The rheological behavior and stability of Mg(OH)2 suspensions were studied in the presence of sodium polyacrylate with different molecular weights under conditions of different ionic strength and counterion valence (K+ and Mg2+). Rheological properties, optical absorbance, and zeta potential measurements were conducted on the Mg(OH)2 particle suspensions to assess the dispersing ability of the sodium polyacrylate dispersants. Adsorption isotherm measurements were applied to investigate the effect of counterions on the adsorption behavior. The results demonstrate that Mg2+ ions destabilize the Mg(OH)2 suspensions more dramatically than K+ ions due to the stronger screening effect and special complexation of Mg2+ ions and carboxyl groups. The effect of molecular weights of NaPA on the rheological properties becomes more pronounced at higher solid loading because the NaPA with a molecular weight of 15,000 g/mol increases the viscosity more obviously than NaPA with a molecular weight of 1200 g/mol. The calculation results of interparticle interaction by the Hamaker 2 program show that the suspensions can achieve good stability with sufficient NaPA dosage, which coincides with the optical absorbance measurement results.

The effects of NO3– and SO42– ions on the H+ concentration in organic phase and crystal morphology of solid product nesquehonite (MgCO3·3H2O) in the coupled reaction–extraction–crystallization process were investigated. During the coupled process, the H+ concentration in organic phase increased with the increase in concentration of NO3– ions and decreased with the increase in concentration of SO42– ions, indicating that NO3– ions promoted the carbonization of MgCl2 while SO42– ions inhibited the same. The rodlike MgCO3·3H2O crystals became short and thick in the presence of both NO3– and SO42– ions. Energy-dispersive X-ray spectroscopy (EDS), inductively coupled plasma atomic emission spectroscopy (ICP-AES), and molecular dynamic simulation were used to clarify the mechanism by which impurity ions modified the structure. The results indicated that the NO3– and SO42– anions could be selectively adsorbed on the top facet (011̅) of MgCO3·3H2O, preventing the growth of crystal surfaces, which results in the decrease in length and increase in diameter of MgCO3·3H2O product. The morphology modification by NO3– ion was mainly due to the selective adsorption of NO3– ions. Both selective adsorption of ions and the incorporation of ions accounted for the morphology modification by SO42– ions.

Herein is reported a novel green process involving natural l-tartaric acid leaching, developed for the sustainable recovery of Mn, Li, Co, and Ni from spent lithium-ion batteries (LIBs). Operating conditions affecting the leaching efficiencies of Mn, Li, Co, and Ni, including the concentrations of l-tartaric acid (C4H6O6) and hydrogen peroxide (H2O2), pulp density, temperature, and leaching time, were investigated. The leaching efficiencies were 99.31% for Mn, 99.07% for Li, 98.64% for Co, and 99.31% for Ni under the optimized conditions (4 vol% H2O2, 2 M l-tartaric acid, 17 g/L pulp density, 70 °C, and 30 min). The leaching mechanism was studied preliminarily based on the structure of l-tartaric acid. The kinetics data for the leaching of Mn, Li, Co, and Ni fit best to the shrinking-core model of chemical control. For the first stage, the activation energies (Eas) for the leaching of Mn, Li, Co, and Ni were 66.00, 54.03, 58.18, and 73.28 kJ/mol, respectively. For the second stage, the Eas for the leaching of Mn, Li, Co, and Ni were 55.68, 53.86, 58.94, and 47.78 kJ/mol, respectively. The proposed hydrometallurgical process was found to be simple, efficient, and environmentally friendly.Keywords: Green process; Kinetics; l-Tartaric acid; Leaching; Recovery; Spent lithium-ion batteries;

•Brines with different feed characteristics were treated by electrodialysis (ED).•The selective affinity of a Selemion CSO membrane was evaluated.•The mass transfer of this process was discussed via a thermodynamic analysis.•A specific transfer phenomenon in a brine system was found and explained.•ED was verified to have wide adaptability for lithium recovery from various brines.Although lithium resources are abundant in the salt lakes located in West China, the majority of these resources have a high Mg/Li ratio, which is problematic because traditional precipitation methods are unsuitable for lithium recovery from this type of brine. In our previous work, constant-current electrodialysis (ED) was applied to comprehensively investigate the effects of operating conditions on the Li+/Mg2+ separation, however, the experimental study considering the feed characteristic diversity and the theoretical analysis of the ionic transfer process considering the feed composition complexity were remained to be perfected. This work focused on resolving the remained questions therein. Initially, we determined the ion-exchange isotherm of the CSO membrane. The selective affinity towards divalent cation was validated, which laid the foundation for the development of the electric double layer (EDL). Then, we investigated the effects of applied voltage on the separation performance and optimized the power mode. The constant-voltage was verified to be a superior power mode compared to the constant-current applied in our previous work. Thereafter, the feed solutions characterized by different Mg/Li ratios, Na/Li ratios, and sulfate concentrations were treated by constant-voltage ED, wherein the partitioning principle was further explained via a thermodynamic analysis of the aqueous species distribution of ions. The results showed that in a high-salinity aqueous system, mass transfer was significantly affected by the complexity of the ions’ existing forms, which notably determined the steric hindrance and charge effect. As a specific transfer phenomenon, we found that sulfate ions provided large benefit to lithium recovery in the salt lake brine system. A natural brine experiment also showed that lithium recovery can be effectively achieved by ED. These observations indicated that ED has a wide adaptability for lithium recovery from brines with different feed characteristics.

