Chang Yang-Chuang, Chen Dong-Hwang
Department of Chemical Engineering, National Cheng Kung University, Tainan, Taiwan 701, Taiwan.
Macromol Biosci. 2005 Mar 15;5(3):254-61. doi: 10.1002/mabi.200400153.
The monodisperse chitosan-conjugated Fe(3)O(4) nanoparticles with a mean diameter of 13.5 nm were fabricated by the carboxymethylation of chitosan and its covalent binding onto Fe(3)O(4) nanoparticles via carbodiimide activation. The carboxymethylated chitosan (CMCH)-conjugated Fe(3)O(4) nanoparticles with about 4.92 wt.-% of CMCH had an isoelectric point of 5.95 and were shown to be quite efficient as anionic magnetic nano-adsorbent for the removal of acid dyes. Both the adsorption capacities of crocein orange G (AO12) and acid green 25 (AG25), as the model compounds, decreased with increasing pH, and the decreasing effect was more significant for AO12. On the contrary, the increase in the ionic strength decreased the adsorption capacity of AG25 but did not affect, obviously, the adsorption capacity of AO12. By the addition of NaCl and NaOH, both AO12 and AG25 could desorb and their different desorption behavior could be attributed to the combined effect of pH and ionic strength. From the adsorption kinetics and thermodynamics studies, it was found that both the adsorption processes of AO12 and AG25 obeyed the pseudo-second-order kinetic model, Langmuir isotherm, and might be surface reaction-controlled. Furthermore, the time required to reach the equilibrium for each one was significantly shorter than those using the micro-sized adsorbents due to the large available surface area. Also, based on the weight of chitosan, the maximum adsorption capacities were 1 883 and 1 471 mg x g(-1) for AO12 and AG25, respectively, much higher than the reported data. Thus, the anionic magnetic nano-adsorbent could not only be magnetically manipulated but also possessed the advantages of fast adsorption rate and high adsorption capacity. This could be useful in the fields of separation and magnetic carriers. [formula in text].
通过壳聚糖的羧甲基化反应及其经由碳二亚胺活化共价结合到Fe(3)O(4)纳米颗粒上，制备了平均直径为13.5 nm的单分散壳聚糖共轭Fe(3)O(4)纳米颗粒。具有约4.92 wt.-%羧甲基化壳聚糖(CMCH)的CMCH共轭Fe(3)O(4)纳米颗粒的等电点为5.95，并且显示出作为用于去除酸性染料的阴离子磁性纳米吸附剂相当有效。作为模型化合物的藏红橙G(AO12)和酸性绿25(AG25)的吸附容量均随pH升高而降低，且对AO12的降低作用更显著。相反，离子强度的增加降低了AG25的吸附容量，但对AO12的吸附容量没有明显影响。通过添加NaCl和NaOH，AO12和AG25均可解吸，且它们不同的解吸行为可归因于pH和离子强度的综合作用。从吸附动力学和热力学研究发现，AO12和AG25的吸附过程均遵循准二级动力学模型、朗缪尔等温线，并且可能受表面反应控制。此外，由于具有大的可用表面积，每种物质达到平衡所需的时间明显短于使用微米尺寸吸附剂的时间。同样，基于壳聚糖的重量，AO12和AG25的最大吸附容量分别为1883和1471 mg x g(-1)，远高于报道的数据。因此，这种阴离子磁性纳米吸附剂不仅可以进行磁控操作，而且具有吸附速率快和吸附容量高的优点。这在分离和磁性载体领域可能是有用的。[文中公式]
