Igberase E, Osifo P, Ofomaja A
a Department of Chemical Engineering , Vaal University of Technology , Vanderbijlpark , South Africa.
Environ Technol. 2017 Dec;38(24):3156-3166. doi: 10.1080/09593330.2017.1290152. Epub 2017 Feb 21.
Chitosan outstanding qualities and efficient way of binding metal ions even to near zero concentration is the major reason for special attention. Modification of chitosan allows the polymer to be applied in numerous field of research. Depending on the modification techniques, chitosan possesses increased adsorption capacity. In this study chitosan beads (CS) were formulated from chitosan flakes, the beads were cross-linked with glutaraldehyde and thereafter grafted with ethyldiaminetetraacetic acid. The stability and amine concentration of the beads were determined. The chemical functionalities of the beads were obtained by Fourier transform infrared spectroscopy, X-ray diffraction and thermogravimetric analysis (TGA). However, in the adsorption studies with Cr(VI), the number of runs in the experiment was obtained by response surface methodology (RSM), and the maximum adsorption capacity (Q) from each run was determined from the Langmuir model. The results of the experiment showed that the non-modified beads were soluble at pH 1-4 and insoluble at pH 5, while the modified beads were insoluble at pH 1-6. The amine concentration of CS, CCS and grafted cross-linked chitosan beads (GCCS) were 4.4, 3.8 and 5.0 mmol/g, respectively. The point of zero charge (pH) of GCCS was found to be 4.4. The quadratic model was significant and adequate in describing the experimental data. The difference between experimental and predicted Q was negligible. From the design matrix and results, increased Q was achieved at pH 5, contact time 70 min, temperature 45°C, adsorbent dosage 5 g and initial concentration 70 mg/l. The desorption of the beads loaded with Cr(VI) was successful with 0.5 M HCl eluant and contact time of 180 min, leading to cost minimization.
壳聚糖具有卓越品质以及能将金属离子结合至近乎零浓度的高效方式，这是其受到特别关注的主要原因。壳聚糖的改性使得该聚合物能够应用于众多研究领域。根据改性技术的不同，壳聚糖的吸附能力会有所增强。在本研究中，壳聚糖珠粒（CS）由壳聚糖薄片制成，这些珠粒用戊二醛交联，随后用乙二胺四乙酸接枝。测定了珠粒的稳定性和胺浓度。通过傅里叶变换红外光谱、X射线衍射和热重分析（TGA）获得了珠粒的化学官能团。然而，在对Cr(VI)的吸附研究中，实验中的运行次数通过响应面法（RSM）获得，每次运行的最大吸附容量（Q）由朗缪尔模型确定。实验结果表明，未改性的珠粒在pH 1 - 4时可溶，在pH 5时不溶，而改性后的珠粒在pH 1 - 6时不溶。CS、交联壳聚糖珠粒（CCS）和接枝交联壳聚糖珠粒（GCCS）的胺浓度分别为4.4、3.8和5.0 mmol/g。发现GCCS的零电荷点（pH）为4.4。二次模型在描述实验数据方面具有显著性和充分性。实验值与预测值Q之间的差异可忽略不计。从设计矩阵和结果来看，在pH 5、接触时间70分钟、温度45°C、吸附剂用量5 g和初始浓度70 mg/l时实现了Q的增加。用0.5 M HCl洗脱剂和180分钟的接触时间成功实现了负载Cr(VI)的珠粒的解吸，从而使成本最小化。
