Preparation and characterization of hydrophobically modified alginate

Summary Biodegradable alginate-derived polymeric surfactants (APSs) with a linear alkyl group (C8, C12, C16) were synthesized by oxidation followed by reductive amination of 2,3-dialdehydic alginate. The oxidized alginates and all APSs were characterized by spectral and X-ray diffractometry analysis. The sonicated suspension test was employed to form self-aggregates in aqueous solution. In the case of 40% CHO-C8 APS, the lowest interfacial tension, 31.5 mNm⁻¹, was obtained at the c.m.c. value of 1.35 g L⁻¹. A biodegradability test on the 30% CHO-C12 APS system suggested that it would be attacked by a soil microorganism, Aspergillus niger. Received: 22 October 2001/ Accepted: 2 November 2001     

Adsorption and heat‐energy‐aid desorption of cationic dye on a new thermo‐sensitive adsorbent: Methyl cellulose/calcium alginate beads

The adsorption and heat‐energy‐aid desorption of methylene blue (MB) on a thermo‐sensitive adsorbent of methyl cellulose/calcium alginate beads (MC/CABs) has been studied. The addition of methyl cellulose intensified the desorption ability of adsorbent, and boosted the difference of adsorption capacity of adsorbent between low temperature and high temperature. At the mass ratio of methyl cellulose to sodium alginate of 2:1, the difference of adsorption capacity of MC/CABs between 20 and 60°C reached 20.48 mg g^?1. The effects of temperature, time and initial MB concentration on adsorption performance were investigated in detail. The MB adsorption on MC/CABs followed the pseudo‐second‐order kinetic model. The equilibrium data was fitted well with Langmuir isotherm. The maximum adsorption capacity of 336.70 mg g^?1 exhibited MC/CABs had a good adsorption capability. Thermodynamic analyses showed high temperature was not favorable to MB adsorption, and MC/CABs had a distinct superiority in desorption of adsorbate with heat‐energy‐aid. Lastly, the possible mechanisms involving in adsorption and heat‐energy‐aid desorption were presented. POLYM. ENG. SCI., 56:1382–1389, 2016. © 2016 Society of Plastics Engineers     

Adsorption behavior of cocamidopropyl betaine under conditions of high temperature and high salinity

The adsorption behavior of cocamidopropyl betaine (CAB) in aqueous solutions and on sandstone surfaces was studied under the conditions of high temperature and high salinity. In aqueous solutions, as temperature increased from 25 to 90°C and salinity increased from 0 to 115,200 ppm, surface tension and the critical micelle concentration (cmc) of CAB both decreased. In the solid/liquid system, when the CAB concentration of salt solutions reached 0.30 wt %, the static saturation adsorption amount on the surface of clean sands was 14.77 mg g^?1 at 90°C. Because of its noticeable saturation adsorption capacity, the adsorption of CAB on the solid/liquid interface agreed with multilayer adsorption. Also, the adsorption amount on the surface of oil sands was greater than on clean sands. Besides, the dynamic saturation adsorption amount and retention amount of 0.07 wt % CAB solution were less than the static adsorption amount. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40424.     

Removal of hexavalent chromium in wastewater by polyacrylamide modified iron oxide nanoparticle

Iron oxide nanoparticle has been successfully modified by polyacrylamide and the polyacrylamide modified magnetic nanoparticles (PMMNs) were applied to remove Cr(VI) in wastewater. The vibrating sample magnetometer (VSM) spectra indicated the large saturation magnetization and superparamagnetic property of the PMMNs. This made the polyacrylamide modified iron oxide easily separate with liquid phase. Scanning electron microscope (SEM) results showed that both the synthesized iron oxide and the PMMNs were nanoscale. Batch adsorption studies had been carried out to determine the effect of pH, contact time, Cr(VI) initial concentration, and coexisting salts on the adsorption of Cr(VI). Maximum removal (98.30%) was observed from an initial concentration of 100 mg L^?1 Cr(VI) at pH 3.0, 30°C. This process followed pseudo‐second‐order kinetics model and the equilibrium time was 40 min. The experimental data fitted the Langmuir isotherm better than Freundlich. Maximum adsorption amount of Cr(VI) by PMMN was 35.186 mg g^?1. The effect of coexisting salts on Cr(VI) removal was not apparent even the concentration of salt was 10 times as big as the low concentration, 0.01M. It had been proposed that the mechanism of Cr(VI) uptake onto PMMN was adsorption‐coupled reduction. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40945.     

