Cheng-Chien Wang

Study on metal ion adsorption of bifunctional chelating/ion-exchange resins

Ion-exchange resin has been considered as a suitable material for the recovery of heavy metals in water treatment. The chelating group, iminodiacetic acid (-R-N(CH 2 COOH) 2 ), was introduced into the weak-acid type (-R-(COOH) - ) -n ) ion-exchange resin to obtain bifunctional ion-exchange resins. Chromic, cupric, cadmium and lead ions were employed for adsorption experiments in this study. In isothermal experiments, the order of heavy metal ion adsorption decreased with increasing diameter of the heavy metal ion when the chelating group content was less than half. On the contrary, the adsorbed amount of lead ion would be higher than that of cadmic ion as the quantity of chelating group content was more than half owing to the stability constant difference (K s [ Pb2+ ] = 10 17.5 > K s[Cd2+] = 10 5.71 in iminodiacetic acid). The adsorption efficiency of bifunctional ion-exchange resins, especially for lead ions, would increase with rising chelating group content (from 0.08 mmol/mmol COOH to 0.31 mmol/mmol COOH). Meanwhile, the working pH range for metal ion adsorption in bifunctional ion-exchange resings was extended from 2.5 down to 0.5. Addition of chelating groups to weak acid ion-exchange resins could increase the adsorption efficiency for metal ions owing to the increased free volume of polymer structure.

Bipolar membrane prepared by grafting and plasma polymerization

Abstract Ce4+-initiated and plasma-induced grafting polymerization was used to prepare bipolar membranes. The former method used the membrane of copoly(2-hydroxylethylene-methacrylate (2-HEMA)/n-butylacrylate (BA)/glycidyl-methacrylate (GMA)) on the surfaces of which were grafted acrylic acid (AA: COO−) and 4-vinyl pyridine (4VP: NH+Cl−), to prepare the bipolar membrane. The latter method utilized the porous PVDF membrane as a substrate, onto one side of which AA (or sodium vinyl sulfonate, SVS) monomer was grafted, and onto the other of which, 4-vinyl pyridine (or N′,N-dimethyl amino ethyl acrylate, DMAEA) monomer was grafted. The contact angle of bipolar membranes dramatically decreased when the ionic polymer covered the surface of the membranes by plasma-grafting polymerization. Meanwhile, the swelling level of bipolar membranes was in the range of 25–50%. Furthermore, the cross-section SEM photographs of bipolar membranes further illustrated a sandwich structure that consisted of anionic polymer, cationic polymer and PVDF substrate. The limiting current increased with the diffusion coefficient and the concentration of electrolysis; however, the critical voltage was independent of the concentration and the kind of electrolysis. The 963 of AA–PVDF–DMAEA bipolar membrane exhibited the best ratio of dissociation rate constants (kd/kd0) of all membranes. Results concerning the efficiency of the current showed plasma-induced preparation of a bipolar membrane is better than Ce4+-initiated preparation.

The effect of different lithium salts on conductivity of comb-like polymer electrolyte with chelating functional group

The behaviors of lithium ions in a comb-like polymer electrolyte with chelating functional group complexed with LiCF3SO3, LiBr and LiClO4 were characterized by differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR) spectroscopy, AC impedance, and 13C solid-state NMR measurement. The comb-like copolymer was synthesized from poly(ethylene glycol) methyl ether methacrylate (PEGMEM) and (2-methylacrylic acid 3-(bis-carboxymethylamino)-2-hydroxy-propyl ester) (GMA-IDA). FT-IR spectra reveal the interactions of Li+ ions with both the ether oxygen of the PEGMEM and the nitrogen atom of the GMA-IDA segments. FT-IR spectra also indicate an increasing anion–cation association consistent with increasing LiCF3SO3 concentrations. Moreover, the 13C solid-state NMR spectra for the carbons attached to the ether oxygen atoms exhibited significant line broadening and a slight upfield chemical shift when the dopant was added to the polymer. These findings indicate coordination between the Li cation and the ether oxygens in the PEG segment. Tg and Td of copolymers doped with salts clearly increase, as shown by DSC and TGA measurements. These results indicate the interactions of Li+ with both PEGMEM and GMA-IDA segments form transient cross-links inside the copolymers. The Vogel–Tamman–Fulcher (VTF)-like behavior of conductivity implies the coupling of the charge carriers with the segmental motion of the polymer chain in this study. The maximum conductivity of copolymers relates to the composition of the copolymers and the concentration of doping lithium ions. In summary, the GMA-IDA unit in the copolymer promotes the dissociation of the lithium salt, the mechanical strength and the conductivity of the polyelectrolyte.