•Li+ or Na+ weakens interactions between counterions and affects the atomic closed packs of the mixtures.•The anions tend to associate with the smaller cations in the mixtures.•Self-diffusion coefficients and ionic conductivities present positive dependences on Li+ or Na+ contents.•Shear viscosities first decreased and then slightly fluctuated with the increase of Li+ or Na+ contents.The effects of LiCl and NaCl on the local structures and transport properties as the self-diffusion coefficients, viscosities and ionic conductivities of molten RbCl and CsCl have been calculated and analyzed in detail at 1100 K across the full composition range by molecular dynamics simulations. For molten RbCl or CsCl, with the gradual addition of a smaller cation (Li+ or Na+), the densities of the mixed salts decrease monotonously, besides, the cationic-anionic interactions and the interactions between cations become weaker, while the corresponding atomic close packing gets a promotion respectively. Influenced by the local structures and interatomic forces simultaneously, the shear viscosities of molten LiCl-RbCl, LiCl-CsCl, NaCl-RbCl and NaCl-CsCl decrease firstly and then present slightly fluctuated variations as the contents of LiCl or NaCl are increased, being in consonance with the available experimental results. In addition, the ionic diffusivity and ionic conductivity of each system present positive composition dependences along with the increase of LiCl or NaCl concentration. Besides, the effects of LiCl on the local structures and transport properties of RbCl and CsCl are more pronounced than those of NaCl.

•Direct leaching of alunite from alunite tailing in KOH solution is proposed.•Optimum leaching conditions of alunite tailings are determined.•A dissolution mechanism of alunite that predicts the reaction order is proposed.•The alunite dissolution is controlled by the surface chemical reaction.Alunite tailings, a secondary resource from copper metallurgy industry in China, are considered a potential resource for both the production of alumina and potash fertilizer, since alunite tailings contain abundant alunite with associated impurities of kaolinite, dickite and quartz. In this work, the direct leaching of alunite from alunite tailings in the highly concentrated KOH solution is proposed. Under appropriate leaching conditions, such as temperature below 90 °C and KOH concentration above 13.5 mol·L− 1, most of alunite is dissolved while kaolinite, dickite and quartz are still remained in the residue. Mastersizer, X-ray diffraction, infrared radiation spectrometer, Raman spectrometer and scanning electron microscopy/energy-dispersive spectroscopy are used to characterize alunite tailings samples before and after leaching. The leaching kinetics of alunite from alunite tailings in the concentrated KOH solution is described using a shrinking core model controlled by the surface chemical reaction. The key kinetics parameters, such as the activated energy and the reaction order, are determined based on the leaching experimental data. The dissolution mechanism of alunite from alunite tailings in the concentrated KOH solution is considered, and is used to account for the reaction order.

•Gradient leaching of alunite tailings in concentrated KOH solution is proposed.•The developed process is cleaner and closed-loop with zero pollute emission.•Thermodynamic analysis is performed to clarify the reaction feasibility.•The leaching ratio of K, Al, Si reaches 99.5%, 84.0% and 5.6% on the optimal conditions.In this work, a gradient leaching process is proposed to treat alunite tailings in order to recover potassium and aluminum. Thermodynamic analysis on the reactions of alunite tailings with potassium hydroxide in the leaching process over the temperature range of 30–120 °C is accomplished. In the gradient leaching process, the main mineral of potassium alunite from alunite tailings is extracted into the concentrated potassium hydroxide solution, while kaolinite and quartz are still remained in the leaching residues. The proposed leaching process is demonstrated to be feasible based on the leaching ratio of potassium, aluminum, silicon elements in the leaching solution by ICP-OES and the mineralogical characterizations of the leaching residues by XRD, IR and Raman spectrometers. Furthermore, the gradient leaching conditions, such as alkali-to-ore mass ratio, leaching temperature, leaching time and potassium hydroxide concentration, are optimized using the response surface method to recover potassium and aluminum from alunite tailings as many as possible and to extract silicon as small as possible. Under the optimal leaching conditions of alkali-to-ore mass ratio 3.3, temperature 81.8 °C, time 41.6 min, and potassium hydroxide concentration 53.9 wt%, the leaching ratio of potassium and aluminum reaches 99.5% and 84.0%, and the leaching ratio of silicon is controlled in 5.6%, respectively. All the obtained results could contribute to affording a green and closed-loop recovering process for potassium and aluminum elements from alunite tailings.

•Effects of cooling rate, stirring rate and impurities on MSZW are investigated.•Nývlt-like equation and 3D nucleation approach estimate MSZW of K2SO4 solution.•The accuracy and sensitivity of ultrasonic sensor are similar with FBRM on MSZW.The metastable zone width (MSZW) and nucleation kinetics of potassium sulfate in the aqueous solution were investigated. MSZW was measured using both the ultrasonic velocity sensor and the focused beam reflectance measurement (FBRM) at different cooling rate, stirring rate and impurities concentration (aluminum ions and silicon ions), and the effects of these conditions on MSZW were discussed in details. In addition, the accuracy and sensitivity of detectors to measure the nucleation temperature of potassium sulfate in the aqueous solution were compared between the ultrasonic velocity sensor and FBRM over a wider range of operating conditions. Although two detectors measured MSZW with an acceptable accuracy, the ultrasonic velocity sensor had a higher sensitivity to the phase transition of potassium sulfate in solution since it directly detected the concentration change of potassium sulfate in solution. Furthermore, both self-consistent Nývlt-like equation method and classical 3D nucleation theory approach were applied to estimate MSZW of potassium sulfate in aqueous solution. According to these classical theories, the nucleation kinetics parameters were calculated based on the measured MSZW data for potassium sulfate aqueous solution with 40 °C, 50 °C and 60 °C saturation temperature, respectively. It was found two approaches could describe MSZW of potassium sulfate aqueous system very well.

