lowest friction coefficient were seen in the AlCrFeNiSi alloy. In the wear tests performed at different loads, the increasing load increased the wear losses. The isothermal oxidation tests were conducted to HEAs at 1000 °C for 5, 25, and 75 h. Each HEAs exhibit very well oxidation resistance under the current conditions due to the selective alumina formation on the surface. It was not detected a dramatic difference in terms of oxidation behaviors of HEAs.

Comprehensive study of simultaneous adsorption of basic red 2 and basic violet 3 by an agro-industrial waste: dynamics, kinetics and modeling

This paper aims to evaluate the simultaneous adsorption of basic red 2 (BR2) and basic violet 3 (BV3) in a binary system in a batch mode using date stones as low cost adsorbents. For both dyes, experimental kinetic data were well fitted by the Brouers–Sotolongo model (R 2 =0.99) and intraparticle diffusion was the controlling step in mass transfer mechanisms. The intraparticle diffusion extent was found to be lower for BR2 (1.13×10 -11 cm 2 /s) than for BV3 (1.11×10 -11 cm 2 /s) when compared to individual solutions (1.24×10 -10 cm 2 /s and 1.76×10 -11 cm 2 /s for BR2 and BV3, respectively). The equilibrium study revealed lower adsorption capacities (41.95 and 88.91 mg/g for BR2 and BV3, respectively) compared to the individual sorption results (92.00 and 136.00 mg/g for BR2 and BV3, respectively) for both dyes. To assess the extent of competition and the preference of dyes for functional sites, competition and separation factors were calculated suggesting an antagonistic effect as well as a greater affinity for BV3 than for BR2 to the adsorption sites. The equilibrium adsorption results were best fitted by modified Langmuir and P-factor Langmuir isotherms for BR2 and BV3, respectively. Besides, based on enthalpy values (16.30 and 30.26 kJ/mol for BR2 and BV3, respectively), the simultaneous adsorption of both dyes was endothermic while the entropy revealed a higher affinity of the investigated adsorbent to BV3. The sorption process in separate systems (BR2 and BV3) was thermodynamically feasible for both dyes with negative free enthalpy values. The comparison to single systems showed an increase of affinity for BV3 contrarily to BR2 and, a decrease of spontaneity with higher extent for BR2.

Electronic nature, optical and mechanical properties of M2Pt2O7 (M = Sc, Y and La) pyrochlores: A DFT study

M2Pt2O7 (M=Sc,Y,andLa) pyrochlores, which are crystalline in face centered cubic (FCC) structure, have been investigated by Generalized Gradient Approximation (GGA) and meta-Generalized Gradient Approximation (meta-GGA) based on Density Functional Theory (DFT). The well-optimized structural parameters have been obtained during the relaxation process and the calculated negative formation enthalpies show their thermodynamic stability and structural synthesizability. Also, the electronic nature have been found to be semiconducting with band gaps as Eg= 1.80 eV (GGA) and 2.49 eV (mBJ) for Sc2Pt2O7, Eg= 1.49 eV (GGA) and 2.20 eV (mBJ) for Y2Pt2O7, and Eg= 0.98 eV (GGA) and 1.75 eV (mBJ) for La2Pt2O7. The calculated mechanical properties indicate that the materials are mechanically stable and it has been found that they are ductile and hard materials. The obtained optical parameters show that M2Pt2O7 (M=Sc,Y,andLa) pyrochlores may be considered in electronic device applications due having suitable band gaps and large absorption coefficients.

Efficient native biosorbent derived from agricultural waste precursor for anionic dye adsorption in synthetic wastewater

In this work, a potential biosorbent is prepared from agricultural waste material (ash seed) without any treatment. This biomaterial could be successfully used as a low-cost adsorbent for the removal of an anionic dye named Cibacron Blue (CB), under optimal conditions. The prepared adsorbent was characterized by scanning electron microscope (SEM) coupled with EDX, Fourier transforms infrared spectrometer (FTIR), thermogravimetric analysis (TGA), and point of zero charge (pHpzc). The adsorption experiments were carried out in batch mode at room temperature. Results show that the rate of CB dye removal exceeds 95 % using a dose of 2 g/L ash seed at C0 = 25 mg/L and pH = 2.2. The kinetic data were analyzed using the pseudo-first-order, pseudo-second-order, Elovich’s, Bangham, intraparticle diffusion, and Boyd kinetic. Results show that the pseudo-second-order model fits better the experimental data. The isotherm data of the CB dye adsorption were analyzed with several theoretical models (Langmuir, Freundlich, and monolayer model coupled to real gaz (MMRG)). It was found that the adsorption process of the CB dye is well described by monolayer model coupled to real gaz (MMRG) compared to other models. The negative enthalpy (ΔH°) and free enthalpy (ΔG°) indicate the physical and spontaneous nature of CB adsorption. Therefore, the prepared material can serve as a potential adsorbent for removal of CB dye from industrial effluents.

Microstructure and mechanical properties of wedge-shaped CuZrAlNd metallic glass ingots

In this study, (Cu43Zr48Al9)100-xNdx (x = 1, 2, 3, or 4 at. %) bulk metallic glasses (BMGs) were successfully prepared by casting in wedge-shaped copper moulds. We studied the effect of rare-earth neodymium (Nd) addition on the glass forming ability (GFA) and mechanical properties of (Cu43Zr48Al9)100-xNdx. The enhancement of GFA in Cu–Zr–Al BMGs with Nd addition could be well explained by the atomic size difference δ, electronegativity difference Δx and negative mixing enthalpy ΔHmix. Of the alloys investigated, the (Cu43Zr48Al9)97Nd3 BMG exhibited the best GFA, with a high compressive strength of 2045 MPa. To prepare the wedge-shaped cast, the melt was subjected to a wide range of cooling rates that allow investigation of the transformed microstructure and dynamics. A U-shaped crystal-to-glass phase transition boundary was obtained. Based on the microstructural analysis of (Cu43Zr48Al9)97Nd3, we found that the equilibrium microstructure of this alloy consists of [CuZr + Cu10Zr7 + CuZr2].