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The solubilities of the quinary system (Li+, Na+, Mg2+//Cl−, SO42−-H2O) at 273.15 K were investigated using the isothermal dissolution method. The diagrams of dry-salt-phase, sodium-phase and water-phase were plotted accurately. The dry-salt-phase diagram of this quinary system includes five invariant points, eleven univariant solubility curves, and seven crystallization zones all saturated with sodium chloride. Two double salts of Li2SO4·3Na2SO4·12H2O and LiCl·MgCl2·7H2O were found, and no solid solution was formed. Pitzer model and its extended Harvie-Moller-Weare (HMW) model were used to fit the solubility equilibrium constants of LiCl·2H2O, Li2SO4·H2O and the two double salts, and the mixing ion-interaction parameters of θLi,Na, θLi,Mg, ψLi,Na,Cl, ψLi,Mg,Cl, ψLi,Na,SO4 and ψLi,Mg,SO4 of this system at 273.15 K, which are not reported in the literature. In addition, the calculated solubilities of the quinary system at 273.15 K were demonstrated, and the comparison between the calculated and experimental data shows that the predicted solubilities obtained by the extended HW model are basically consistent with experimental data.

The solubilities and refractive indices in the systems Na2SO4–NaBO2–H2O and NaCl–Na2SO4–NaBO2–H2O at 323.15 K were studied by the isothermal dissolution method. The phase diagram of the ternary system is composed of two single-salt crystallizations for Na2SO4 and NaBO2·4H2O. A comparison of the diagrams of system Na2SO4–NaBO2–H2O from 288.15 K to 323.15 K shows that the crystallization region of NaBO2·4H2O changes greatly as the temperature increasing, and the solid phase of mirabilite at 288.15 K and 298.15 K transforms into the nardite at 308.15 K and 323.15 K. The dry-salt diagram of the quaternary system consists of four salt crystallization fields for NaCl, NaBO2·4H2O, NaCl·NaBO2·2H2O and Na2SO4, five univariant solubility curves and two invariant points. On the basis of the Pitzer model, the lacking Pitzer parameters and dissolution equilibrium constants of the solid phases in this quaternary system were fitted with the solubilities and other thermodynamic properties in this study and literature. The calculated solubilities in the two systems are in good agreement with the experimental data.

The pH values, solubilities and water activities in the system LiB(OH)4–NaB(OH)4–H2O at 323.15 K were investigated. The mole fractions of boron species were calculated in the aqueous borate solutions, and the distribution and relevant mechanism were also discussed. The solubility diagrams in the ternary system were drawn at 323.15 K. The phase diagram consists of two single salt regions for LiB(OH)4 and NaB(OH)4·2H2O, one invariant point co-saturated with the above salts. On the basis of the Pitzer model, the Pitzer binary parameters and mixing parameters were fitted with the water activities, saturated vapour pressure and solubilities in the ternary system. The dissolution equilibrium constants (Ksp) of LiB(OH)4 and NaB(OH)4·2H2O were calculated using the experimental solubility data. The calculated solubilities with the parameters and Ksp agree well with the experimental data.

The phase and physicochemical properties diagrams of the quaternary system (Li2B4O7 + Na2B4O7 + Mg2B6O11) at 288.15 K and 0.1 MPa were constructed using the solubilities, densities, and refractive indices measured. In the phase diagrams of the system there are one invariant point, three univariant isothermic dissolution curves, and three crystallization regions corresponding to Li2B4O7 · 3H2O, Na2B4O7 · 10H2O, and Mg2B6O11 · 15H2O, respectively. The solution density, refractive index of the quaternary system changes regularly with the increasing of Li2B4O7 concentration. The calculated values of density and refractive index using empirical equations of the quaternary system are in good agreement with the experimental values.

Solubilities, densities, refractive indices, and pH values for the ternary system (MgSO4 + Mg2B6O11 + H2O) at (288.15, 298.15, and 308.15) K and 0.1 MPa, obtained using the method of isothermal dissolution equilibrium, are reported for the first time. On the basis of the experimental data, the phase diagrams and the physicochemical properties of density, refractive index, and pH versus concentration of magnesium sulfate were plotted. It was found that there are one invariant point, two univariant curves, and two crystallization regions corresponding to inderite (Mg2B6O11·15H2O, Inde) and epsomite (MgSO4·7H2O, Eps). The crystallized area of inderite is larger than that of epsomite at three temperatures, indicating that the solubility of inderite is lower than that of epsomite. Comparison of the phase diagrams at (288.15, 298.15, and 308.15) K shows that the areas of Inde and Eps increase with increasing temperature. There are no solid solutions and double salts at these three temperatures in this system. T...

Combining the methods of isothermal dissolution equilibrium and the wet-residue solid phase (Schreinemarkers rule), the phase equilibria of the ternary systems (LiCl + LiBO2 + H2O) and (Li2SO4+ LiBO2 + H2O) at 323.15 K and 0.1 MPa were investigated. On the basis of the experimental data on solubilities and the physicochemical properties including density, refractive index and pH value, the phase diagrams and physicochemical properties versus composition diagrams of the two systems were plotted. For the two systems, there are both in one invariant point, two univariant curves, and two crystallization regions corresponding to lithium metaborate dehydrate (LiBO2·2H2O, Lb2), lithium chloride monohydrate (LiCl·H2O i.e. Lc1, in the former) and lithium sulfate monohydrate (Li2SO4·H2O i.e. Ls1, in the later), and the area of the crystallization region of Lb2 is the largest when compared with those of Lc1 and Ls1, and those results demonstrate that the solubility of lithium metaborate is the lowest. A comparison of the phase diagrams between this work at 323.15 K and the literature at (288.15, 298.15 and 308.15) K in the former system, the crystallization region of LiBO2·8H2O existed at 288.15, 298.15 and 308.15 K is disappeared at 323.15 K. Relationships between solubility and temperature for LiBO2 and LiCl are both in positive correlation obviously. However, a comparison of the phase diagrams between this work at 323.15 K and the literature at (288.15, 298.15) K in the later system, it was found that the mineral LiBO2·8H2O existed at 288.15 and 298.15 K is replaced by LiBO2·2H2O, and the component of Li2SO4 in the solution has a relatively strong salting-out effect to LiBO2, and the concentrations of LiBO2 in the solution are decreased considerably with the increasing of lithium sulfate concentration in the solution. The calculated values of refractive index using empirical equations for the two ternary systems are in good agreement with the experimental values.