•Interpretation of crystallization phenomena via prenucleation cluster.•About 80% calcium stably existed in the solution more than 1 h.•Significant influence of local mixing on induction time.•Evidence of formation of monohydrocalcite via aggregation.Crystallization of calcium carbonate under high concentration of magnesium was studied. Interesting phenomena were observed. Approximately 80% of calcium ions stably existed in the solution up to 60 min after amorphous calcium carbonate was separated by centrifugation, and induction time was significantly affected by concentration and feeding rate of sodium carbonate when other operating conditions remained unchanged. Experiments and computer simulation have proved that prenucleation cluster exists during crystallization of calcium carbonate in solutions. This paper tried to figure out specific crystallization process of calcium carbonate under high concentration of magnesium, and to interpret unforeseen phenomena combining with the idea of prenucleation cluster. With regarding prenucleation cluster which can incorporate magnesium into its structure as amorphous calcium carbonate, most of the phenomena including significant influence of local mixing could be better understood. Prenucleation cluster played an important role in crystallization of calcium carbonate, which was related to the induction time, morphology and final product, thus more fundamental studies of prenucleation cluster structure and magnesium role in it should be done.

•Leaching behavior of LiNi1/3Co1/3Mn1/3O2 cathode was investigated.•The leaching efficiencies for Li, Ni, Co, and Mn reached 99.7%.•Leaching kinetics of LiNi1/3Co1/3Mn1/3O2 were clearly faster than those of LiCoO2.•“Cubic rate law” was revised to describe the leaching kinetics optimally.•A simple and environmentally sound recycling process was proposed.In view of the importance of environmental protection and resource recovery, recycling of spent lithium-ion batteries (LIBs) and electrode scraps generated during manufacturing processes is quite necessary. An environmentally sound leaching process for the recovery of Li, Ni, Co, and Mn from spent LiNi1/3Co1/3Mn1/3O2-based LIBs and cathode scraps was investigated in this study. Eh–pH diagrams were used to determine suitable leaching conditions. Operating variables affecting the leaching efficiencies for Li, Ni, Co, and Mn from LiNi1/3Co1/3Mn1/3O2, such as the H2SO4 concentration, temperature, H2O2 concentration, stirring speed, and pulp density, were investigated to determine the most efficient conditions for leaching. The leaching efficiencies for Li, Ni, Co, and Mn reached 99.7% under the optimized conditions of 1 M H2SO4, 1 vol% H2O2, 400 rpm stirring speed, 40 g/L pulp density, and 60 min leaching time at 40 °C. The leaching kinetics of LiNi1/3Co1/3Mn1/3O2 were found to be significantly faster than those of LiCoO2. Based on the variation in the weight fraction of the metal in the residue, the “cubic rate law” was revised as follows: θ(1 − f)1/3 = (1 − kt/r0ρ), which could characterize the leaching kinetics optimally. The activation energies were determined to be 64.98, 65.16, 66.12, and 66.04 kJ/mol for Li, Ni, Co, and Mn, respectively, indicating that the leaching process was controlled by the rate of surface chemical reactions. Finally, a simple process was proposed for the recovery of valuable metals from spent LiNi1/3Co1/3Mn1/3O2-based LIBs and cathode scraps.Download high-res image (194KB)Download full-size image

The thermal dissociation of tri-n-octylamine hydrochloride (TOAHCl) was investigated using both the quantum chemical simulation and experimental methods. The pathway through which a mixture of tri-n-octylamine (TOA) and hydrogen chloride (HCl), rather than di-n-octylamine (DOA) and 1-chlorooctane, are produced has been determined through transition state (TS) search with Intrinsic Reaction Coordinate (IRC) calculations. Particularly, strong agreement between the experimental FTIR spectra and that of TOA demonstrates the same result for the first time. Moreover, the thermal dissociation of TOAHCl proceeds in two continuous steps, which is different from the low molecular mass amine hydrochlorides. The experimental enthalpy of the dissociation was 70.793 \(\hbox {kJ mol}^{-1}\) with DSC measurement which is very close to the density functional theory (DFT) calculation result 69.395 \(\hbox {kJ mol}^{-1}\). Furthermore, with the aid of DFT calculations, some other important thermochemical characteristics such as crystal lattice energy with the value of 510.597 \(\hbox {kJ mol}^{-1}\) were evaluated by means of Born–Fajans–Haber cycle.

•Separation of aminoglutethimide racemate by VARICOL and SMB processes is compared.•VARICOL process with various column configurations is assessed.•Separation conditions of VARICOL process are designed by transport-dispersive model.The separation of aminoglutethimide enantiomers by the continuous multicolumn chromatographic processes were investigated experimentally and theoretically, where the columns were packed with cellulose tris 3,5-dimethylphenyl-carbamate stationary phase (brand name Chiralcel OD) and mobile phase was a mixture of n-hexane and ethanol with monoethanolamine additive. The continuous enantioseparation processes included a synchronous shifting process (SMB) and an asynchronous shifting process (VARICOL), which allowed reducing the column number (here from six-column SMB to five-column VARICOL process). Transport-dispersive model with the consideration of both intraparticle mass transfer resistance and axial dispersion was adopted to design and optimize the operation conditions for the separation of aminoglutethimide enantiomers by SMB process and VARICOL process. According to the optimized operation conditions, experiments were carried out on VARICOL-Micro unit using five-column VARICOL process with 1/1.5/1.5/1 configuration and six-column SMB process with 1/2/2/1 configuration. Products of R-aminoglutethimide (R-AG) enantiomer and S-aminoglutethimide (S-AG) enantiomer with more than 99.0% purity were obtained continuously from extract stream and raffinate stream, respectively. Furthermore, the experiemntal data obtained from five-column VARICOL process were compared with that from six-column SMB process, the feasibility and efficiency for the separation of guaifenesin enantiomers by VARICOL processes were evaluated.

