Geochemistry of the upper Han River basin, China: 2: Seasonal variations in major ion compositions and contribution of precipitation chemistry to the dissolved load

A total of 252 water samples were collected from 42 sites across the upper Han River basin during the time period from 2005–2006. Major ions (Cl⁻, NO₃⁻, SO₄²⁻, HCO₃⁻, Na⁺, K⁺, Ca²⁺ and Mg²⁺), Si, water temperature, pH, EC and TDS were determined and consequently correlation matrix, analysis of variance, factor analysis and principal component analysis were performed in order to identify their seasonal variations and atmospheric inputs into river solutes. The results reveal that pH, EC, TDS, Cl⁻, SO₄²⁻, HCO₃⁻, Ca²⁺ and Mg²⁺, K⁺ and Si generally tend to show the minimum compositions in months belong to the rainy season, while the dry season for NO₃⁻ and Na⁺. NO₃⁻, Mg²⁺ and Si have the maximum concentrations in months belong to the rainy season. By comparing the major ions relating to hydrological regime, NO₃⁻, contrary to other elements, has higher concentration in the rainy season. The overall water quality is non-polluted, while there are indications of enrichment of inorganic anions including NO₃⁻ causing water entrophication in the near future. The atmospheric inputs contribute to river solutes is limited with a mean inputs of approximate 1% in the basin. The understanding of the major ion dynamics would help water quality conservation in the basin for China's interbasin water transfer project.     

Scleral Lens Sensor for Ocular Electrolyte Analysis

The quantitative analysis of tear analytes in point-of-care settings can enable early diagnosis of ocular diseases. Here, a fluorescent scleral lens sensor is developed to quantitatively measure physiological levels of pH, Na⁺, K⁺, Ca²⁺, Mg²⁺, and Zn²⁺ ions. Benzenedicarboxylic acid, a pH probe, displays a sensitivity of 0.12 pH units within pH 7.0–8.0. Crown ether derivatives exhibit selectivity to Na⁺ and K⁺ ions within detection ranges of 0–100 and 0–50 mmol L⁻¹, and selectivities of 15.6 and 8.1 mmol L⁻¹, respectively. A 1,2 bis(o-aminophenoxy)ethane-N,N,-N',N'-tetraacetic-acid-based probe allows Ca²⁺ ion sensing with 0.02–0.05 mmol L⁻¹ sensitivity within 0.50–1.25 mmol L⁻¹ detection range. 5-Oxazolecarboxylic acid senses Mg²⁺ ions, exhibiting a sensitivity of 0.10–0.44 mmol L⁻¹ within the range of 0.5–0.8 mmol L⁻¹. The N-(2-methoxyphenyl)iminodiacetate Zn²⁺ ion sensor has a sensitivity of 1 µmol L⁻¹ within the range of 10–20 µmol L⁻¹. The fluorescent sensors are subsequently multiplexed in the concavities of an engraved scleral lens. A handheld ophthalmic readout device comprising light-emitting diodes (LEDs) and bandpass filters is fabricated to excite as well as read the scleral sensor. A smartphone camera application and an user interface are developed to deliver quantitative measurements with data deconvolution. The ophthalmic system enables the assessment of dry eye severity stages and the differentiation of its subtypes.     

Ion-selective properties of metastable (VO)<Subscript>0.09</Subscript>V<Subscript>0.18</Subscript>Mo<Subscript>0.82</Subscript>O<Subscript>3</Subscript> · 0.54H<Subscript>2</Subscript>O

This paper describes a thin-film solid electrode with an ion-sensitive membrane based on the mixed oxide (VO)_0.09V_0.18Mo_0.82O₃ · 0.54H₂O. The electrode is selective for tetravalent vanadium in the concentration range 3 ≤ pC _V ⁴⁺ ≤ 5 and acidity range 4.5 ≤ pH ≤ 6, with a slope close to the theoretical value. In the range 1 ≤ pH < 5, the electrode responds to changes in hydrogen ion concentration, with a slope of 50 ± 2 mV/pH. Its alkali-metal-ion response shows up in the range 1 ≤ pC _M ⁺ ≤ 4 for pH ≥ 6. We examine the effect of the Li⁺, K⁺, Na⁺, Cs⁺, Rb⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Co²⁺, Ni²⁺, Mn²⁺, Al³⁺, Cr³⁺, and VO₂⁺ ions on the potential of the electrode and determine its selectivity coefficients for these cations.     