The solubility data, composition of the solid solutions, and refractive indices of the LiCl–LiBr–H2O and CaCl2–CaBr2–H2O systems at 288.15 K were studied with the isothermal equilibrium dissolution method. The solubility diagrams and refractive index diagrams of the two systems were plotted at 288.15 K. There is no invariant point, one univariant solubility curve saturated with solid solution, and one crystallization field of the solid solution in the phase diagrams. The two systems belong to the solid solution type, and no double salts formed in the systems. The refractive indices calculated with an empirical equation agree well with the experimental data. By combining the composition equations and solubility equilibrium constant equations of the solid solutions, the solubilities of the two systems at 288.15 K were calculated on the basis of the Pitzer and Harvie–Weare models. The calculated solubilities agree well with the experimental results.

The heat capacities on two minerals of hungchaoite (MgB4O7&middot, 9H2O, Hu) and mcallisterite (MgB6O10&middot, 7.5H2O, Mc) have been measured with a precision calorimeter at temperatures ranging from 306.15 to 355.15 K, experimentally. It was found that there are no phase transition and thermal anomalies, and the molar heat capacities against temperature for the minerals of hungchaoite and mcallisterite were fitted as C p , m , Hu &nbsp, = &nbsp, &minus, 27019.23675 + 229.55286 T &nbsp, &nbsp, 0.63912 T &nbsp, 2 &nbsp, + &nbsp, ( 5.95862 &nbsp, &times, 10 &nbsp, 4 ) &nbsp, T &nbsp, 3 and C p , mMc &nbsp, 9981.88552 &nbsp, 84.10964 T &nbsp, 0.22685 T &nbsp, ( 2.0593 &nbsp, 3 , respectively. The molar heat capacities and thermodynamic functions of (HT-H298.15), (ST-S298.15), and (GT-G298.15) at intervals of 1 K for the two minerals were obtained for the first time. These results are significant in order to understand the thermodynamic properties of those minerals existing in nature salt lakes, as well as applying them to the chemical engineering process design.

A novel, facilely prepared, recyclable sodium carboxymethyl cellulose–ammonium phosphomolybdate composite (CMC–AMP) was synthesized by chemical cross-linking and used for Cs+ removal. The effects of adsorbent dosage, pH value, initial Cs+ concentration, contact time, temperature and competitive ions on adsorption were investigated. The results showed that CMC–AMP with good mechanical properties could effectively adsorb Cs+ in a wide pH range. In addition, the adsorption process of CMC–AMP was better fitted with the Lagergren first-second model and Langmuir isotherm model. Furthermore, CMC–AMP can be reused five times using ammonium chloride as the eluent without an obvious decrease in absorption activity. The results reveal that CMC–AMP can be used as a low cost and recyclable Cs+ adsorbent.

Chloride widely exists in the environment and will cause serious interference for arsenic speciation analysis. The determination of four arsenic species including arsenite (As(III)), arsenate (As(V)), monomethylarsenate (MMA), and dimethylarsonate (DMA) in samples containing high concentrations of Cl− was carried out in this work by coupling of liquid chromatography (LC) with hydride generation atomic fluorescence spectrometry (HG-AFS). The interference of Cl− was successfully eliminated by coupling two anion-exchange chromatographic columns in series and eluting with 35.0 mmol L−1 (NH4)2HPO4 (pH = 6.00). A novel pre-treatment system was subsequently developed to realize on-line column switch and pre-reduction of As(V). The analysis time was shortened by an isocratic elution but programmed flow rate method, and the sensitivity of As(V) was also enhanced by the introduction of pre-reduction using the developed system. The proposed method can resist at least 10 g L−1 Cl− without any pre-treatment operations. Since LC-HG-AFS is low-cost and can be afforded or self-assembled by most labs, the developed method can be adopted as a routine analysis method for arsenic species in chloride-bearing samples, such as urine and seawater.

A sensitive and accurate simultaneous continuous analysis for six arsenic species including arsenobetaine (AsB), arsenocholine (AsC), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenite (AsIII), and arsenate (AsV) has been developed by high performance liquid chromatography with inductively coupled plasma mass spectrometry (HPLC-ICP-MS). An anion-exchange column of Hamilton PRP-X100 (Switzerland) was applied for separation of the six arsenic species with gradient elution of 1.25 mmol/L Na2HPO4 and 11.0 mmol/L KH2PO4 as the mobile phase A and 2.5 mmol/L Na2HPO4 and 22.0 mmol/L KH2PO4 as the mobile phase B. The linearity ranges for AsB, AsC, MMA, DMA, AsIII, and AsV were between 0.5 and 50.0 μg/L, and the detection limits of the six arsenic species were all within 0.01–0.35 ng/L. The relative standard deviations (RSDs) were within 2.26–3.68% and the recovery rates of samples ranged from 95 to 103%. The proposed method was applied for the arsenic speciation analysis of sediment pore-water samples, which were taken from the supernatant after centrifugation and filtration.

The metastable zone width (MZW) of lithium metaborate salts at various concentrations was determined using the laser technique. The solubility data for lithium metaborate salts was nearly the same in the presence of NaCl at various concentrations. The MZW of lithium metaborate salts decreased when the stirring rate increased, but increased remarkably with increasing cooling rates and an increasing concentration of sodium chloride. The apparent secondary nucleation order for lithium metaborate salts was obtained using the N&yacute, vlt&rsquo, s approach. The apparent secondary nucleation order m of lithium metaborate salts is 4.00 in a pure LiBO2&minus, H2O system with an improved linear regression method. The m for lithium metaborate salts was enlarged in the system LiBO2&minus, NaCl&minus, H2O.

