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Salt lakes with large reserves of mineral resources are widely distributed in China. In addition to aboundant inorganic substances, there also exist a mass of organic compounds in the brine. It is realized these organic compounds can produce serious negative effects on the process equipment and products quality. In this work, the decolorization and COD removal of the brine by ozonation were investigated in a bubble column reactor. The effects of contact time, ozone-air flow rate, pH and temperature on the decolorization and COD removal were investigated. It was found that the decolorization and COD removal rates increased with increasing ozone-air flow rate and contact time, while increased first and then decreased with increasing temperature and pH. Under the optimal conditions, color removal reached 47.3% and COD was reduced by 42.2%. Thus, ozonation can be used as the pretreatment method for decolorization and COD removal of the brine.

Bi2WO6-WO3heterojunctions were first prepared using hydrothermal method with the assistance of cetyltrimethylammonium bromide (CTAB). And Bi2WO6-WO3was further fabricated by depositing Pt on the surface using the photo-assisted deposition method. These catalysts were characterized by XRD, SEM, FTIR, BET and DRS. It is found that Pt-Bi2WO6-WO3acting as a novel visible light-driven photocatalyst exhibited excellent photocatalytic activity in degradation of Methyl Orange (MO) under visible light irradiation. The highest photocatalytic activity of Pt-Bi2WO6-WO3photocatalyst is attributed to the synergistic effect of Pt surface plasmon resonance and Bi2WO6-WO3heterojunction structure.

Pure and F, Fe-codoped TiO2 were prepared by sol-hydrothermal process, in which titanium (IV) n-butoxide, Fe (NO3)2·6H2O and NH4F were used as precursors. And the samples were characterized by X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), and N2 adsorption-desorption method. The results showed that the F, Fe-codoped samples were principally single-phase anatase structures, and the particles possessed higher BET area than that of pure TiO2. The photocatalytic activity and reusability of the catalysts under UV light (365nm) was investigated with neutral red as the model compound. The results showed that F (2.0%), Fe (4.0%) codoped TiO2 had the highest photocatalytic activity among all as-prepared samples. The kinetic study showed that this photocatalytic process coincided with the Langmuir-Hinshelwood (L-H) pseudo first order reaction model.

Carboxymethyl cellulose (CMC)-supported layered double hydroxides (CMC-LDHs) were synthesized by ion exchange method. The raw cellulose, unsupported LDH and CMC-LDHs were characterized by XRD, and FTIR. The CMC-LDHs was applied to adsorb boron with batch adsorption in aqueous solution, and the conditions influencing its adsorption amount were investigated. The experimental results showed that the CMC-LDHs had higher adsorption amount than the precursor, and the adsorption amount increased with increasing the contact time, boron concentration, and the pH.

Investigations were conducted to purify crude Li2CO3 via direct carbonation with CO2-water solutions at atmospheric pressure. The experiments were carried out in a slurry bubble column reactor with 0.05 m inner diameter and 1.0 m height. Parameters that may affect the dissolution of Li2CO3 in the CO2-water solutions such as CO2-bubble perforation diameter, CO2 partial pressure, CO2 gas flow rate, Li2CO3 particle size, solid concentration in the slurry, reaction temperature, slurry height in the column and so on were investigated. It was found that the increases of CO2 partial pressure, and CO2 flow rate were favorable to the dissolution of Li2CO3, which had the opposite effects with Li2CO3 particle size, solid concentration, slurry height in the column and temperature. On the other hand, in order to get insight into the mechanism of the refining process, reaction kinetics was studied. The results showed that the kinetics of the carbonation process can be properly represented by 1−3(1−X)2/3+2(1–X)=kt+b, and the rate-determining step of this process under the conditions studied was product layer diffusion. Finally, the apparent activation energy of the carbonation reaction was obtained by calculation. This study will provide theoretical basis for the reactor design and the optimization of the process operation.

Gluconate-intercalated hydrotalcites were prepared from precursor by ion-exchange method. The products were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and energy dispersive spectroscopy (EDS) studies. This kind of new adsorbent was applied to adsorb boron in the refined brine, and the conditions influencing its adsorption amount were investigated. The experimental results showed that the adsorbent synthesized in this article had higher adsorption amount of boron than the precursor without gluconate intercalation, and the adsorption amount increased with increasing the contact time, boron concentration, and the pH whereas decreased with increasing chloride concentration and temperature. The adsorbent can be well regenerated by calcination and reintercalation of the gluconate into the calcinated product. Furthermore, the kinetic studies were also investigated. The pseudo-first-order, pseudo-second-order, and intraparticle diffusion models were used to fit the experimental data, and the results showed that the pseudo-first-order model best described the boron adsorption process. © 2010 American Institute of Chemical Engineers Environ Prog, 2010

