The solid–liquid equilibrium of the quaternary system Na+,K+//HPO42–,Cl––H2O and its subsystems Na+//HPO42–,Cl––H2O, Na+, K+//HPO42–,Cl––H2O, Na+,K+//HPO42––H2O at 298.2K were investigated by the isothermal solution saturation method. The solubility of salts and the equilibrium solid phases were determined. The ternary phase diagram, quaternary dry-salt phase diagram, and the water-content diagram were constructed. There is one invariant point, two univariant curves, and four crystallization regions in the ternary system Na+//HPO42–,Cl– −H2O and K+//HPO42–,Cl––H2O. The ternary system Na+,K+//HPO42––H2O contains two invariant points, three univariant curves, and six crystallization regions. The quaternary system Na+,K+//HPO42–,Cl––H2O contains three invariant points, seven univariant curves, and five crystallization regions corresponding to KCl, NaCl, Na2HPO4·12H2O, Na2HPO4·7H2O, and K2HPO4·3H2O. In the quaternary system, KCl occupies the largest crystallization region while K2HPO4·3H2O crystallization region is the smallest. Three kinds of hydrated salts were found in the system while there is no double salts or solid solution. HPO42– is the main factor that affects the relative water content in the liquid phase. All the data and results obtained in this paper are of great significance to the crystallization technology of K2HPO4 and the new production process of KH2PO4.

·The study disposed waste with waste to achieve value added utilization of waste.·FHA was obtained with a rod-like and developed space connected structure.·FHA showed a high specific surface area and adsorption amount.·FHA was a low-cost and high efficient adsorbent for the removal of cadmium (II).The excellent precursor of fluor-hydroxyapatite composites (FHA) was prepared by hydrothermal method using fluorine-contained silica (F-SiO2) and hydrated lime (HL) as raw materials. And a new adsorbent FHA was obtained and employed as an adsorbent for the removal of Cd2+ from aqueous solution. Series of adsorption properties of FHA for the removal of Cd2+ from aqueous solution were investigated at various conditions. The influence of different adsorption parameters, such as solution pH, initial concentration of Cd2+, temperature and contact time on the adsorption efficiencies of FHA for Cd2+ were studied and discussed. The results showed that the adsorption process was in agreement with the Langmuir isotherm model and pseudo-second-order kinetic model. The Langmuir adsorption isotherm constant corresponding to adsorption amount, qm, was found to be 236.41 mg/g. Various thermodynamic parameters such as △G0, △H0 and △S° were calculated, which indicated the spontaneous and endothermic nature of the adsorption process. At the appropriate conditions, FHA was an excellent adsorbent for the removal of Cd2+ from aqueous solution. And it was confirmed that the adsorption mechanism of Cd2+ by FHA was mainly determined by ion-exchange and monolayer chemical adsorption.Download high-res image (192KB)Download full-size image

•The differences among three breakage kernels in CFD–PBM simulations are discussed for a spray fluidized-bed crystallizer.•We have some modifications to the GZ and CT breakage kernels.•The GZ breakage kernel describes the PSD well in consideration of the attrition effects.In this work, a computational fluid dynamics (CFD) model coupled with population balance model (PBM) is applied to simulate the evolution of potassium sulphate particle growth process and the liquid-solid two-phase flow behaviors in a spray fluidized-bed crystallizer (SFBC). In order to describe the hydrodynamics of particles and the growth process fully, the kinetics model of particle growth, aggregation and breakage kernels is incorporated into the coupled model by using a user-defined function (UDF). Three particle breakage kernels based on the Kolmogorov turbulence theory (Coulaloglou and Tavlarides), attrition theory (Ghadari and Zhang) and kinetic energy theory (Luo and Svendsen) are considered in this work respectively. The three theories are modified to consider the particle flow behaviors and particle size distributions (PSD) under the same spray velocity. The CFD-PBM model is also used to predict the distributions of relative parameters in the liquid-solid two-phase flow in the SFBC via three breakage kernels. Furthermore, the variations of the solution temperature, particle velocity, crystallizer voidage and particle concentrations are obtained with consideration of particle growth process. The comparison and analysis of the kernels are studied and the simulation results show the difference among these breakage kernels. Meanwhile, the research reveals that the GZ kernel is in better agreement with fluidization phenomenon, and it agrees well with experimental data. This model provides essential information for crystallizer design and optimization.Download high-res image (63KB)Download full-size image