In order to obtain a well understanding of the toxicity and ecological effects of trace elements in the environment, it is necessary to determine not only the total amount, but also their existing species. Speciation analysis has become increasingly important in making risk assessments of toxic elements since the toxicity and bioavailability strongly depend on their chemical forms. Effective separation of different species in combination with highly sensitive detectors to quantify these particular species is indispensable to meet this requirement. In this paper, we present the recent progresses on the speciation analysis of trace arsenic, mercury, selenium and antimony in environmental and biological samples with an emphasis on the separation and detection techniques, especially the recent applications of high performance liquid chromatography (HPLC) hyphenated to atomic spectrometry or mass spectrometry.

The solid–liquid phase equilibria of the quinary system (Li+, Na+, K+//Cl−, B5O8− - H2O) saturated with NaCl at 298.15 K and 101.325 kPa were investigated with the isothermal dissolution method. On the basis of experimental data, the dry-salt phase diagram, water-phase diagram and sodium-phase diagram in the quinary system were established for the first time. In this quinary dry-salt phase diagram, there are three invariant points corresponding to F1 (NaCl + KCl + LiCl·H2O + LiB5O8·5H2O), F2 (NaCl + KCl + LiB5O8·5H2O + KB5O8·4H2O) and F3 (NaCl + LiB5O8·5H2O + NaB5O8·5H2O + KB5O8·4H2O), seven isothermal dissolution curves, and five crystallization regions saturated with NaCl corresponding to LiCl·H2O, KCl, LiB5O8·5H2O, NaB5O8·5H2O, KB5O8·4H2O. The areas of crystallized regions decrease according to the order of NaB5O8·5H2O, KB5O8·4H2O, LiB5O8·5H2O, KCl, and LiCl·H2O, which all are saturated with sodium chloride. It was found that neither double salt nor solid solution was formed. In addition, the diagram of physicochemical properties including densities and refractive indices against J(B5O8−) was also established, and it shows that density and refractive index of the solution in the quinary system change regularly with the increasing of Janecke index J(B5O8−) in the solution. These results on the phase diagram of the quinary system can supply a theoretical guide to separate and purify the valuable alkali pentaborates.

In this work, novel Prussian blue analogs-based layered double hydroxide (PBA@ZnTi-LDH) was in situ synthesized and used for radioactive Cs+ removal from wastewater. The results suggested that this PBA@ZnTi-LDH prepared using LDH as skeleton and transition metal source showed higher adsorption capacity (243.9 mg/g) and water stability than conventional PBAs, and promising application in scale-up Cs+ removal. Thus, it was granulated by calcium alginate and the PBA@ZnTi-LDH/CaALG exhibited favorable post-separation and fixed-bed adsorption ability at different Cs+ concentrations and flow rates, highlighting its application perspective on Cs+ removal from various kinds of wastewater. Moreover, the real-world Cs+ removal was preliminarily explored using natural complex Cs+-containing water. As a result, this stable and easily separated PBA@ZnTi-LDH/CaALG showed high removal efficiency, selectivity and good reusability, which was promising in scale-up Cs+ removal from the real-world wastewater.

The efficient recovery of Sr2+ from brine is a great challenge due to the interference of a large number of coexisting ions. Herein, a new-type spherical Sr2+ adsorbent with a diameter of about 2–3 mm was developed by the ion-imprinting method using low-cost and high hydrophilic sodium alginate (SA). It was found that although SA could be granulated in HCl solution, it showed no adsorption ability for Sr2+. However, when SA was ion-imprinted with Sr2+ and then eluted with HCl, the material exhibited excellent adsorption performance. Especially, after modification with thioglycollic acid, the maximum adsorption capacity reached approximately 177 mg·g−1, which was far higher than that of the spherical materials reported at present. The Sr2+ in the material could be eluted easily with 0.05 mol·L−1 HCl at an eluent dosage of only 0.02 L·g−1, and the Sr2+ concentration in the eluate was nearly 25 times higher than that in the original solution. Because of the ion-sieve effect, the developed adsorbent presented high stability and selectivity when used for Sr2+ recovery from oilfield water. The attenuation of adsorption capacity was only 0.42% after five adsorption-desorption. The separation factors between Sr2+ and other ions were all higher than 54, indicating that the selective recovery of Sr2+ is almost unaffected by coexisting Na+, K+, Mg2+, and Ca2+. All these properties suggest that the proposed material has excellent properties and can be used as a candidate for selective recovery of Sr2+ from oilfield water or other liquid strontium resources.

The improvement of post-separation performance of powdery lithium ion sieve with the guarantee of high adsorption capacity and fast kinetics remains to be a huge challenge. Herein, a novel granular and porous titanium-based lithium ion sieve (PIS) was developed using agar-assisted strategy and used for lithium recovery from geothermal water. The agar acted as both spherality-shaping and sacrificial porogenic agent. As a result, PIS had a 64-fold larger diameter (2.8 mm) than powdery ion sieve (IS), which could be easily separated by filtration and then reused with a steady performance. Due to its loose microstructures and rich porosity, PIS showed high adsorption capacity (25.8 mg/g) and rapid kinetic (equilibrium time 6 h) in geothermal water. In addition, the separation factors of competitive ions related to Li+ were 1162.3, 273.7 and 328.5 for Na+, K+ and Ca2+, respectively, exhibiting benign selectivity in natural geothermal water. Thus, this granular PIS with enhanced post-separation ability, high capacity and fast kinetic could be considered as a promising candidate for lithium recovery from geothermal water. Moreover, this simple and green method could be easily popularized to prepare other porous adsorbents.

The extraction of Mg2+ by di-(2-ethylhexyl) phosphoric acid (P204) was carried out to separate lithium and magnesium. To facilitate the direct electrodeposition of metallic magnesium from the magnesium-rich organic phase, different diluents and ionic liquids were investigated. It was found that tributylhexylphosphonium bis (trifluoromethyl sulfonyl) imide ionic liquid ([P4446][NTf2]) can serve as an excellent supporting electrolyte to solve the electroconductibility of the weak polarity organic phase. The electroconductivity was further increased by more than 1500 times by the use of methyl isobutyl ketone (MIBK) as a diluent. The single-stage extraction rate of Mg2+ at a concentration up to 76.87 g/L reached 68.4% using 40% P204 + 55% MIBK + 5% [P4446][NTf2] at R(O/A) = 6:1, and the electroconductivity of organic phase was 254.5 μS·cm−1 after extraction. The extraction mechanism and thermokinetics indicated that both [P4446][NTf2] and MIBK do not participate in the extraction process, and the extraction is an obvious endothermic process.

