DSpace at VNU: Synthesis of organoclays and their application for the adsorption of phenolic compouds from aqueous solution

Journal of Industrial and Engineering Chemistry 19 (2013) 640–644 Contents lists available at SciVerse ScienceDirect Journal of Industrial and Engineering Chemistry journal homepage: www.elsevier.com/locate/jiec Synthesis of organoclays and their application for the adsorption of phenolic compounds from aqueous solution Van Noi Nguyen a, Thi Dieu Cam Nguyen b,*, Thanh Phuong Dao a, Hung Thuan Tran c, Dinh Bang Nguyen a, Dae Hee Ahn d a Faculty of Chemistry, Hanoi University of Science, Vietnam National University, Hanoi, Viet Nam Faculty of Chemistry, Quy Nhon University, Viet Nam Advanced Materials Technology Center, National Center for Technological Progress, Hanoi, Viet Nam d Department of Environmental Engineering and Biotechnology, Myongji University, Republic of Korea b c A R T I C L E I N F O Article history: Received 12 May 2012 Accepted 22 September 2012 Available online 28 September 2012 Keywords: Organoclays Quaternary ammonium salts Organic Sorption A B S T R A C T Organoclays were synthesized by exchanging inorganic cations between layers in Thanh Hoa bentonite using organic cations including benzylhexadecyldimethylammonium (BHDDM+), dimethyldioctadecylammonium (DMDOD+) and benzylstearyldimethylammonium (BSDM+) Inserting organic cations increases material interlayer distance significantly (from 15 A˚ to 40 A˚) and simultaneously enhances affinity of materials toward organic pollutants The results show that adsorption capacity of organics on organoclays strongly depends on affinity between organic substances and ammonium cations rather than on interlayer distance of organoclays This means that the sorption of organoclays for organic contaminants was significantly influenced by the nature of the surfactants added to the clay ß 2012 The Korean Society of Industrial and Engineering Chemistry Published by Elsevier B.V All rights reserved Introduction During recent decades, zeolite with microporous system has been applied in many industrial processes, such as adsorptive materials, oxidation catalysts However, applications of zeolite are limited, because small pore size (d < 1.5 nm) makes it hard for transformation of complex and large molecules Therefore, finding new materials with larger pore system has been an interest of many scientists [1,2] The use of bentonite in wastewater treatment has received increasing attention and currently offers a very attractive method for pollution remediation Besides it is plentiful, inexpensive and available in many countries, bentonite is known having layered structure and to be quite porous material It is widely used in a large number of many fields In environmental treatment, bentonite is often used as a natural adsorptive material [3] Bentonite is naturally capable of adsorbing organic substances; however, the adsorption capacity is not high enough to be applied in practice Hence, it needs to be modified to enhance adsorption capacity, and amine salts have been generally employed as costeffective reagents Once hydrocarbon chain inserted into layers can increase interlayer distance and hydrophobic property, leading to higher affinity toward organic substances [4,5] Organoclays, * Corresponding author Tel.: +84 98 322 2831 E-mail address: nguyendieucam@hus.edu.vn (T.D.C Nguyen) prepared by intercalating clays with surfactant cations, have been considered as potential sorbents for removing organic pollutants from water [6–12] Quaternary ammonium organoclays may be divided into two groups depending on the structure of the organic cation and the mechanism of sorption [13] The first group, called adsorptive organoclays, includes clays that contain short-chain quaternary ammonium ions, such as tetramethylammonium or trimethylbenzylammonium Sorption on this type of organoclays is characterized by Langmuir-type isotherms, which are commonly associated with specific sorption sites The second group of organoclays, called organophilic