The solubility data of the quaternary system K+//H2PO42–, SO42–, Cl––H2O is basically required for the design and optimization of the crystallization process of KH2PO4 which is produced by the solvent extraction method using the wet-process H3PO4 and KCl as the raw materials. In this study, the solubility data of the quaternary system K+//H2PO42–, SO42–, Cl––H2O at 298.2 K and 323.2 K were investigated by the isothermal solution saturation method. The solubilities of salts and equilibrium solid phases were determined. The phase and water content diagrams were constructed based on the experimental results. The appearance of the phase diagram at 323.2 K is similar to that at 298.2 K, while the crystallization area of each salt varies slightly with the changing of temperature. The phase diagrams both contain one quaternary invariant point, three univariant curves, and three crystallization regions corresponding to KH2PO4, K2SO4, and KCl. The crystallization region of K2SO4 is the largest, while that of KCl is the smallest. The order of the three salts solubilities is KCl > KH2PO4 > K2SO4. The water content reaches its minimum value at the quaternary invariant point at each temperature.

The design and enlargement of extraction equipment require kinetic data on the extraction system. In this study, the extraction kinetics of phosphoric acid from the phosphoric acid—calcium chloride solution by tri-n-butyl phosphate (TBP) was investigated using a constant-interfacial-area cell with laminar flow. The extracted complexes were demonstrated to be H3PO4·TBP, H3PO4·2TBP, and H3PO4·3TBP by equilibrium studies. The effects of stirring speed, temperature, and interfacial area on the extraction rate were investigated. The results indicate that the extraction process is under mixed control by the extraction reaction at the interface and the diffusion of the reactant in the aqueous phase. The extraction rate is first-order with respect to H3PO4 and TBP with a rate constant of 10–5.34 L·mol–1·s–1. A mixed-control regime model is proposed. The forward extraction rate constant and the diffusion coefficient of the reactant in the aqueous phase were calculated to be 6.86 × 10–6 and 6.47 × 10–5 L·mol–1·s–1, respectively.

•LLE data for 1-butanol + water + tri-n-butyl phosphate (TBP) + ammonium chloride were obtained.•The reliability is given by the calculation of the uncertainties.•The data were correlated with NRTL model and the relevant interaction parameters are estimated with the experimental data.•The influence of temperature and different concentrations of ammonium chloride has been investigated.In this paper, the liquid–liquid equilibrium (LLE) and tie-line data of the system containing 1-butanol + water + tri-n-butyl phosphate (TBP) + ammonium chloride have been studied at 298.15, 308.15 and 318.15 K under atmospheric pressure. The influence of temperature and different concentrations of ammonium chloride have been investigated. In addition, nonrandom two-liquid (NRTL) model is applied to the system, and the relevant interaction parameters are regressed with the experimental data. The quality of the correlation is measured by the rmsd (rmsd≤0.0131rmsd≤0.0131). The results show that the calculated values by NRTL model are in agreement with the determination of LLE data of the studied system in the investigated conditions.

The preparation of fine phosphoric products, for example sodium dihydrogen phosphate (NaH2PO4) from wet-process phosphoric acid (WPA), has been gaining interest in recent years. However, there are some undesirable impurities (Fe3+, Al3+, and Mg2+) in WPA, which will degrade the quality of the phosphoric products. Enhancing the pH of the solution, often to 4–4.5, can remove most of the metal ions, but the presence of some metal ions such as Fe3+ has great impact on the crystallization of the NaH2PO4. Therefore, in order to get industrial grade NaH2PO4 products, the neutralized NaH2PO4 solution should be purified. The extraction of Fe3+ from NaH2PO4 solution with colloidal liquid aphrons (CLAs) was investigated. The good extraction efficiency of Fe3+ with CLAs was verified. Meanwhile, to study the advantages of the CLAs process, the major influencing factors on the extraction efficiency for Fe3+ were investigated, and the optimal influencing factors for removal of Fe3+ with CLAs were presented. The results of the extraction experiments from practical NaH2PO4 solution show that superior grade NaH2PO4 can be obtained by three cross-flow extractions under the appropriate conditions.