The solubility corresponding solution physicochemical properties (densities, refractive indices and pH) in the quaternary system (NaCl + NaBO2 + Na2B4O7 + H2O) were investigated at 298.15 K by the isothermal dissolution equilibrium method. The dry-salt phase diagram, water content diagram, refractive index diagram and pH diagram were drawn. There are four crystallization fields corresponding to NaCl, NaBO2·4H2O, Na2B4O7·10H2O, NaCl·NaBO2·2H2O, five univariant curves and two invariant points in the phase diagram of the quaternary system. The solubility, concentrations of boron species B(OH)3, B(OH)4−, B3O3(OH)4−, B4O5(OH)42− and OH− in the system were calculated using the Pitzer model. The variation trends for calculated solubility curves and pH curves are consistent with the experimental results. The distributions of different boron species were obtained in the mixed borate solution. The distributions of four boron species were obtained in the mixed borate solution. The main boron species in the mixed borate solution are B(OH)4− and B4O5(OH)42−. The mole fractions of the four boron species are mainly affected by m(B) in the solution but less by m(Cl−).

Solubilities, densities and refractive indices of the aqueous quaternary system of lithium sulfate, lithium metaborate, and lithium carbonate at 288.15, 298.15, 308.15 K and 0.1 MPa were determined with isothermal dissolution method. According to the experimental results, the dry-salt phase diagrams, water-phase diagrams, and the diagrams of physicochemical properties including density, pH, and refractive index versus composition of lithium sulfate at three temperatures were plotted. In the dry-salt phase diagrams at three temperatures, there are four crystallization regions corresponding to lithium metaborate octahydrate (LiBO2·8H2O, LB), lithium carbonate (Li2CO3, LC), and lithium sulfate monohydrate (Li2SO4·H2O, LS), and three univariant-solubility curves corresponding to minerals of LS, LB, and LC, and one invariant point of three coexisted minerals (LS + LB + LC). A comparison of the phase diagrams at 288.15, 298.15, and 308.15 K shows that the areas of lithium sulfate monohydrate and lithium metabor...

The solubilities and densities of the solutions in the ternary system LiCl–NaCl–H2O at 308 and 348 K were determined by the method of isothermal dissolution equilibrium. There are one invariant point, two univariant isotherm dissolution curves, and two crystallization regions corresponding to monohydrate (LiCl · H2O) and NaCl, respectively. This system at both temperatures belongs to hydrate type I, and neither double salt nor solid solution was found. A comparison of the phase diagram for the ternary system at 273–348 K shows that the area of crystallization region of LiCl · H2O is decreased with the increasing of temperature, while that of NaCl is increased obviously. The solution density of the ternary system at two temperatures changes regularly with the increasing of LiCl concentration.

The metastable solubilities and the physicochemical properties including density, refractive index, pH and conductivity in the ternary system (Li2SO4 + K2SO4 + H2O) at T = 308.15 K were determined experimentally using the isothermal evaporation method, and the metastable phase diagram and the physicochemical properties versus composition diagram were plotted. In the metastable phase diagram, there are two invariant points, three univariant curves and three crystallization regions corresponding to lithium sulfate monohydrate (Li2SO4 · H2O), double salt (K2SO4 · Li2SO4) and arcanite (K2SO4). It was found that the double salt of K2SO4·Li2SO4 belongs to the incongruent double salt, and the hydrate of Li2SO4 · H2O belongs to hydrate type I. On the basis of Pitzer model of the electrolyte solution theory, the mixing-ion parameter of θLi,K, \({\Psi _{Li,K,S{O_4}}}\) and the metastable equilibrium constants of the solid phases K2SO4, Li2SO4 · K2SO4 and Li2-SO4 · H2O at 308.15 K were obtained for the first time. The calculated metastable solubility data for this ternary system at 308.15 K agree well with the experimental values, and this result indicates that the mixing-ion parameters and the metastable equilibrium constants obtained in this work are reliable.

The solubilities and the refractive indices of the MgBr2–MgSO4–H2O system at 333.15 K were studied with the isothermal equilibrium solubility method. The phase diagram and refractive index diagram were plotted for this system at 333.15 K. The system belongs to hydrate II type. The phase diagram is constituted of three invariant points cosaturated with two salts, four univariant solubility isotherms saturated with one salt, and four stable crystallization fields in the ternary system corresponding to MgSO4·6H2O (Hex), MgSO4·4H2O (Tet), MgSO4·H2O (Kie), and MgBr2·6H2O (Mb). The calculated refractive index data agree well with the experimental results. Combining the experimental solubility data of the ternary system, the Pitzer binary parameters for MgBr2 and MgSO4, and the Pitzer mixing ion-interaction parameter θBr,SO4, the Pitzer parameter ψMg,Br,SO4 and the solubility equilibrium constants Ksp of solid phases in the ternary system at 333.15 K were fitted using the Pitzer and Harvie–Weare (HW) model. Then...

The solubilities and physicochemical properties, including density, refractive index, and pH, of the ternary system (LiCl + Li2SO4 + H2O) at T = (288.15 and 308.15) K and p = 0.1 MPa were determined with the isothermal dissolution equilibrium method. The phase diagram in the ternary system at 288.15 K consists of one invariant point, two univariant solubility curves, and two crystallization regions corresponding to Li2SO4·H2O and LiCl·H2O. A similar structure can be found in this system at 308.15 K. This ternary system belongs to hydrate type I at two temperatures, and neither double salts nor solid solutions were formed at the investigated temperatures. The crystallized area of LiCl·H2O decreases with increasing temperature, while that of Li2SO4·H2O increases obviously. The solution density, refractive index, and pH value of the ternary system (LiCl + Li2SO4 + H2O) at the two temperatures change regularly with the mass fraction of lithium. The Pitzer–Harvie–Weare thermodynamic model of aqueous electrolyt...

