[Adsorption Behavior of Pb(â ¡) Ion Imprinted Magnetic Composite Adsorbent in Aqueous Solution by FAAS].

Pb(Ⅱ) Ion Imprinted Magnetic Composite Adsorbent (Pb(Ⅱ)-MICA) was prepared for the quick separation of Pb(Ⅱ) from aqueous solutions by bulk polymenrization with chitosan as the functional monomer, the magnetic iron oxide nano-particles as carrier and epichlorohydrin as the cross-link agent. The Pb(Ⅱ)-MICA and MNICA were characterized by FTIR. The Effects of the adsorption process including pH, contact time, initial concentration and temperature were investigated by FAAS. It was found that with the increasing of PH value, the adsorption capacity of Pb(Ⅱ)-MICA for Pb(Ⅱ) reached the peak in the range of pH 5.0～6.0. The maximum adsorption capacity was 32.48 mg·g-1 when the adsorption time was up to 120 min. The relative selectivity coefficient of Pb(Ⅱ) and other metal ion on Pb(Ⅱ) -MICA were 28.11, 91.14, 76.54, 33.06 times compared with MNICA. The results show that the Pb(Ⅱ)-MICA displayed strong affinity for Pb(Ⅱ) in the solution and exhibited selectivity for Pb(Ⅱ) ion in the presence of Cu2+，Cd2+，Ni2+ and Zn2+. The Langmuir adsorption isotherm models were fit to the adsorption equilibrium data well (r2=1, the saturation adsorption capacities were 33.87 mg·g-1). The adsorption dynamics and thermodynamics of Pb(Ⅱ) -MICA for Pb(Ⅱ) were investigated, the results indicated a Langmuir mono-layer mode process of Pb(Ⅱ) on the Pb(Ⅱ)-MICA was dominated by chemical action. An exothermic and spontaneous adsorption process of Pb(Ⅱ) on the Pb(Ⅱ)-MICA was driven by enthalpy.

[Preparation of polyacrylonitrile/natural sand composite materials and analysis of adsorption properties of Pb(II) on it by FAAS].

Surfaces of natural sand particles were modified with (3-chloropropyl) trichlorosilane, so that bridging groups were introduced on the surfaces of natural sand particles; By grafting polyacrylonitrile onto the modified surfaces of the natural sand particles, a novelpolyacrylonitrile/natural sand composite material was prepared from the acrylonitrile, the azobisisobutyronitrile, the divinylbenzene and the modified natural sand particles, which are as functional monomer, initiator, either skeleton monomer or cross-linking agent and carrier respectively; the composite materials were characterized by using infrared spectroscopy and scanning electron microscopy; On the FTIR spectrum, the main characteristic peaks of various functional groups including nitrile, benzene ring, and silicon hydroxyl, which were from functional monomer, cross-linking agent and carrier respectively, were observed. On the SEM, two different cross section morphologies having different density which were from acrylonitrile and modified sand particles were observed; This proved that the polyacrylonitrile was decorated on modified sand particles during our preparation process. After preparing the composite materials, micro-column of separation and preconcentration was prepared using the composite materials as filler; the adsorption of some toxic heavy metal ions onto the composite materials was observed by flame atomic absorption spectrometry (FAAS); The results show that the adsorption of Pb2+ onto the composite materials was more stronger than the absorption of other toxic heavy metal ions, therefore, in this paper, the adsorption of Pb2+ onto the composite materials was mainly studied, at room temperature, when pH and flow rate of solution were 5. 4 and 4 mL x min(-1) respectively, the trace Pb(II) ions could be quantitatively adsorbed onto the composite materials; the maximum adsorption capacity of Pb(II) on the composite materials can reach 62.9 mg x g(-1). The column was eluted by 0.5 mol x L(-1) HCl and recovery of Pb(II) was more than 96%.

Photopolymerisation and characterization of maleylatedcellulose-g-poly(acrylic acid) superabsorbent polymer.

A novel biodegradable superabsorbent polymer has been prepared from maleylated cotton stalk cellulose (MCSC) crosslinker and acrylic acid (AA) by ultraviolet (UV) photopolymerization in aqueous solution at room temperature, and irgacure 651 as a photoinitiator. The resulting superabsorbent was characterized by FT-IR, (1)H NMR, SEM and TGA. The effects of preparation conditions such as degree of substitution (DS), amount of maleylated cotton stalk cellulose, exposed time, photoinitiator amount and monomer concentration on the water absorbency and the monomer conversion in graft were evaluated. The swelling kinetics, salt-resistance, water retention capacity and biodegradability of the MCSC-g-PAA superabsorbent were investigated. It was found that, the obtained superabsorbent have good swelling degree that greatly affected by its composition and preparation conditions. Owing to its considerable good water retention capacity, being economical and environment-friendly, it might be useful for its application in agriculture field.

