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The abundance and chemical composition of dissolved organic matter (DOM) in the brine of solar ponds influence efficiency of mineral extraction and rates of brine evaporation, and cause undesired odor and color of the products. In this paper, we report an investigation on changes of DOM compositions in solar ponds from salt lake brine through different approaches. The results showed that the DOM was primarily composed of carbohydrates, aliphatic and aromatic compounds. Dissolved organic carbon (DOC) analysis revealed that the concentration of DOC in solar pond increased with exposure time, and up to 15−fold upon evaporation/irradiation of salt lake brine. Analyses with the elemental composition, Fourier transform infrared spectroscopy (FTIR) and cross polarization magic angle spinning (CP/MAS) 13C nuclear magnetic resonance (NMR) indicated that the relative abundance of aliphatic compounds (including functionalized ones) increased in solar pond process, while an opposite phenomenon was observed for carboxylic acid moieties, aromatics and carbohydrates. Pyrolysis−gas chromatography−mass spectrometry (Py−GC−MS) revealed that most of the DOM in salt lake brine contained methylene chain, terpenoid-like, carbohydrate and/or aromatic structures. The presence of some sulfur-containing organics implied some anaerobic biotic decays, but microbiological processes were probably subordinate to photo-induced DOM transformations. In the salt lake brine, exposure-driven decay decreased the abundance of polysaccharides and increased that of mono- and polyaromatic pyrolysis products. Finally, the implications and guidelines for removing DOM from brine in the process of brine resource exploitation were discussed.

The quantity and quality of dissolved organic matter (DOM) in the brine of solar ponds influence the efficiency of mineral extraction and brine evaporation rates. Here we report a characterization study of DOM in solar ponds of oilfield-produced brines using different approaches. The results showed that the concentrations of dissolved organic carbon and total dissolved solids exhibited a 2–3 fold increase with exposure time in the ponds. Analyses with two-dimensional correlation spectroscopy of attenuated total reflectance Fourier transform infrared spectroscopy and proton nuclear magnetic resonance, indicated that the aromatic and carboxylic acid structures in the DOM, were more susceptible to degradation/transformation compared with aliphatics, while aliphatics exhibited a preferential decline with increasing exposure time in the solar ponds. The relative abundance of aliphatic compounds (including functionalized ones) gradually decreased by 17.1% (r = −0.94, P

A novel dilution method was developed to extract boron from sulfate-type salt lake brine in the Qinghai Tibet plateau. The boron-concentrated brine was prepared by evaporation after magnesium removal using Na 2 SO 4 ·10H 2 O solid. The extraction process parameters such as boron concentration, dilution ratio, temperature, initial precipitation time, aging time, and extraction efficiency of boron were tested. The results showed that the solution pH after dilution with deionized water increased from 4.2 to 8.0, indicating dissociation of polyborate ions in brine by hydrolysis to give monoborate species and hydroxide ions. The initial precipitation time and aging time were observed to be strongly influenced by the boron concentration, dilution ratio, and temperature. A low temperature, high boron concentration and moderate mass dilution ratio (water/brine) were beneficial to boron extraction, allowing for an extraction efficiency of more than 80%. The only salts that precipitated from diluted brine were magnesium borates. The obtained results indicated the application potential of the novel technology of boron extraction from salt lake brine.

A strategy for the hydrometallurgical processing of potassium, boron, and lithium for the comprehensive utilization of Da Qaidam lake brine based on freezing and natural evaporation was developed. This process involves five major crystallization steps: remove sulfate by crystallizing mirabilite at low temperature, deposit carnallite through natural evaporation, enrich boron and lithium by eliminating magnesium through the addition of mirabilite and further evaporation, crystallize borate by brine dilution, and crystallize lithium sulfate monohydrate through further evaporation. In this study, potassium, boron, and lithium salt deposits with relatively high grades and yields were obtained through the controlled crystallization processes. This process provides a feasible and environmentally-friendly alternative for the comprehensive utilization of the Da Qaidam lake brine.

The synthesis of pinnoite (MgB2O(OH)6) in boron-containing brine was established with a novel dilution method. Effects of temperature, precipitation time, boron concentration and mass dilution ratio on the formation of pinnoite were investigated. The products obtained were characterized by X-ray diffraction (XRD), Raman, thermogravimetric and differential scanning calorimeter (TG-DSC), and scanning electron microscopy. The transformation mechanism of pinnoite with different dilution ratios was assumed by studying the crystal growth of pinnoite. The results showed that pinnoite was synthesized above 60 °C in the diluted brine. There were two reaction steps – precipitation of amorphous solid and the formation of pinnoite crystals – during the whole reaction process of pinnoite when the dilution ratio is more than 1.0 at 80 °C. While in the 0.5 diluted brine, only one reaction step of pinnoite crystal formation was observed and its transformation mechanism was discussed based on dissociation of polyb...