Nickel and cobalt sorption on anaerobic granular sludges: kinetic and equilibrium studies

The kinetics and equilibria of sorption of the divalent metal ions cobalt and nickel onto anaerobic granular sludge are described. Single component and binary equimolar systems were studied at different pH values (pH 6, 7 and 8). The kinetic modelling of metal sorption by anaerobic granular sludge has been carried out using Lagergren equations. On fitting the experimental kinetic data both in first‐ and pseudo‐second‐order equations, the regression analysis of a pseudo‐second‐order equation gave a higher r² value, indicating that both external mass transfer and intra‐particle diffusion are involved in the sorption process. The experimental isotherm data were analysed using the Langmuir, Freundlich and Redlich–Peterson equations. The Redlich isotherm, a combination of the Langmuir and Freundlich equations, was found to have the highest regression correlation coefficients at pH 7. At pH 8, the Langmuir mechanism dominated for cobalt and nickel adsorption. In contrast, at pH 6, the Freundlich equation gave a better correlation coefficient which suggests a more heterogeneous adsorption at that pH. The maximal adsorption capacity of the granular sludge, as determined by the Langmuir equation, for cobalt or nickel in single systems (8.92 mg g^?1 Co TSS; 9.41 mg g^?1 Ni TSS, pH 7) compared with binary systems (8.06 mg g^?1 Co TSS; 8.43 mg g^?1 Ni TSS, pH 7) showed no great difference in the accumulation of these metals onto granular sludge. Copyright © 2004 Society of Chemical Industry     

Kinetics and equilibrium of cobalt ion adsorption on cross‐linked polyethylenimine membrane

The kinetics and equilibrium of cobalt ion adsorption on crosslinked polyethylenimine (PEI) membrane were studied by the spectroscopic method in terms of time, cobalt ion concentration, and temperature. It was found that the adsorption of cobalt ion on crosslinked PEI membrane obeyed the pseudofirst‐order kinetic model and the equilibrium adsorption amount of cobalt ion on crosslinked PEI membrane was closely related to the initial cobalt ion concentration. The equilibrium adsorption amount increased with the decrease of temperature and obeyed a Langmuir isotherm to give the equilibrium constant for the adsorption of cobalt ion on crosslinked PEI membrane under various temperatures. Based on Van't Hoff equation the enthalpy and entropy of the adsorption of cobalt ion on crosslinked PEI membrane were determined to be ?12.9 kJ mol^?1 and ?107 J mol^?1 K^?1, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Surfactant Synthesis via Lipase Esterification of Methyl α-d-Glucopyranoside with Selected Aliphatic Carboxylic Acids

Lipase‐catalyzed esterification and properties of synthesized carbohydrate esters were investigated. Methyl α‐d ‐glucopyranoside was the acyl group acceptor and different carbon atom chain lengths of aliphatic carboxylic acids (C12, C14 and C16) as the acyl group donors were applied in the esterification. Physico‐chemical studies on the synthesized carbohydrate esters were carried out. It was found that melting point for the methyl 6‐O‐hexadecanoyl‐α‐d ‐glucopyranoside was the highest consecutively followed by methyl 6‐O‐tetradecanoyl‐α‐d ‐glucopyranoside and methyl 6‐O‐dodecanoyl‐α‐d ‐glucopyranoside. Liquid crystal properties of the synthesized carbohydrate ester synthesized were evaluated via optical polarized microscopy. It was found that the liquid crystal textures for mono‐substituted carbohydrate esters were of the smectic phase. In a quaternary system (carbohydrate ester/n‐butanol/n‐hexadecane/water), a maximum 34 % of water (by mass) was contained in the monophasic region of methyl 6‐O‐tetradecanoyl‐α‐d ‐glucopyranoside and a maximum of 52 % water (by mass) was contained in a monophasic methyl 6‐O‐dodecanoyl‐α‐d ‐glucopyranoside. For methyl‐6‐O‐dodecanoyl‐α‐d ‐glucopyranoside, its concentration at aggregation was 5.2 × 10^?4 mM, with minimum air/water surface tension of 26 mN m^?1. The Gibbs energy of micellization was calculated at ?50 kJ mol^?1. The maximum adsorption density of methyl 6‐O‐dodecanoyl‐α‐d ‐glucopyranoside was determined at 4 × 10^?6 mol m^?2 while its minimum area per surfactant molecule at the air/water surface was 47 Ų.     