Using a synthetic body fluid (SBF) solution of 27 mM HCO3− to make bone substitutes more osteointegrative

A Tris–HCl-buffered synthetic body fluid (SBF) solution, mimicking the human blood plasma, with the following ion concentrations of 27 mM HCO₃⁻, 2.5 mM Ca²⁺, 1.0 mM HPO₄²⁻, 142 mM Na⁺, 125 mM Cl⁻, 5 mM K⁺, 1.5 mM Mg²⁺, and 0.5 mM SO₄²⁻ was used as an aqueous medium to process a number of bone substitute materials under the so-called biomimetic conditions of 37 °C and pH 7.4. This solution was named as Tris–SBF-27 mM. Firstly, collagen sponges were soaked in Tris–SBF-27 mM solution at 37 °C and were found to be fully covered with nanoporous apatitic calcium phosphate (Ap-CaP). The composites of collagen–Ap-CaP biomaterials are expected to be used in orthopedic and dental surgery. Secondly, Ap-CaP short whiskers or microrods with a novel nanotexture and surface areas higher than 45 m²/g were synthesized in Tris–SBF-27 mM solution. Thirdly, calcium sulfate cements doped with CaHPO₄ (monetite), were shown to have apatite-inducing ability upon ageing in Tris–SBF-27 mM. CaHPO₄ addition in calcium sulfate was found to improve its mechanical strength, measured after cement setting reaction. Pure calcium sulfate cement pellets were not stable in Tris–SBF-27 mM solutions and crumbled into a powder. All the samples were characterized by SEM, XRD, FTIR, surface area and mechanical strength measurements.     

Efficient Co-Adsorption and Highly Selective Separation of Cs+ and Sr2+ with a K+-Activated Niobium Germanate by the pH Control

¹³⁷Cs and ⁹⁰Sr are hazardous to ecological environment and human health due to their strong radioactivity, long half-life, and high mobility. However, effective adsorption and separation of Cs⁺ and Sr²⁺ from acidic radioactive wastewater is challenging due to stability issues of material and the strong competition of protons. Herein, a K⁺-activated niobium germanate (K-NGH-1) presents efficient Cs⁺/Sr²⁺ coadsorption and highly selective Cs⁺/Sr²⁺ separation, respectively, under different acidity conditions. In neutral solution, K-NGH-1 exhibits ultrafast adsorption kinetics and high adsorption capacity for both Cs⁺ and Sr²⁺ (q_m^Cs = 182.91 mg g⁻¹; q_m^Sr = 41.62 mg g⁻¹). In 1 M HNO₃ solution, K-NGH-1 still possesses q_m^Cs of 91.40 mg g⁻¹ for Cs⁺ but almost no adsorption for Sr²⁺. Moreover, K-NGH-1 can effectively separate Cs⁺ from 1 M HNO₃ solutions with excess competing Sr²⁺ and Mⁿ⁺ (Mⁿ⁺ = Na⁺, Ca²⁺, Mg²⁺) ions. Thus, efficient separation of Cs⁺ and Sr²⁺ is realized under acidic conditions. Besides, K-NGH-1 shows excellent acid and radiation resistance and recyclability. All the merits above endow K-NGH-1 with the first example of niobium germanates for radionuclides remediation. This work highlights the facile pH control approach towards bifunctional ion exchangers for efficient Cs⁺/Sr²⁺ coadsorption and selective separation.     

Determination of the ionic composition and oxidation state of uranium on the surface of oxides UO<Subscript>2+<Emphasis Type="Italic">x</Emphasis></Subscript> from the XPS data

The elemental and ionic composition of uranium oxides UO_2+x was determined using a procedure based on characteristics of the structure of the X-ray photoelectron spectra of outer and inner electrons of various uranium oxides. Although the bulk composition of the initial sample was close to the stoichiometry of UO₂, the surface had the composition UO_2.26 (6% U⁴⁺, 68% U⁵⁺, and 26% U⁶⁺, XPS). Samples kept at 70 and 150°C for a long time in simulated natural water (pH 7.0 ± 0.1) containing Ca²⁺, Na⁺, K⁺, and HCO₃⁻ ions were also examined. In the course of 6-month leaching, the fluorite-like structure of UO_2+x is preserved, but secondary U⁶⁺ phases, including schoepite, are formed on the sample surface. The oxygen coefficient k _O = 2 + x in UO_2+x on the surface of the examined samples was determined by XPS in relation to the temperature and time of keeping in water.     