organoclays, is composed of clays that contain long-chain quaternary ammonium ions, such as hexadecyltrimethylammonium or didodecyldimethylammonium Sorption by this group is also characterized by Langmuir or Freundlich-type isotherms, but linear interval is over wider range of solute concentrations In this work, bentonite from Thanh Hoa, Vietnam was modified for the first time by different organic quaternary ammonium cations, such as benzylhexadecyldimethylammonium, dimethyldioctadecylammonium and benzylstearyldimethylammonium to adsorb phenolic compounds, including phenol, phenol red and direct blue DB 53 (Table 1) These aromatic compounds are common pollutants that can be found in different types of polluted water as dye wastewater, wood manufacturing wastewater [14,15] It was shown that organoclays containing surfactants with aromatic rings were better suited for removing toxic aromatic 1226-086X/$ – see front matter ß 2012 The Korean Society of Industrial and Engineering Chemistry Published by Elsevier B.V All rights reserved http://dx.doi.org/10.1016/j.jiec.2012.09.018 V.N Nguyen et al / Journal of Industrial and Engineering Chemistry 19 (2013) 640–644 Table Surfactants and phenolic compounds used in this study 641 Table Effect of pH of bentonite suspension on d0 value of organoclays Compound Formula MW BHDDM chloride BSDM chloride DMDOD chloride Phenol Phenol red (phenolsulfonphthalein) DB 53 (direct blue 53) CH3(CH2)15N(CH3)2CH2C6H5Cl CH3(CH2)17N(CH3)2CH2C6H5Cl [CH3(CH2)17]2N(CH3)2Cl C6H5OH C19H14O5S C34H24N6Na4O14S4 381.5 409.5 585.50 94.11 354.38 960.80 organic compounds, such as phenolic compounds, from aqueous solution [16,17] Materials and methods pH d0 value of organoclay (A˚) Bent-BHDDM Bent-DMDOD Bent-BSDM 10 34.87 35.69 34.87 35.07 34.87 38.89 39.53 38.82 40.57 38.55 37.00 37.23 36.50 37.81 37.93 To characterize adsorption of different phenolic compounds using organoclays, the Langmuir adsorption isotherm was employed The linear form of Langmuir adsorption isotherm equation is presented as follows: Ce Ce ẳ ỵ q qmax k Á qmax 2.1 Synthesis of organoclays Bentonite from Thanh Hoa, Vietnam has undergone a purification protocol composed of several stages: disintegration to disperse the layers of clay and recovery of the fraction of clay lower than mm, and then saturated by sodium chloride solution (0.1 mol/L) Thus the recovered bentonite known as sodium bentonite was washed several times with distilled water until free of chloride ions as indicated by AgNO3, and then dried at ambient temperature The surfactants used to modify the bentonite are cationic surfactants, including benzylhexadecyldimethylammonium chloride (BHDDM chloride), benzylstearyldimethylammonium chloride (BSDM chloride), and dimethyldioctadecylammonium bromide (DMDOD bromide) provided by Sigma–Aldrich (Table 1) Organoclays were prepared by insertion of the aforementioned quaternary ammonium salt between the layers of the bentonite by a simple cationic exchange The effects of various parameters such as surfactant dose, temperature, pH and reaction time on d0 value of organoclays were investigated All the samples were maintained under constant agitation during 24 h, and washed several time with distilled water until no chloride ions were detected by AgNO3 Organoclays were recovered by centrifugation and dried at 70 8C 2.2 Adsorption experiments All experiments were performed in batch with 0.1 g ogranoclays and 100 ml of synthetic wastewater containing from 50 to 1500 mg/L aqueous phenol compounds solution Phenol concentration was measured by spectrophotometric method employing 4-aminoantipyrin as coloring agent, complex formed has maximum absorption at 510 nm Phenol red and DB 53 concentrations were determined through their absorption at lmax of 432 nm and 622 nm, respectively [18] where q is the adsorption capacity at certain time, qmax is the maximum adsorption capacity, Ce is the concentration of adsorbate at equilibrium, k is the Langmuir constant Results and discussion 3.1 Effects of synthesis parameters