Modulated gluconic acid production from immobilized cells of Aspergillus niger ORS‐4.410 utilizing grape must

BACKGROUND: Gluconic acid (GA) production by immobilized cells of mutant Aspergillus niger ORS‐4.410 on polyurethane sponge (PUS) and calcium‐alginate (Ca‐alginate) was evaluated in repeated batches of solid state surface fermentation (SSF) and submerged fermentation (SmF) conditions, respectively, utilizing rectified grape must as carbon source. RESULTS: The passive immobilization of cells in fermentation medium solid support of having 0.4 cm³ cube size, 4% spore suspension, 0.6 g inoculum of PUS immobilized cells at 32 °C and 2.0 L min^?1 resulted in the maximum GA production (88.16 g L^?1) with a 92.8% yield, while the Ca‐alginate matrix with a 0.5 cm diameter bead size, 2–3% spore suspension, 15 g inoculum at 34 °C and 150 rpm agitation speed revealed 67.19 g L^?1 GA with a 85.2% yield. Repeated use of PUS showed higher levels of GA (110.94 g L^?1) in the third–fourth fermentation cycles with 95–98% yield and 22.50 g L^?1 d^?1 productivity under SSF that was 2.5‐fold higher than the productivity obtained from a typical fermentation cycle, and 54% greater than the productivity obtained with repetitive use of Ca‐alginate immobilized cells of A. niger under SmF. CONCLUSION: Using immobilized cells of A. niger in PUS, the rectified form of grape must can be utilized for GA production as an alternative source of carbohydrate by replacing the conventional fermentation conditions. Copyright © 2008 Society of Chemical Industry     

Syntheses and adsorption properties for Hg2+ of chelating resin of crosslinked polystyrene‐supported 2,5‐dimercapto‐1,3,4‐thiodiazole

A novel chelating resin with functional group containing S and N atoms was prepared using chloromethylated polystyrene and 2,5‐dimercapto‐1,3,4‐thiodiazole (also called bismuththiol I, BMT) as materials. Its structure was characterized by infrared spectra and elementary analysis. The results showed that the content of the functional group was 2.07 mmol BMT g^?1 resin, 47% of which were in the form of monosubstitution (PS‐BMT‐1) and 53% in the form of double substitution (PS‐BMT‐2). The adsorption for mercury ion was investigated. The adsorption dynamics showed that the adsorption was controlled by liquid film diffusion. Increasing the temperature was beneficial to adsorption. The Langmuir model was much better than the Freundlich model to describe the isothermal process. The adsorption activation energy (E_a), ΔG, ΔH, and ΔS values calculated were 18.56 kJ·mol^?1, ‐5.99 kJ·mol^?1, 16.38 kJ·mol^?1, and 37.36, J·mol^?1·K^?1, respectively. The chelating resin could be easily regenerated by 2% thiourea in 0.1 mol·L^?1 HCl with higher effectiveness. Five adsorption–desorption cycles demonstrated that this resin was suitable for repeated use without considerable change in adsorption capacity. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1646–1652, 2004     

Novel type of alginate gel‐based adsorbents for heavy metal removal

Various alginate gel‐based adsorbents were investigated for the removal of heavy metals: alginate beads, alginate capsules, and alginate gel‐coated adsorbent. Of these, alginate capsules showed the greatest Pb²⁺ uptake capacity of 1560 mg g^?1 of dry sodium alginate, and the alginate gel‐coated adsorbent, prepared simply by forming a thin alginate film on an inert matrix, achieved rapid adsorption equilibrium within 10 min. Adsorbed metals were readily removed from the alginate gel‐based adsorbents using eluents such as HNO₃ and could be reused for up to 10 adsorption–desorption cycles without marked loss of metal uptake capacity. Alginate gel‐coated adsorbents could be prepared in a dried state and have great application potential for the removal of heavy metals from contaminated water. Copyright © 2004 Society of Chemical Industry     

