Solid-liquid equilibria in relevant subsystems of LiBr-NaBr-KBr-MgBr2-CaBr2-H2O system at 298.15 K.

In view of the composition characteristics of lithium, calcium and bromine rich in Nanyishan oil and gas field brine of western Qaidam Basin, Qinghai Province, as well as based on the results reported in relevant literature, the phase equilibrium relationship of ternary system LiBr-CaBr2-H2O at 298.15 K was studied by isothermal dissolution equilibrium method. The equilibrium solid phase crystallization regions, as well as the compositions of invariant point, in phase diagram of this ternary system were clarified. On basis of the above ternary system research, the stable phase equilibria of quaternary systems (LiBr-NaBr-CaBr2-H2O, LiBr-KBr-CaBr2-H2O and LiBr-MgBr2-CaBr2-H2O), as well as quinary systems (LiBr-NaBr-KBr-CaBr2-H2O, LiBr-NaBr-MgBr2-CaBr2-H2O and LiBr-KBr-MgBr2-CaBr2-H2O) were further carried out at 298.15 K. According to the above experimental results, the corresponding phase diagrams at 298.15 K were drawn, which revealed the phase relationship of each component in solution and the law of crystallization and dissolution, and meanwhile summarized changing trends. The research results of this paper lay a foundation for further research on the multitemperature phase equilibria and thermodynamic properties of lithium and bromine containing high-component brine system in later stage, and also provide basic thermodynamic data for guiding the comprehensive development and utilization of this oil and gas field brine resource.

Surface-Enhanced Raman Spectroscopic Investigation of PAHs at a Fe3O4@GO@Ag@PDA Composite Substrates.

A method for surface-enhanced Raman spectroscopy (SERS) sensing of polycyclic aromatic hydrocarbons (PAHs) is reported. Fe3O4@PDA@Ag@GO is developed as the SERS substrate prepared by classical electrostatic attraction method based on the enrichment of organic compounds by graphene oxide (GO) and polydopamine (PDA) and the good separation and enrichment function of Fe3O4. The morphology and structure of the SERS substrate were represented by transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD) and the UV-visible absorption spectrum (UV-vis spectra). The effect of different temperatures on SERS during synthesis was investigated, and it was found that the best effect was achieved when the synthesis temperature was 90 °C. The effect of each component of Fe3O4@PDA@Ag@GO nanocomposites on SERS was explored, and it was found that Ag NPs are of great significance to enhance the Raman signal based on the electromagnetic enhancement mechanism; apart from enriching the polycyclic aromatic hydrocarbons (PAHs) through π-π interaction, GO also generates strong chemical enhancement to the Raman signal, and PDA can prevent Ag from shedding and agglomeration. The existence of Fe3O4 is favored for the fast separation of substrate from the solutions, which greatly simplifies the detection procedure and facilitates the cycle use of the substrate. The experimental procedure is simplified, and the substrate is reused easily. Three kinds of PAHs (phenanthrene, pyrene and benzanthene) are employed as probe molecules to verify the performance of the composite SERS substrate. The results show that the limit of detection (LOD) of phenanthrene pyrene and benzanthene detected by Fe3O4@PDA@Ag@GO composite substrate are 10-8 g/L (5.6 × 10-11 mol/L), 10-7 g/L (4.9 × 10-10 mol/L) and 10-7 g/L (4.4 × 10-10 mol/L), respectively, which is much lower than that of ordinary Raman, and it is promising for its application in the enrichment detection of trace PAHs in the environment.

Preparation of Fe3O4@PDA@Au@GO Composite as SERS Substrate and Its Application in the Enrichment and Detection for Phenanthrene.

In this study, highly active Fe3O4@PDA@Au@GO surface-enhanced Raman spectroscopy (SERS) active substrate was synthesized for application in the enrichment and detection of trace polycyclic aromatic hydrocarbons (PAHs) in the environment. The morphology and structure were characterized by transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD) and UV-visible absorption spectrum (UV-vis spectra). The effect of each component of Fe3O4@PDA@Au@GO nanocomposites on SERS was explored, and it was found that gold nanoparticles (Au NPs) are crucial to enhance the Raman signal based on the electromagnetic enhancement mechanism, and apart from enriching the PAHs through π-π interaction, graphene oxide (GO) also generates strong chemical enhancement of Raman signals, and polydopamine (PDA) can prevent Au from shedding and agglomeration. The existence of Fe3O4 aided the quick separation of substrate from the solutions, which greatly simplified the detection procedure and facilitated the reuse of the substrate. The SERS active substrate was used to detect phenanthrene in aqueous solution with a detection limit of 10-7 g/L (5.6 × 10-10 mol/L), which is much lower than that of ordinary Raman, it is promising for application in the enrichment and detection of trace PAHs.

Cyclodextrin derivatives used for the separation of boron and the removal of organic pollutants.

Adsorption plays an important role in seawater desalination, wastewater treatment, and, especially, boron removal from natural aqueous systems. In this paper, two sponge-like multifunctional polymers based on a cyclodextrin backbone were synthesized and used as adsorbents for the removal of boron, methylene blue (MB), methyl orange (MO), and phenol. The syntheses were carried out by esterification, atom transfer polymerization, and nucleophilic addition reaction. The polymers were characterized by 1H NMR spectroscopy, IR spectroscopy, XRD, XPS, and SEM. The performance of the two different adsorbents was investigated considering the effect of pH, initial concentration, and the anions and cations in an aqueous solution of borates. The experimental data were fitted with an adsorption isothermal model, adsorption kinetic model and other models. Both adsorbents exhibited high adsorption capacities (B: 31.05 mg/g and 20.45 mg/g, MB: 29.43 mg/g and 32.29 mg/g, MO: 47.36 mg/g and 49.23 mg/g, phenol: 5.04 mg/g and 4.35 mg/g, respectively) and a fast adsorption rate. The boron adsorption was found to be an exothermic process. The adsorbents show promising potential for the removal of boron and benzene-containing organic pollutants from aqueous solution.