Using HG – AFS as a powerful tool to study valence transformations of Te, we found that, in presence of HCl and at high temperature, Te can form volatile species and be lost during sample digestion and pre-reduction steps. It was also noticed that the chemical valences of Te can be modified under different chemical and digestion conditions and even by samples themselves with certain matrices. KBr can reduce Te(VI) to Te(IV) in 3.0 M HCl at 100 °C, but when HNO 3 was >5% (v/v) in solution, Br 2 was formed and caused serious interference to Te measurements. HCl alone can also pre-reduce Te(VI) to Te(IV), only when its concentration was ≥6.0 M (100 °C for 15min). Among 10 studied chemical elements, only Cu 2+ caused severe interference. Thiourea is an effective masking agent only when Cu 2+ concentration is equal or lower than 10 mg/L. Chemical reagents, chemical composition of sample, as well as the modes of digestion can greatly affect Te valences, reagent blanks and analytical precisions. A protocol of 2–step–digestion followed by an elimination of HF is proposed to minimize reagent blank and increase the signal/noise ratios. It is important to perform a preliminary test to confirm whether a pre-reduction step is necessary; this is especially true for samples with complex matrices such as those with high sulfide content. The analytical detection limits of this method in a pure solution and a solid sample were 100 ng/L and 0.10 ± 0.02 μg/g, respectively.

The solubilities and the refractive indices in the ternary system LiBO2−Li2B4O7−H2O at 298.15 K and 323.15 K were determined with the isothermal dissolution method. The phase diagrams and refractive index diagrams were drawn with the experimental values. The phase diagrams at 298.15 K and 323.15 K consist of one invariant point, two univariant curves and two crystallization regions corresponding to Li2B4O7·3H2O, LiBO2·8H2O (at 298.15 K) and LiBO2·2H2O (at 323.15 K). Based on the Pitzer model, the mixing ion-interaction parameters ( θ B ( O H ) 4 − , B 4 O 5 ( OH ) 4 2 − and Ψ L i + , B ( O H ) 4 − , B 4 O 5 ( O H ) 4 2 − ) at 298.15 K and 323.15 K were fitted with the solubility data. A comparison shows that the calculated solubilities in the ternary system at 298.15 and 323.15 K agree well with the experimental data. The phase diagram and Pitzer model for the ternary system were then used to conduct isothermal evaporation simulation. Different salt will be obtained if the original solution point in different unsaturated regions.

As a new-type of liquid mineral resource of cesium including salt lake brine, geothermal water, underground water and seawater, the recovery of cesium is of great significance for its importance strategic purpose in modern industry, and the parameterization of ion-interaction model is essential to understand the ion-interaction of cesium borate solutions. In this paper, the dilution enthalpies on Cs2B4O7 aqueous solutions from 0.03900 to 0.54815 mol·kg−1 and CsB5O8 aqueous solutions from 0.02072 to 0.09889 mol·kg−1 at 298.15 K and 1.325 kPa were determined by the high-precision adiabatic microcalorimeter BT2.15 (Setaram, France), and the dissolution enthalpies for Cs2B4O7·5H2O and CsB5O8·4H2O were measured by the multi-channel microcalorimeter TAM-IV (TA, America). On the basis of experimental dilution enthalpies, the apparent molar enthalpies of Cs2B4O7 and CsB5O8 aqueous solutions were derived, and the diagrams of apparent molar enthalpy against molalities of Cs2B4O7 and CsB5O8 in aqueous solutions were plotted. And then, according to the Pitzer ion-interaction model of apparent molar enthalpy of electrolyte, Pitzer single parameters i.e. FMX ( β MX 0 L , β MX 1 L , β MX 2 L and C MX L , M = Cs+, X = [B4O5(OH)4]2− or [B5O6(OH)4]−) were obtained for the first time. The calculated apparent molar enthalpies for Cs2B4O7 and CsB5O8 aqueous solutions agree well with the experiment values, indicating that the single salt parameters obtained for Cs2[B4O5(OH)4] and Cs[B5O6(OH)4] in this work are reliable.

Considering the urgency of removing hazardous radioactive 137Cs, Cs+ adsorption and environmental remediation from aqueous solutions has been given widespread concern. Composite materials (CMs) have recently emerged with good potential application in Cs+ adsorption. Herein, recent developments in the field of Cs+ adsorption covering the synthesis and performance of composite materials are reviewed. This is followed by a preliminary summary for composite materials and their further prospects in Cs+ adsorption. Based on the scope of the core and supporting materials, composite materials are classified into several categories. Along this line, the representative composite materials are introduced in view of synthesis methods and adsorption performance. Moreover, some emerging novel materials are also briefly described. Overall, this review intends to provide a preliminary database for composite materials and further guide the exploration and design of more composite materials with excellent adsorption performance in respective fields of radioactive contamination, wastewater treatment and radioisotope recycling.

The isopiestic equilibria for the systems {Li2B4O5(OH)4 + H2O}, {LiB5O6(OH)4 + H2O} and {Li2B4O5(OH)4 + LiB5O6(OH)4 + H2O} at 288.15 K and ambient pressure were measured by the isopiestic method using a modified gravimetric isopiestic apparatus. The water activities and osmotic coefficients were determined based on the sodium chloride standard reference solution. On the basis of Pitzer model, an extended Pitzer model was developed to describe the thermodynamic properties of the aqueous systems containing different forms of lithium borates, then the Pitzer single salt parameters β(0), β(1), β(2) and Cϕ for the binary systems {Li2B4O5(OH)4 + H2O} and {(LiB5O6(OH)4 + H2O} and mixing ion-interaction parameters θ B 4 O 5 OH 4 , B 5 O 6 OH 4 and ψ Li , B 4 O 5 OH 4 , B 5 O 6 OH 4 for the ternary system {Li2B4O5(OH)4 + LiB5O6(OH)4 + H2O} were fitted with the experimental osmotic coefficients using the Fortran 97 program. Meanwhile, the water activities were calculated by the Pitzer parameters, and the good agreement between the calculated water activities and experimental results of this ternary system indicated that the Pitzer parameters obtained in this work were reliable.

