Arh Hwang Chen

The chemically crosslinked metal-complexed chitosans for comparative adsorptions of Cu(II), Zn(II), Ni(II) and Pb(II) ions in aqueous medium

The chemically crosslinked metal-complexed chitosans were synthesized by using the ion-imprinting method from a chitosan with four metals (Cu(II), Zn(II), Ni(II) and Pb(II)) as templates and glutaraldehyde as a crosslinker. The influences of adsorption conditions, including molar ratios of crosslinker/chitosan and pH changes, were studied. They were used to investigate for comparative adsorptions of Cu(II), Zn(II), Ni(II) and Pb(II) ions in an aqueous medium. They were demonstrated the comparative adsorptions of Cu(II), Zn(II), Ni(II) and Pb(II) ions in the orders of the adsorbed amounts with templates: Cu(II) approximately Pb(II)>Zn(II) approximately Ni(II), Zn(II)>Cu(II) approximately Pb(II)>Ni(II), Ni(II)>Pb(II)>Zn(II)>Cu(II) and Pb(II) approximately Cu(II)>Zn(II)>Ni(II), respectively. In addition, the dynamical study showed to be well followed the second-order kinetic equation in the adsorption process. At the same time, the equilibrium adsorption data were fitted in three adsorption isotherm models, namely, Langmuir, Freundlich, and Dubinin-Radushkevich to show very good fits in the Langmuir isotherm equation for the monolayer adsorption process. The most important aspect of the chemically crosslinked metal-complexed chitosans with glutaraldehyde demonstrated to afford a higher adsorption capacity, and a more efficient adsorption toward metals in an aqueous medium.

Biosorption of azo dyes from aqueous solution by glutaraldehyde-crosslinked chitosans

The crosslinked chitosan microparticles prepared through homogeneous coupling reaction and microparticle formation using a sodium hydroxide solution showed the largest adsorbed amounts toward the RB5 and 3R dyes than those from the three other methods through heterogeneous coupling reaction and microparticle formation using sodium hydroxide or sodium tripolyphosphate solutions. The dynamical experimental study showed that the dye adsorption accurately followed the second-order adsorption process. The experimental isotherm data were analyzed using three isotherm models, namely, Langmuir, Freundlich, and Dubinin-Radushkevich. The results revealed that the adsorption behavior of the RB5 and 3R dyes on the microparticles fitted well with the Langmuir model. In addition, the mean adsorption energy (E) from the Dubinin-Radushkevich isotherm and the activation energy (E(a)) from Arrhenius equation indicated that the adsorption process might be the dual nature of the process, physisorption and chemisorption, and was predominant on the chemisorption process The competitive adsorption showed that the adsorption of the 3R dye on the microparticles in the mixture solution was much more affected by the existence of the RB5 dye than the other way around. Furthermore, it was also found that the crosslinked chitosan microparticles can be regenerated and reused for dye adsorption.

Biosorption of Cu(II), Zn(II), Ni(II) and Pb(II) ions by cross-linked metal-imprinted chitosans with epichlorohydrin

Cross-linked metal-imprinted chitosan microparticles were prepared from chitosan, using four metals (Cu(II), Zn(II), Ni(II), and Pb(II)) as templates, and epichlorohydrin as the cross-linker. The microparticles were characterized by Fourier transform infrared spectroscopy, solid state (13)C nuclear magnetic resonance spectroscopy, and energy-dispersive X-ray spectroscopy. They were used for comparative biosorption of Cu(II), Zn(II), Ni(II) and Pb(II) ions in an aqueous solution. The results showed that the sorption capacities of Cu(II), Zn(II), Ni(II), and Pb(II) on the templated microparticles increased from 25 to 74%, 13 to 46%, 41 to 57%, and 12 to 43%, respectively, as compared to the microparticles without metal ion templates. The dynamic study showed that the sorption process followed the second-order kinetic equation. Three sorption models, Langmuir, Freundlich, and Dubinin-Radushkevich, were applied to the equilibrium isotherm data. The result showed that the Langmuir isotherm equation best fitted for monolayer sorption processes. Furthermore, the microparticles can be regenerated and reused for the metal removal.

Competitive biosorption of azo dyes from aqueous solution on the templated crosslinked-chitosan nanoparticles.

The nanoparticles of templated crosslinked chitosan, ECH-RB5 and ECH-3R, were prepared through the imprinting process using Remazol Black 5 (RB5) and Remazol Brilliant Orange 3R (3R) dyes, respectively, as templates and ECH as a crosslinker. The nanoparticles exhibited significantly higher adsorption capacities of the dyes than other nanoparticles formed without a dye template and with three crosslinkers (ECH, GLA, and EGDE). The adsorption of the dyes on the nanoparticles was affected by the initial pH, dye concentration, and temperature. The results were in accordance with the second-order and the Langmuir adsorption models. Meanwhile, the E values of the dyes calculated using the Dubinnin-Radushkevich model revealed that the adsorption process may be due to the dual nature of the process, physisorption and chemisorption, and that adsorption was predominant in the chemisorption process. The adsorption processes in the nanoparticles were spontaneous and exothermic. Moreover, competition adsorption through analysis of the intraparticle diffusion model apparently favored the 3R dye more than the RB5 dye on the nanoparticles in mixture solution B. The nanoparticles for the adsorption of the dyes were regenerated efficiently through the alkaline solution and were then reused for dye removal.