Mean Activity Coefficients of KCl in KCl + SrCl2 + H2O Ternary System at 288.15 K Determined by EMF Method.

In this work, the studies of thermodynamic mean activity coefficients of KCl in the KCl-SrCl2-H2O ternary system have been made. A cell without liquid junction battery cell, K-ISE|KCl(mA), SrCl2(mB)|Cl-ISE, was used to study the activity coefficients in this mixed system KCl-SrCl2-H2O at 288.15 K by the electromotive force method. The total ionic strengths ranges are 0.0100-1.0000 mol·kg-1 with different ionic strength fractions yb of SrCl2, that is, yb = (0, 0.2, 0.4, 0.6, and 0.8). The results show that the K-ISE and Cl-ISE have a good Nernst response. Accordingly, the electromotive forces of the mixed system were measured by using the ion selective electrode listed above, and the mean activity coefficients are also determined with Nernst equation. Using the activity coefficient data, the mixed ion interaction parameters θK,Sr and ψK,Sr,Cl of Pitzer equations at 288.15 K were fitted by Matlab with linear regression method, respectively. Furthermore, those parameters were applied to calculate the values of the mean activity coefficients of SrCl2. Finally, the osmotic coefficients, water activity, and the excess Gibbs free energy of this system were evaluated by Pitzer's equations.

[Determination of Iodine and Iodate in Brine and Seafood Simultaneously by Ultraviolet Absorption Spectrometry].

The iodide in samples was oxidized to iodate by bromine water, which could be removed by formic acid, and iodate could be transformed to I3- with excess of I- in phosphoric acid, the iodate in samples could be transformed directly to I3- with excess of I- in phosphoric acid. The I3- solution had strong absorption at 350 and 288 nm, and the absorbance had a linear relationship to the concentration of I3- in a certain range. Total content of iodide and iodate had been detected after samples were oxidized by bromine water and the content of iodate had been detected directly, and the content of iodide was obtained by difference of the two results. Based on this, the method had been established to detect iodide and iodate in brine and seafood simultaneously by ultraviolet absorption spectrometry. The volumes of bromine water, formic acid, phosphoric acid and potassium iodide had been optimized. The effect of illumination, temperature and time also had been discussed. The optional reagents condition for iodide was: 2 drops of 3% bromine water, 0.5 mL of 10% formic acid, 4 mL of 20% phosphoric acid and 1 mL of 100 g x L(-1 KI. The optional reagents condition for iodate was: 0. 2 mL of 20% phosphoric acid and 1 mL of 100 g x L(-1) KI. The absorbance were determined after reacting for 30 min at room temperature and natural light conditions. Under the optimized conditions, the concentration of iodide and iodate in the range of 0 - 1.2 and 0 -1.5 mg x L(-1) were well agreed with Lambert Beer law. The sample blank was detected for twelve times and the detection limit of iodide and iodate were 1.54 and 14.8 µg x L(-1) respectively. The RSD of twelve times determination of 0.8 mg x L(-1) of iodide and iodate were 0.097% and 0.067%, respectively. The iodide and iodate in Zhabuye brine, Hong Feng underground brine, kelp, seaweed and sea cabbage had been detected, the recovery experiments also had been conducted at the same time, the recovery of iodide and iodate were between 80% - 120%. All the results met the requirement of analytical chemistry.

[Pretreatment of Aluminum-Lithium Alloy Sample and Determination of Argentum and Lithium by Spectral Analysis].

Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), Flame Atomic Absorption Spectrometry (FAAS) and Visible Spectrometry (VS) was applied for determination of Ag and Li in lithium-aluminium alloy standard sample and test sample, their respective advantages and disadvantages were compared, the excellent selectivity of ICP-OES was confirmed by analyses of certified standard sample. Three different sample digestion methods were compared and discussed in this study. It was found that the better accuracy would be obtained by digesting sample with chloroazotic acid while the content of Li was measured by FAAS, and it was better to digest sample with hydrochloric acid and hydrogen peroxide while determining Ag and Li by ICP-OES simultaneously and determining Ag by FAAS and VS. The interference of co-existing elements and elimination methods was detailedly discussed. Ammonium hydroxide was added to adjust the sample solution into alkalescent and Al, Ti, Zr was precipitated by forming hydroxide precipitation, Mg and Cu was formed complex precipitation with 8-hydroxyquinoline in this condition, then the interference from matrix element to determinate Ag by FAAS was eliminated. In addition, phosphate was used to precipitate Ti to eliminate its interference for determination of Li by FAAS. The same treatment of determination for Ag by FAAS was used to eliminate the interference of matrix element for determination of Ag by VS, the excess of nitrate was added into sample and heated to release Ag+ from silver chloride complex, and the color of 8-hydroxyquinoline was eliminated because of decomposed by heating. The accuracy of analysis result for standard sample was conspicuously improved which confirms the efficient of the method to eliminate interference in this study. The optimal digestion method and eliminate interference method was applied to lithium-aluminium alloy samples. The recovery of samples was from 100.39% to 103.01% by ICP-OES determination for Ag, and from 100.42% to 103.01% by ICP-OES determination for Li. The recovery ranged from 95.91% to 99.98% by FAAS determination for Ag, and ranged from 98.04% to 99.98% for FAAS determination of Li. The recovery was from 98.00% to 101.00 by VS determination for Ag, the analysis results all meet the analysis requirement.