Papers by Author: Jun Sheng Yuan

Abstract: Polysulfone (PS) hollow fiber microporous membrane was used as substrate, the micropores of which were filled with surface-modified zeolites suspension on the outer surface by vacuum method, and then zeolite-filled poly(piperazine-amide)/PS hollow fiber composite membrane was synthesized on the substrate by interfacial polymerization reaction with piperazine (PIP) aqueous solution and trimesoyl chloride (TMC) n-hexane solution. The substrate membrane and synthetic composite membrane were characterized by scanning electron microscopy (SEM). A thin poly(piperazine-amide) active skin layer was synthesized on the substrate and the surface-modified zeolite particles were successfully embedded in the surface micropores of the substrate. The separation factors of the sample to K⁺ are 4.25, 60.46 and 93.61 in the mixed K⁺-Na⁺, K⁺-Ca²⁺ and K⁺-Mg²⁺ solutions respectively, which indicates that the sample has preference selectivity to K⁺ and can be used as a potential ion-exchange membrane for potassium continuous extraction from seawater.

Abstract: Based on preparing high purity powdered lithium ion-sieve precursor LiMn2O4, using lithium carbonate and manganese carbonate as raw materials, through roasting at high temperature of 800°C, laminar lithium ion-sieve precursor was prepared by commixing poly (vinyl chloride) (PVC) and powdered precursor in DMF (N, N-dimethylformamide) as solvent, and then powder and lithium ion-sieve flat sheet membrane was obtained through washing with HCl solution respectively. Their adsorption capacity and morphology was also characterized. The results show that both powdered lithium ion-sieve and laminar one have high adsorption capacity and selectivity for Li in solutions, and the effect of their retest is good. All these can provide a good foundation for the further study on lithium ion-sieve flat sheet membrane and lithium extraction from seawater.

Abstract: Solid solutions with different compositions, mNH₄Cl·KCl and NH₄Cl·nKCl (m，n≥1), were prepared by the constant speed cooling method. The thermal stability of the solid solutions was determined by TG-DTA. The results show that mNH₄Cl·KCl crystals change its crystal form at 180°C, decompose into ammonia and hydrogen chloride gas at 330°C, melt at 790°C, and finally evaporate at around 820°C. Its evaporation temperature increases with the increasing of potassium chloride content in the samples. The Solid solution of NH₄Cl·nKCl decomposes to ammonia and hydrogen chloride gas at 230°C, melts at 790°C, and evaporates at 800°C. The continuous specific heat curve of the solid solution (NH₄, K)Cl were also determined. These data provide a theoretical basis for further research on solid solution properties.

Abstract: The diffusion trajectory of NH₄⁺, the configuration of NH₄⁺ and water molecular in hydrated clinoptilolite and K⁺-NH₄⁺ ion exchange process in the channel of clinoptilolite were simulated using the Materials Studio 4.3 software package’s CASTEP module. The results show that among these four hydrogen atoms in NH₄⁺, only one is involved in the effective hydrogen bond with the oxygen atom in the framework. It was also proved that changing the distribution of the Al-site has no influence on the distribution of the extra-framework of NH₄⁺. The interaction between particles in the channel and the zeolite framework causes the K⁺-NH₄⁺ ion-exchange process to take place, which means that clinoptilolite possesses better selectivity to K⁺ than to NH₄⁺. The structure parameters of the final product agree well with the reference, which indicate the formation of K-clinoptilolite.

Abstract: Potassium ionic sieve membrane was synthesized on porous α-Al2O3 tube support by the hydrothermal synthesis. The zeolite membranes were characterized by means of XRD and SEM. And the single-gas permeability through the membranes and selectivity to K+, Na+, Ca2+, Mg2+ were measured. The results show that the ideal separation factor is 3.68, which is close to Knudsen diffusion ratio 3.74 for H2/N2; the separation factors of the potassium ionic sieve membrane are , , respectively, indicating its high separation selectivity to potassium ion.

Abstract: Natural clinoptilolite collected from Chicheng of Hebei province in China, was treated with physical modification using sodium/ammonium salts, chemical modification using NaOH or NaAlO₂, and physicochemical modification using NaOH or NaAlO₂ and NaCl in order, respectively. And its adsorption capacity of NH₄⁺ in different conditions was investigated. The results show that modified clinoptilolite has the same crystal structure, and the clinoptilolite modified with NaOH or NaAlO₂ has good uptake of ammonia ion; the concentration of NaAlO₂ has apparent influence on the removal of ammonia nitrogen, and the perfect concentration is 0.1 mol/L and the uptake could reach 0.92 mmol/g in the 100 mg/L NH₄⁺ solution; the existence of K⁺、Na⁺、Ca²⁺、Mg²⁺ decreases the uptake of ammonia ion on clinoptilolite modified with 0.1 mol/L NaAlO₂.

Abstract: To meet increasing demand for lithium, it is very essential for exploiting the lithium resources dissolved in seawater, groundwater and brine. It’s prospected that extracting lithium from solution with lithium ion-sieve, that is, spinel lithium magnesium oxides. Preparing high effective lithium ion-sieve is the heart of the technology. Magnesium oxide (MnOOH), the precursor (Li1.6Mn1.6O4) and the lithium ion-sieve were prepared successively, and their structure and properties were characterized with AAS, XRD and SEM. The results show that fibrous MnOOH is synthesized via hydrothermal reaction of KMnO4 and ethanol at 120°C for 24 h, and brown Li1.6Mn1.6O4 with little impurity is prepared with the Li/Mn mole ratio 4 after hydrothermal reaction of MnOOH and 4 mol/L LiOH at 120°C for 24 h and roast 4 h at 400°C, then lithium ion-sieve is obtained after washing 24 h with 0.5 mol/L HCl solutions and its adsorption capacity for Li+ reaches 38.26 mg/g, which has considerable potentiality comparing to its theory value. All these suggested that synthesis of single phase Li1.6Mn1.6O4 should be essential for next study on extraction lithium with lithium ion-sieve from seawater, groundwater and brine.