[Synthesis of crosslinked polymer containing beta-cyclodextrin and its adsorption for Pb2+ and Zn2+ studied by AAS].

Crosslinked copolymer(AA/beta-CD-AA/ABE) containing beta-cyclodextrin was synthesized by microwave heating with acylation, allyl-biphenyl-ether(ABE), crylic acid(AA) as monomer and N, N-methylenebisacrylamide (MBA) as cross-linking agent, and characterized by means of FTIR. The adsorption of Pb2+ and Zn2+ on the synthesized copolymer and the factors (adsorption time, pH and temperature) which affect the adsorption capacity were investigated by atomic absorption spectrometry (AAS) as the detection means. The results show that the optimum experimental conditions of adsorption: 35 degrees C, 2 h and pH 2-3, adsorbance Q for Pb2+ reached maximum 29.5 mg x g(-1); 30 degrees C, 3 h and pH 3-4, adsorbance Q for Zn2+ reached maximum 43.7 mg x g(-1); the adsorption equilibriums for Pb2+ and Zn2+ fit the Freundlich on the whole.

[Study on the adsorption behavior of beads of maleic anhydride-co-styrene to Pb(II) by FAAS].

The crosslinked polymer beads was synthesized by free emulsion polymerization using maleic anhydride and styrene. The chemical structure and morphology of the polymer beads were analyzed using FTIR and SEM. And the dynamic adsorption properties of beads for Pb(II) was studied by atomic adsorption spectrometry(AAS). The relevant factors influencing adsorption and desorption were investigated. The results showed that in the solution at pH 5, when the sample flow rate was 1.0 mL x min(-1), the adsorption rate of Pb(II) reached more than 95%. Using 1 moL x L(-1) nitrate acid as the best eluant the absorbates were desorbed at the flow rate of 0.5 mL x min(-1), the recovery of Pb(II) reached more than 99%. Under the optimum conditions, the adsorption capacity could be up to 26.5 mg x g(-1), the detection limits(3sigma11) were 2.1 microg x L(-1) and relative standard deviation (RSD) was 2.5%. The method has been applied to the determination of trace lead in water samples with satisfactory results.

Solid-state synthesis of poly(3',4'-dimethoxy-2,2':5',2"- terthiophene): comparison with poly(terthiophene) and poly(3',4'-ethylenedioxy-2,2':5',2"- terthiophene).

A new terthiophene monomer: 3',4'-dimethoxy-2,2':5',2"-terthiophene (TMT) was synthesized and characterized by ¹H-NMR, ¹³C-NMR and FTIR. The solid-state oxidative polymerizations of TMT were performed in various ratios of oxidant (FeCl3) to monomer (TMT). The resulting polymers were characterized by ¹H-NMR, FTIR, UV-vis-NIR, GPC, X-ray diffraction, CV, as well as TGA and conductivity measurements. The structure and properties of poly (TMT) were compared with those of polyterthiophene [poly(TT)] and poly (3',4'-ethylenedioxy-2,2':5',2"-terthiophene) [poly(TET)] prepared under the same polymerization conditions. After comparative analysis with poly(TT) and poly(TET), the effects of the dimethoxy substituent and FeCl3 on the structural and physicochemical properties of the poly(TMT)s were discussed in depth. The comparison suggested that the dimethoxy-substituted polymer did not display higher crystallinity, thermal stability, conductivity and electrochemical activity than ethylenedioxy substituted one. The results also showed that the effect of FeCl3 on poly(TMT) was similar that seen with the poly(TT), in which the oxidation degree, electrochemical activity and conductivity increased steadily with increasing [FeCl3/[TT] ratio. Furthermore, the poly(TMT) and poly(TT) are mostly made up of dimers with a small amount of higher molecular weight components.

Transfer of photoenergy in pi-conjugated polymers. Two types of photoluminescence that involve energy transfer along a polymer chain.

Two types of energy transfer in pi-conjugated polymers have been investigated using time-resolved photoluminescence (PL) techniques: type i, perpendicular-type energy transfer from the 2,3-di(p-tolyl)quinoxaline unit to the pi-conjugated main chain of poly[2,3-di(p-tolyl)quinoxaline-5,8-diyl], and type ii, parallel-type energy transfer from the oligo(pyridine-2,5-diyl) (O-Py) unit to the oligo(selenophene-2,5-diyl) (O-Se) unit in a block-type copolymer of O-Py and O-Se. Both types of energy transfer were very fast with a time constant shorter than approximately 0.1 ns; in particular, the type ii energy transfer took place with a time constant of approximately 5 ps. Both pi-conjugated polymers were considered to contain segments with various effective pi-conjugation lengths, and the energy transfer to the segment with a larger effective pi-conjugation length and a smaller pi-pi* transition energy required a longer transition time. A polarizing film was obtained by utilizing the perpendicular-type energy transfer.