A novel coupled reaction–extraction–alcohol precipitation process was proposed to mineralize CO2 as MgCO3·3H2O directly by abandoned MgCl2. Rod-like crystal MgCO3·3H2O was obtained, and the conversion rate of MgCl2 increased sharply by using this novel coupled reaction–extraction–alcohol precipitation process. The effect of an added C1–C3 alcohol precipitation agent on the conversion rate of MgCl2 was in the following order: ethanol > isopropanol > n-propanol > methanol. Moreover, the optimal conditions for the highest conversion rate of MgCl2 by single-factor experiments were obtained as follows: initial concentration of MgCl2 solution is 2 mol·L–1, volume ratio of ethanol and aqueous phase is 2, mole ratio of N235 and aqueous phase is 2, volume ratio of diluent and N235 is 0.5, with a stirring rate of 300 r·min–1 at 298.15 K and at atmospheric pressure.

Production of phosphoric acid by using wet process technology in China is challenging due to high impurities (P2O5 present is less than 25 wt %). Extraction of phosphoric acid from such low concentration mixtures needs to be improved. Moreover, the separation of chloride and phosphate ions is also important for the subsequent production of phosphate fertilizers. In this study, an organic solvent composed of trialkyl amine (N235), isoamyl alcohol, and sulfonated kerosene was developed to extract phosphoric acid. Pseudoternary phase equilibria, two phase densities, and the viscosities were determined at 298.15 K and atmospheric pressure. Results show that unlike other common organic solvents, the proposed solvent exhibits relatively higher extraction capacity even at low phosphoric acid concentration (P2O5 less than 25 wt %). The separation factor of chloride and phosphate ions reaches up to 39.45 and is several orders of magnitude lager than other common organic solvents including alcohols, cyclohexane, and tri-n-butyl phosphate (TBP). In addition, the solubility of organic solvent in the aqueous phase is close to zero, while the water content in the organic phase keeps nearly constant at a low concentration of around 5 wt %. All of these indicated that the developed solvent mixture is efficient for the extraction of phosphoric acid.

N235 in isoamyl alcohol solution acts as an efficient extraction system for the revovery of hydrochloric acid (HCl) at very low concentrations in a coupled reactive extraction–crystallization process. In this study, the extraction equilibrium of N235 + isoamyl alcohol + HCl + H2O system was investigated systematically. The formation of the extraction complex in the organic phase was determined by using the experimental data and it was confirmed to be (HCl)4(R3N)4(H2O)8. Further, the thermodynamic model was then established by using Pitzer equation to calculate the activities of all the species. The values of the interaction parameters obtained by regression are as follows: βR3N,4:4:8(org) = 2.8782 and β4:4:8,4:4:8(org) = 11.4764. The extraction equilibrium constant is ln K4:4:8 = 38.0274. The thermodynamic model was demonstrated to be reliable and suitable for the N235 + isoamyl alcohol + HCl + H2O system.

The process of activating coal spoil (CS) in order to recover aluminum as a high value product was investigated. The CS was first characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD) and thermo-gravimetric analysis-differential scanning calorimetry (TGA-DSC) in order to determine the chemical and mineral compositions of the CS. Then a mechanothermal activation method was adopted to increase the aluminum activity in the coal spoil. Over 95% of the aluminum in the CS could be extracted using this activation method. The mechanothermal activation process promoted the destruction of kaolinite structures and hindered the formation of amorphous γ-Al2O3. This resulted in a high aluminum leaching activity in the mechanothermally activated CS.

A coupled reaction-solvent extraction process was used to remove HCl from a simulated distiller waste. The extraction performances of various extractants and diluents were compared and the apparent basicity of N235 (a mixture of tertiary amines) in various diluents was determined. The best results were obtained using N235 and isoamyl alcohol as the extractant and diluent, respectively. The yield of HCl from the coupled extraction was 75% with this extraction system. The mechanisms for the removal of HCl in both the direct and coupled extractions were investigated. For the coupled extraction, the formation of an R3NHCl ion-pair complex was involved in the HCl removal. For the direct extraction, the mechanism involved the formation of hydrogen bonds at high concentrations of HCl.

Compared with traditional methods, computational fluid dynamics–population balance model (CFD–PBM) simulations are much more efficient for the design of extractors. In this study, the CFD–PBM framework was established for a pilot-scale rotating-disk contactor. The Euler–Euler approach incorporated with the realizable k–ε model was used for the two-phase simulation. For droplet coalescence and breakage, predictive closures based on the model of Luo and Svendsen were employed for further verification. The species transport model was also solved to estimate axial mixing. The model was validated first by comparing the flow field with referenced particle image velocimetry data. Then the predicted key parameters of droplet diameter, dispersed-phase holdup, and Peclet number were compared with empirical correlations for a comprehensive validation. The results indicate that the predictive CFD–PBM is suitable for the design of extraction columns. Its average deviations on the three parameters are 15.7%, 12.9%, and 15.2%, respectively. The model also successfully predicts the regular variations of the droplet diameter and holdup with the rising agitation rate, which contribute to the validation.

