The influence of Mn2+ and Ni2+ ions on the surface properties of the aluminium oxide samples using Q-TG and Q-DTG data

The paper presents the complex studies of adsorption and porosity of pure and modified–aluminium oxides samples. The presence of Mn²⁺ and Ni²⁺ modifiers on the aluminium oxide surface causes increase in water adsorption capacity and its decrease in the case of benzene and n-octane. This is due to decrease of specific surface area, volume and radius of pores as a result of surface impregnation and microcrystals formation during modification with manganese and nickel chlorides. Microcrystals formation on the surface and porosity decrease where confirmed by the AFM and SEM studies. From the Q-TG and Q-DTG data, the energies of liquid desorption from the surface of the samples and the functions of desorption, energy distribution were calculated. High degree of nonlinearity of the run of the functions resulting from great heterogeneity of the studied surface was found. Adsorption of cations creates more homogeneous surface of aluminium oxide, and it is responsible for the change in adsorbate molecule interaction energy and changes mechanism of adsorption and desorption as well as thickness and structure of the adsorbed film. From the experimental data some parameters characterizing adsorption properties and porosity of the studied samples were determined using the measuring methods (thermal analysis, sorptomate, porosimetry, AFM).     

Radiation Stability of Copper Films under Irradiation with He<Superscript>2+</Superscript> Ions

The effect of irradiation of copper films with low-energy He²⁺ ions on their structural properties has been studied. The surface morphology and structural properties of the samples before and after irradiation have been examined by scanning electron microscopy, energy dispersive analysis, and X-ray diffraction. Bombardment of the initial samples with He²⁺ ions at a fluence of 1 × 10¹⁶ion/cm² alters the surface morphology of copper films and leads to the formation of nanoscale inclusions of hexagonal shape. An increase in the fluence to 1 × 10¹⁷ ion/cm² and higher results in the formation of cracks and amorphous oxide inclusions on the sample surface.     

Thermodynamics of citrate complexation with Mn<Superscript>2+</Superscript>, Co<Superscript>2+</Superscript>, Ni<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript> ions

Isothermal titration calorimetry has been used to determine the stoichiometry, formation constants and thermodynamic parameters (ΔG ^o, ΔH, ΔS) for the formation of the citrate complexes with the Mn²⁺, Co²⁺, Ni²⁺ and Zn²⁺ ions. The measurements were run in Cacodylate, Pipes and Mes buffer solutions with a pH of 6, at 298.15 K. A constant ionic strength of 100 mM was maintained with NaClO₄. The influence of a metal ion on its interaction energy with the citrate ions and the stability of the resulting complexes have been discussed.     

Sorption of Cu<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript> by Natural Biomaterial: Duck Feather

Feather fibers were modified by treatment with 5% tannic acid (TA) solution. Kinetics of the modification was investigated as a function of the reaction time. The maximum loading of TA on feather reached 8.3% after being treated by TA for 9 h. The adsorption of metal cations (Cu²⁺, Zn²⁺) by unmodified and TA-modified feather fibers was investigated as a function of fiber weight gain, temperature, and pH of the metal solution. The adsorption was enhanced at alkaline pH and ambient temperature and increased with the weight gain of TA. The maximum uptake of metal cations (Cu²⁺, 0.77 mmol/g; Zn²⁺, 0.95 mmol/g) was obtained by TA-modified feather at weight gain: 8.3%, pH 11, while at the acidic pH, the adsorption of metal cations by either unmodified or TA-modified feather was negligible. The influence of anions on the adsorption of metal cations was also studied. The uptake of Cu²⁺ from chloride was higher and faster than that from nitrate. Desorption of the metals was performed at acidic pH 2.5 for 48 h. The feather–TA–metal complexes exhibited higher stability for metal cations than the feather–metal complexes. All these experiments reveal that TA-modified feather fibers have good adsorption to metal cations and can be used as metal adsorbent in wastewater treatment.     

