ABILITY OF Cu 2+ -MONTMORILLONITE TO ACCEPT AN TOXIC POLLUTANTS. Janíková Veronika 1, Jóna Eugen 1, Janík Róbert 1, Pavlík Viliam 2

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1 ABILITY OF Cu 2+ -MONTMORILLONITE TO ACCEPT AN TOXIC POLLUTANTS Janíková Veronika 1, Jóna Eugen 1, Janík Róbert 1, Pavlík Viliam 2 1 Department of Material Technologies and Environment, Faculty of Industrial Technologies, Alexander Dubček University of Trenčín, Ivana Krasku 491/30, Púchov, Slovak Republic, i.janikova.v@gmail.com 2 Department of Inorganic Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, Bratislava, Slovak Republic ABSTRACT It is global problem that toxic pollutants are in the permanent contact to people through soil and water. Nowadays, it is important to eliminate these pollutants for future generations and to keep environment in the health condition. In relation to this article, aromatic organic compounds like benzene, phenol and aniline were chosen. These are used in various branches of industry, mainly in rubber industry or for production of dyes and in addition, phenol is commonly used in cosmetics or in food industry. Montmorillonite is clay mineral consisting of 2:1 sheets (tetrahedral:octahedral) and interlayer space where exchangeable cations and water molecules are present. Due to its structure, montmorillonite is able to accept some compounds or pollutants. This is the reason why it is mainly used as the covering material of radioactive waste in order to remove toxic pollutants. For investigation of toxic pollutants removing, XRD powder diffraction, infrared spectroscopy and thermal analysis were used. Our results show that Cu 2+ -montmorillonite is able to accept toxic benzene ring-based pollutants into interlayer. This mentioned ability can be proven on the basis of the investigation results relating to difference of interlayer distance, typical frequencies of OH group or NH2 group, while these results were supplemented by thermal properties. INTRODUCTION Montmorillonite (MMT) is a very soft phyllosilicate mineral of the smectite family, having two SiO4 - tetrahedral sheets sandwiching a central AlO6 - octahedral sheet (type 2:1). Chemically, it is (Na, Ca)x(Al)2(Si4O10)(OH)2. n H2O (Abou-El-Sherbini KS and col., 2010). After the adsorption of organic cations, interlayer space of montmorillonite can be changed from hydrophilic to hydrophobic state. Based on the mentioned fact, the resulting materials (organoclays) have been used as efficient adsorbens of hydrophobic organic contaminants. Therefore, montmorillonite can simultaneously remove organic cations from wastewater and it has been considered as low-cost and high-efficient adsorbent for wastewater containing different organic contaminants (Zhu R. and col., 2014). Clays interact with many organic compounds to form substances of varying stabilities and properties. The clays in soil and sediments are closely associated with organic materials. Clay minerals with a negative charge are neutralized by inorganic exchangeable cations such as Na + or Cu 2+. In the past, organo-clays have been utilized in the manufacture of lubricants, paper, and paints, cosmetic and medical products. Recently, the interest in utilisation clays has 179