Orthorhombic LiMnO2 (o-LiMnO2), spinel Li1.6Mn1.6O4 precusors, and spinel H1.6Mn1.6O4 ion sieves were synthesized by a combination of controlled redox precipitation and solid-phase reaction. o-LiMnO2 was synthesized by a controlled redox precipitation using Mn(OH)2, LiOH, and (NH4)2S2O8. Spinel Li1.6Mn1.6O4 precursor was prepared by the heat treatment of o-LiMnO2. Further, an ion sieve (H1.6Mn1.6O4) was synthesized by the acid (HCl) treatment of Li1.6Mn1.6O4. The effect of redox precipitation and solid-phase reaction on the structure and ion-exchange property of the ion sieve was examined by powder X-ray diffraction, scanning electron microscopy, and Li+-selective adsorption measurements. The results showed that the ion sieve exhibited highly selective adsorption capacity for Li+ (3.88 mmol·g–1) from Qarhan salt lake brine, which was significant for the Li+ extraction from low-grade brine.

The gas–liquid reactive crystallization process of CO2 gas and LiOH solution was systematically studied by a falling film column to prepare Li2CO3 crystals. Three important parameters concerning the fluid dynamic characteristics of the falling film column were obtained: the Reynolds number, the falling film thickness, and the exposure time. Li2CO3 is the intermediate product during the reactive absorption process, and the final pH of the solution should be controlled within the range of 9.0–9.5 to achieve high product yields. The effects of operating variables on the absorption rate, crystallization rate, and particle size distribution were experimentally explored and theoretically analyzed. Results showed that higher temperatures and LiOH concentrations significantly enhance reactants utilities. A novel method was adopted to quantitatively describe the interaction between absorption and crystallization, and results proved that the crystallization process promotes the transport of CO32– ions from the interfacial liquid film to the bulk solution and, thus, facilitates the overall absorption process. Product characterizations were performed by SEM, XRD, and ICP-MS.

The air core is an important phenomenon in a hydrocyclone. The steady state of the air core plays a key role in the performance and separation efficiency of a hydrocyclone. The unsteady structure of the air core reflects the unsteady flow field and exacerbates this unsteadiness, thus affecting the steadiness and homogeneity of the flow field, which will lead to lower separation efficiency. The effects of the ratio of the vortex-finder diameter to the spigot diameter (Do/Du) on the steady state of the air core were studied by computational fluid dynamics in this paper. In this approach, the Reynolds stress model used to describe the turbulent fluid flow and the volume-of-fluid multiphase model simulated the interface between the liquid and air core. The results show that the steady state of the air core is mainly decided byDo/Du. Different ranges of Do/Du lead to different steady states of the air core. No air core appeared inside the hydrocyclone with a Do/Du of 1.2. The discontinuous ones occur when Do/Du enlarges to 1.6 and 1.8. Through the continuous air core grown in the hydrocyclone with a Do/Du larger than 1.8, the rules of the steady state were different. In addition, the operation conditions of the inlet velocity did not change the trend of the steady state of the air core in a certain hydrocyclone.

A spherical PVC–MnO2 ion sieve of 2.0–3.5 mm diameter was prepared by the antisolvent method using synthesized Li4Mn5O12 ultrafine powder as the precursor, poly(vinyl chloride) as the binder, and N-methyl-2-pyrrolidone as solvent. Batch experiments of the adsorption capacity (isotherm) and adsorption rate of Li+ on the spherical PVC–MnO2 ion sieve were studied. Spherical PVC–MnO2 had a high adsorption capacity for Li+, and the isotherm data were well fitted by the Langmuir model; the adsorption kinetics were well described by the Lagergren equation. Furthermore, a mathematical model was set up to calculate the film mass transfer coefficient (kf) and pore diffusivity (Dp) of the adsorbent. Continuous flow experiments for study of Li+ adsorption breakthrough and the subsequent desorption (elution) in a PVC–MnO2 packed column were carried out employing six feed solutions of various pH values and concentrations of Li+, Na+, K+, and Mg2+ for simulating brine samples of various salt lakes and/or seawaters. After the adsorption treatment to concentrate the Li+ on PVC–MnO2, the column was regenerated by 1.0 mol/L HCl which supplied H+ to accomplish elution of the adsorbed Li+ by ion exchange. The experimental results demonstrate that PVC–MnO2 had high selectivity for Li+ and that its adsorption of Li+ from the feed were little affected by Na+, K+, and Mg2+ also present in the feed solution. Spherical PVC–MnO2 is an attractive medium for large scale lithium extraction from brine or seawater.

The feasibility and efficiency of adsorption technology were evaluated experimentally and theoretically for CO2 capture from the flue gas in an existing coal-fired power plant, where a three-bed VPSA unit was set up to test 282 kg of adsorbent materials. In this work, the experimental results are reported for zeolite 5A as the adsorbent. The composition of the flue gas after dehydration was 15.0 vol % CO2, 76.5 vol % N2, and 8.5 vol % O2. With a three-bed seven-step VPSA process including rinse and pressure equalization steps, 85% CO2 was obtained with recovery of 79% from flue gas at a feed flow rate of 46.0 Nm3/h. The experimentally measured energy consumption was 2.37 MJ/(kg of CO2). The experimental work was compared with numerical simulations through the multibed VPSA modeling framework developed in a previous work. The simulated results were found to agree well with the experimental results.