Incorporation of Mg<Superscript>2+</Superscript>, Sr<Superscript>2+</Superscript>, Ba<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript> into aragonite and comparison with calcite

We have investigated the presence of foreign ions into the bulk structure and the external surfaces of aragonite using periodic ab-initio methods. Four cations isovalent to Ca²⁺ were studied: Mg²⁺, Sr²⁺, Ba²⁺ and Zn²⁺. The calculations were performed at structures (bulk, surface) that contain four and eight CaCO₃ units. Our results, at the Hartree-Fock level, show that the incorporation of those ions into aragonite depends strongly on their size. Mg²⁺ and Zn²⁺, due to their smaller size, can substitute Ca²⁺ ions in the crystal lattice while the incorporation of Sr²⁺ and Ba²⁺ into aragonite is energetically less favoured. Examination of the [011], [110] and [001] surfaces of aragonite revealed that the surface incorporation reduces the energetic cost for the larger ions. These systems provide challenging examples for most shape analysis methods applied in Mathematical Chemistry.     

Facile one-pot synthesis of nano-zinc hydroxide by electro-dissolution of zinc as a sacrificial anode and the application for adsorption of Th<Superscript>4+</Superscript>, U<Superscript>4+</Superscript>, and Ce<Superscript>4+</Superscript> from aqueous solution

Facilely synthesized zinc hydroxide nanoparticles by electro-dissolution of zinc sacrificial anodes were investigated for the adsorption of thorium (Th⁴⁺), uranium (U⁴⁺) and cerium (Ce⁴⁺) from aqueous solution. Various operating parameters such as effect of pH, current density, temperature, electrode configuration, and electrode spacing on the adsorption efficiency of Th⁴⁺, U⁴⁺ and Ce⁴⁺ were studied. The results showed that the maximum removal efficiency was achieved for Th⁴⁺, U⁴⁺ and Ce⁴⁺ with zinc as anode and stainless steel as cathode at a current density of 0.2 A/dm² and pH of 7.0. First- and second-order rate equations were applied to study the adsorption kinetics. The adsorption process follows second order kinetics model with good correlation. The Langmuir, Freundlich adsorption models were applied to describe the equilibrium isotherms and the isotherm constants were determined. The experimental adsorption data were fitted to the Langmuir adsorption model. Thermodynamic parameters such as free energy (ΔG°), enthalpy (ΔH°), and entropy changes (ΔS°) for the adsorption of Th⁴⁺, U⁴⁺ and Ce⁴⁺ were computed to predict the nature of adsorption process. Temperature studies showed that the adsorption was endothermic and spontaneous in nature.     

Interaction energies of histidine with cations (H<Superscript>+</Superscript>, Li<Superscript>+</Superscript>, Na<Superscript>+</Superscript>, K<Superscript>+</Superscript>, Mg<Superscript>2+</Superscript>, Ca<Superscript>2+</Superscript>)

The imidazol side group of histidine has two nitrogen atoms capable of being protonated or participating in metal binding. Hence, histidine can take on various metal-bound and protonated forms in proteins. Because of its variable structural state, histidine often functions as a key amino acid residue in enzymatic reactions. Ab initio (HF and MP2) calculations were done in modeling the cation (H⁺, Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺) interaction with side chain of histidine. The region selectivity of metal ion complexation is controlled by the affinity of the side of attack. In the imidazol unite of histidine the ring nitrogen has much higher metal ion (as well as proton) affinity. The complexation energies with the model systems decrease in the following order: Mg²⁺ > Ca²⁺ > Li⁺ > Na⁺ > K⁺. The variation of the bond lengths and the extent of charge transfer upon complexation correlate well with the computed interaction energies.     

High-yield preparation of rod-like CaSO<Subscript>4</Subscript>/Fe<Superscript>0</Superscript> magnetic composite for effective removal of Cu<Superscript>2+</Superscript> in wastewater

In this study, a simple approach was described for the fabrication of CaSO₄/Fe⁰ composite used as a novel adsorbent for the reductive removal of Cu²⁺ from aqueous solutions. The magnetic CaSO₄/Fe⁰ composite was prepared by a solid state reaction at 550 °C in the H₂ atmosphere using CaSO₄·2H₂O/α-FeOOH as a precursor. The structure and morphology of the as-synthesized magnetic composite were characterized by X-ray diffraction, field emission scanning electron microscopy and a superconducting quantum interference device, respectively. Results showed that the CaSO₄/Fe⁰ composite with a rod-like shape could be easily acquired from the CaSO₄·2H₂O/α-FeOOH precursor with the ratio of 1:0.5 at 550 °C in the H₂ atmosphere for 1 h. The CaSO₄/Fe⁰ composite exhibited enhanced performance relevant to the reductive removal of Cu²⁺. The removal amount of Cu²⁺ increased linearly with increasing of concentration of Cu²⁺ in wastewater. Possible removal mechanisms were proposed as follows: (1) the formation of Cu₂O by fast reduction of Cu²⁺ with Fe⁰ nanoparticles on interface of CaSO₄/Fe⁰ composite, (2) proper adsorption of Cu²⁺ on the surface of CaSO₄/Fe⁰ composite, (3) the hydrous iron oxide (HIO) such as Fe (OH)₃ and FeOOH in situ generated on the rest of CaSO₄/Fe⁰ composite could further adsorb Cu²⁺ from wastewater.     

