Department of Chemistry, Vaal University of Technology, P. Bag X021, Vanderbiljpark, 1900, South Africa; Department of Chemistry/Biochemistry & Molecular Biology, Federal University, Ndufu Alike Ikwo (FUNAI), Ebonyi State, Nigeria.
Department of Chemistry, Vaal University of Technology, P. Bag X021, Vanderbiljpark, 1900, South Africa.
J Environ Manage. 2018 Jul 15;218:139-147. doi: 10.1016/j.jenvman.2018.04.060. Epub 2018 Apr 17.
The realization that the observed kinetic coefficient (k) varies with time in most real-time adsorption system, as against the constant value conceived in the most widely-applied adsorption kinetic models, have attracted much attention in recent time. Understanding the factors that control the extent/degree of time dependency (otherwise known as fractal-like kinetics), is therefore central in taking manipulative advantage of this phenomenon in critical adsorption applications. This study therefore deployed non-fractal-like and fractal-like kinetic approach to study the adsorption of tetracycline on monodispersed starch-stabilized magnetite nanocomposite (MSM). MSM was synthesized by in-situ coprecipitation of magnetite in the presence of starch, and successfully characterized with classical solid-state techniques. Isotherm studies indicated that MSM has heterogenous surface adsorption sites. Equilibrium and kinetic data indicated the existence of π-cation interaction as the underlying mechanism, while pH study revealed that tetracycline was adsorbed in its zwitterion form. Though the non-fractal kinetic models exhibited some level of relevance in explaining the tetracycline adsorption interactions, the best fitting of the fractal-like pseudo second order model to the adsorption kinetic data, indicated that the real-time adsorption kinetics occurred in fractal-like manner. The study also revealed that the degree of time dependency of k had negative correlation with the initial tetracycline concentration. Apart from developing a low-cost strategy for addressing tetracycline water pollution, the result of this study serves a positive step towards gaining manipulative control of adsorption mechanism in potential application of MSM for targeted drug delivery and controlled release of tetracycline antibiotics.
最近，人们意识到在大多数实时吸附系统中，观察到的动力学系数 (k) 随时间变化，而不是在最广泛应用的吸附动力学模型中设想的恒定值，这引起了广泛关注。因此，理解控制时间依赖性程度的因素（也称为分形动力学）对于在关键吸附应用中利用这种现象具有重要意义。本研究因此采用非分形和分形动力学方法研究了四环素在单分散淀粉稳定磁铁矿纳米复合材料（MSM）上的吸附。MSM 通过在淀粉存在下原位共沉淀合成，并通过经典的固态技术成功进行了表征。等温研究表明，MSM 具有异质表面吸附位。平衡和动力学数据表明，π-阳离子相互作用是潜在的机制，而 pH 值研究表明四环素以两性离子形式被吸附。虽然非分形动力学模型在解释四环素吸附相互作用方面表现出一定程度的相关性，但分形拟二级模型对吸附动力学数据的最佳拟合表明，实时吸附动力学以分形方式发生。该研究还表明，k 的时间依赖性程度与初始四环素浓度呈负相关。除了开发一种低成本策略来解决四环素水污染问题外，这项研究的结果还朝着在潜在应用中对吸附机制进行操纵控制迈出了积极的一步，例如将 MSM 用于靶向药物输送和四环素抗生素的控制释放。