Effect of humic acids and iron hydroxides deposited on the surface of clay minerals on the 137Cs immobilization

The effect exerted on the relationships of ¹³⁷Cs sorption by humic acids and iron hydroxides deposited on the surface of clay minerals, montmorillonite and kaolinite, differing in the exchange capacity, was studied. The presence of humic acids and Fe(OH)₃ deposited on the mineral surface leads to an increase in the ¹³⁷Cs sorption in a wide pH range (pH 4–9), suggesting the participation of functional groups of humic acids and ferrinol groups of iron(III) hydroxide in binding of the metal ions. The Na⁺, K⁺, and Ca²⁺ ions, on the contrary, with an increase in their concentration in aqueous solution decrease the immobilization of cesium radionuclides and favor their migration in the environment.     

Ion-selective properties of nanostructured alkali-metal-doped vanadium oxide

We have studied thin-film electrodes based on nanoparticulate vanadium oxide doped with alkalimetal cations. The hydrogen function of the electrodes manifests itself in the pH range 2–5, with a slope of 55, 54, and 54 ± 2 mV/pH for M _x V₂O₅·nH₂O with M = Li, Na, and K, respectively. Their sensitivity range is 10⁻⁴ to 10⁻¹ mol/l. The electrode potential as a function of concentration follows the Nernst equation with a slope of 55, 55, and 57 ± 2 mV/pC for M = Li, Na, and K, respectively. The Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Sr²⁺, and Ba²⁺ selectivity coefficients of the electrodes are determined.     

Enhanced red-emitting phosphor Na<Subscript>2</Subscript>Ca<Subscript>3</Subscript>Si<Subscript>2</Subscript>O<Subscript>8</Subscript>:Eu<Superscript>3+</Superscript> by charge compensation

A series of novel red-emitting Na₂Ca_3???x Si₂O₈:xEu³⁺ phosphors were synthesized by solid state reactions. The phosphors can strongly absorb 395 nm light, and show red emission with a good color purity. The excitation and emission spectra properties of Na₂Ca₃Si₂O₈:Eu³⁺ were characterized. Na₂Ca₃Si₂O₈:Eu³⁺ with self-compensated and alkali metal ions charge compensated approaches (2Ca²⁺→Eu³⁺ + M⁺, M?=?Li⁺, Na⁺, K⁺) have investigated, which found that the red emission of luminescent intensity can be greatly enhanced, and shows superior luminescent property to the commercial Y₂0₃S:Eu³⁺. The present work implies that the efficient charge compensated phosphors are promising candidates as red-emitting phosphor for w-LEDs.     

Micro-goethite in percolated water from Fushui Reservoir in Hubei Province,China

The sediments in the percolated water from Fushui Reservoir have been studied. The cause for formation of a special-shaped micro-goethite in the modern depositional environment (reservoir) as well as the action and the significance of microorganism in the biomineralization of iron are discussed in this paper. Tests show that the main cations in the percolated water include Ca²⁺, Mg²⁺, K⁺ and Na⁺, with minor Fe²⁺ and Fe³⁺, whereas the main anion is HCO₃⁻. The sediments from the percolated water are mainly oxidized products of iron. The mineral phase and the form of the particles from percolated water in Fushui Reservoir are studied by such means as powder X-ray diffraction (XRD), differential thermal analysis (DTA), infrared spectroscopic analysis (IR), Mössbauer spectrum, transmission electron microscope (TEM) and scanning electron microscope (SEM). The main mineral phases include goethite, quartz, illite, montmorillonite and small amounts of calcite, only slightly crystallized. The Mössbauer spectral characteristics and the special form of goethite imply that goethite originated from ferric bacteria. The following results can be reached: the sediments in Fushui Reservoir are mainly composed of amorphous ferric hydroxide colloid and weakly crystalline goethite; the genesis of goethite is related with ferric bacteria.     