Thermodynamics of resolvation of Mg<Superscript>2+</Superscript>, Ca<Superscript>2+</Superscript>, Cd<Superscript>2+</Superscript>, and Cu<Superscript>2+</Superscript> ions in aqueous-ethanol mixtures on the basis of volta potential difference method

The volta potential difference method at 298.15 K was used to determine the real primary medium effect for magnesium, calcium, cadmium, and copper ions, and also the real Gibbs transfer energy of these ions from water into a mixed water ethanol (EtOH) solution. The surface potential value at the nonaqueous solution/gas phase interface $ \Delta \chi _{H_2 O}^{EtOH} $ \Delta \chi _{H_2 O}^{EtOH} was obtained. With account for this value, chemical thermodynamic characteristics of the studied ions in the water-ethanol solvent were calculated and the effect of composition and nature of the mixed solvent on the values obtained was analyzed. The dependence of variation in the thermodynamic characteristics of cation resolvation was established on their crystallographic radius that corresponds to the following sequence: Ca²⁺ < Cd²⁺ < Cu²⁺ < Mg²⁺.     

Complex formation of maleic acid with the Zn<Superscript>2+</Superscript>, Ni<Superscript>2+</Superscript>, Co<Superscript>2+</Superscript>, Cu<Superscript>2+</Superscript> in aqueous solution

The process of complex formation of maleic acid (H₂L) with the ions Zn²⁺, Ni²⁺, Co²⁺, Cu²⁺ was studied by potentiometric titration in a wide range of concentration ratios at 298 K and I = 0.1 mol/l (NaNO₃). The moieties ZnL, CoL, NiL, NiL ₂ ^2? , CuL, and CuL ₂ ^2? were detected and their stability constants were determined.     

Effect of temperature on the sorption behavior of sodium potassium fluorophlogopite with respect to the heavy metal ions Cd<Superscript>2+</Superscript>, Hg<Superscript>2+</Superscript>, and Pb<Superscript>2+</Superscript>

The effect of temperature on the sorption behavior of a synthesized gel structurally close to the fluorine mica mineral, sodium potassium fluorophologopite, was studied for the heavy metal ions Cd²⁺, Hg²⁺, and Pb²⁺. The synthesized gel was characterized by X-ray powder pattern, energy dispersive spectrometry, infrared spectroscopy, and thermogravimetric analysis and was found to have the composition Na_0.5K_0.5Mg(AlSi₃O₁₀)F₂·6H₂O. The effect of temperature on sorption was studied with respect to varying concentrations of metal ions. The overall sorption capacity of the synthesized gel was found to depend on the number of ion active groups per unit weight of the material. The data were expressed in terms of distribution coefficients (K _d). Sorption data followed Freundlich adsorption isotherms. Studies showed that sorption decreased as the concentration of metal ions increased and increased as the temperature grew, which was evidence that the process was endothermic. The text was submitted by the authors in English.     

Preparation of graphene oxide and its application in Ni<Superscript>2+</Superscript> removal

Graphene oxide (GO) has been prepared by the modified Hummers method using graphite as starting material. The product was studied by the X-ray diffraction (XRD), Raman spectroscopic, transmission electron microscopic (TEM), and scanning electron microscopic (SEM) analyses. Adsorption capacity of GO for heavy metal ions was studied for the example of the Ni²⁺ ions and the adsorption kinetics and adsorption isotherm were determined. It was shown that the adsorption equilibrium curves are adequately described by the Langmuir equation.     