Modification of multi-walled carbon nanotubes by plasma treatment and further use as templates for growth of CdS nanocrystals

In this study, we present a novel method for preparing multi-walled carbon nanotubes (MWCNTs) grafted with a poly(2-methacrylic acid 3-(bis-carboxymethylamino)-2-hydroxy-propyl ester) (GMA-IDA)-cadmium sulfide complex (CNTs-G-ICdS complex) through plasma-induced grafting polymerization. The characteristics of the MWCNTs after being grafted with the GMA-IDA polymer were monitored by a Fourier transform infrared (FT-IR) spectroscope. Scanning electronic microscopy (SEM) shows that the amount of GMA-IDA grafted onto the MWCNTs increases with the concentration of GMA-IDA monomer. The complex resulting from GMA-IDA polymer grafting onto the MWCNTs, CNTs-G-I (15%), shows excellent dispersion properties in aqueous solution and has high Zeta potential values over a wide range of pH values, from 2 to 12. Moreover, Raman spectroscopy was used to confirm the successful chemical modification of MWCNTs through the plasma treatment. The chelating groups, -N(CH(2)COO(-))(2) in the GMA-IDA polymer grafted on the surface of the CNTs-G-I, are the coordination sites for chelating cadmium ions, and are further used as nano-templates for the growth of CdS nanocrystals (quantum dots). Moreover, TEM microscopy reveals that the size of the CdS nanocrystals on the CNT surfaces increases with increasing S(2-) concentration. In addition, high resolution x-ray photoelectron (XPS) spectroscopy was used to characterize the functional groups on the surface of the MWCNTs after chemical modification by the plasma treatment and grafting with GMA-IDA polymer.

Quasi-solid DSSC based on a gel-state electrolyte of PAN with 2-D graphenes incorporated

A hybrid polymer gel electrolyte (PGE) comprising of polyacrylonitrile (PAN) with graphene incorporated in a mixture of iodide redox electrolyte was prepared for the first time for use in quasi-solid dye-sensitized solar cells (DSSC). The exfoliated 2-D graphenes were dispersed homogenously within the PGE and facilitate the diffusion of I−/I3− ion pairs in the electrolyte system. The ratio of graphene in the PAN PGE was optimized to maximize the ionic conductivity and photoelectronic properties of the DSSC. The energy conversion efficiency of the DSSC achieved by using this hybrid PGE with 0.2 wt% Gr is 5.41%, which is 1.5 times the value of the liquid-state cell (3.72%).

Effects of passivation treatments on titanium alloy with nanometric scale roughness and induced changes in fibroblast initial adhesion evaluated by a cytodetacher

Passivation treatments of titanium alloy alter not only its nanosurface characteristics of oxides and ion release but also surface roughness (Ra), and wettability as well, where nanosurface characteristics of oxides include chemistries of oxides, amphoteric-OH groups adsorbed on oxides, and oxide thickness. Consequently, the passivation treatment affects the alloys cyto-comparability. In this study, we polish specimens to achieve nanometric scale roughness. In addition, treatment effects are evaluated for surface topology, roughness, wettability, and responses of fibroblasts consisting of MTT assay, initial adhesion strength, and morphology. The initial adhesion strength is measured using a cyto-detacher that achieves nano-Newton resolution. Results reveal that (1) the treatment effects on the percentage of Ti--OH basic groups and wettability are nearly collinear; (2) the Ra of passivated Ti-6Al-4V ranges from 1.9 to 7.4 nm; (3) the initial adhesion strength of fibroblast ranges from 58 to 143 nN, and it is negatively correlated to the Ra; (4) the passivation results in distinguishable morphologies, which further substantiate the negative correlation between cell initial adhesion force and Ra; and (5) our results fall short of confirming previous reports that found positively charged functional groups promoting fibroblast attachment and spread. Potential causes of the inconsistency are addressed.

The environment of lithium ions and conductivity of comb-like polymer electrolyte with a chelating functional group

Abstract The behavior of lithium ions in a comb-like polymer electrolyte with a chelating functional group have been characterized by differential scanning calorimeter (DSC), dynamic mechanical analysis (DMA), Fourier transform infrared (FTIR) spectroscopy, ac impedance and 7Li solid-state NMR measurements. The comb-like copolymer is synthesized by poly(ethylene glycol-methyl ether methacrylate) (PEGMEM) and (2-methylacrylic acid 3-(bis-carboxymethylamino) -2-hydroxy-propyl ester) (GMA-IDA). FTIR and 7Li solid-state NMR spectra demonstrate the interactions of Li+ ions with both the ether oxygen of the PEGMEM and the nitrogen atom of the GMA-IDA segments. Moreover, 7Li solid-state NMR shows that the lithium ions are preferentially coordinated to the GMA-IDA segment. The Tg increases for the copolymers doped with LiClO4. These results indicate the interactions of Li+ with both PEGMEM and GMA-IDA segments form transient cross-links. The Vogel–Tamman–Fulcher (VTF)-like behavior of conductivity implies the coupling of the charge carriers with the segmental motion of the polymer chains. The dependence of the maximum conductivity on the composition of the copolymers and the doping lithium ion concentration was determined. The GMA-IDA unit in the copolymer improves the dissociation of the lithium salt, the mechanical strength and the conductivity.