Double-perovskite Ca3TeO6:Sm3+, Na+ orange–red-emitting phosphors for UV-based white light-emitting diodes

A series of double-perovskite orange–red-emitting Ca_(3?2x)Sm_xNa_xTeO₆ (x?=?0.01–0.25) phosphors have been synthesized via high-temperature method. The single-phase and orthorhombic structure of Ca₃TeO₆:Sm³⁺, Na⁺ phosphors was confirmed by X-ray powder diffraction. Under 405 nm excitation, Ca₃TeO₆:Sm³⁺, Na⁺ phosphors emitted a series of orange–red emission due to the transition of Sm³⁺ from ⁴G_5/2 to ⁶H_J/2 (J?=?5, 7, 9, and 11). The optimal Sm³⁺-doping concentration of Ca_(3?2x)Sm_xNa_xTeO₆ (x?=?0.01–0.25) was x?=?0.10. The thermal-quenching temperature of Ca₃TeO₆:0.10Sm³⁺, 0.10Na⁺ phosphor was above 480 K. A white light-emitting diode (w-LED) based on 410 nm UV chip was successfully fabricated, and it presented a good correlated color temperature and a high color-rendering index (R_a). Therefore, orange–red-emitting Ca₃TeO₆:Sm³⁺, Na⁺ phosphors have potential applications in UV-based w-LEDs.

     

Effects of a site substitution of bivalent ions on Ag(Nb0.8Ta0.2)O3 ceramics

Bivalent ions equivalent substitution and equimolar substitution for Ag⁺ in silver niobate tantalate ceramic were studied, which will result in Ag_0.98A_0.01(Nb_0.8Ta_0.2)O₃ and Ag_0.98A_0.02 (Nb_0.8Ta_0.2)O₃ respectively, where A²⁺ = Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Cu²⁺, Pb²⁺. The samples were synthesized by traditional solid method and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effects of a little Ag⁺ (in mol ratio 2 %) on the dielectric properties in Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Cu²⁺, Pb²⁺ substituted samples, and the influences of radius and ionic electronegativity on the dielectric properties were discussed. The results showed that the substitution of most bivalent ions except large Ba²⁺ ions for a little Ag⁺ (in mol ratio 2 %) showed no obvious change on the perovskite structure and microstructure of Ag(Nb_0.8Ta_0.2)O₃ ceramics. Basically, the dielectric properties of equivalent substituted samples were better than that of equimolar equimolar substituted samples, Ca²⁺ equivalent substituted samples showed lower dielectric loss, and Cu²⁺ equivalent substituted samples showed higher dielectric constant.     

A potential Eu-activated Ca10K(PO4)7 red phosphor for white light-emitting diodes

New red Ca₁₀K(PO₄)₇:Eu³⁺, K⁺ phosphors were synthesized by solid state reaction and their photoluminescence properties as well as those by co-doping Mo⁶⁺ under near ultraviolet excitation were investigated. From the excitation spectra monitored at 611 nm, it can be seen that the strongest excitation peak is situated at 393 nm, well matching with the emission wavelength of near-ultraviolet chips for white LEDs. Upon 393 nm excitation, the brightness of Ca₉K(PO₄)₇:0.5Eu³⁺, 0.5 K⁺ with the optimal Eu³⁺-doping concentration is about 2.3 times stronger than that of the commercial red Y₂O₃:Eu³⁺ phosphor. The introducing of Mo⁶⁺, which results in a possible variety for the excited energy level of the host, can enhance the brightness of Eu³⁺ to be maximized by about 15%. The CIE chromaticity coordinates of Ca₉K(PO₄)₇:0.5Eu³⁺, 0.5 K⁺ are calculated to (0.654, 0.345), which are close to the (0.67, 0.33) standard of the National Television System Committee. All the above results indicate Eu³⁺-activated Ca₁₀K(PO₄)₇ is a potential candidate for white LEDs.     

Effect of soil compositions on the electrochemical corrosion behavior of carbon steel in simulated soil solution

In this study, effect of cations, Ca²⁺, Mg²⁺, K⁺, and anions, SO₄^2–, HCO₃^–, NO₃^– on electrochemical corrosion behavior of carbon steel in simulated soil solution was investigated through potentiodynamic polarization curves and electrochemical impedance spectroscopy. The results indicate that the Ca²⁺and Mg²⁺ can decrease the corrosion current density of carbon steel in simulated soil solution, and K⁺, SO₄^2–, HCO₃^–, and NO₃^– can increase the corrosion density. All the above ions in the simulated soil solution can decrease its resistivity, but they have different effect on the charge transfer resistivity. This finding can be useful in evaluating the corrosivity of certain soil through chemical analysis, and provide data for construction engineers.     

The calculated defect structure of bulk and {001} surface cation dopants in MgO

Lattice defect calculations are presented for the cation doping of the bulk and {001} surface of MgO by Li⁺, Na⁺, Be²⁺, Ca²⁺, Fe²⁺, Al³⁺, Sc³⁺, Fe³⁺, Ti⁴⁺ and Si⁴⁺. Interionic potentials are derived from electron-gas calculations while the lattice relaxation methods are essentially those introduced by Lidiard and Norgett. An emphasis is placed on the differences between the bulk and surface, and, where possible, a comparison is made with the available experimental data.     

