Chunnuan Ji

Adsorption of Pb(II) from aqueous solution by silica-gel supported hyperbranched polyamidoamine dendrimers.

The adsorption properties of silica-gel supported hyperbranched polyamidoamine dendrimers (SiO(2)-G0-SiO(2)-G4.0) have been investigated by batch method. The effect of pH of the solution, contact time, initial Pb(II) ion concentration, temperature and coexisting metal ions have been demonstrated. The results indicated that the optimum pH value was 5. Adsorption kinetics was found to follow the pseudo-second-order model and controlled by film diffusion. The adsorption isotherms were fitted by Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models. Langmuir isotherm model was found to be more suitable to describe the equilibrium data, suggesting the uptake of Pb(II) ions by monolayer adsorption. From D-R isotherm model, the calculated mean free energy E demonstrated the adsorption processes occurred by chemical ion-exchange mechanism. FTIR analysis revealed that amine groups were mainly responsible for the adsorption of Pb(II) by amino-terminated adsorbents, while CO of ester groups also participated in the adsorption process of ester-terminated ones. The adsorbents can selectively adsorb Pb(II) from binary ion systems in the presence of Mn(II), Cu(II), Co(II), and Ni(II). Based on the results, it is concluded that SiO(2)-G0-SiO(2)-G4.0 had great potential for the removal of Pb(II) from aqueous solution.

Adsorption behaviors of Hg(II) on chitosan functionalized by amino-terminated hyperbranched polyamidoamine polymers

The adsorption behaviors of Hg(II) on adsorbents, chitosan functionalized by generation 1.0-3.0 of amino-terminated hyperbranched polyamidoamine polymers (denoted as CTS-1.0, CTS-2.0 and CTS-3.0, respectively), were studied. The optimum pH corresponding to the maximum adsorption capacities was found to be 5.0 for the three adsorbents. The experimental equilibrium data of Hg(II) on the three adsorbents were fitted to the Freundlich and the Langmuir models, and it is found that the Langmuir isotherm was the best fitting model to describe the equilibrium adsorption. The kinetics data indicated that the adsorption process of Hg(II) ions on CTS-1.0, CTS-2.0 and CTS-3.0 were governed by the film diffusion and followed pseudo-second-order rate model. Thermodynamic analysis and FTIR analysis revealed that the adsorption behaviors of Hg(II) ions on the three adsorbents could be considered as spontaneous, endothermic and chemical sorption process, resulting in their higher adsorption capacities at higher temperature.

Synthesis of porous acrylonitrile/methyl acrylate copolymer beads by suspended emulsion polymerization and their adsorption properties after amidoximation

Porous acrylonitrile (AN)/methyl acrylate (MA) copolymer beads were prepared by suspended emulsion polymerization. The cyano groups in AN/MA copolymer beads were converted to amidoxime (AO) groups by reaction with hydroxylamine hydrochloride (NH(2)OH.HCl) to remove metal ions in aqueous solution. The untreated AN/MA and amidoximated AN/MA (AO AN/MA) copolymer beads were characterized by FTIR spectroscopy, SEM, and porous structural analysis. Both mesopores and macropores were presented in AN/MA and AO AN/MA copolymer beads. Qualitative experiments of adsorption were conducted to evaluate modified and unmodified resins on fixing Hg(2+), Ag(+), Cu(2+), Fe(3+) and Pb(2+) from aqueous solution using batch extractions. It was found that AO AN/MA copolymer beads have excellent adsorption capacities for Hg(2+), Ag(+) and Cu(2+), especially for Hg(2+), and it have good selectivity for Hg(2+). The equilibrium was established in 10h through adsorption kinetics study. The Langmuir model was much better than the Freundlich model to describe the isothermal process.

Removal and recovery of Hg(II) from aqueous solution using chitosan-coated cotton fibers

Two types of chitosan-coated cotton fibers (SCCH and RCCH) were applied to remove and recover Hg(II) ions in aqueous solution. The adsorption kinetics and isotherms of the two fibers for Hg(II) were investigated at different temperatures. The results revealed that the adsorption kinetic processes of SCCH and RCCH fibers for Hg(II) followed the pseudo second-order model at lower temperatures and the pseudo first-order model at higher temperatures. Both the Langmuir and Freundlich models well described the adsorption isotherms of SCCH and RCCH fibers for Hg(II) in the temperature range studied. SCCH and RCCH fibers selectively adsorbed Hg(II) from binary ion systems in the presence of Pb(II), Cu(II), Ni(II), Cd(II), Zn(II), Co(II), Mn(II) and Ag(I). Increased temperature was beneficial to adsorption. The recovery of Hg(II) from aqueous solutions was also studied as a function of sample flow rate and volume, concentration and volume of eluent, elution rate, quantity of adsorbents added and concomitant ions. The results showed that the two fibers efficiently enriched and recovered Hg(II) in the presence of alkali and alkaline earth metals and some heavy metals under optimum conditions. The RCCH fiber exhibited better stability than the SCCH fiber following repeated use.

Preparation and adsorption properties of crosslinked polystyrene-supported low-generation diethanolamine-typed dendrimer for metal ions

Two novel chelating resins, polystyrene supported G1.0 diethanolamine-typed dendrimer (PS-DEA) and G2.0 diethanolamine-typed dendrimer (PS-(DEA)(2)), were prepared by anchoring low-generations diethanolamine-typed dendrimer into crosslinked polystyrene in this paper. Fourier transform-infrared spectra (FTIR), scanning electron microscopy (SEM) and elemental analysis were employed to character their structures. The results of adsorption for metal ions showed that the resins had good adsorption capacities for Cu(2+), Ag(+) and Hg(2+), especially PS-DEA for Cu(2+). The adsorption kinetics and adsorption isotherms of PS-DEA for Cu(2+) and PS-(DEA)(2) for Hg(2+) were studied. The results showed that the adsorption kinetics of the two resins can be modeled by pseudo second-order rate equation wonderfully and Langmuir and Freundlich equations could well interpret the adsorption of PS-(DEA)(2) for Hg(2+) and PS-DEA for Cu(2+), respectively. The adsorption mechanism of the resins for Cu(2+) was confirmed by X-ray photoelectron spectroscopy (XPS).