The thermodynamic properties including enthalpy, entropy and Gibbs free energy are important parameters, which can provide a theoretical basis for utilizing salt lake resources. In addition, the dissolution equilibrium constant (K), activity coefficient (γ) and osmotic coefficient (Φ) of inorganic salt solution, especially for sodium borate, are critical and fundamental, but scarce owing to the difficulty to measure them. These data are not only important theoretical basis in analytical and physical chemistry, but also reliable information in determining chemical production processes. In this paper, the dissolution enthalpies (∆Hsθ) of sodium metaborate tetrahydrate (NaBO2·4H2O) and sodium metaborate dehydrate (NaBO2·2H2O) were determined using a microcalorimeter TAM IV. Based on our experimental data and the Pitzer electrolyte model, values of dissolution equilibrium constant (K, 8.7986 mol2·kg−2 for NaBO2·4H2O, 9.9560 mol2·kg−2 for NaBO2·2H2O), activity coefficient (γ, 0.2932), osmotic coefficient (Φ, 0.7999) of NaBO2 were measured with precision. According to the designed thermochemical cycle and the basic formula of thermodynamics, the standard enthalpy of formation (∆Hfθ), the standard entropy of formation (∆Sfθ), the standard Gibbs free energy (∆Gfθ), the standard enthalpy of dissolution (∆Hsθ), the standard entropy of dissolution (∆Ssθ), and the dissolution Gibbs free energy (∆Gsθ) of NaBO2·4H2O and NaBO2·2H2O at 298.15 K, which are not reported in the literature, were obtained with exactitude. These results indicate that the dissolution of both hydrates are all endothermic, spontaneous and entropy driven processes.

The solid–liquid phase equilibria of systems LiCl–NaCl–CaCl2–SrCl2–H2O and CaCl2–SrCl2–H2O at 273.15 K and 0.1 MPa were investigated with the isothermal equilibrium method. The solid–liquid equilibrium phase diagrams were constructed with the experimental solubilities. The phase diagram in the ternary system consists of one univariant solubility curve saturated with solid solution (Ca,Sr)Cl2·6H2O, and one crystallization field of the solid solution. There are three invariant points, seven isothermal univariant curves, and five crystallization regions saturated with NaCl corresponding to (Ca,Sr)Cl2·6H2O, SrCl2·2H2O, LiCl·2H2O, CaCl2·4H2O and LiCl·CaCl2·5H2O in the dry-salt diagram of the quinary system. The areas of crystallization zones decrease according to the above order. The J(NaCl), J(H2O), refractive index and density of the solution gradually change regularly with the increasing of J(CaCl2) in the solution. These results on phase diagrams of the quinary system can supply theoretical reference for lithium salts and strontium salts separation from calcium chloride type brine.

As a unique and indispensable element in modern battery and energy industries, the recovery of lithium has attracted wide attention worldwide. In this work, the recovery of low concentration of Li+ in geothermal water was carried out by a green and novel FePO4/K2NiFe(CN)6 [FPO/KNiFC] electrochemical ion pump technique. Different K2MFe(CN)6 (M = Cu, Co, or Ni) was synthesized and used to construct an electrochemical ion pump with FePO4. It was found that K2NiFe(CN)6 has excellent electrochemical properties, and the recovery of Li+ is mainly restricted by the insertion capacity and rate of the FePO4 electrode. This problem was successfully solved by the modification of electrode using multiwalled carbon nanotube. Even though the optimized ion pump system has a low single insertion capacity for low concentrations of Li+, a cycle extraction method was developed and successfully realized high-effective recovery of Li+ from geothermal water. Subsequently, a multi-stage extraction device was designed and proposed for the continuous recovery of low concentrations of Li+.

In order to guide the separation of valuable lithium and potassium pentaborate productions, the phase equilibria for the two reciprocal quaternary systems (Na+, K+//Cl−, B5O8− - H2O) and (Li+, K+//Cl−, B5O8− - H2O) at 298.15 K and atmospheric pressure were studied using the isothermal dissolution method. Based on experimental data, the phase diagrams as well as the diagrams between physicochemical properties including densities and refractive indices against J(K+) in the two systems were established for the first time. For the former system, there are four crystallization zones corresponding to halite (NaCl, Ha), sylvite (KCl, Sy), sodium pentaborate pentahydrate (NaB5O8·5H2O, Sp5) and potassium pentaborate tetrahydrate (KB5O8·4H2O, Pp4), two invariant points of three solid phases existed (Ha + Sy + Pp4) and (Ha + Sp5 + Pp4), and five univariant curves, but for the later system, there are also four crystallization zones corresponding to Sy, Pp4, lithium chloride monohydrate (LiCl·H2O, Lc1) and lithium pentaborate pentahydrate (LiB5O8·5H2O, Lp5), two invariant points of three solid phases existed (Sy + Lc1 + Pp4) and (Lc1 + Pp4 + Lp5), and five univariant curves, respectively. The diagrams for the physicochemical properties including density and refractive index against J(K+) in the solution of two systems were also established.

As a new-type liquid lithium resource, the recovery of lithium from geothermal water is of great significance due to the increasing importance of lithium in modern industry. In this work, different lithium manganese oxides (LMOs), including LiMn2O4, Li1.66Mn1.66O4, and Li4Mn5O12, were synthesized and applied for selective recovery of lithium from geothermal water. It was found that the powdery Li4Mn5O12 exhibits high performances for low concentrations of Li+ and was then successfully granulated using chitosan (CTS) at a mass ratio of CTS/LMO = 3:2. The hydrophily of CTS leaded to a serious dissolution loss of CTS/LMO under acidic conditions, but it was successfully solved by direct cross-link of the spherical material using ethylene glycol diglycidyl ether (EGDE), by which the dissolution loss in 0.25 mol/L HCl was decreased from 27.65% to no more than 0.6%. The equilibrium adsorption capacity of Li+ in geothermal water reached 8.98 mg/g at 303.15 K, while the attenuation of adsorption capacity was no more than 1.1% after five times adsorption-desorption cycles. The separation factors between Li+ and other ions were all higher than 51 with a distribution coefficient of Li+ reaching up to 1113.27 mL/g. All these properties demonstrate that the developed material has high selectivity and stability, and can be used as a candidate for selective recovery of lithium from geothermal water or other solutions.