Adsorption of Remazol Black 5 from aqueous solution by the templated crosslinked-chitosans

The templated crosslinked-chitosan microparticles prepared using the imprinting method with the Remazol Black5 (RB5) dye as a template, epichlorohydrin (ECH) as a crosslinker, and sodium hydroxide (NaOH) solution used for the microparticle formation showed the highest adsorption capacity for the RB5 dye compared with those that used other methods with or without a template, three crosslinkers, and two microparticle formations. The results showed that the adsorption of the RB5 dye on the microparticles was affected by the microparticle size, the initial dye concentration, the initial pH value, as well as the temperature. Both kinetics and thermodynamic parameters of the adsorption process were estimated. These data indicated an exothermic spontaneous adsorption process that kinetically followed the second-order adsorption process. Equilibrium experiments fitted well the Langmuir isotherm model, and the maximum monolayer adsorption capacity for the RB5 dye was 2941 mg/g. The competition study showed that the adsorption of the RB5 dye on the microparticles in the mixture solution was much less affected by the existence of the 3R dye than the other way around. Furthermore, the microparticles could be regenerated through the desorption of the dye in pH 10.0 of NaOH solution and could be reused to adsorb the dye again.

Recognition of molecularly imprinted polymers for a quaternary alkaloid of berberine

Selective and affinitive imprinted polymers incorporating a quaternary alkaloid of berberine (BER) were prepared using a non-covalent imprinting method. The results showed that, compared to other imprinted polymers, the polymer AD-10 had not only a higher of the ratio of Q(MIP)/Q(BP) for BER adsorption, and but also a larger of the ratio of Q(MIP,B)/Q(MIP,P) for BER and palmatine (PAL) adsorptions. Spectrophotometric analysis demonstrated that a 1:1 cooperative hydrogen-bonding complex might be predominating in the pre-polymerization between the BER template and AA monomer. Adsorption experiments of BER on the polymer AD-10 were in accordance with the second-order and Langmuir adsorption models. The E value (5.70 kJ/mol) calculated from the Dubinin-Radushkevich model indicated that the adsorption followed a physisorption process. In addition, a Scatchard plot showed a single straight line with an equilibrium dissociation constant (K(D)) of 65.80 μmol/L. SPE analyses of a mixture of BER and PAL and the methanol extract from the cortices of Phellodendron wilsonii showed that AD-10 had more efficiency, and higher specificity and selectivity for SPE in the concentration and determination of BER and its extraction from natural products.

PHOTOCATALYTIC DECOLORIZATION OF REMAZOL BLACK 5 AND REMAZOL BRILLIANT ORANGE 3R BY MESOPOROUS TIO2

Mesoporous TiO2 microparticles (TiO2-11) were prepared through the micelle hydrothermal method using a 1:1 M ratio of 1-tetradecylamine:Ti(OiPr)4. TiO2-11 microparticles exhibited significantly higher decolorization percentage of Remazol Black 5 (RB5) and Remazol Brilliant Orange (3R) dyes than other TiO2 microparticles formed with different molar ratios of 1-tetradecylamine:Ti(OiPr)4, and P25 and anatase TiO2. The results showed that the decolorization of the dyes by the microparticles was affected by the different irradiation wavelengths, catalyst dosages, dye concentrations, initial pH values, as well as electron acceptors. The kinetic experiments with varying initial pH values were in accordance with the second-order model. In addition, the adsorption study of the dyes in the dark fitted well with the Langmuir isotherm model. With the addition of 20 mmol/mL of three electron acceptors, H2O2, KBrO3, and (NH4)2S2O8, the decolorization of the RB5 and 3R dyes increased by 54% and 35%, 59% and 41%, and 36% and 33%, respectively. Hence, this technique for the preparation of the mesoporous TiO2 microparticles can facilitate more efficient decolorization of dyes in an aqueous solution.

Asymmetric Synthesis and Characterization of Chiral 2,2′‐Diamino‐3,3′‐diethoxycarbonyl‐8,8′‐diphenyl‐1,1′‐biazulene

Abstract rac‐2,2′‐Diamino‐3,3′‐diethoxycarbonyl‐8,8′‐diphenyl‐1,1′‐biazulene was synthesized from diethyl 2‐aminoazulene‐1,3‐dicarboxylate and was optically resolved into two enantiomers of S‐form and R‐form. The enantioselective oxidative couplings with two chiral amines [(−)‐sparteine and (R)‐(+)‐α‐methylbenzylamine] and ferric chloride catalyst, and the asymmetric couplings with two chiral oxovanadium(IV) complexes of ethyl 2‐amino‐4‐phenylazulene‐1‐carboxylate, easily yielded chiral 2,2′‐diamino‐3,3′‐diethoxycarbonyl‐8,8′‐diphenyl‐1,1′‐biazulene. Therefore, the introduction of two phenyl groups at the 8‐ and 8′‐postions of each azulene ring using phenyl magnesium bromide via an addition–oxidation–decarboxylation mechanism resulted in 1,1′‐biazulene forming a chiral C2 axis.