The crystallization kinetics of Li 2 CO 3 from LiHCO 3 solutions was studied by a non-evaporation volume-constant batch reactor. The factors influencing the crystallization process such as initial concentration, temperature and stirring speed were investigated and discussed. In the experiment, CO 2 was stripped from a slightly acidic solution of LiHCO 3 by stirring resulting in critical supersaturation and precipitation of Li 2 CO 3 . The reduction of the Li + concentration was recorded as a function of time by determination with flame atomic absorption spectrometry (FAAS), and the pH values were also measured. The results showed that the crystallization rate increased and the induction period shortened with increase in the initial concentration and temperature. In addition, high stirring speed could significantly promote this process. Thermodynamic parameters at critical conditions such as the surface free energy and critical radius of nucleus were estimated based on the crystallization theory and experimental results. The results showed that the crystallization kinetics of this process coincided with the second-order reaction rate equation, and the apparent activation energy of the process was obtained. The analysis of the crystal growth mechanism showed that the growth of Li 2 CO 3 from LiHCO 3 solutions was mainly controlled by diffusion.

This paper describes the results from an experimental study of the purification of LiHCO3 solution which is used to produce high-purity Li2CO3 by ion exchange. Generally, there are some amounts of Ca2+ and Mg2+ in the LiHCO3 solution whose contents exceed the requirements to produce qualified high-purity Li2CO3, so they need to be removed from the solution. There are many methods available to remove divalent metal ions from solutions, among which the ion exchange is the most simple and efficient one. Investigations of the performance of the chelating resin Amberlite IRC747 for its adsorption for Ca2+ and Mg2+ in LiHCO3 solutions were conducted. Batch studies showed that the SDM-A model could describe the adsorption isotherm data well, and the Kannan particle diffusion model could describe the exchange kinetics properly. The study for column operation showed that breakthrough points of Ca2+ and Mg2+ both advanced with increasing the feed flow rate, and the penetration function model could describe the effluent curves adequately. HCl and LiOH of 1 mol·L− 1 respectively were used to regenerate resins with good effect. This study will provide the basic reference for process operation and the reactor design to purify the LiHCO3 solution by ion exchange.

Boron removal by ion exchange resin from refined brine which was used to produce low-boron lithium salts was studied. A new boron-specific resin, XSC-800 was used in the experiments for the separation of boron. The column-mode and batch-mode sorption studies were both performed so as to obtain the optimum conditions for boron removal from refined brine. Parameters such as flow rate of brine, boron concentration, temperature, pH, height/diameter (H/D) ratio of the column, anion concentration, stirring speed and diameter of the resin were investigated. The results showed that the removal effect of boron by XSC-800 improved with increasing temperature, pH, H/D ratio, and with decreasing the flow rate of brine, boron concentration, chloride anion concentration and diameter of the resin. While the stirring speed and the recycles of the resin had no significant effects on boron removal. As a result, boron can be removed from refined brine much completely by the resin at the optimum conditions. On the other hand, kinetics of the exchange process was studied by using the moving boundary model. In order to describe the kinetics more accurately, the model was modified by introducing a time correction factor. The results showed that the rate-determining step of this process under the conditions studied was controlled by particle diffusion. In addition, the apparent activation energy Ea of the process was found to be 20.38 kJ/mol.

Refining of crude Li2CO3 produced from salt lake brines of Qinghai, China, by direct carbonation with CO2-water solutions under different conditions was studied. The process is based on the reaction of Li2CO3 with CO2-water solutions to convert the former to the more soluble lithium bicarbonate. The carbonation experiments were carried out in a three-phase mechanically agitated slurry-bed reactor. The parameters that may affect the dissolution of Li2CO3 in CO2-water solution such as CO2 pressure, temperature, CO2 flow rate, solid concentration, particle size of Li2CO3, slurry filling degree, agitator shape and agitation speed were investigated. The effects of immersion time of Li2CO3 in the slurry before carbonation as well as multiple carbonation cycles were also examined. Refining of crude Li2CO3 produced from salt lake brines of Qinghai, China, by direct carbonation with CO2-water solutions under different conditions was studied. The process is based on the reaction of Li2CO3 with CO2-water solutions to convert the former to the more soluble lithium bicarbonate. The carbonation experiments were carried out in a three-phase mechanically agitated slurry-bed reactor. The parameters that may affect the dissolution of Li2CO3 in CO2-water solution such as CO2 pressure, temperature, CO2 flow rate, solid concentration, particle size of Li2CO3, slurry filling degree, agitator shape and agitation speed were investigated. The effects of immersion time of Li2CO3 in the slurry before carbonation as well as multiple carbonation cycles were also examined.