Surface complexation modeling of soluble molybdenum adsorption by Mn3O4

BACKGROUND: Mo is a harmful element that should strictly be limited in electrolytic manganese dioxide but can readily be removed by Mn₃O₄. However, as its adsorption mechanism is not yet clear the aims of this work are to clarify the absorption phenomena and specific reaction processes of Mo onto Mn₃O₄. RESULTS: Some theoretical parameters have been obtained: the total surface site density and protonation constants (N_T = 6.84 × 10^?3 mol g^?1, , ) were obtained by non‐linear data fitting of acid‐base titrations. Distribution of soluble Mo species derived from thermodynamic calculations showed that the concentration of poly‐molybdenum acid ion was extraordinarily low and could be ignored when the concentration of soluble Mo was 1 mg L^?1. The adsorption isotherm followed the Freundlich adsorption equation. Under the conditions V = 0.15 L, W = 2 g L^?1, [Mo]_T = 1.12 mg L^?1, T = 80 °C, P = 1.013 × 10⁵ Pa, 1.0 mol L^?1 MnSO₄ and pH range 1–6.5, the non‐electrostatic model (NEM) was used to quantify Mo adsorption. CONCLUSION: The surface adsorption complexation modeling of Mo onto Mn₃O₄ can be successfully applied to predict adsorption rates of Mo onto Mn₃O₄ at different pH values, with an absolute error less than 6%. Copyright © 2009 Society of Chemical Industry     

Study on preparation and properties of PVA‐SA‐PHB‐AC composite carrier for microorganism immobilization

Polyvinyl alcohol(PVA) bead crosslinked with boric acid has been widely utilized as a microorganism immobilization carrier. However, it has some disadvantages such as drastic cell viability loss, small adsorption capacity and mass transfer limitation. To improve upon these drawbacks, a new method to prepare PVA composite pieces with the addition of activated carbon (AC) and poly‐3‐hydroxybutyrate(PHB) was explored through a combination of freezing/thawing and the boric acid method and by using Tween‐80 to improve the mass transfer performance of hydrophobic organics. m‐Cresol and pyrene were used as representative compounds with benzene ring structures to model hydrophilic and hydrophobic organics in order to test the performance of PVA pieces. The results showed that, compared with the boric acid method alone, a combination of freezing/thawing and the boric acid method led to a decrease in total organic carbon(TOC) loss from 0.315 g g^?1 to 0.033 g g^?1 and increased the oxygen uptake rate(OUR) of microorganisms from 0.03 mg L^?1·min^?1 to 0.22 mg L^?1 min^?1. The m‐cresol equilibrium adsorption amount of the PVA‐SA(sodium alginate)‐PHB‐AC piece was 2.80 times that of the PVA‐SA piece. The diffusion coefficient of pyrene in the PVA‐SA‐PHB‐AC piece increased from 0.53×10^?9 m² min^?1 to 2.30×10^?9 m² min^?1 with increasing concentrations of Tween‐80 from 1000 mg L^?1 to 5000 mg L^?1. The PVA‐SA‐PHB‐AC composite carrier demonstrated great scope for immobilizing microorganisms for practical wastewater bio‐treatment. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39837.     

Enhanced swelling and methylene blue adsorption of polyacrylamide‐based superabsorbents using alginate modified montmorillonite

Polyacrylamide/sodium alginate modified montmorillonite (PAM/SA‐MMT) superabsorbent composites were synthesized by free‐radical polymerization under normal atmospheric conditions. They were characterized by X‐ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy (FTIR). Their water absorbency and methylene blue (MB) adsorption behaviors were studied. Compared with PAM/MMT composites, PAM/SA‐MMT composites demonstrated greater water absorbency (863 g g^?1 in distilled water and 101 g g^?1 in 0.9 wt % NaCl solution) and higher adsorption capacity of 2639 mg g^?1 for MB. The adsorption behaviors of the composites showed that the isotherms and adsorption kinetics were in good agreement with the Langmuir equation and pseudo‐second‐order equation, respectively. FTIR analysis suggested that the MB adsorption of PAM/SA‐MMT composites via a mechanism combined electrostatic, H‐bonding and hydrophobic interaction. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 40013.     

Improved synthesis of a branched poly(ethylene imine)‐modified cellulose‐based adsorbent for removal and recovery of Cu(II) from aqueous solution