Liquid–liquid equilibrium and tie line data for the nitric acid/phosphoric acid/water/tri-n-octylamine (TOA) system have been determined at 298.15 K for HNO3 mass fractions of 0.028 to 0.26 and H3PO4 mass fractions of 0.00 to 0.19. The distribution coefficients of nitric acid (D1) and water (D3) were studied, and the separation factors β(HNO3/H3PO4) was also investigated. The results show that TOA is very selective, since only small quantities of water and phosphoric acid are present in the organic phase, which indicates the good ability of TOA to extract nitric acid from nitric acid/phosphoric acid mixtures. The experimental tie line data were correlated using the nonrandom two-liquid (NRTL) model. TOA can be used as an effective extractant to separate nitric acid from the HNO3/H3PO4/H2O system.

The ternary system of K2SO4 + KH2PO4 + H2O at (298.15 and 333.15) K was investigated by the method of isothermal solution saturation and moist residues. Thus the solubility data of the system were obtained, and phase diagrams of K2SO4 + KH2PO4 + H2O at (298.15 and 333.15) K were constructed on the basis of the solubility data. The solid phase in the system mentioned above was also identified. The crystallization field of potassium sulfate and potassium dihydrogen phosphate (KDP) were determined, and the crystallization field of potassium sulfate was larger than that of potassium dihydrogen phosphate. The density of saturated solutions for the systems studied at (298.15 and 333.15) K was also measured. The solubility data, density, and the phase equilibrium diagrams for the ternary system can provide the fundamental basis for the preparation of potassium dihydrogen phosphate in potassium sulfate and potassium dihydrogen phosphate aqueous mixtures.

The extraction of Mg2+ from ammonium dihydrogen phosphate (MAP) solution by extractant (D2EHPA) and its mixture, including acidic extractant (HEHPEHE), alkaline extractant (TOA) and neutral extractant (TBP) respectively, is investigated. The good extraction selectivity of Mg2+ with D2EHPA from ammonium dihydrogen phosphate solution is verified, which is found to be associated with the cation exchange and chelation capability of D2EHPA on the basis of its molecular structure. The related thermodynamic data are also obtained in terms of experimental results as follows: the extraction enthalpy is 2.659×10−2 (J·mol−1·K−1), the free energy is 1.501×103 (J·mol−1) and the entropy is 4.441 (J·mol−1). Meanwhile, the major influencing factors, such as the initial pH, the initial concentration of extractant, phase ratio and the extraction temperature on the extraction ratios of Mg2+, are studied, and the optimal process conditions are obtained. As shown in the extraction experiments for practical MAP solution, superior grade MAP can be obtained by three levels of extraction under optimal condition.

Single crystals of rifapentine have been grown by cooling technique. The crystal structure analysis and the molecular arrangement of these crystals have been determined using X-ray diffraction (XRD) method. From single-crystal XRD studies, it is found that the compound crystallizes in the monoclinic system with a space group P21, and the corresponding lattice parameters were calculated (a = 12.278(3) Å, b = 19.768(4) Å, c = 12.473(3) Å, Z = 2, beta = 112.35(3)°). FT-IR spectra are recorded to identify the various functional groups present in the compound. The UV–Vis spectrum of rifapentine takes place at a wavelength of 236, 255, 334 and 474 nm, respectively. The thermal stability of the crystal is determined from TG/DTA curves.

Liquid−liquid equilibrium and tie line data in the system phosphoric acid/water/tri-n-butyl phosphate/calcium chloride has been determined at 298.15 K, in the concentration range from w = 0.028 to 0.20 phosphoric acid and w = 0 to 0.25 calcium chloride. Distribution coefficients of phosphoric acid and separation factors of water and calcium chloride were determined to establish the extracting capability of tri-n-butyl phosphate. The results show that tri-n-butyl phosphate can serve as an adequate extractant to recover phosphoric acid from dilute phosphoric acid containing calcium chloride.