2 been increased while the given interest has been mainly devoted to smectites because of their high cation exchange capacity (CEC) and ability to remove organic pollutants from water through the surface area (Koh SM. and Dixon JB, 2001). Organo-montmorillonites are montmorillonites that have been modified with organic pollutants as components in the synthesis of clay-based polymer nanocomposites and as precursors in the preparation of mesopourus materials (He H. and col., 2010). Organoclays have been also used in many other applications. These applications are connected with their utilisation as adsorbents, rheological control agents, paints, grease, cosmetics, personal care products, oil well drilling fluids, etc. (Betega de Paiva L. and col., 2008). Including phenol, polar organic molecules can replace the water which normally occupies the interlayer space of montmorillonite. Phenol and phenol substituents are important chemicals in the manufacture of synthetic resins, pharmaceutical products, dyes and agrochemicals. Their toxicity is high and they may accumulate in the environment (Janík R. and col., 2013). Benzene and phenol or phenolic compound are very harmful to organisms even at very low concentration due to their toxicity, foul odour and carcinogenic properties. These compound are present in effluents of the petroleum refining, coke furnaces, batteries, coal gasification plants, ply board manufacturing industries, etc. (Janíková V. and col., 2013). Aniline is frequently used by the chemical industry in several processes such as the synthesis of dyes and production of some pesticides. It is also a common by-product of paper and textile industries. Aniline is known as a toxic water pollutant and its presence in wastewater, even in very low concentration, has been shown as harmful to aquatic environment. It was found out that the adsorption of specific organic contaminants by high valence metal cation-saturated montmorillonite was improved because of stronger H-bonding between more polar water molecule in connection with high valence metal cations in comparison with its connection with low valence cations and polar organic compounds (Zheng H. and col, 2009). XRD diffraction, IR study and thermal analysis are very important for characterization of organo-montmorillonites (Janík R. and col., 2013). MATERIALS AND METHODS Preparation of samples The monoionic form of montmorillonite (Cu 2+ -MMT) was prepared from Ca 2+ - montmorillonite in the following way: the stock of CuCl2 solution with pre-determined concentration (c = 1 mol.dm -3 ) and water were added to Ca 2+ -MMT and this suspension was being mixed for five hours every day during five days (the mixing process was repeated after 24 hour). After sedimentation, solution of CuCl2 and water was poured and then, the same solution of CuCl2 and water were added to the suspension again. This mentioned process was repeated five times. As a result, CuCl2 was washed by water until Cl - was eliminated completely. A presence of Cl - was investigated by help of 2% AgNO3solution. After this process, Cu 2+ -MMT was dried by heating at 60 C. After drying, this sample was crushed to a powder and prepared for pre-determined analysis. Merck Millipore provided benzene and aniline which were in a liquid form and phenol was in the form of powder and these organic compounds were used for interaction with Cu 2+ -MMT. Benzene (B = 0.18 ml) and phenol (P = 8.4 g) were added separately to 1 g of Cu 2+ -MMT (for each one organic compounds) and these solutions were mixed with 100 ml of distilled water. Solutions were being mixed until MMT was completely solvated and reaction was finished. This phenomenon was indicated by change of colour of original solution and solution under the mixing process. When the samples were sedimented, they were removed and the water was evaporated from solution. Aniline (A = 5 ml) in its clear liquid state was poured into small beaker and then it was placed into desiccator to preserve the vacuum. Cu 2+ - MMT (the weight of MMT was 1g) in three Petri bowls was also added into the same desiccator in its 180

3 powder form. The beaker with aniline solution was in the centre and three Petri bowls with Cu 2+ -MMT were around the aniline for 21 days. Analytical methods Diffractometer Bruker D8 Discover was used for X-ray powder diffraction while these settings were used: - CuKα, range = θ, - power = 12 kw, - heating rate = 0.05 degree - time of measurement = 1 sec. Using Nicolet 5700 FTIR, ATR method (Attenuated Total Reflectance) and KBr pellet method were utilised for analysis of IR spectra. RESULTS AND DISCUSSION Diffraction properties and colours of studied samples In relation to the prepared samples, there was the change not only in colour, but also in interlayer distances. These changes are summarized in table I. Table I Diffraction data and colour changes of studies samples from X-ray powder diffraction. Sample 2 θ / d001 / nm Δd001 / nm colour Cu 2+ -MMT turquoise Cu 2+ -MMT + B light-green Cu 2+ -MMT + P gold Cu 2+ -MMT + A green-black Cu 2+ - MMT + A Cu 2+ - MMT + B INTENSITY Cu 2+ - MMT 4000 Cu 2+ - MMT + P ,5 4 4,5 5 5,5 6 6,5 7 7,5 8 8,5 9 2 THETA / o Fig. 1 XRD diffraction peaks of studied samples with Cu 2+ montmorillonite. The basal spacing was changed after interaction of Cu 2+ -MMT with organic compounds. In the case of Cu 2+ -MMT + B, basal spacing increased by 0.23 nm and in the case of Cu 2+ -MMT + P, it was by 0.28 nm. Relating to Cu 2+ -MMT + A, basal spacing increased by 0.26 nm. The observed changes based on different values of intelayer distance and different colours lead to conclusion that organic compounds with benzene ring involving 181