This study focuses on an improved synthesis of a branched poly (ethylene imine) (PEI)‐modified cellulose‐based adsorbent (Cell‐g‐PGMA‐PEI). We aim to improve the adsorbent capacity by reducing side reaction of epoxide ring opening during graft copolymerization of glycidyl methacrylate (GMA) onto cellulose which increases the content of epoxy groups, anchors to immobilize branched PEI moieties. FTIR spectra provided the evidence of successful graft copolymerization of GMA onto cellulose initiated by benzoyl peroxide (BPO) and modification with PEI. The amount of epoxy groups of Cell‐g‐PGMA was 4.35 mmol g^?1 by epoxy titration. Subsequently, the adsorption behavior of Cu(II) on cell‐g‐PGMA‐PEI in aqueous solution has been investigated. The data from the adsorption kinetic experiments agreed well with pseudo‐second‐order model. The adsorption isotherms can be interpreted by the Langmuir model with the maximum adsorption capacity of 102 mg g^?1 which was largely improved compared with the similar adsorbent reported. The dynamic adsorption capacity obtained from the column tests was 119 mg g^?1 and the adsorbent could be regenerated by HCl of 0.1 mol L^?1. Results indicate that the novel pathway for the synthesis of Cell‐g‐PGMA‐PEI exhibits significant potential to improve the performance of adsorbents in removal and recovery of Cu(II) from aqueous solution. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Characterization and adsorption performance of Zr‐doped akaganéite for efficient arsenic removal

BACKGROUND: A new adsorbent, Zr‐doped akaganéite, having a tunnel structure and efficient arsenic adsorption capacity, was prepared by homogeneous co‐precipitation with urea. Formation of the synthesized adsorbent was studied in detail. RESULTS: The adsorbent was characterized by X‐ray powder diffraction (XRD), transmission electron microscopy (TEM), X‐ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and the determination of Cl^? leakage showed that an appropriate amount of Zr⁴⁺ was doped into akaganéite (β‐FeOOH) by substitution of Fe³⁺ and possessed a similar tunnel structure to Fe³⁺. The morphology, surface area and tunnel structure changed greatly compared with β‐FeOOH with more ? OH groups and Cl^? introduced into the tunnel structure after doping with Zr⁴⁺. The Zr‐doped β‐FeOOH exhibited highly effective adsorption of arsenic with a capacity for As(III) and As(V) of 120 and 60 mg g^?1 at neutral pH. On the basis of Cl^? release during adsorption and analyses of zeta potential along with XPS and FTIR spectra, the adsorption of arsenic on Zr‐doped β‐FeOOH was verified as inner‐sphere adsorption with the ? OH groups in the tunnel structure of the adsorbent the main adsorption sites at arsenic high concentrations. CONCLUSION: The Zr⁴⁺ was doped into β‐FeOOH by substitution of Fe³⁺. The ? OH groups in the tunnel structure of the adsorbent were the main adsorption sites at high arsenic concentrations, and the adsorption occurred by an inner‐sphere adsorption process. © 2012 Society of Chemical Industry     

Synthesis, Surface and Thermodynamic Properties of Substituted Polytriethanolamine Nonionic Surfactants

Three series of nonionic surfactants derived from polytriethanolamine containing 8, 10, and 12 units of triethanolamine were synthesized. Structural assignment of the different compounds was made on the basis of FTIR and ¹H‐NMR spectroscopic data. The surface parameters of these surfactants included critical micelle concentration (CMC), surface tension at the CMC (γ_CMC), surfactant concentration required to reduce the surface tension of the solvent by 20 mN m^?1 (pC₂₀), maximum surface excess (Γ_max), and the interfacial area occupied by the surfactant molecules (A_min) using surface tension measurements. The micellization and adsorption free energies were calculated at 25 °C.     

Removal of aqueous toxic Hg(II) by functionalized mesoporous silica materials

BACKGROUND: Hg(II) is one of the most toxic metals and has received particular attention in environmental pollution. Hg(II) pollution is common in water sources, so rapid and efficient methods must be developed for its removal from water samples. Mesoporous silica (MS) is an ideal adsorbent due to its high surface area and biocompatibility. The efficiency and selectivity of MS adsorbents can be improved by surface modification. RESULTS: A new sorbent for trace Hg(II) removal was developed by grafting 1‐(3‐carboxyphenyl)‐2‐thiourea (CPTU) onto SBA‐15 mesoporous silica. The optimum pH range for Hg(II) adsorption was 3‐7 and the maximum static adsorption capacity was 64.5 mg g^?1. An enrichment factor of 150 was obtained with a relative standard deviation < 1.5% (n = 8). Common coexisting ions did not interfere with the adsorption of Hg(II) under optimal conditions. Quantitative recovery was achieved by stripping with a mixed solution of 1 mol L^?1 HCl and 5% CS(NH₂)₂. Efficient adsorption capacity of the recycled material could still be maintained at a level of 95% at the 7th cycle. CONCLUSION: 1‐(3‐carboxyphenyl)‐2‐thiourea functionalized SBA‐15 mesoporous silica was synthesized and applied for Hg(II) removal from water samples with high efficiency and selectivity. Copyright © 2012 Society of Chemical Industry     

