Metal-Organic Framework-101 (MIL-101): Synthesis, Kinetics, Thermodynamics, and Equilibrium Isotherms of Remazol Deep Black RGB Adsorption

Hindawi Journal of Chemistry Volume 2018, Article ID 8616921, 14 pages https://doi.org/10.1155/2018/8616921 Research Article Metal-Organic Framework-101 (MIL-101): Synthesis, Kinetics, Thermodynamics, and Equilibrium Isotherms of Remazol Deep Black RGB Adsorption Vo Thi Thanh Chau,1 Huynh Thi MinhThanh,2 Pham Dinh Du,3 Tran Thanh Tam Toan,4 Tran Ngoc Tuyen,4 Tran Xuan Mau ,4 and Dinh Quang Khieu 4 1 Tran Quoc Tuan High School, Quảng Ngãi 570000, Vietnam Department of Chemistry, Qui Nhon University, Bı̀nh Ðịnh 590000, Vietnam 3 Faculty of Natural Sciences, Thu Dau Mot University, Thủ Dầu Một 820000, Vietnam 4 University of Sciences, Hue University, Hue 530000, Vietnam 2 Correspondence should be addressed to Dinh Quang Khieu; Received 7 January 2018; Revised 11 April 2018; Accepted 14 May 2018; Published 24 June 2018 Academic Editor: Hossein Kazemian Copyright © 2018 Vo Thi Thanh Chau et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. In the present paper, the synthesis of metal-organic framework-101 (MIL-101) and Remazol Deep Black RGB (RDB) adsorption on MIL-101 were demonstrated. The kinetics of RDB adsorption on MIL-101 was studied using Weber’s intraparticle diffusion model and the pseudo-first- and pseudo-second-order kinetic models. Particularly, the statistical method of piecewise linear regression and multinonlinear regression was employed to analyse the adsorption data according to the previously mentioned kinetic models. The results indicated that the adsorption process followed the three-step pseudo-first-order kinetic equation, which was consistent with the results of the intraparticle diffusion model with three linear segments. This model best described the experimental data. In addition, the adsorption isotherm data were studied using five adsorption models, namely, Langmuir, Freundlich, Redlich–Peterson, Toth, and Sips in nonlinear forms, and the Langmuir model is the most appropriate for the experimental data. The values of energies of activation of adsorption were calculated, and they revealed that the adsorption process was of endothermic chemical nature. A statistical comparison using Akaike information criterion to estimate the goodness of fit of the kinetic and isotherm models was presented. 1. Introduction It is well known that wastewater from textile industries, pulp mills, and dyestuff manufacturing has been a potential threat to environment [1, 2]. Various treatment processes such as physical separation, chemical oxidation, and biological degradation have been widely investigated to remove dyes from wastewaters [3]. Among these processes, adsorption technology is considered as one of the most competitive methods because it does not require high operating temperature and has a simple operation as well as low cost, and several coloring materials can be removed simultaneously [4]. MIL-101 has demonstrated good performance in storage and adsorption of gas such as hydrogen storage [5], adsorption of CO2 and CH4 [6], and long-chain alkanes [7]. However, there are very few reports studying the adsorption of dyes from aqueous solutions [8–10]. MOFs in general and MIL-101 in particular exhibit high efficiency for adsorption of dyes from aqueous solutions due to their unique structures such as large surface areas, ordered porosity, and high density of adsorption sites (anion and cation). MIL-101 demonstrates excellent adsorption properties for dyes, such as methyl orange (MO), xylenol orange (XO), and uranine. For expanding applications of MIL-101, studying the adsorption of this material for Remazol Deep Black RGB (denoted as RDB) used widely in dye industry will be a concern of this work. Azo dyes with an azo group are widely used in many textile industries due to their low cost, high solubility, and stability. These dyes and their intermediate products are toxic, carcinogenic, and mutagenic to aquatic life. Remazol Deep Black RGB is a common diazo reactive dye, widely used in textile industries [11]. It is stable and hard to degrade biologically due 2 Journal of Chemistry OH NaO3SOCH2CH2O2S NH2 N=N N=N NaO3S SO3Na SO2CH2CH2OSO3Na Scheme 1: Molecular structure of RDB. to the presence of aromatic rings. Thus, RDB removal from textile wastewater has drawn much attention among researchers. Several techniques including adsorption, electrochemistry, and biosorption for RDB treatment have been reported. Soloman et al. [11] applied the electrochemical treatment to hydrolyze Remazol Black. They demonstrated that the performance of the batch recirculation system was better than other reactor configurations studied in terms of capacity utilization and energy consumption. Brazilian pine-fruit shells (Araucaria angustifolia) in their natural form were used as an adsorbent for the removal of RDB dye from aqueous effluents [12]. A biosorption process to discard azo dyes by fungi (Aspergillus flavus) was investigated in batch reactors [13]. Ninety percent of the dye in a 100 mg/L solution was removed. Recently, Thanh et al. [14] reported that iron doping to ZIF-8 significantly enhances RDB adsorption capacity. Fe–ZIF-8 also exhibits photocatalytic degradation of RDB under visible light [15]. Batch adsorption studies focus on two main trends: (i) designing and optimizing experiments with the evaluation of the influence of the experimental variables—this approach enables to estimate the magnitude of the influence of the factors affecting the process and their interactions [16]—and (ii) kinetics, thermodynamics, and equilibrium isotherm adsorption studies [14, 17]. For the latter, several models are used to study adsorption kinetics and isotherms. The parameters in these models are calculated with linear or nonlinear regression approaches. However, the number of parameters in each mode is different. For example, the Langmuir isotherm model contains two parameters, while the Redlich–Peterson isotherm model has three parameters. It is obvious that the greater the number of model parameters, the lower the relative errors (REs) or the sum of squared errors (SSEs). Therefore, the model compatibility needs to be evaluated including SSEs or REs and the number of model parameters as well as the experimental points. However, in the majority of current publications, the goodness of fit for models is estimated based on only the REs or SSEs. To the best of our knowledge, the research on this issue is limited. In the present study, MIL-101 was employed as an adsorbent for removing RDB dye. The effects of initial concentration, adsorbent particle size, agitation speed, temperature, and pH on the adsorption behavior of RDB onto MIL-101 were investigated. The adsorption kinetic and isothermal studies and the goodness of fit for models were addressed. 2. Experimental 2.1. Materials. Chromium (III) nitrate nona (...truncated)