Dragan Ecaterina Stela, Apopei Loghin Diana Felicia, Cocarta Ana Irina
"Petru Poni" Institute of Macromolecular Chemistry , Grigore Ghica Voda Alley 41 A, Iasi 700487, Romania.
ACS Appl Mater Interfaces. 2014 Oct 8;6(19):16577-92. doi: 10.1021/am504480q. Epub 2014 Sep 17.
Ionic composites based on cross-linked chitosan (CS) as matrix and poly(amidoxime) grafted on potato starch (AOX) as entrapped chelating resin were prepared as beads, for the first time in this work, by two strategies: (1) thorough mixing of previously prepared AOX in the CS solution followed by the bead formation and (2) thorough mixing of the potato starch-g-poly(acrylonitrile) (PS-g-PAN) copolymer in the initial CS solution, followed by bead formation, the amidoximation of the nitrile groups taking place inside the beads. Ionotropic gelation in tripolyphosphate was used to obtain the composite beads, and in situ covalent cross-linking by epichlorohydrin was carried out to stabilize the beads in the acidic pH range. Fourier transform infrared spectroscopy and the swelling ratio values in the acidic pH range confirmed the influence of the synthesis strategy on the structure of the CS/AOX composites. Scanning electron microscopy was employed to reveal the morphology of the novel composites, both before and after their loading with Cu(2+). The binding capacity of Cu(2+) ions as a function of sorbent composition, synthesis strategy, pH, sorbent dose, contact time, initial concentration of Cu(2+), and temperature was examined in batch mode. The main difference between the composites prepared with the two strategies consisted of the higher sorption capacity and the much faster settlement of the equilibrium sorption for the composite prepared by the in situ amidoximation of PS-g-PAN. The Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, and Sips isotherms were applied to fit the sorption equilibrium data. The maximum equilibrium sorption capacity, qm, evaluated by the Langmuir model at 25 °C was 133.15 mg Cu(2+)/g for the CS/AOX composite beads prepared with the first strategy and 238.14 mg Cu(2+)/g for the CS/AOX composite beads prepared with the second strategy, at the same AOX content. The pseudo-second order kinetic model well fitted the sorption kinetics data, supporting chemisorption as the mechanism of interaction between the chelating composites and the Cu(2+) ions. The CS/AOX composite sorbents could be reused up to five sorption/desorption cycles with no significant decrease in Cu(2+) sorption capacity.
在本研究中，首次采用两种策略制备了以交联壳聚糖（CS）为基质、接枝在马铃薯淀粉上的聚偕胺肟（AOX）为包埋螯合树脂的离子复合材料微球：（1）将预先制备的AOX充分混合于CS溶液中，随后形成微球；（2）将马铃薯淀粉-g-聚（丙烯腈）（PS-g-PAN）共聚物充分混合于初始CS溶液中，随后形成微球，腈基的偕胺肟化反应在微球内部进行。采用三聚磷酸钠中的离子凝胶化法制备复合微球，并通过环氧氯丙烷进行原位共价交联，以在酸性pH范围内稳定微球。傅里叶变换红外光谱和酸性pH范围内的溶胀率值证实了合成策略对CS/AOX复合材料结构的影响。采用扫描电子显微镜揭示了新型复合材料在负载Cu(2+)前后的形态。以分批模式研究了Cu(2+)离子的结合容量与吸附剂组成、合成策略、pH、吸附剂剂量、接触时间、Cu(2+)初始浓度和温度的关系。两种策略制备的复合材料之间的主要差异在于，通过PS-g-PAN原位偕胺肟化制备的复合材料具有更高的吸附容量和更快的平衡吸附沉降速度。应用Langmuir、Freundlich、Temkin、Dubinin-Radushkevich和Sips等温线拟合吸附平衡数据。在相同AOX含量下，由Langmuir模型在25℃评估的最大平衡吸附容量qm，对于采用第一种策略制备的CS/AOX复合微球为133.15 mg Cu(2+)/g，对于采用第二种策略制备的CS/AOX复合微球为238.14 mg Cu(2+)/g。准二级动力学模型很好地拟合了吸附动力学数据，支持化学吸附作为螯合复合材料与Cu(2+)离子之间的相互作用机制。CS/AOX复合吸附剂可重复使用多达五个吸附/解吸循环，Cu(2+)吸附容量无显著下降。