Synthesis of luminescent and rodlike CdS nanocrystals dispersed in polymer templates

A simple synthetic route for the preparation of luminescent and rodlike CdS nanocrystals embedded in poly(BA -co-GMA -co-GMA-IDA) (PBGM) copolymer templates, by soap-free emulsion copolymerization, is presented. In this study, GMA-IDA chelating groups within the copolymer were the coordination sites for chelating Cd2+, at which nanosized CdS nanocrystals were grown by the dry method (H2S) and the wet method (Na2S). The particle size and morphology of CdS nanocrystals were observed by transmission electron microscopy (TEM) and atomic force microscopy (AFM). TEM observations demonstrate that the mean diameters of CdS nanoparticles can be prepared between 1 and 2 nm inside the matrix of PBGM membranes by the dry method and between 3 and 6 nm by the wet method. AFM images reveal that CdS nanocrystals on the surfaces of PBGM membranes formed by the dry method have rodlike morphology. The optical absorption spectra indicate a clear blue-shift in the absorption edge for the PBGM-CdS membranes, such that the bandgaps calculated from the absorption spectra are higher than those calculated for the bulk CdS. The particle sizes, estimated from the bandgaps, are in the nanometre range, suggesting that both the particle size and the bandgap can be adjusted via the mole fraction of GMA-IDA in the PBGM membranes. Luminescence spectrophotometry of the samples also indicates a blue-shift in the emission spectra.

Kinetic study of the mini-emulsion polymerization of styrene

A broad particle-szie distribution in mini-emulsion polymerization is generally attributed to the long induction period and homogeneous nucleation in the aqueous phase. In this study, the high dissociation rate of the interfacial redox initiator system cumene hydroperoxide/ferrous ion/ethylenediaminetetraacetic acid/ sodium formaldehyde sulfoxylate (CHP-Fe2+-EDTA-SFS), which could produce hydrophobic radicals and decrease homogeneous nucleation in the aqueous phase, was used to prepare the mini-emulsion polymerization. Polystyrene particles of narrow size distribution were obtained, and their molecular weights were also very narrow (polydispersity index = 1.5–2.0). The effects of the initiator concentration, the ratio of surfactant/cosurfactant (sodium lauryl sulfate/cetyl alcohol, SLS/CA), the styrene concentration and the reaction temperature in the mini-emulsion polymerization of styrene were also investigated. When higher CHP and SFS concentrations or higher reaction temperature were used in the mini-emulsion polymerization, the polymerization rate and conversion became higher. The order of SLS:CA ratios for preparing polymer particles of high stability was 1:3 > 1:10 > 1:16 > 1:0.

Preparation and characterization of luminescent CdS nanoparticles immobilized on poly(St-co-GMA-IDA) polymer microspheres

Luminescent CdS nanoparticles immobilized on copolymer microspheres were produced by the chemical precipitation of poly(St-co-GMA-IDA)?Cd2+ (PSG?Cd2+) complexes. PSG latex was prepared by the soap-free emulsion copolymerization of styrene (St) and 2-methacrylic acid 3-(bis-carboxymethylamino)-2-hydroxy-propyl ester (GMA-IDA). GMA-IDA chelating groups within copolymer latex have coordination sites for chelating metal ions, at which CdS particles were grown. The presence of ethanol as a cosolvent improved both the particle monodispersity and the surface charge. Fourier transform infrared (FT-IR) spectroscopy spectra were obtained to elucidate the characteristics of GMA-IDA in the PSG latex. The size distribution, morphology and structure of CdS nanoparticles were measured by transmission electron microscope (TEM) and x-ray diffraction (XRD) analysis. The growth kinetics of CdS nanoparticles were studied by TEM and obtaining photoluminescence (PL) spectra. The size and morphology of CdS particles were influenced by the amount of the chelating, iminodiacetic acid group on the surface of the copolymer microsphere, the concentration of Cd2+ ions and the pH. The PSG-A3?CdS sample with [Cd2+]/[GMA-IDA] = 1/6, pH = 3.5, which was formed from ultrafine CdS particles with mean diameters below 5?nm immobilized on the surface of copolymer microspheres, emitted photons with a higher energy than other samples in this investigation.