This paper reports the densities of CsB5O8 (aq) in the range of salt concentrations from 0.02526 to 0.08148 mol·kg−1, which were determined by an accurate Anton Paar Digital vibrating-tube densimeter at 5 K intervals from 283.15 to 363.15 K and 101 kPa. The apparent molar volume (Vϕ), the coefficient of thermal expansion (α), apparent molar expansibility of the solute (ϕE) were calculated and variations of these properties against temperature and concentration were revealed minutely. According to Pitzer ion-interaction apparent molar volume model of aqueous electrolyte system, the Pitzer single salt parameters i.e. FMX ( β M X 0 v , β M X 1 v and C M X v , M = Cs+, X = [B5O6(OH)4]-), the temperature-dependence equation [FMX (i, p, T) = a1 + a2ln(T/298.15) + a3(T-298.15) + a4/(620-T) + a5(T-227), i = β M X 0 v , β M X 1 v and C M X v ] as well as their coefficients ai (i = 1 to 5) in the binary system were obtained, which is not reported in the literature. The fitted results of single salt parameters β M X 0 v , β M X 1 v and C M X v were in good agreement with the experiment values, indicating that the single salt parameters and temperature relational coefficients for Cs[B5O6(OH)4] obtained in this work are reliable.

Volumetric properties for the ionic membrane mixture electrolytes in chlor-alkali industry were investigated for the first time. The densities for the binary system (NaClO3 + H2O) with molality of NaClO3 up to 9.2311 mol·kg−1 and the ternary system (NaClO3 + NaCl + H2O) with molality of NaClO3 from 0.8 to 3.0 mol·kg−1 and NaCl from 0.65 to 2.3 mol·kg−1 over the temperature range from (283.15 to 363.15) K at intervals of 5 K and ambient pressure were determined experimentally using an accurate digital vibrating - tube densimeter. The derived properties of apparent molar volume (Vϕ) for the two systems were obtained based on the experimental data. On the basis of volumetric property data on the binary and ternary systems, the Pitzer single-salt parameters (β(0)ν MX, β(1)ν MX and C(0)ν MX, MX = NaClO3) and mixing ion-interaction parameters (θv Cl,ClO3, ψv Na,Cl,ClO3) were parameterized according to Pitzer ion-interaction theory of single salt electrolyte and mixture electrolytes, and their temperature-dependence equations [FMX (i, p, T) = ai,1 + ai,2ln(T/298.15) + ai,3(T-298.15) + ai,4/(620-T) + ai,5(T-227), i = 1 to 3 for β(0)ν MX, β(1)ν MX and C(0)ν MX and i = 1 and 2 for θv Cl,ClO3, ψv Na,Cl,ClO3, respectively] as well as their relative temperature correlation coefficients ai for those parameters were also obtained for the first time by the least square fitting. Vice versa, the volumetric properties of electrolytes for the two systems at any temperatures between 283.15 and 363.15 K can be quantitatively acquired based on the parameterized model of electrolytes.

Isopiestic molalities and water activities for the commercial absorption refrigerants LiBr and SrBr2 at 288.15 K were accurately measured using an improved isopiestic method. And the solubilities for the absorption refrigeration systems were determined by the isothermal dissolution equilibrium method, meanwhile, the refractive indices and densities were measured. The Pitzer and HW model was used to correlate the measured water activities and solubilities, simulate the thermodynamic properties and predict the data in the phase equilibrium process for the absorption refrigeration systems, and the predicted data agreed well with the experimental solubilities. On the basis of the Pitzer ion-interaction parameters and solubility product constant (Ksp) obtained in this work, the ion-interactions between alkali metal ions with Sr2+ and phase equilibrium behaviors were illustrated on the molecular level, which could give an essential guide for the designing of absorption refrigeration system.

The dilution enthalpies of LiBO2 (aq) from 0.0398 to 0.7684 mol·kg−1 and LiB5O8 (aq) from 0.0521 to 0.8067 mol·kg−1 at 298.15 K and 101.325 kPa were investigated using the microcalorimeter BT 2.15. The apparent molar enthalpies on two lithium borates were obtained, and the diagrams of their apparent molar enthalpy against molality for LiBO2 (aq) and LiB5O8 (aq) were also plotted. Considering the constructers of BO2- and B5O8- in aqueous solution are existed as in [B(OH)4]- and [B5O6(OH)4]-, the Pitzer single-salt parameters ( β M X ( 0 ) L , β M X ( 1 ) L , β M X ( 2 ) L , C M X L ) for LiB(OH)4 and LiB5O6(OH)4 were obtained for the first time. A comparison between the calculated apparent molar enthalpies for LiBO2 (aq) and LiB5O8 (aq) based on Pitzer model and those determined experimentally agree well, which indicate that the Pitzer single parameters of LiB(OH)4 and LiB5O6(OH)4 obtained are reliable.

With the increasing demands for lithium, the recovery of lithium from liquid minerals has become a research focus worldwide. The green recovery of a low concentration of lithium from geothermal water was carried out in this work based on the LiFePO4/FePO4 technique. The composite LiFePO4 electrode was prepared first and then electrochemically delithiated to obtain a FePO4 electrode. When the LiFePO4 and FePO4 electrodes were used to construct an electrochemical system in an H-type electrolytic cell, it had high response to low concentrations of Li+ at 1.0 V. The electrochemical adsorption capacity was successfully increased by 57.02% which was 17.10 mg g−1 in the geothermal water by using PEG-6000 as a poregen to obtain pore structures on the surface of electrode. The recovery rate of Li+ reached 90.65% after eight adsorption-desorption cycles. Subsequently, a novel electrochemical device was proposed for the recovery of low concentrations of Li+ by the LiFePO4/FePO4 technique. Only electrical energy was consumed and no organic solvents or other toxic reagents were used during the recovery process. All these properties make the developed method a green and promising candidate for the recovery of Li+ from geothermal water.