The reductive decomposition of calcium sulfate (CaSO4) to calcium sulfide (CaS) was one of the most important methods for anhydrite resource utilization. When CaSO4 was decomposed reductively by carbon monoxide (CO), usually there were CaS and/or calcium oxide (CaO) in the decomposition products of CaSO4 depending on the reaction temperature and reactant concentrations. In this paper, the mechanism of CaSO4 reductive decomposition by CO was studied in the framework of density functional theory (DFT). In the calculation, the exchange-correlation term was approximated by Perdew–Wang (PW91), a functional within the generalized gradient approximation (GGA) family. To study the interaction of CO and CaSO4, the transition states of CaSO4 decomposition and the minimum energy path (MEP) were analyzed. The results showed that the CaS product could be obtained when CaSO4 was reduced by CO with the 4:1 stoichiometric ratio of CO and CaSO4, and the decomposition of CaSO4 to CaSO3 was the rate-determining step, and activation energy in this step was 191.19 kJ/mol. With the increase of the reaction temperature, the CaO product could be obtained with a 1:1 stoichiometric ratio of CO and CaSO4, and the activation energy is 318.28 kJ/mol during the process. It was found that the CaS product was formatted at a lower reaction temperature and a higher mole ratio of CO and CaSO4, and the CaO product was preferred at a higher reaction temperature and a lower mole ratio of CO and CaSO4.

Carbon dioxide removal from flue gas with a two-stage vacuum pressure swing adsorption (VPSA) process, which uses activated carbon (AC) beads as the adsorbent, was investigated both theoretically and experimentally. First, single-column VPSA experiments were studied for CO2/N2 separation with high CO2 feed concentration. Then, a two-stage VPSA process composed two columns for each stage was designed, and the effects of different parameters were investigated. The first-stage VPSA unit operates with a four-step Skarstrom cycle, which includes feed pressurization, adsorption, blowdown, and counter-current purge with N2. For the second-stage VPSA process, a cycle with feed pressurization, adsorption, pressure equalization, blowdown and pressure equalization was employed. With the proposed two-stage VPSA process, a CO2 purity of 95.3% was obtained with 74.4% recovery. The total specific power consumption of the two-stage VPSA process is 723.6 kJ/kg-CO2, while the unit productivity is 0.85 mol-CO2/kg·h.

A hydrocyclone, as a common liquid/solid grading instrument, was chosen to separate calcium sulfate particles from crude carnallite during the KCl production process on the Tibetan Plateau in China, because CaSO4 particles are independent of KCl particles and have a smaller particle size distribution. The local altitude on the Tibetan Plateau in China is over 3000 m, so the effects of low atmospheric pressure on the separation performance of the hydrocyclone should be considered. In this article, the computational fluid dynamics (CFD) simulation technique was used to investigate the hydrodynamics and particles separation performance of an industrial hydrocyclone with a 428-mm diameter at both plain and plateau atmospheric pressures. In this CFD approach, the Reynolds stress model (RSM) was used to describe the turbulent fluid flow, the volume of fluid (VOF) multiphase model was used to simulate the interface between the liquid phase and the air core, and the stochastic Lagrangian model was used to track the particle flow. The mathematical models deveoped for the industrial hydrocyclone were tested by comparing the predicted results with the flow fields measured by Hsieh (Ph.D. Thesis, The University of Utah, Salt Lake City, UT, 1988). According to the simulation results, the environmental atmospheric pressures on the plain and plateau had effects mainly on the flow field inside the air core and near the interface between the air core and the liquid phase. It was found the direction of the axial velocity on the cylinder part and the values of the tangential velocity changed under the different environmental atmospheric pressures. When the industrial hydrocyclone was operated in the plateau environment, the separation efficiency for small particles decreased about 10% at the overflow, which was not good for CaSO4 removal, but there was no effect on the particles size larger than 350 μm, and more energy was consumed, although the difference in the split ratio was small.

In this study, on the basis of simulation of the electric field, the design optimization methods for 120 and 250 kA magnesium electrolysis cells were developed. A 3D numerical model was built to simulate the electric field at the steady state to obtain the minimum resistance voltage which has a significant effect on the energy consumption in the magnesium electrolysis process. The major optimization was focused on adjustment of structural parameters, such as the relative positions of the anode and cathode, electrolyte height in the cell, and so on. An orthogonal design approach was used to optimize the structural parameters in a 120 kA cell, and the optimization criterion was applied to magnify the design of a 250 kA cell. The resistance voltage in the optimized 250 kA cell was computed, and the minimum resistance voltage was 1631.3 mV among the provided solutions. Hence, the developed model and simulation results would be useful for the design optimization of a magnesium electrolysis cell.

During the industrial magnesium production, the thermal balance in a magnesium electrolysis cell is the key factor for regular operations. If the thermal balance is broken, the efficiency of the regular production declines seriously because of too high or too low of a temperature in the magnesium cell. The thermal balance in the magnesium cell is determined directly by the thermal field, which is based on the electric field energy. The thermoelectric field in the magnesium cell must be studied by coupling for the high correlation between the two fields. A three-dimensional half of a full cell model was developed through the finite element analysis software to coupling study the thermoelectric field in a 120 kA magnesium electrolysis cell. Through numerical calculation, the distribution of the voltage and temperature were obtained. Moreover, the total heat generation and dissipation in the cell are influenced by the changes of the current intensity because the electric field is the source of the thermal field. When the current intensity changed, the thermal balance may be broken. To investigate the effects on the fluctuation of the current intensity that occurred in the practical production, the thermal balance in the magnesium cell was studied by changing the current intensity from 115 to 125 kA. With the changes of the current intensity, the corresponding electrolyte depth must be carried out to maintain the thermal balance. From the simulation results, the electrolyte depth has a linear relation with the current intensity on the basis of the thermal balance in the cell and the method is an efficient way to maintain the thermal balance in the cell.