Thermal behavior of Cd<Superscript>2+</Superscript> and Co<Superscript>2+</Superscript> phenyl-vinyl-phosphonates under non-isothermal condition

The thermal behavior of Cd²⁺ and Co²⁺ phenyl-vinyl-phosphonates was studied using two different experimental strategies: the coupled TG-EGA (FTIR) technique by decomposition in nitrogen respectively air, and the kinetic analysis of TG data obtained in dynamic air atmosphere at four heating rates. In nitrogen two decomposition steps were observed: the loss of crystallization water, respectively the decomposition of the phenyl-vinyl radical. In air, the same dehydration was observed as the first step, but the second one is a thermooxidation of the organic radical with formation of the pyrophosphoric anion. The kinetic analysis of the TG non-isothermal data was performed by the isoconversional methods suggested by Friedman and Flynn, Wall and Ozawa, as well as by the non-parametric (Sempere-Nomen) method. All processes put in evidence in TG curves exhibit strong changes of the activation energy values with the conversion degree, which mean that these processes are complex ones. Assuming that each of these processes consists in two steps, the application of non-parametric method leads to average values of the activation energy close to the average values of this parameter obtained by isoconversional methods.     

Synthesis and Properties of Surface Molecular Imprinting Adsorbent for Removal of Pb<Superscript>2+</Superscript>

A new chitosan imprinting adsorbent using diatomite as core material was prepared by using the surface molecular imprinting technology with the Pb²⁺ as imprinted ion. The preparation process conditions of the surface molecular imprinting adsorbent were studied. The adsorbent was characterized by using Fourier transform infrared (FTIR) spectrum. FTIR spectrum indicated that it was cross-linked by epichlorohydrin. The new imprinting adsorbent could provide a higher adsorption capacity for Pb²⁺, which reached 139.6 mg/g increasing 32.3% compared with cross-linking chitosan adsorbent (the initial Pb²⁺ concentration of 600 mg/L). The adsorption velocity was quick and the equilibration time of the imprinting adsorbent for Pb²⁺ was 3 h that shortened about 40% compared with cross-linking chitosan adsorbent. It had a more wide pH range of 5–7 than that of cross-linking chitosan adsorbent. The new imprinting adsorbent can be reused for up to ten cycles without loss of adsorption capacity. In the kinetics and isotherm study, the pseudosecond order model and Langmuir model could represent the adsorption process.     

Near-infrared quantum cutting in Tb<Superscript>3+</Superscript> and Yb<Superscript>3+</Superscript>-doped Y<Subscript>2</Subscript>O<Subscript>3</Subscript> nanophosphors

Properties of the quantum-cutting phosphors are dependent on various factors such as dopant concentration, crystallinity, homogeneity, particle size and surface morphology. Effective control of the above parameters can enhance the quantum-cutting ability of the phosphor material. Nano-sized particles of Y₂O₃:Tb³⁺,Yb³⁺ were prepared with a solution-based co-precipitation method and subsequent calcination. Effective control of the reaction parameters and doping concentration helped to produce uniform nanostructures with high quantum-cutting efficiency up to 181.1 %. The energy transfer mechanism between Tb³⁺ and Yb³⁺ was studied by considering their spectroscopic properties and time-resolved spectroscopy. The high efficiency and small particle size of the quantum-cutting phosphor Y₂O₃:Tb³⁺,Yb³⁺ make it a suitable candidate for its application in solar cells.     

The standard thermodynamic characteristics of resolvation of the K<Superscript>+</Superscript>, Ca<Superscript>2+</Superscript>, Cd<Superscript>2+</Superscript>, and Br<Superscript>−</Superscript> ions in water-acetone mixtures

The standard real and chemical thermodynamic characteristics of transfer of the K⁺, Ca²⁺, Cd²⁺, and Br^? ions from water into water-acetone solvents of various compositions were analyzed to study the rules governing the solvation of these ions in mixed solvents and its special features. All calculations were performed within the framework of the vertical jet method at 298.15 K. The energy of resolvation as a function of ion charges and crystallographic radii was found to increase in the series K⁺ < Ca²⁺ < Cd²⁺ < Al³⁺     

An imprinted polymer for removal of Cd<Superscript>2+</Superscript> from water samples: Optimization of adsorption and recovery steps by experimental design