Solubilities and refractive indices in the ternary system NaCl–NaBO2–H2O at 323.15 K were investigated with the dissolution equilibrium method. The phase diagram of this system consists of three single-salt crystallization regions for NaBO2·4H2O, NaCl·NaBO2·2H2O and NaCl, three univariant solubility curves and two invariant points. A comparison of the diagrams of this system from 288.15 to 323.15 K shows that area of NaBO2·4H2O region decreased whereas the areas of NaCl·NaBO2·2H2O increased obviously with temperature increasing. The Pitzer binary parameters of NaB(OH)4, Pitzer mixing parameters θ Cl - , B OH 4 - and ψ Na + , Cl - , B OH 4 - , and the dissolution equilibrium constants of NaB(OH)4·2H2O and NaCl·NaB(OH)4 were fitted with the solubility data on the basis of Pitzer model. The variation trends for calculated solubility curves are in accordance with the experimental results. The results show that the other boron species except B(OH)4− in the solution for the system NaCl–NaB(OH)4–H2O can’t be neglected. The assumption of only one boron containing ionic species B(OH)4− in the solution is not very accurate, but the calculated results with the assumption can still describe the experimental values. The Pitzer parameters and Ksp values obtained in this study are capable of solubility calculation for the system containing B(OH)4−.

Densities for aqueous solutions of Cs2B4O7 at the molalities of (0.16635–0.69694) mol·kg−1 were measured with an Anton Paar Digital vibrating-tube densimeter at temperatures from 283.15 K to 363.15 K and 101 kPa. According to experimental data, apparent molar volume (Vϕ), partial molar volume ( V ¯ ϕ ), and the coefficient of thermal expansion (α) of the Cs2B4O7 aqueous solution were calculated, and their distributive behaviors against temperature and molality have been discussed in details. Considering the structure of Cs2B4O7 in aqueous solution system is in the form of Cs2[B4O5(OH)4], the Pitzer single-salt parameters ( β M , X 0 v , β M , X 1 v , β M , X 2 v and C M , X v ) for Cs2[B4O5(OH)4] as well as temperature-dependence correlations were obtained for the first time on the basis of Pitzer ion-interaction apparent molar volume model of electrolytes. The deviations between the Pitzer single-salt parameters of Cs2[B4O5(OH)4] fitted at each temperatures based on the experimental data and those of the calculated values corresponding to the temperature-dependence equations on Pitzer single-salt parameters are all within ±0.1, indicating that the single-salt parameters and their temperature-dependence equations obtained in this work are reliable.

A novel ammonium molybdophosphate (AMP)/ polyvinyl alcohol (PVA)/ sodium alginate (SA) composite hydrogel (APS) was prepared for Cs+ removal and enrichment from radioactive wastewater. Batch experiments with the subject of AMP concentration, pH value, initial Cs+ concentration, contact time, temperature, competing ions were investigated. The results showed this APS hydrogel with high permeability and stability could effectively adsorb Cs+ at widely broad pH value range and low Cs+ concentration within a short time. Adsorption thermodynamic parameters indicated the endothermic and spontaneous nature of the adsorption process, and the Lagergren pseudo-second order model was found to exhibit the best correlation with the adsorption results. Equilibrium data was better described by the Langmuir isotherm equation, and the maximum adsorption capacity of APS hydrogel calculated was in consistent with the experimental results. Furthermore, the APS hydrogel could be easily reused at least five times without obvious decrease in absorption activity and selectivity using ammonia nitrate as the eluent, and what’s more, the Cs+ concentration in eluent was approximately concentrated for 2 times after single cycle. All the results suggest that the environmental friendly and low-cost APS hydrogel could be used as effective and selective material for Cs+ removal and enrichment from wastewater.

With the isothermal dissolution equilibrium method and wet-residue method, the solubility data as well as physicochemical properties including density, refractive index, and pH value of the two ternary systems (NaCl + NaBO2 + H2O) and (Na2SO4 + NaBO2 + H2O) at 298.15 K and 0.1 MPa have been experimentally determined, and the relatively phase diagrams have been established for the first time. In the ternary system (NaCl + NaBO2 + H2O), two invariant points, three univariant curves, and three crystallization regions corresponding to sodium chloride (NaCl), sodium metaborate tetrahydrate (NaBO2·4H2O), and a congruent double salt teepleite (NaCl·NaBO2·2H2O) were detected. While in the ternary system (Na2SO4 + NaBO2 + H2O), there are one invariant point, two univariant curves, and two crystallization regions corresponding to NaBO2·4H2O and mirabilite (Na2SO4·10H2O). The physicochemical properties (density, refractive index, and pH value) in the two systems present a regular variation versus that with the chang...

The solubilities in the quaternary system NaCl–KCl–SrCl2–H2O and its subsystem KCl–SrCl2–H2O at 288.15 K were investigated with the isothermal dissolution method. The phase diagram of the ternary system is composed of two single-salt crystallizations for KCl and SrCl2·6H2O, two solubility univariant curves, and one cosaturated point. The dry-salt diagram of the quaternary system consists of three single-salt crystallization fields for NaCl, KCl, and SrCl2·6H2O, three solubility univariant curves, and one invariant point. By combination of the determined solubilities and Pitzer binary parameters obtained in the literature, the lacking Pitzer mixing parameters θNa,Sr, θK,Sr, ΨNa,Sr,Cl, and ΨK,Sr,Cl and the solubility product constants of the solid salts for the systems were fitted on the basis of the Pitzer model. The model was then used to calculate the solubilties of the two systems. The theoretical results calculated using the model coincide with the experimental values.

The efficient transformation of CO

The heat capacity of lithium pentaborate pentahydrate has been measured using an adiabatic calorimeter at the temperature from 297 to 375 K. No phase transition and thermal anomalies were observed. The molar heat capacity of LiB5O8·5H2O can be expressed as Cp,m (J·mol−1·K−1) = 396.79376 + 35.87528 [T-(Tmax+Tmin)/2]/[(Tmax-Tmin)/2] + 0.16494[T-(Tmax+Tmin)/2]/[(Tmax-Tmin)/2]2 + 8.3083[T-(Tmax+Tmin)/2]/[(Tmax-Tmin)/2]3, where T is the temperature in Kelvin, Tmax=375 K, and Tmin=297 K. The thermodynamic functions of (HT-H298.15), (ST-S298.15), and (GT-G298.15) of LiB5O8·5H2O are obtained via the molar heat capacity at the temperature of 5 K intervals.