High cis‐1,4 polyisoprene or cis‐1,4/3,4 binary polyisoprene synthesized using 2‐(benzimidazolyl)‐6‐(1‐(arylimino)ethyl)pyridine cobalt(II) dichlorides

Polyisoprene (PI) with a high content of cis‐1,4 (up to 95%) or cis‐1,4/3,4 binary structures was synthesized using a cobalt system in toluene. The cobalt system, which exhibited high activities (up to 3.50 × 10⁶ g PI (mol Co)^?1 h^?1), contained a series of 2‐(benzimidazolyl)‐6‐(1‐(arylimino)ethyl)pyridine cobalt(II) dichlorides activated with ethylaluminium sesquichloride. The nature of the ligands and the reaction conditions significantly affected both the catalytic performance of the cobalt complexes as well as the structures of the resultant PI. The stereospecific polymerization of isoprene could be tuned via changing either the co‐catalyst or solvent: for example, increased content of 3,4 PI (up to 36.6%) was achievable in heptane in the presence of diethylaluminium chloride. Sequence distribution analysis by ¹³C NMR spectroscopy indicated that most 3,4 units occurred randomly in the PI chains. © 2013 Society of Chemical Industry     

Study of the synthesis of chitosan derivatives containing benzo‐21‐crown‐7 and their adsorption properties for metal ions

Three new chitosan crown ethers, N‐Schiff base‐type chitosan crown ethers (I, III), and N‐secondary amino type chitosan crown ether (II) were prepared. N‐Schiff base‐type chitosan crown ethers (I, III) were synthesized by the reaction of 4′‐formylbenzo‐21‐crown‐7 with chitosan or crosslinked chitosan. N‐Secondary amino type chitosan‐crown ether (II) was prepared through the reaction of N‐Schiff base type chitosan crown ether (I) with sodium brohydride. Their structures were characterized by elemental analysis, infrared spectra analysis, X‐ray diffraction analysis, and solid‐state ¹³C NMR analysis. In the infrared spectra, characteristic peaks of C?N stretch vibration appeared at 1636 cm^?1 for I and 1652 cm^?1 for II; characteristic peaks of N? H stretch vibration appeared at 1570 cm^?1 in II. The X‐ray diffraction analysis showed that the peaks at 2θ = 10° and 28° disappeared in chitosan derivatives I and III, respectively; the peak at 2θ = 10° disappeared and the peak at 2θ = 28° decreased in chitosan‐crown ether II; and the peak at 2θ = 20° decreased in all chitosan derivatives. In the solid‐state ¹³C NMR, characteristic aromatic carbon appeared at 129 ppm in all chitosan derivatives, and the characteristic peaks of carbon in C?N groups appeared at 151 ppm in chitosan crown ethers I and III. The adsorption and selectivity properties of I, II, and III for Pd²⁺, Au³⁺, Pt⁴⁺, Ag⁺, Cu²⁺, and Hg²⁺ were studied. Experimental results showed these adsorbents not only had good adsorption capacities for noble metal ions Pd²⁺, Au³⁺, Pt⁴⁺, and Ag⁺, but also high selectivity for the adsorption of Pd²⁺ with the coexistence of Cu²⁺ and Hg²⁺. Chitosan‐crown ether II only adsorbs Hg²⁺ and does not adsorbs Cu²⁺ in an aqueous system containing Pd²⁺, Cu²⁺, and Hg²⁺. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1886–1891, 2002     

Microencapsulation of tannase by chitosan–alginate complex coacervate membrane: synthesis of antioxidant propyl gallate in biphasic media

Tannase microencapsulated by a chitosan–alginate complex coacervate membrane has been used for synthesis of the food additive antioxidant, propyl gallate. Matrix experiments using standard L9 orthogonal array were used to evaluate the effects of the microencapsulation process on the synthesis of propyl gallate in biphasic media. The statistical analysis of signal‐to‐noise ratio and decomposition of variance (ANOVA) were performed to estimate the optimum levels and determine the relative magnitude of the effects of the three control factors which were chitosan, alginate and hardening time. The optimized capsule for synthesis was formed by dropwise addition of a 15 kg m^?3 chitosan and 20 kg m^?3 CaCl₂ solution into a 14 kg m^?3 alginate solution, stirred for 20 min, then hardened for 30 min in 20 kg m^?3 CaCl₂. Copyright © 2004 Society of Chemical Industry