Mallakpour Shadpour, Khadem Elham
Organic Polymer Chemistry Research Laboratory, Department of Chemistry, Isfahan University of Technology, Isfahan 84156-83111, Islamic Republic of Iran; Research Institute for Nanotechnology and Advanced Materials, Isfahan University of Technology, Isfahan 84156-83111, Islamic Republic of Iran.
Organic Polymer Chemistry Research Laboratory, Department of Chemistry, Isfahan University of Technology, Isfahan 84156-83111, Islamic Republic of Iran.
Sci Total Environ. 2019 Nov 10;690:1245-1253. doi: 10.1016/j.scitotenv.2019.06.431. Epub 2019 Jul 3.
In this research, crosslinked nanocomposite (NC) films involving chitosan (CS) and various percentages of nitrogen-doped graphene quantum dot (NGQD) were prepared via ultrasonic acoustic accompanied by adding glutaraldehyde as a crosslinking agent (henceforth nominated as CCS/NGQD NC). The objective of this study is the design of a safe adsorbent of CCS/NGQD NC under easy and low-cost conditions to investigate the mechanisms of Cd(II) ion sorption and find an appropriate model for the kinetics of removal. By comparing adsorption ability of CCS/NGQD NC films 2, 5 and 8 wt% under the same conditions, the CCS NC film with 5 wt% of NGQD was selected as the best mass ratio to investigate the adsorption process. To understand the nature of the sorption behavior, the experimental data were used to calculate pseudo-first-order, pseudo-second-order, and intra-particle diffusion kinetic models, and various isotherm models in linear and nonlinear regression. In addition, some error functions were applied to detect, either linear or nonlinear model is suitable to examine the experimental data and prevent any huge mistakes. The linear Freundlich equation well describes the uptake of Cd(II) ion by CCS film and CCS/NGQD NC film 5 wt%. Based on linear Langmuir, the maximum adsorption capacities of CCS film and CCS/NGQD NC film 5 wt% were 34.46 and 35.00 mg·g, respectively. Kinetic analysis indicates that the mechanism of removal is described by nonlinear pseudo-second order model for CCS film and linear pseudo-second order model for the CCS/NGQD NC film 5 wt%. Also, thermodynamic parameters were analyzed in different temperatures. The obtained thermodynamic values prove that Cd(II) ion adsorption on both adsorbents is feasible, spontaneous and endothermic.
在本研究中，通过超声辅助并添加戊二醛作为交联剂，制备了包含壳聚糖（CS）和不同百分比氮掺杂石墨烯量子点（NGQD）的交联纳米复合（NC）薄膜（以下简称CCS/NGQD NC）。本研究的目的是在简便且低成本的条件下设计一种安全的CCS/NGQD NC吸附剂，以研究Cd(II)离子的吸附机制，并找到合适的去除动力学模型。通过比较相同条件下2 wt%、5 wt%和8 wt%的CCS/NGQD NC薄膜的吸附能力，选择含有5 wt% NGQD的CCS NC薄膜作为最佳质量比来研究吸附过程。为了解吸附行为的本质，利用实验数据计算了伪一级、伪二级和颗粒内扩散动力学模型，以及线性和非线性回归中的各种等温线模型。此外，应用了一些误差函数来检测线性或非线性模型是否适合检验实验数据，并防止出现重大错误。线性Freundlich方程很好地描述了CCS薄膜和5 wt%的CCS/NGQD NC薄膜对Cd(II)离子的吸附。基于线性Langmuir模型，CCS薄膜和5 wt%的CCS/NGQD NC薄膜的最大吸附容量分别为34.46和35.00 mg·g。动力学分析表明，CCS薄膜的去除机制由非线性伪二级模型描述，5 wt%的CCS/NGQD NC薄膜的去除机制由线性伪二级模型描述。此外，还分析了不同温度下的热力学参数。获得的热力学值证明，两种吸附剂对Cd(II)离子的吸附都是可行的、自发的且吸热的。