Vacuum pressure swing adsorption (VPSA) for CO2 capture has attracted much research effort with the development of the novel CO2 adsorbent materials. In this work, a new adsorbent, that is, pitch-based activated carbon bead (AC bead), was used to capture CO2 by VPSA process from flue gas. Adsorption equilibrium and kinetics data had been reported in a previous work. Fixed-bed breakthrough experiments were carried out in order to evaluate the effect of feed flowrate, composition as well as the operating pressure and temperature in the adsorption process. A four-step Skarstrom-type cycle, including co-current pressurization with feed stream, feed, counter-current blowdown, and counter-current purge with N2 was employed for CO2 capture to evaluate the performance of AC beads for CO2 capture with the feed compositions from 15–50% CO2 balanced with N2. Various operating conditions such as total feed flowrate, feed composition, feed pressure, temperature and vacuum pressure were studied experimentally. The simulation of the VPSA unit taking into account mass balance, Ergun relation for pressure drop and energy balance was performed in the gPROMS using a bi-LDF approximation for mass transfer and Virial equation for equilibrium. The simulation and experimental results were in good agreement. Furthermore, two-stage VPSA process was adopted and high CO2 purity and recovery were obtained for post-combustion CO2 capture using AC beads.

A computational fluid dynamics (CFD) model was developed for the simulation and optimization of an existing continuous DTB crystallizer with KCl productivity of 0.1 million tons per year. The multiple reference frame (MRF) method was used in the CFD simulation. Both the hexagonal grid and the tetrahedral grid were adopted to divide meshes in this industrial DTB crystallizer, and in total 866 388 cells were used for CFD simulation. The fluid flow field in the DTB crystallizer was calculated using FLUENT6.3 software with the Reynolds-averaged Navier−Stokes equation combined with the widely used κ−ε turbulence model. The crystal size distribution and the coefficient of variation of crystal product were studied by CFD simulation of two-phase flow model. The impeller shapes and various operating conditions were optimized to reduce the energy consumption of the crystallization process and to increase the KCl product quality. Based on the CFD optimization design, a new impeller was retrofitted into an existing continuous DTB crystallizer with the KCl productivity of 0.1 million tons per year located at Qinghai salt lake plant in China, and its excellent performance was confirmed against data collected using the original impeller.

The multiphase transport phenomena frequently take place in metallurgical processes, for example, in the electrolysis process of magnesium, where there exists three-phase flow including liquid magnesium, molten electrolyte, and chlorine gas under the electromagnetic field. In this paper, the three-phase flow behaviors under the electromagnetic field in the advanced diaphragmless electrolytic cell were investigated by CFD simulation. The governing equations of the internal flow field in the electrolytic cell were established, where the standard k−e turbulence model and the VOF multiphase flow model were adopted for the comprehensive description of the flow characteristics of multiphase flow in the electrolytic cell, and the Lorentz force was added to the momentum equation of fluids as the momentum source term to combine the effect of electromagnetic field with the flow field. The order coupling method was adopted for the calculation of the coupled field. The numerical simulation on the three-phase flow field considering the effect of electromagnetic field was done using FLUENT6.3 software, the numerical simulations on the electric field and the magnetic field were carried out using Ansys 11.0 software, respectively, and the connection between the finite element software ANSYS and the control volume software Fluent was built using the user-defined function (UDF). According to the analysis on the distributions of the electromagnetic field and the flow field, the optimum flow circulation in the advanced diaphragmless electrolytic cell was obtained, which is very helpful for the design in the electrolysis process of molten magnesium salt.

A set of laser apparatus was used to explore the induction period and the primary nucleation of lithium carbonate. Results show that the induction period increases with the decrease of supersaturation, temperature and stirring speed. Through the classical theory of primary nucleation, many important properties involved in primary nucleation under different conditions were obtained quantitatively, including the interfacial tension between solid and liquid, contact angle, critical nucleus size, critical nuleation free energy etc.

Owing to the high ratio of Mg2+ to Li+ in most of the salt lake brines in China, it is difficult to extract lithium. Therefore, the separation efficiency of a nanofiltration membrane was investigated in this study. Operating conditions such as operating pressure, inflow water temperature, pH, and Mg2+/Li+ ratio were investigated. Relationship between the rejection rates of magnesium and lithium was established. Moreover, the extractions of lithium from salt lake brines were also evaluated. The results indicate that the separation of magnesium and lithium was highly dependent on the Mg2+/Li+ ratio, operating pressure, and pH. When the Mg2+/Li+ ratio was <20, the competitive coefficient was sensitive to the Mg2+/Li+ ratio. The permeate flux of membrane for the East Taijiner brine was higher than that for the West Taijiner brine.