on engineered organoclays properties 3.1.1 Effect of the nature and dose of quaternary ammonium salts Interlayer distances of organoclay at different amount of quaternary ammonium salts obtained from XRD patterns are shown in Table It is clear that interlayer distance of organoclay depends on nature and amount of organic ammonium salts BentDMDOD has larger distance than Bent-BSDM, and Bent-BHDDM has the smallest value In details, interlayer distances of BentBHDDM, Bent-BSDM, and Bent-DMDOD with 100% cation exchange capacity (CEC) organic ammonium salt are 27.01 A˚, 32.16 A˚ and 40.57 A˚, respectively According to Lagaly and Hackett [19,20], for organoclay with interlayer distance larger than 22.7 A˚, organic cations lie between bentonite layers as pseudo-three layers The obtained results are higher than those in some other publications [21–24] From data in Table 2, it can be concluded that the optimal ammonium salts dose to synthesize Bent-BHDDM, Bent-DMDOD and Bent-BSDM are 125, 100 and 150% CEC, respectively 3.1.2 Effect of pH It is clear that when pH is in the range of 6–10, under optimal doses of ammonium salts, interlayer distances of organoclays not vary significantly (Table 3) This observation agrees with explanations of some authors that charge of quaternary ammonium cations in clay does not change with pH, and they are kept between layers by electrostatic force [25] Table Effect of quaternary ammonium salt dose on d0 of organoclays Quaternary ammonium salt dose (%CEC) 25 50 75 100 125 150 175 a d0 value of organoclay (A˚) Bent-BHDDM Bent-DMDOD Bent-BSDM 15.60a 18.48 21.88 23.80 27.01 35.59 – – 15.60a 25.12 27.36 37.51 40.57 40.86 41.52 – 15.60a 19.05 21.32 23.82 32.16 35.59 37.05 37.01 The distance of natural bentonite Table Effect of temperature on d0 of organoclays Temperature (8C) d0 value (A˚) Bent-BHDDM Bent-DMDOD Bent-BSDM 35 45 55 65 75 85 32.47 33.28 35.09 35.58 33.89 32.97 39.39 39.12 40.57 39.76 38.97 38.26 35.17 34.97 37.80 37.20 37.00 36.89 V.N Nguyen et al / Journal of Industrial and Engineering Chemistry 19 (2013) 640–644 642 Table Effect of reaction time on d0 value Time (h) d0 (A˚) Bent-BHDDM Bent-DMDOD Bent-BSDM 33.89 33.34 35.59 34.30 32.76 38.65 39.22 39.52 39.39 39.36 36.60 37.23 37.93 37.40 34.51 From results in Table 2, the pH of was chosen for the synthesis of Bent-BHDDM and Bent-DMDOD, while the pH of 10 was chosen for the synthesis of Bent-BSDM 3.1.3 Effect of temperature It can be seen from Table that interlayer distance of three studied organoclays, under optimal doses of ammonium salts, does not depend significantly on temperature From the data in Table the temperature of 65 8C was chosen for synthesizing Bent-BHDDM, and the temperature of 55 8C was chosen for synthesizing Bent-DMDOD and Bent-BSDM 3.1.4 Effect of reaction time Although exchange reaction is quite fast (about 40–120 min), in order for cations to be stable between clay layers, reaction solution should be kept in longer time, the optimal reaction time to synthesize Bent-BHDDM, Bent-DMDOD and Bent-BSDM are h (Table 5) To prove that quaternary ammonium cations were successfully immobilized on bentonite layers in organoclays, samples synthesized at optimal conditions were characterized by IR spectroscopy (Figs 1–3) It can be seen that in IR spectra of Bent-BHDDM, BentDMDOD and Bent-BSDM, there are peaks characterized for (i) – CH3 and –CH2– stretching modes at 2850 cmÀ1 and 2920 cmÀ1, and (ii) C–N stretching of organic ammonium cations at 1467 cmÀ1 Results obtained from IR spectra agree with reports of other authors [26,27] There are also peaks characterized for bentonite, such as peaks of Si–O vibration in SiO4 tetrahedron at 420–470 cmÀ1; peaks of Al–O vibration in octahedron at 815 cmÀ1 The presence of OH groups in the water absorbed is proved by the appearance of peaks at 3400–3600 cmÀ1 However, the peak intensity in the IR spectra of organoclays is lower than that in bentonite’s IR spectrum, and these results Fig IR spectra of bentonite and Bent-BHDDM Fig IR spectrum of Bent-BSDM