Measurements of the solubility and metastable zone width (MSZW) of borax decahydrate (disodium tetraborate decahydrate) within chloride, sulfate and carbonate solutions were carried out. The MSZW was measured by the conventional polythermal method with turbidity technology. The results showed that the addition of impurities decreased solubility. The main factor reducing solubility is the common ion effect, but the salt effect is also significant in the complex system. The addition of impurities broadened the MSZW. The MSZW was wider at first, then decreased with the addition of NaCl, yet the MSZW widened with the addition of Na2SO4 within the concentration range studied. This can be explained by adsorption and diffusion. The data of solubility and MSZW were analyzed by applying the Van&rsquo, t Hoff equation and the classical 3D nucleation theory approach, respectively. By calculating the corresponding parameters, the experimental phenomena are further explained from the perspective of thermodynamics and dynamics.

Solubility and metastable zone width (MSZW) of aqueous sodium dichromate solutions in different concentration of sodium chromate were studied experimentally by the polythermal method using a turbidity monitoring technique. The effects of cooling rate R, saturation temperature T0 of sodium dichromate and concentration ci of sodium chromate on the MSZW were studied. The results show that the MSZW widens with increasing cooling rate R but it narrows with increasing saturation temperature T0 of sodium dichromate and concentration ci of sodium chromate. The experimental data were analyzed by using an equation, based on the classical three-dimensional nucleation theory, relating MSZW with cooling rate R.

In this work, a facile approach of covalent layer-by-layer assembly was applied to fabricate a bilayer nanofilm which renders roughened copper foam superhydrophobic with robust performances. Before constructing the bilayer nanofilm, the surface of the foam was roughened by using KOH–K2S2O8 as the oxidation system, giving rise to hierarchical structures of flower-like protrusions and petals. A multifunctional polymeric nanofilm, capable of resisting copper corrosion and serving as an activated interface simultaneously, was first introduced onto the copper surface by heating self-assembled monolayers (SAMs) of one triazinedithiolsilane compound (designated as TESPA). Then, perfluorodecyltrichlorosilane (abbreviated as PFDTCS) was anchored onto the TESPA-modified copper surface. Consequently, a bilayer nanofilm of PFDTCS–TESPA is generated on the hierarchical foam that possesses outstanding superhydrophobic capability. The as-prepared foam exhibits excellent reusability and separation efficiency. After fifty recycles, the separation efficiency exceeds 98% while the surface still retains remarkable superhydrophobicity. The improved efficiency and recycle number are outstanding compared to those of similar systems reported previously. X-ray photoelectron spectroscopy (XPS) was conducted to reveal the mechanism of the robust performances of the bilayer-coated foam. The results show that TESPA can react with copper oxide (CuO) through SH groups yielding TESPA SAM. Upon heating, the newly formed disulfide units (–SS–) and siloxane networks (SiOSi) of the TESPA polymeric nanofilm protect the copper; the outward silanol groups (SiOH) endow the surface with activating ability. PFDTCS can covalently bond to the TESPA polymeric nanofilm via these SiOH groups. The specific arrangement of PFDTCS–TESPA and the chemical bonds of Cu(I)S, as well as the three-dimensional (3D) cross-linked textures of –SS– units and SiOSi networks, cooperatively enhance the chemical durability of the bilayer. The design strategy of preparing the bilayer nanofilm via an interlayer (e.g., TESPA as a molecular adhesive displayed in this work) can also be applied in other superhydrophobic systems for improved long-term utilization.

A new acentric mixed metal borate of composition K2Ba[B4O5(OH)4]2·10H2O, has been successfully obtained by slow evaporation solution method. The compound crystallizes in the Orthorhombic space group Pna21 (No.33) with a = 16.8668(7) A, b = 13.0903(5) A, c = 11.5529(5) A and Z = 4. [B4O5(OH)4]2− clusters serve as fundamental building unit linking with BaO8, K1O6, K2O7 by common O atoms to form three-dimensional layer structure. The second harmonic generation measurements in the powder samples reveal that the compound exhibits approximately 0.5 times that of KH2PO4 (KDP) and phase matching.

The solubility and metastable zone width of boric acid in the simulated oilfield brine system of NaCl–KCl–CaCl2–H2O were studied at low temperature by the turbidity method. The nucleation kinetic constant A and the interfacial energy γ of boric acid were calculated with nucleation theory. Results showed that the solubility of boric acid in the simulated oilfield brine system was mainly determined by the coexisting salt of CaCl2 and decreased with increasing concentrations of CaCl2, even though the presence of NaCl and KCl has a salt-in effect on the solubility. However, the metastable zone width was affected by the three coexisting salts and it changes differently with the varied concentrations. The possible reason can be explained by the dependence of the interfacial energy γ on the slat concentration. On the basis of the above results, the crystallization behavior of boric acid during oilfield brine evaporation was investigated for the first time. It was deeply affected by the coexisting salts in brine.

