3RD INTERNATIONAL CONGRESS ON TECHNOLOGY - ENGINEERING & SCIENCE - Kuala Lumpur - Malaysia (2017-02-09)

Effect Of Thermal And Chemical Modifications Of Halloysite On Anionic Dye Removal

Dyes are widely used in the textile, rubber, paper, and cosmetic industries [1]. After use, they are generally released into effluents. Their presence in wastewaters causes serious problems for the environment. This study examines the ability of raw and modified halloysite for removing anionic dye. In this context, raw halloysite (H), the form calcined at 600 °C (H600), and that processed at 600 °C and with 5N HCl (H600-5N), were prepared, characterized by XRD, FTIR, and nitrogen adsorption, and used for the uptake of Congo red (CR) from synthetic solutions. The adsorption of CR was studied by taking into account the effects of contact time, solution concentration, and temperature. Thermodynamic data were also determined. The FTIR spectra show that when halloysite is treated at 600 °C (H600) significant changes occur in the vibrational spectrum. The majority of the peaks characteristic of halloysite disappeared. This indicate the dehydroxylation of structural aluminol groups [2]. This indicates that H600 is almost amorphous in nature evidencing a large degree of structural disorder. After thermally treated, and acid-activated, the sample indicate the formation of silica nanoparticles and the formation of amorphous silica [3] and the depopulation of octahedral sheet, subsequent to the dissolution of alumina [4]. The acid treatment mainly attacks the octahedral sheet of which the centers are occupied by Al3+. The textural parameters of halloysitic solids show that the specific surface area, SBET, after thermal treatment at 600°C. remains constant As the rew halloysite, the texture of H600 represented by mesopores, with 98% of the total volume of pores. After thermo-chemical activation the specific surface area is 503 m2 g-1 for H600-5N, again 63 m2 g-1 for H. The acid attack also increases the volume of the micropores. The kinetics shows the equilibrum reached after 2 h of contact. The kinetic data follow the pseudo-second order model with contribution of intraparticle diffusion. Using the classification of Giles et al. [5], the obtained isotherms are L-shaped. The capacity in CR, at equilibrium, increases with adsorption temperature, reaching 85.6 mg g-1 for H600-5N. Affinity follows the sequence : H600-5N > H600 > H. the high adsoption capacity of H600-5N explain by its textural properties. The intermediate adsorption of H600, is due to the amorphisation of the structure, and highlights a large degree of structural disorder. The Redlich–Peterson model describes suitably the equilibrium data. The thermodynamic parameters reveal a non spontaneous and endothermic process. These results show the efficiency of halloysitic solids for treating wastewater containing anionic dyes. Figure 1. FTIR spectra of H, H600, and H600-5N. Keywords: Adsorption; Characterization; Congo red; Halloysite; Modification. References [1] Dawood, S., Sen, T.K., Removal of anionic dye Congo red from aqueous solution by raw pine and acid-treated pine cone powder as adsorbent, equilibrium, thermodynamic, kinetics, mechanism and process design. Water, Res, 46, 1933–1946 ( 2012) [2] Kadi, S., Lellou, S., Marouf-Khelifa, K., Schott, J., GenerBatonneau, I., Khelifa, A., Preparation, characterization and application of thermally treated Algerian halloysite, Micropor. Mesopor. Mater, 158, 47–54 (2012). [3] Nguetnkam, J.P., Kamga, R., Villieras F., Ekodeck, G.E., Razafitianamaharavo, A., Yvon, J., Assessment of the surface areas of silica and clay in acid-leached clay materials using concepts of adsorption on heterogeneous surfaces, J. Colloid Interface Sci, 289, 104–115 (2005). [4] Abdullayev, E., Joshi, A., Wei, W., Zhao, Y., Lvov, Y., Enlargement of halloysite clay nanotube lumen by selective etching of aluminum oxide, ACS Nano 6, 7216–7226 (2012). [5] Giles, C.H., MacEwan, T.H., Nakhwa, S.N., Smith, D., Studies in adsorption. Part XI. A system of classification of solution adsorption isotherms, and its use in diagnosis of adsorption mechanisms and in measurement of specific surface areas of solids, J. Chem. Soc, 60 3973–3993 (1960).
Fatiha Bessaha, Nouria Mahrez, Kheira Marouf-Khelifa, Amine Khelifa