Separation strategies for Jordanian phosphate ore with siliceous and calcareous gangues were investigated by combined beneficiation and characterization techniques. To avoid ore resource waste and save the separation cost, it is noteworthy that different size fractions of Jordanian phosphate ore produced by sieving should be processed by different methods. The 74–300 μm size fraction which has fewer gangues than coarser and finer size fractions is treated by scrubbing to increase P2O5 grade up to 30%. The coarser size fraction (> 300 μm) requires secondary grinding. The finer size fraction (< 74 μm) with 23.85% P2O5 grade is processed by flotation to remove quartz gangue. The acid conditions can improve the flotation performance remarkably. The dissolution of carbonates at low pH value facilitates the quartz flotation. At pH 4.8, the P2O5 grade, P2O5 recovery and quartz removal ratio are 30.82%, 82.00% and 62.20%, respectively. Calcination can be employed to separate calcite gangue; however, it should be applied after quartz flotation to avoid the formation of CaSiO3 phase. To improve the flotation performance, the amount of < 45 μm particles should be reduced, and an alternative method is avoiding over-grinding.Research Highlights►Separation strategies for siliceous and calcareous phosphate ore are consisted of sieving, scrubbing and flotation. ►Sieving is the important first step. Different size fractions of Jordanian phosphate ore are produced. ►The > 74 μm size fraction is treated by scrubbing to increase P2O5 grade up to 30%, except > 300 μm size fraction which needs secondary grinding. ►The < 74 μm size fraction is processed by flotation to remove quartz gangue. At pH 4.8, the P2O5 grade is increased from 23.85% to 30.82%. ►Calcination is an alternative method to separate calcite gangue from < 74 μm size fraction, but it should be applied after quartz flotation.

The present work is focused on the relationship between effective segregation coefficient keff and temperature of melting zone for purification of phosphorus by zone melting method. Values of keff at four temperatures of melting zone are obtained for zone pass n=1 at travel velocity of molten zone v=5×10−3 m·h−1 and initial impurity concentration C0≤10 μg·g−1. lnkeff is a linear function of 1/T. The keff values of Al, Ca, Cr, Fe, Cd and Sb increase with temperatures while that of Mg is almost constant. The purification is acceptable at lower temperature of melting zone such as 323 K. The variations of enthalpy and entropy between impurities and phosphorus in the liquid and solid phases are also presented.

Rifapentine, an important antibiotic, was crystallized from methanol solvent in the form of its methanol solvate. The crystal structure of rifapentine methanol solvate belongs to monoclinic, space group P21, with the unit cell parameters of a = 1.2278(3) nm, b = 1.9768(4) nm, c = 1.2473(3) nm, Z = 2, and β = 112.35(3)°. The parallelepiped morphology was also predicted by Materials Studio simulation program. The influence of intermolecular interaction was taken into account in the attachment energy model. The crystal shape fits the calculated morphology well, which was performed on the potential energy minimized model using a generic DREIDING 2.21 force field and developed minimization protocol with derived partial charges.

Selective separation of silica from a siliceous–calcareous phosphate ore that had been sieved into different size fractions is investigated by a combination of chemical analysis, zeta potential measurement and FTIR and XPS techniques. Scrubbing is a better choice than flotation for removing silica from the coarse fractions. The P2O5 grade of the coarse fractions is increased to about 30% by scrubbing and the product yields are higher than those obtained by flotation. The silica in the fine fraction is separated by reverse flotation. An alkyl amine salt (DAH) is an effective collector and the P2O5 grade of the fine fraction can be increased by 7% to beyond 30% under acidic conditions. The higher zeta potential obtained using DAH suggests that it is more strongly absorbed onto the ore particles than the other cationic collectors. FTIR and XPS results confirm physical absorption of the cationic collector onto the ore surface. They also indicate that calcite is dissolved at low pH values, which increases the Si concentration on the ore surface.