A chelating resin with bis [2 -(2 -benzothiazolylthioethyl )sulfoxide] : Synthesis, characterization and properties for the removal of trace heavy metal ion in water samples

A new chelating resin containing bis[2-(2-benzothiazolylthioethyl)sulfoxide] was synthesized using chloromethylated polystyrene as material and characterized by elemental analysis and infrared spectra. The adsorption capacities of the newly formed resin for Hg(2+), Ag(+), Cu(2+), Zn(2+), Pb(2+), Mn(2+), Ni(2+), Cd(2+) and Fe(3+) were investigated over the pH range 1.0-6.0. The resin exhibited no affinity for alkali or alkaline earth metal ions. The maximum adsorption capacities of the resin for Hg(2+), Ag(+), Cu(2+), Zn(2+), Pb(2+), Mn(2+), Ni(2+), Cd(2+) and Fe(3+) were 1.49, 0.96, 0.58, 0.11, 0.37, 0, 0.24, 0.36 and 0.25mmolg(-1), respectively. In column operation it had been observed that Hg(2+) and Ag(+) in trace quantity could be separated from different binary mixtures and Hg(2+) could be effectively removed from industrial wastewater and the natural water spiked with Hg(2+) at usual pH.

Suspended Emulsion Copolymerization of Acrylonitrile with Methyl Acrylate: Effects of Reaction Parameters on the Polymerization

Acrylonitrile/methyl acrylate copolymers were synthesized by suspended emulsion polymerization with water as dispersed phase and monomers as continuous phase, potassium peroxydisulphate (KPS) as initiator, Span-80 as emulsifier, and poly(vinyl alcohol) (PVA) as suspending agent. Effects of reaction parameters such as water/monomer mass ratio, concentration of initiator, polymerization temperature and agitation rate on polymerization conversion and the particle size distribution of acrylonitrile/methyl acrylate copolymers were studied. It was found that polymerization conversion increased with an increase of water/monomer mass ratio, concentration of initiator and polymerization temperature, while the agitation rate had no significant effect on the polymerization conversion. Particle size distribution became narrower with an increase of water/monomer mass ratio and agitation rate. Under the same initiator concentration and polymerization temperature, particle size distribution became wider along with polymerization time. The differential scanning calorimetry (DSC) results indicated that the peak temperature of the copolymers decreased with increasing MA content.

Hg(II) adsorption using amidoximated porous acrylonitrile/itaconic copolymers prepared by suspended emulsion polymerization

Initially, porous acrylonitrile/itaconic acid copolymers (AN/IA) were prepared by suspended emulsion polymerization. Successively, the cyano groups in AN/IA copolymers were converted to amidoxime (AO) groups by the reaction with hydroxylamine hydrochloride. The structures of the AN/IA and amidoximated AN/IA (AO AN/IA) were characterized by infrared spectroscopy, scanning electron microscopy, and porous structural analysis. The adsorption properties of AO AN/IA for Hg(II) were investigated. The results show that AO AN/IA has mesopores and macropores, and surface area of 11.71 m(2) g(-1). It was found that AO AN/IA has higher affinity for Hg(II), with the maximum adsorption capacity of 84.25 mg g(-1). The AO AN/IA also can effectively remove Hg(II) from different binary metal ion mixture systems. Furthermore, the adsorption kinetics and thermodynamics were studied in detail. The adsorption equilibrium can quickly be achieved in 4 h determined by an adsorption kinetics study. The adsorption process is found to belong to the second-order model, and can be described by the Freundlich model.

Pore structure control factors of polyamine-bridged polysilsesquioxanes by sol–gel method and their structure-adsorption properties for Au(III)

ABSTRACT A series of bridged polysilsesquioxane (BPS) materials was synthesized by the sol–gel method from 3-chloropropyl trimethoxysilane, diethylenetriamine (DETA) or ethylenediamine. Tetraethyl orthosilicate (TEOS) and/or one of the two templates, hexadecyl trimethyl ammonium bromide (CTAB) or P123, were used in the co-condensation process to construct some of the porous adsorbents. The adsorption of Au(III) was the highest for samples without TEOS, especially for the DETA series with CTAB template. This study elucidates the synthesis and applications of BPS materials. Graphical Abstract

Preparation of Porous m -aramid/cellulose Blend Membranes with High Moisture and Air Permeability by an Enzymatic Degradation Method

Enzyme degradation method was adopted to prepare porous m-aramid/cellulose blend membranes with high air permeability, water absorbency and moisture permeability. This facile preparation process started by casting a blend membrane from a DMAc/LiCl solution containing m-aramid and cellulose. An enzyme was then used to degrade the cellulose in the blend membrane, resulting in porous structures. Five enzymes including cellulase, chitosanase, papain, lipase, and glucose oxidase, were evaluated and cellulase was found to be optimal. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to characterize the miscibility and the morphology of the m-aramid/cellulose blend membranes before and after degradation, respectively. The thermal stability of the blend membranes were characterized by thermogravimetric analysis (TGA). The properties including air permeability, water absorbency and moisture permeability of the m-aramid/cellulose blend membranes greatly improved after degradation as compared to those of the pure m-aramid. This paper provided a new approach to preparing novel textile materials with high comfortability.