Improved optical photoluminescence by charge compensation in the phosphor system CaMoO4:Eu3+

It has been found that charge compensated CaMoO₄:Eu³⁺ phosphors show greatly enhanced red emission under 393 and 467 nm-excitation, compared with CaMoO₄:Eu³⁺ without charge compensation. Two approaches to charge compensation, (a) 2Ca²⁺ → Eu³⁺ + M⁺, where M⁺ is a monovalent cation like Li⁺, Na⁺ and K⁺ acting as a charge compensator; (b) 3Ca²⁺ → 2Eu³⁺ + vacancy, are investigated. The influence of sintering temperature and Eu³⁺ concentration on the luminescent property of phosphor samples is also discussed.     

Effect of compositional variations on charge compensation of AlO4 and BO4 entities and on crystallization tendency of a rare-earth-rich aluminoborosilicate glass

This paper presents the structural and crystallization study of a rare-earth-rich aluminoborosilicate glass that is a simplified version of a new nuclear glass proven to be a potential candidate for the immobilization of highly concentrated radioactive wastes that will be produced in the future. In this work, we studied the impact of changing the nature of alkali (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺) or alkaline-earth (Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺) cations present in glass composition on glass structure (by ²⁷Al and ¹¹B nuclear magnetic resonance spectroscopy) and on its crystallization tendency during melt cooling at 1 K/min (average cooling rate during industrial process). From these composition changes, it was established that alkali cations were preferentially involved in charge compensation of (AlO₄)⁻ and (BO₄)⁻ entities in the glassy network comparatively to alkaline-earth cations. Whatever the nature of alkali cations, glass compositions containing calcium gave way to the crystallization of an apatite silicate phase bearing calcium and rare-earth (RE) cations (Ca₂RE₈(SiO₄)₆O₂, RE = Nd or La) but melt crystallization tendency during cooling strongly varied with the nature of alkaline-earth cations.     

Type,stability, and acidity of hydroxyl groups of HNaK-erionites

The concentration and acid strength of the hydroxyl groups of a series of HNaK erionites have been investigated by means of temperature programmed activation (t.p.a.), temperature programmed desorption (t.p.d.) of ammonia, and transmission absorption i.r. spectroscopy. With an increasing degree of NH₄⁺ exchange, primarily Na⁺, at first, and, subsequently, K⁺ cations are replaced. During activation of these materials, NH₃ desorbs in a temperature interval from 540 to 900 K, leading to hydroxyl groups. However, it is impossible to decompose NH₄⁺ quantitatively without dealumination, if the degree of NH₄⁺ exchange is higher than 85%. Five types of hydroxyl groups are present, characterized by i.r. bands at approximately 3741, 3691, 3660, 3618-3608, and 3566 cm⁻¹. The assignment of these bands is discussed. Only the OH groups represented by the bands at 3660, 3618–3608, and 3566 cm⁻¹ adsorb ammonia under the conditions employed. The concentration and strength of the bridging hydroxyls (3618-3608 cm⁻¹), associated with framework Al³⁺, increase with increasing degree of ion exchange.     

Photoluminescence properties of Y0.95 − xMxBO3:Eu3+ (M = Ca,Sr, Ba,Zn, Al, 0 ≤ x ≤ 0.1) in 100–450 nm regions

The single phases of Y_0.95 − xM_xBO₃:5%Eu³⁺ (M = Ca, Sr, Ba, Zn, Al, 0 ≤ x ≤ 0.1) were synthesized successfully by solid-state reaction. Their luminescent properties were studied under UV and VUV excitation. The results indicated that with the incorporation of Ca²⁺, Sr²⁺, Ba²⁺, Zn²⁺ or Al³⁺ into the host lattice of YBO₃:Eu³⁺, the high symmetry around Eu³⁺ was destroyed and the ratio of red emission(⁵D₀–⁷F₂) to orange one (⁵D₀–⁷F₁) increased, leading to a better chromaticity. Furthermore, the co-doping ions such as Ca²⁺, Zn²⁺ and Al³⁺ were beneficial to enhance the luminescent intensity of Eu³⁺. These phenomena were evaluated, and possible explanations were proposed.