Chi Won Hwang

Synthesis of polyketone-g-vinylbenzyl chloride anion exchange membrane via irradiation and its properties

AbstractA novel anion exchange membrane composed of aminated polyketone-g-vinylbenzyl chloride was synthesized via60Co γ-ray irradiation grafting technique. Total irradiation dose and concentration of monomers were set as variables to determine degree of grafting. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy equipped with energy dispersive X-ray spectrometer (SEM-EDS) were used to characterize the grafted membranes. Water uptake (WU) and swelling ratio (SR) were measured with a gravimetric method. A titration method was used to detect ion exchange capacity (IEC), whereas electrical resistance (ER) and ion conductivity (IC) were measured with a LCR meter. Our method has boosted the degree of grafting up to 97.6% from 3.7% as total irradiation dose and monomer concentration have been increased. WU and SR were in the ranges 1.5%-35.6% and 0.35%-20.9%, respectively. Also, IEC has taken values ranging between 0.2 and 1.19 meq/g. IC has varied within the range 0.01-0.3 S cm-1, and it has shown a rising trend as IEC increased. In this study, the optimum synthesis conditions have been 70 kGy of total irradiation dose and 50wt% of monomers. The membrane synthesized here is potentially superior to Nafion membrane in terms of several properties.

Synthesis and properties of sodium vinylbenzene sulfonate-grafted poly(vinylidene fluoride) cation exchange membranes for membrane capacitive deionization process

In this study, a poly(vinylidene fluoride)-graft-sodium 4-vinylbenzene sulfonate copolymer (PVDF-g-PSVBS) was prepared by grafting sodium 4-vinylbenzene sulfonate (SVBS) onto dehydrofluorinated poly(vinylidene fluoride) (PVDF). The PVDF-g-PSVBS cation exchange membranes were prepared using a casting method. The structure of the membranes was investigated with Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. Morphology using scanning electron microscope with energy-dispersive X-ray analysis (SEM-EDS) demonstrated as increasing the degree of grafting, the sulfur element is uniformly distributed and increased. The effects annealing temperature on the properties of the PVDF-g-PSVBS membranes were investigated. To prepare the consistent and homogeneous membranes, it was suggested that the annealing temperature of PVDF-g-PSVBS membranes is below 60 °C. The salt removal efficiency for application to the membrane capacitive deionization (MCDI) process was conducted.

Synthesis of polyketone-g-sodium styrene sulfonate cation exchange membrane via irradiation and its desalination properties

AbstractUsing the radiation grafting technique, polyketone membranes were graft copolymerized with sodium styrene sulfonate (SSS) in the presence of additives such as Mohr’s salt and H2SO4. Fourier-transform infrared (FT-IR) spectroscopy was used to characterize the grafted membranes. Water uptake (WU), ion exchange capacity (IEC) and electrical resistance (ER) of the prepared membranes were measured in order to evaluate their physical properties The prepared membranes were applied to the membrane capacitive deionization (MCDI) process, in which their salt removal rates were evaluated and compared to those of CDI (capacitive deionization) process. The degree of grafting rose from 14.4% to 81.4% as the irradiation dose and the monomer concentration were increased. The water uptake ranged from 7.9% to 34.2%. The ionexchange capacity was observed between 0.43 meq/g and 1.1 meq/g, and the electrical resistance had values ranging from 12.2 Ω·cm2 to 2.1 Ω·cm2. The electrical resistance decreased as the ion-exchange capacity was extended. When the prepared cation exchange membrane was used in the MCDI process, the salt removal rate reached 87.6%, which was much higher than 28.8% of CDI process.

Synthesis of lithium ion selective porous phenolic microsphere adsorbents with lithium manganese oxide (LMO) by template and their lithium ion adsorption properties

This study involves the synthesis of a phenolic porous LMO (lithium manganese oxide) adsorbent by the polycondensation method and the preparation of porous LMO microsphere adsorbent with a spinel structure by the carbonization method. The structure of the porous LMO precursor was confirmed, and the crystalline structure, compressive strength, BET surface area, morphology, and acid resistance of the porous adsorbent were analyzed by XRD, UTM, BET surface area, and SEM. The crystalline structure of the adsorbent was spinel, and the carbonized surface had a wrinkled structure. The specific surface was 97.9–120.0 m2/g, and the compressive strength decreased to 2.4–9.7 MPa as the LMO content increased. In addition, the adsorbent was stable against acid due to its cross-linked structure. In pure solution, the breakthrough of lithium was at over 8 hours, which was more rapid than that of the onewith LMO powder adsorbent. Moreover, the selective breakthrough of lithium from artificial seawater occurred after 6 hours, selectivity was very high at greater than 90%, and the desorption rate was faster than that of the LMO for the LMO powder adsorbent. As a result, the selective adsorption of lithium from seawater had a high economic efficiency.