A new ion-imprinted polymer（ⅡP） was synthesized by copolymerization of 4-vinylpyridine（monomer）, ethyleneglycoldimethacrylate（cross-linker） and 2,2-azobis-isobutyronitrile（initiator） in the presence of Cd²⁺ and quinaldic acid（complexing agent）.It was found that the adsorption capacity of IIP and blank polymer were 45.0 and 6.2 mg g^-1, respectively.The relative selectivity coefficients of the imprinted polymer for different binary mixture were also calculated. Compared to non-imprinted polymer（NIP）,theⅡP had higher selectivity for Cd（Ⅱ）.TheⅡP was used as a sorbent for cadmium extraction from water samples by using a simple batch extraction procedure.The effect of different parameters on Cd²⁺ extraction and its recovery from theⅡP were evaluated and optimized by using experimental design methodology.The optimized adsorption/desorption procedure was applied for cadmium removal from the real water samples.The obtained recoveries proved that thisⅡP could be used for removal of trace cadmium ions from water samples.     

Enhancement of the photoluminescence and long afterglow properties of Ca<Subscript>2</Subscript>MgSi<Subscript>2</Subscript>O<Subscript>7</Subscript>:Eu<Superscript>2+</Superscript> phosphor by Dy<Superscript>3+</Superscript> co-doping

The Ca₂MgSi₂O₇:Eu²⁺ and Ca₂MgSi₂O₇:Eu²⁺, Dy³⁺ long afterglow phosphors were synthesized under a weak reducing atmosphere by the traditional high temperature solid state reaction method. The synthesized phosphors were characterized by powder X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX) techniques. The luminescence properties were investigated using thermoluminescence (TL), photoluminescence (PL), long afterglow, mechanoluminescence (ML), and ML spectra techniques. The crystal structure of sintered phosphors was an akermanite type structure, which belongs to the tetragonal crystallography. TL properties of these phosphors were investigated, and the results were also compared. Under the ultraviolet excitation, the emission spectra of both prepared phosphors were composed of a broad band peaking at 535 nm, belonging to the broad emission band. When the Ca₂MgSi₂O₇:Eu²⁺ phosphor is co-doped with Dy³⁺, the PL, afterglow and ML intensity is strongly enhanced. The decay graph indicates that both the sintered phosphors contain fast decay and slow decay process. The ML intensities of Ca₂MgSi₂O₇:Eu²⁺ and Ca₂MgSi₂O₇:Eu²⁺, Dy³⁺ phosphors were proportionally increased with the increase of impact velocity, which suggests that this phosphor can be used as sensors to detect the stress of an object.     

Photoacoustic and photoluminescence studies on ThO<Subscript>2</Subscript>:Sm<Superscript>3+</Superscript>

Nanocrystalline ThO₂:Sm³⁺ was synthesized using wet-chemical route and characterized using X-ray diffraction (XRD), photoacoustic (PA) and photoluminescence (PL) spectroscopy. PA absorptions of Sm³⁺ doped samples are found to be quite weak as compared to Nd³⁺, while PL of Sm³⁺ was intense. As the energy gap between lowest luminescent levels and highest non-luminescent level in samarium ion is around 7000 cm^?1; it is highly fluorescing compared to Nd³⁺ which has close by levels. Through photoacoustic data it was pointed out that large covalent character exists in ThO₂:Nd³⁺ compared to ThO₂:Sm³⁺.     

Factors affecting the sorption behavior of Cs<Superscript>+</Superscript> and Sr<Superscript>2+</Superscript> using biosorbent material

In this study, saw dust has been used as precursor for production of low cost activated carbon using potassium hydroxide (KOH) and steam activation technique. The activated carbon was used to remove Cs⁺ and Sr²⁺ ions from aqueous solutions by batch operation, and the extent of adsorption was investigated as a function of solution pH, temperature, shaking time, and initial concentration. The influence of interfering ions was also investigated. The removal of metal ions was pH dependent and the adsorption capacity reaches its maximum 43% and 61.5% at pH 5.0 and 6.0 for Cs⁺ and Sr²⁺ ions, respectively. Thermodynamic studies showed different behaviours where an endothermic, non-spontaneous process was shown for Cs⁺ while an exothermic, spontaneous process was obtained for Sr²⁺. The kinetic data of both ions was described well by pseudo-second order rate equation. The two equilibrium models (Langmuir and Freundlich) have been also applied. Desorption studies indicated that HCl was the most effective desorbing eluent. The investigated adsorbent showed good results towards cesium and strontium removal from aqueous media that could be a promising method due to its low-cost and good efficiency.