•Ultrasonic cleaning was used to separate cathode materials and Al foil.•The peel-off efficiency of cathode materials achieved nearly 99%.•Not only all cathode materials were recycled, but Al was recycled in metallic form.•A simple and efficient process for recycling of spent LIBs was proposed.Cathode materials are difficult to separate from Al-foil substrates during the recycling of spent lithium-ion batteries (LIBs), because of the strong bonding force present. In this study, ultrasonic cleaning was used to separate and recycle these cathode materials. The mechanism of separation was ascribed to the dissolution of polyvinylidene fluoride (PVDF) and the cavitation caused by ultrasound. Based on this mechanism, the key parameters affecting the peel-off efficiency of cathode materials from Al foil was identified as solvent nature, temperature, ultrasonic power, and ultrasonic time. The peel-off efficiency of cathode materials achieved ∼99% under the optimized conditions of N-methyl-2-pyrrolidone (NMP) cleaning fluid, 70 °C process temperature, 240 W ultrasonic power, and 90 min of ultrasonication. The cathode materials separated from Al foil displayed a low agglomeration degree, which is beneficial to the subsequent leaching process. Finally, a new, environmentally-sound process was proposed to efficiently recycle cathode materials and Al from spent LIBs, consisting of manual dismantling, ultrasonic cleaning, and picking.Download high-res image (198KB)Download full-size image

•A parallel synthesis platform was used to determine the solubility.•SDBS can inhibit crystal nucleation and promote growth.•Mechanisms of SDBS were explored from view of kinetics and surface tension.This study investigated the cooling crystallization of aluminum sulfate to explore the basic data for the recovery of aluminum resources from coal spoil. First, the metastable zone width (MSZW) of aluminum sulfate was reported. A parallel synthesis platform (CrystalSCAN) was used to determine the solubility from 10 °C to 70 °C, and an automatic lab reactor (LabMax) equipped with focused beam reflectance measurement (FBRM) was adopted to determine the supersolubility. The effects of operating variables on MSZW were experimentally explored. Results show that the MSZW of aluminum sulfate decreases with increasing stirring speed, while it increases with increasing cooling rate.Second, the continuous crystallization kinetics of aluminum sulfate was investigated in a laboratory-scale mixed-suspension mixed-product removal (MSMPR) crystallizer at a steady state. Growth kinetics presented size-dependent growth rate, which was well fitted with the MJ3 model. Both the growth rate (G) and the total nucleation rate (BTOT) were correlated in the power law kinetic expressions with good correlation coefficients.Third, aluminum sulfate products were modified by sodium dodecylbenzenesulfonate (SDBS). Crystals with large sizes and regular hexagonal plate morphologies were obtained. These crystals reveal that SDBS can inhibit crystal nucleation and promote crystal growth.

The cubic phase LiMn2O4 spinel is synthesized via a directly soft chemistry method via hydrothermal reaction of Mn(NO3)2, LiOH and H2O2 at 383 K for 5–10 h, more favorable to control the nanocrystalline structure with well-defined pore-size distribution and high surface area than traditional solid-phase reaction at high temperature. Further, the 1D MnO2 nanorod ion-sieves with lithium ion selective adsorption property is prepared by the acid treatment process to completely extract lithium ions from the LiMn2O4 lattice. The effects of hydrothermal conditions on the nanostructure, chemical stability and ion-exchange property of the LiMn2O4 spinel and MnO2 ion-sieve are examined via powder X-ray diffraction (XRD), N2 adsorption–desorption at 77 K, high-resolution transmission electron microscopy (HRTEM), selected-area electron diffraction (SAED) and lithium ion selective adsorption measurements. The results show that the 1D MnO2 nanorods might be utilized in lithium extraction from aqueous environment including brine, seawater and waste water.

Mesoporous titania nanoribbons were synthesized via an optimized soft hydrothermal process and the derived titania ion-sieves with lithium selective adsorption property were accordingly prepared via a simple solid-phase reaction between Li2CO3 and TiO2 nanomaterials followed by the acid treatment process to extract lithium from the Li2TiO3 ternary oxide precursors. First, mesoporous titania nanoribbons were prepared and the formation mechanism was discussed; second, the physical chemistry structure and texture were characterized by powder X-ray diffraction (XRD), (high-resolution) transmission electron microscopy (TEM/HRTEM), selected-area electron diffraction (SAED) and N2 adsorption–desorption analysis (BET); third, the lithium selective adsorption properties were tested by the adsorption isotherm, adsorption kinetics measurement and demonstrated with the distribution coefficient of a series of alkaline and alkaline–earth metal ions.

•Electrodialysis (ED) was used to treat a saline water with a high Mg/Li ratio.•The main objective of this study was to significantly reduce the Mg/Li ratio.•The Mg/Li ratio can be decreased as high as 21.8 times via ED, and the Li+ recovery can reach over 90%.•ED was proven to be technically and economically feasible to separate lithium from salt lake brine with high Mg/Li ratio.•The selective separation mechanism of ED was qualitatively discussed.Salt lake brine is an abundant lithium resource and has great developing value and potentiality. But the Mg/Li ratio of some salt lakes in China and Dead Sea in Jordan is extremely high. In this study, electrodialysis (ED) with monovalent selective ion-exchange membranes was used to investigate the separation performance of Li+/Mg2 + from synthetic multinary mixture. The effects of operating conditions on the lithium recovery, permselectivity, and Mg/Li ratio of the product were evaluated. The results indicate that ED with monovalent selective ion-exchange membranes has a significant separation effect on Li+/Mg2 +. When the optimized parameters were used in ED, the Mg/Li mass ratio of the product stream was reduced to 8.0 (18.8 times compared to a feed Mg/Li ratio of 150), and simultaneously, the Li+ recovery reached to 95.3%. Compared to nanofiltration, ED exhibited superiority both technically and economically for the fractionation of Li+/Mg2 +. It was also verified that the presence of co-existing cations would not be detrimental to the feasibility of lithium extraction using ED. Meanwhile, the separation mechanism of ED process was discussed qualitatively.