V.N Nguyen et al / Journal of Industrial and Engineering Chemistry 19 (2013) 640–644 643 Fig IR spectrum of Bent-DMDOD In organoclays, N atoms are held on bentonite surface through attractive electrostatic force with negative-charged bentonite surface, and alkyl tails (RR1R2R3)N+ orient toward inside pores These alkyl tails can act as liquefied organic solvent, and they have affinity toward organic substances [28,29] Phenols adsorption takes place on organophilic centers of organoclays Experiment data were obtained at temperature 30 Ỉ 8C, and the pH values of phenol, phenol red, and DB 53 solutions were 6, and 2, respectively Straight lines were obtained by plotting Ce/q against Ce for the adsorption of phenolic compounds onto organocalys as shown in Figs 4–6 The values of qmax and k calculated from the slopes and intercepts of the Langmuir plots and r-square are reported in Table Results in Table show that adsorption of phenolic compounds on Bent-BHDDM, Bent-BSDM and Bent-DMDOD fits well with Langmuir isotherm model Maximum adsorption capacity values obtained from this model indicate that the organoclays are capable of adsorbing phenols in aqueous solution Ability to adsorb phenol red and DB 53 (substances with aromatic rings) of Bent-DMDOD is much lower than those of Bent-BHDDM and Bent-BSDM This shows that adsorption capacity strongly depends on affinity between organic substances and ammonium cations rather than on interlayer distance Although Bent-DMDOD possesses largest interlayer distance (39.22 A˚) but its adsorption capacity is lower than Bent-BHDDM (33.34 A˚) and Bent-BSDM (37.41 A˚) It can be explained through the fact that for Bent-BHDDM and Bent-BSDM the ammonium cations containing aromatic rings were employed, these two materials attract phenols more than Bent-DMDOD, which does not contain aromatic rings On the other hand, for phenolic compounds with less aromatic rings (phenol), adsorption capacity does not depend much on nature of organic ammonium cation Phenol, phenol red and DB 53 molecules have smaller size than interlayer distances of organoclays It means that these molecules can diffuse into pore system of organoclays Organoclays adsorb molecules with small size stronger than those with bulk structure This can be explained by the fact that DB 53 and phenol red molecules have large size, they could hinder a part of adsorption centers of organoclays, prevent other molecules to get to adsorption centers, resulting in a lower adsorption capacity Fig Langmuir adsorption isotherm of phenolic compounds on Bent-BHDDM Fig Langmuir adsorption isotherm of phenolic compounds on Bent-BSDM show that organophilic property of organoclays is higher than that of bentonite 3.2 Adsorption of phenolic compounds on organoclays V.N Nguyen et al / Journal of Industrial and Engineering Chemistry 19 (2013) 640–644 644 Modified bentonites possess higher organophilic property Phenol, phenol red, and DB 53 were found to be adsorbed strongly on organoclays comprising alternating organic and inorganic layers Adsorption behavior of the three adsorbate–adsorbent systems was described well by Langmuir isotherm model Langmuir maximum adsorption capacities of Bent-BHDDM, Bent-BSDM and Bent-DMDOD on phenol, phenol red and DB 53 are quite high From this study, it can be concluded that the natural bentonite source in Vietnam would be used as precursor materials to synthesize potential adsorbents for treating phenolic compounds in wastewater Acknowledgement Fig Langmuir adsorption isotherm of phenolic compounds on Bent-DMDOD Table Langmuir isotherm constants for adsorption of phenolic compounds This project is supported by Vietnam National Foundation for Science and Technology Development, project number 104.99 153.09 References Compound qmax (mmol/g) k (L mmolÀ1) r-squared Bent-BHDDM Phenol Phenol red DB 53 0.92 0.54 0.50 0.20 Â 10À2 3.06 Â 10À2 2.93 Â 10À2 0.99 0.99 0.99 Bent-BSDM Phenol Phenol red DB 53 0.70 0.67 0.49 0.89 Â 10À2 1.85 Â 10À2 3.28 Â 10À2 0.98 0.98 0.98 Bent-DMDOD Phenol Phenol red DB 