4 benzene, phenol and aniline were successfully intercalated into interlayer space of Cu 2+ - MMT. Spectral (IR) properties of studied samples Infrared spectra of Cu 2+ -MMT with benzene, phenol and aniline are shown in Fig. 2 and spectral data of these samples are presented in table II. Fig. 2 Infrared spectra of studied samples with Cu 2+ -MMT. Spectral data of Cu 2+ -MMT and Cu 2+ -MMT with organic compounds show some characteristic peaks which could be assigned to specific group. Based on literature (Milata V., 2007) and Kowalska (Kowalska M., 1994), we can divide these peaks and their vibrations to three groups - asymmetric, valence and deformation. Table II shows specific vibrations of some groups while these vibrations are typical for each one sample and its observed frequencies. For Cu 2+ -MMT + B, frequencies are in the range of cm -1 which could be assigned to asymmetric vibration of benzene ring. In case of Cu 2+ -MMT + P, there is higher number of frequencies and it indicates that phenol was intercalated into interlayer space of Cu 2+ -MMT. Besides frequencies at values of 1595, 1498 and 1473 cm -1 which can be assigned to asymmetric vibration of skeleton of aromatic ring, there are also other frequencies: 1228 cm -1 (valence vibration of C - O) and 1151 cm -1 (deformation vibration of C - OH). Sample of Cu 2+ -MMT + A mainly shows NH + valence or deformation vibration (2962 cm -1 and 3361 cm -1 ) and C - N valence vibration (1259 cm -1 ). 182

5 Table II Spectral data of studied samples. Sample Observed frequencies / cm -1 Type of vibration asymmetric valence deformation 3612 H O H 1631 H O H Cu 2+ -MMT 1024 Si O 910 Al Al OH 835 Al Fe OH 515 Si O Al Cu 2+ -MMT + B benzene ring Cu 2+ -MMT + P 1595, 1498, 1473 skeleton of aromatic ring 1228 C O 1151 C OH Cu 2+ -MMT + A 2962 NH N H 1521 NH 1259 C N CONCLUSION The obtained results from X-ray powder diffraction, infrared spectroscopy confirmed that toxic aromatic organic compounds (benzene, phenol and aniline) were intercalated successfully into interlayer space of Cu 2+ -MMT. X-ray powder diffraction confirmed intercalation based on positive difference between interlayer distances. The infrared spectroscopy confirmed that there were vibrations relating to OH groups and NH + group. The preliminary investigation and results relating to thermal analysis also confirm the intercalation of toxic compounds into interlayer distances. Acknowledgement: This work was supported by KEGA No. 006 TnUAD 4/2014 and KEGA No. 003 TnUAD 4/2014. REFERENCIES Zheng H, Liu D, Zheng Y, Liang S, Liu Z (2009) Sorption isotherm and kinetic modeling of aniline on Cr-bentonite. J. Haz. Mat. 167: He H, Ma Y, Zhu J, Yuan P, Qing Y (2010) Organoclays prepared from montmorillonites with different cation exchange capacity and surfactant configuration. App. Clay Sci. 48: Abou-El-Sherbini KS, Hassanien MM (2010) Study of organically-modified montmorillonite clay for the removal of copper(ii). J. Haz. Mat. 184: Betega de Paiva L, Morales AR, Díaz FRV (2008) Organoclays: Properties, preparation and applications. App. Clay Sci. 42: Janík R, Jóna E, Pavlík V, Lizák P, Mojumdar SC (2013) Interactions of 2,5- and 3,5- dimethylphenols with Co-exchanged montmorillonite. J. Therm. Anal. Calorim. Zhu R, Chen Q, Liu H, Ge F, Zhu L, Zhu J, He H (2014) Montmorillonite as a multifunctional adsorbent can simultaneously remove crystal violet, cetyltrimethylammonium, and 2-naphtol from water. App. Clay Sci : Koh SM, Dixon JB (2001) Preparation and application of organo-minerals as sorbents of phenol, benzene and toluene. App. Clay Sci. 18: Janíková V, Janík R, Jóna E (2013) The use of the monoionic form of montmorillonite for removal of toxic organic pollutants. Hut. Listy LXVI, ISSN

6 Kowalska M, Güller H, Cocke DL (1994) Interaction of clay minerals with organic pollutants. Sci. Tot. Environ., Milata V, Segľa P (2007) Vybrané metódy molekulovej spektroskopie. Slovenská Technická Univerzita v Bratislave,