Pinnoite (MgB2O(OH)6) for the first time was synthesized using the solid–liquid–solid conversion method. The effects of reaction time, pH value and concentrations of magnesium and borate were investigated. Pinnoite was synthesized under the optimum condition of 8 mmol hungtsaoite and 1% boric acid solution at 80 °C. The products were determined using X-ray diffraction, Fourier-transform infrared spectroscopy, TG-DSC and a UV–vis spectrometer. The change processes of the surface morphology of pinnoite were investigated using scanning electron microscopy. In addition, the formation mechanism of pinnoite was discussed according to the changes in the content of precipitation and pH value.

A magnesium hydroxide coprecipitation method for the determination of trace elements in high-salt samples from salt lake brines by inductively coupled plasma optical emission spectrometry (ICP-OES) was developed. Some effects on the coprecipitation and analysis, such as the pH value and Na and Mg amounts in primary brines, have been thoroughly investigated and optimized. After adjusting the pH to 8.70, associated with sodium hydroxide, the complicated matrix was removed from high salt brines, and thus trace amounts of Al, Co, Cu, Fe, Mn, Ni, V, and Zn were simultaneously coprecipitated and precisely determined. Recoveries of all the determined trace elements in the samples of both synthesized and real salt lake brines were more than 90%. The detection limit in the range of 0.62–14.4 μg L−1 was obtained and the precision was less than 3% relative standard deviation. The optimized method has been successfully applied for the determination of trace elements in the intercrystal brine mined from Dachaidan salt lake located in the Qaidam Basin, China.

The experiment data on the solubility and metastable zone width (MSZW) of sodium dichromate dihydrate have been determined in the temperature range from (290.45 to 319.76) K using the conventional polythermal method by turbidity monitoring technique. Based on the solubility data, the dissolution enthalpy and entropy of sodium dichromate dihydrate were calculated by the van’t Hoff equation. Two approaches were used to estimate the nucleation kinetics of sodium dichromate dihydrate from the MSZW data, the self-consistent Nývlt-like equation and the novel equation of three-dimensional nucleation theory. The notable factors affecting MSZW of sodium dichromate dihydrate such as cooling rate, initial composition, stirring rate, and presence of seed particles have been evaluated in this paper. It was observed that the MSZW of sodium dichromate dihydrate has an obvious decrease with the increase of initial composition, rotation frequency of stirring, and the mass of seed particles, respectively. Nevertheless, the...

The solubility and nucleation of borax decahydrate in the presence of Cl– and SO42– ions have been studied by two different methods: polythermal crystallization and isothermal crystallization. The results revealed that both anions had a salt-in effect on the solubility. A noticeable widening of the metastable zone was observed after the addition of the two anion impurities. For the isothermal crystallization, two different nucleation mechanisms were obtained. When the supersaturation ratio S > 1.3, the nucleation appears to be homogeneous, whereas at the supersaturation ratio S < 1.25, heterogeneous nucleation predominates. From the prolonged induction period in the presence of the two anions, we conclude that the nucleation of borax decahydrate was suppressed after the addition of impurities. The values of the interfacial energy γ calculated by isothermal method are lower than those obtained by polythermal method due to the underestimated values of ln S.

The solubility of sodium chromate tetrahydrate has been investigated in the temperature range from 290.15 K to 325.15 K using the conventional polythermal method by means of the laser technique. The metastable zone width (MZW) and the apparent nucleation order of sodium chromate tetrahydrate were calculated. The effects of cooling rate, initial composition, stirring rate, and seed particles on the MZW were also studied. The results show that the MZW of sodium chromate tetrahydrate first increases and then narrows with increasing initial composition. The MZW becomes wider by reducing the cooling rate and the mass of seed particles, whereas the MZW will be reduced by enhancing the rotation frequency of stirring and the diameter of seed particles.

The solubility and the metastable zone width of sodium tetraborate decahydrate in solutions containing lithium chloride have been measured at temperature a range of (20 to 35) °C. It is found that the lithium impurity has a salt-in effect on the solubility of sodium tetraborate decahydrate. The metastable zone width broadens with an increase of the impurity concentrations. This increase can be attributed to the absorption mechanism on the crystal surface. The apparent nucleation order of sodium tetraborate decahydrate with and without impurity was calculated by a modified regression method. The results show that the addition of lithium impurity has no great effect on the apparent nucleation order of sodium tetraborate decahydrate.

The solubility and ultra solubility of borax decahydrate both in pure and impure solutions have been determined in the temperature range from (0 to 30) °C by means of the conventional polythermal method using the laser technique. The metastable zone width and the apparent nucleation order of borax were calculated. The effects and the action mechanism of KCl on metastable zone property of borax were studied. It was found that the presence of KCl made an increase in the solubility and a decrease in the metastable zones of borax. However, the trends in the changes of metastable zone width at low impurity concentrations were different from high concentrations because of the adsorption equilibria on the crystals.