53 0.64 0.303 0.335 0.69 Â 10À2 1.43 Â 10À2 0.28 Â 10À2 0.98 0.98 0.98 3.3 Discussion on adsorption mechanism From literature and experimental data, it can be suggested that when modifying bentonite using quaternary ammonium cations, these cations are kept between bentonite layers, replacing Na+ cations in original bentonite Then, these organic cations exist in ‘‘liquid form’’ [30] and they have affinity toward organic substances It can be observed that increasing pH leads to a decrease in adsorption capacity of phenolic compounds At high pH phenols exist in ion forms, hence they are more polar Attractive force between quaternary ammonium cations and polar molecules is weaker than that between these cations and non-polar molecules This again verifies the idea of ‘‘liquid form’’ above Conclusions Thanh Hoa bentonite was successfully modified by three different ammonium salts: benzyl hexadecyl dimethyl ammonium chloride, benzyl stearyl dimethyl ammonium chloride and dimethyl dioctadecyl ammonium bromide by wet method [1] L.B de Paiva, A.R Morales, F.R Valenzuela Dı´az, Applied Clay Science 42 (2008) [2] X Wang, K.S.K Lin, J.C.C Chan, S Cheng, Journal of Physical Chemistry B 109 (2005) 1763 [3] P.S Nayak, B.K Singh, Desalination 207 (2007) 71 [4] N Yıldız, R Gonulsen, H Koyuncu, A Calımlı, Colloids and Surfaces A 260 (2005) 87 [5] R.S Juang, S.H Lin, K.H Tsao, Journal of Colloid and Interface Science 254 (2002) 234 [6] K Esumi, M Matoba, Y Yamanaka, Langmuir 12 (1996) 2130 [7] A Dabrowski, Advances in Colloid and Interface Science 93 (2001) 135 [8] S Al-Asheh, F Banat, L Abu-Aitah, Separation and Purification Technology 33 (2003) [9] S.L Bartelt-Hunt, S.E Burns, J.A Smith, Journal of Colloid and Interface Science 266 (2003) 251 [10] K Esumim, K Yoshida, K Torigoe, Y Koide, Colloids and Surfaces A 160 (1999) 247 [11] J-H Kim, S.S.W.S Shin, D.-I Song, S.J Choi, Korean Journal of Chemical Engineering 23 (2006) 63 [12] B Chen, L Zhu, J Zhu, B Xing, Environmental Science and Technology 39 (2005) 6093 [13] Y.H Shen, Colloids and Surfaces A 232 (2004) 143 [14] R Othaman, A Susilo, H Habaki, R Egashira, Asian Journal of Chemical Engineering (2009) [15] A Khenifi, Z Bouberka, F Sekrane, M Kameche, Z Derriche, Adsorption 13 (2007) 149 [16] S Andini, R Cioffi, F Montagnaro, F Pisciotta, L Santoro, Applied Clay Science 31 (2006) 126 [17] L Zhu, B Chen, X Shen, Environmental Science and Technology 34 (2000) 468 [18] APHA/AWWA/WEF, 20th ed., Washington, DC, USA, 1998 [19] E Hackett, E Manias, E.P Giannelis, Journal of Chemical Physics 108 (1998) 7410 [20] G Lagaly, M.F Gonzalez, A Weiss, Clay Minerals 11 (1976) 173 [21] T Kwolek, M Hodorowicz, K Standnick, J Czapkiewicz, Journal of Colloid and Interface Science 264 (2003) 14 [22] J.Y Lee, H.K Lee, Materials Chemistry and Physics 85 (2004) 410 [23] N Yilmaz, S Yapar, Applied Clay Science 27 (2004) 223 [24] Y Tang, Y Hu, L Song, Z Gui, Z Chen, W Fan, Polymer Degradation and Stability 82 (2003) 127 [25] T.A Wolf, T Demirel, R.E Bauman, Journal of the Water Pollution Control Federation 58 (1986) 68 [26] Y Xi, Z Ding, H Hongping, Spectrochimica Acta A61 (2005) 515 [27] S Yariv, Thermochimica Acta 274 (1996) [28] J Zhu, H He, L Zhu, X Wen, F Deng, Journal of Colloid and Interface Science 286 (2005) 39 [29] H Zhao, K.L Nagy, J.S Waples, G.F Vance, Environmental Science and Technology 34 (2000) 4822 [30] R.A Vaia, R.K Teukolsky, E.P Giannelis, Chemistry of Materials (1994) 1017  ... 37.40 34.51 From results in Table 2, the pH of was chosen for the synthesis of Bent-BHDDM and Bent-DMDOD, while the pH of 10 was chosen for the synthesis of Bent-BSDM 3.1.3 Effect of temperature It... against Ce for the adsorption of phenolic compounds onto organocalys as shown in Figs 4–6 The values of qmax and k calculated from the slopes and intercepts of the Langmuir plots and r-square... capacity at certain time, qmax is the maximum adsorption capacity, Ce is the concentration of adsorbate at equilibrium, k is the Langmuir constant Results and discussion 3.1 Effects of synthesis