Synthesis of conductive polymer-coated mesoporous MCM-41 for textile dye removal from aqueous media

J Nanostruct Chem (2017) 7:217–229 DOI 10.1007/s40097-017-0232-7 ORIGINAL RESEARCH Synthesis of conductive polymer-coated mesoporous MCM-41 for textile dye removal from aqueous media Ali Torabinejad1 • Navid Nasirizadeh1 • Mohammad Esmail Yazdanshenas1 Habib-Allah Tayebi2 • Received: 4 March 2017 / Accepted: 27 June 2017 / Published online: 19 July 2017 Ó The Author(s) 2017. This article is an open access publication Abstract In this paper, we aimed to evaluate Acid Blue 62 removal from aqueous media, using mesoporous silicate MCM-41, loaded with polypyrrole (PPy) and polyaniline (PAni) composites. PPy/MCM-41 nanocomposite showed higher performance than PAni/MCM-41 due to its smaller molecule size. For characterizing the synthesized composites, different methods were applied. The Langmuir model showed the greatest agreement with the experimental findings (qm, 55.55 mg g-1). The kinetic study also confirmed the compatibility between the pseudo-secondorder model and adsorption. Moreover, we measured Gibbs free energy changes (DGo) and enthalpy changes (DHo). Considering the negative DGo and positive DHo, AB62 adsorption on PPy/MCM-41 nanocomposite can be considered a spontaneous, endothermic reaction. Keywords Adsorption  Acid Blue 62  Polypyrrole  Polyaniline  MCM-41 Introduction The presence of dyes in industrial wastewaters is a major issue in different countries. Different industries, including textile printing, plastic, pharmaceutical, and food industries, use dyes in their procedures. About 20% of dye production in the world is lost during the dyeing process & Navid Nasirizadeh 1 Department of Textile and Polymer Engineering, Yazd Branch, Islamic Azad University, Yazd, Iran 2 Department of Textile Engineering, Islamic Azad University of Qaemshahr, Qaemshahr, Iran [1]; therefore, the presence of dyes in wastewater is inevitable. Dye removal from wastewater is significant, as the quality of water greatly depends on color; even a very low dosage of dye (\1 ppm) can be easily seen in water and is found to be unfavorable. Besides, most dyes result in the occurrence of diseases, such as skin inflammation, skin irritation, carcinomas, and mutations in humans [1]. Removal of colored contaminants from wastewater is carried out using various techniques, including biological and physicochemical technologies. Oxidation [2], coagulation–flocculation [3], separation of membranes [4], and adsorption [5, 6] are among the major processes involved in treatment. Among the mentioned processes, adsorption is the most frequently used technique, showing feasibility, high yield rate, and less expenditure [5]. Species in the adsorption process are moved to the solid phase and can minimize the effluent volume [1]. Researchers have recently introduced favorable adsorbents [5–7]. Highly porous materials such as mobile crystalline material-41 (MCM-41) [8, 9], modified hexagonal mesoporous silica (HMS) [5, 10], and nanoporous silica (SBA-15) [11] seem to be appropriate for removing different dyes. Different types of surfactants are used for the preparation of these materials. Surfactants act as templates throughout sol–gel and hydrothermal processes. The main characteristics of mesoporous materials include great specific surface area, uniform and limited pore size distribution, and great thermal stability [12, 13]. Recently, MCM-41 has been used for the adsorption of dyes from wastewater. Considering the presence of SiO and SiOH (known to adsorb cationic dyes and inhibit anionic dye adsorption), the structure of MCM-41 is negatively charged [14]. The importance of interaction 123 218 J Nanostruct Chem (2017) 7:217–229 between MCM-41 and safranin (a large positively charged dye) was examined in a previous study [15]. To enhance the MCM-41 capacity in adsorbing specific substances, it is necessary to make surface modifications. Considering the adsorbent–adsorbate interactions, surface modifications also improve the selectivity of MCM-41 [16]. Amines, as well-known functional groups, have been used in many studies for surface modification of different types of adsorbents. To eliminate mercury ions from water, MCM-41 was functionalized with diethylenetriamine (DETA) [9]. In a previous study, aminopropyltrimethoxysilane (APTS) was applied for MCM-41 (NH3 ? -MCM-41) modification to remove four types of anionic dyes from the aqueous media [16]. Transition metals including nickel are extensively applied for the modification of MCM-41 structure [17]. In a previous study, to remove methyl blue from aqueous solutions, highly ordered nickel-supplemented MCM-41 adsorbents were synthesized (with varying nickel contents) [14]. Overall, according to our literature research, few studies have been conducted on the use of polypyrrole (PPy)/MCM-41 and polyaniline (PAni)/MCM-41 in anionic dye adsorption. With this background in mind, PPy/MCM-41 and PAni/ MCM-41 nanocomposites were synthesized in the current study. Nanocomposites were described using different methods, including transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) analysis, and BET method. Through performing batch experiments, the efficiency of PPy/MCM-41 and PAni/MCM-41 in AB62 elimination from aqueous media was also examined. Moreover, the significance of solution pH, contact time, temperature, and adsorbent dose was evaluated. Finally, thermodynamic and kinetic evaluations were performed to measure the parameters. Materials and methods Substances The reagents used for the preparation of samples and experimental tests included cetyl-trimethyl-ammonium bromide (CTMABr), ammonium hydroxide, tetraethyl ortho silicate (TEOS, SiC8H20O4), aniline, pyrrole, potassium iodate (KIO3), ferric chloride, sulfuric acid, acetone, hydrochloric acid (HCl), NaOH, Na2HPO4, NaH2PO4, and deionized water (Merck Co., Germany). Moreover, Dystar Co. (Germany) provided anionic dye (Acid Blue 62 or AB62, kmax = 595 nm). Figure 1 illustrates the chemical composition of AB62. 123 Fig. 1 Molecular structure of dye Acid Blue 62 MCM-41 synthesis MCM-41 synthesis was performed in line with the technique proposed by Kamarudin et al. [18]. In brief, 2.4 g of cetyltrimethylammonium bromide (CTMABr) as the template was added to deionized water (120 g) and stirred to form a uniform solution. Afterward, ammonium hydroxide (8 mL) was added and stirred over 5 min. Following that, 10 mL of tetraethyl orthosilicate (TEOS), as the silicon source, was added and stirred for 24 h. The solution was moved to a steel autoclave and stored at 145 °C for 2 days. The pH was adjusted typically during 48–72 h to attain stability. The obtained product was filtered, washed, and stored at 100 °C for 1 day. In the final step, calcination was performed at 600 °C for 5 h. PAni/MCM-41 nanocomposite preparation For the preparation of PAni/MCM-41, potassium iodate (KIO3, 1 g) and 1 M sulfuric (...truncated)