ARTICLE IN PRESS JID: JTICE [m5G;July 19, 2015;14:8] Journal of the Taiwan Institute of Chemical Engineers 000 (2015) 1–10 Contents lists available at ScienceDirect Journal of the Taiwan Institute of Chemical Engineers journal homepage: www.elsevier.com/locate/jtice Removal of methyl orange (MO) from aqueous solution using cationic surfactants modified coffee waste (MCWs) Ridha Lafi ∗ , Amor Hafiane Laboratory of Wastewater Treatment, CERTE, BP 273, Soliman 8020, Tunisia article info Article history: Received 6 January 2015 Revised 18 May 2015 Accepted 28 June 2015 Available online xxx Keywods: Methyl orange Modified coffee waste Surfactant Adsorption Kinetics Thermodynamics abstract In this present work, a commercial coffee waste was treated using cationic surfactants cetyltrimethyl ammo- nium bromide (CTAB) or cetylpyridinium chloride (CPC) to enhance its adsorption capacity for the removal of methyl orange dye (MO, anionic dye) from aqueous solutions. A series of experiments were undertaken in an agitated batch to assess the effect of key parameters such as pH, contact time, adsorbent dose and ionic strength. Maximum methyl orange dye adsorption onto modified commercial coffee waste (MCWs) was ob- served at pH 3.5 with 0.1 g/50 ml of adsorbent dose. Modeling study shows that pseudo-second-order kinetic model and Langmuir adsorption isotherm model provide better fitness to the experimental data. The maxi- mum adsorption capacity (62.5 mg/g at 25 °C) was obtained with CPC modified commercial coffee waste. Cal- culated thermodynamic parameters G 0 , H 0 and S 0 showed that adsorption is spontaneous and exother- mic. The FT-IR analysis showed that possible mechanisms controlling MO adsorption on the MCWs included electrostatic interactions and hydrophobic interaction. © 2015 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved. 1. Introduction Removal of toxic dyes from the environment is an important chal- lenge. Ideally, a removal processes must be simple, effective and in- expensive. Conventional methods of dyes removal from wastewa- ter have been used. These methods include biological and physico– chemical processes [1,2]. The activated carbon with large surface area is effective and widely used as adsorbent [3], but its cost is quite high. Therefore, many researchers pay attention to the use of dif- ferent types of low-cost materials from biomass products such as peanut husk [4,5], sugarcane bagasse [6,7], peanut hulls [8], wheat straw [9,10] as adsorbent. Commercial coffee waste can be used as an available adsorbent to remove cationic dyes from wastewater [11,12]. The chemical composition of the insoluble coffee waste cell’s wall is largely made up of lignin and some structural proteins that contain hydroxyl and carboxylic groups. However the capacity about anionic dyes was very low. To enhance the remove of the anionic pollutants, several researchers used cationic surfactant to modify agricultural products [13–16]. But investigations using commercial coffee waste modified by surfactants for dyes adsorption were not, in our knowl- edge, reported in the literature. Therefore in the present study, two cationic surfactants cetyltrimethyl ammonium bromide (CTAB) and cetylpyridinium chloride (CPC) were used to modify the surface of CW to enhance its capacity toward anionic pollutants. Methyl orange ∗ Corresponding author. Tel.: +216 79 325 750; fax: +216 79 325 802. E-mail address: ridha.lafi@yahoo.fr (R. Lafi). (MO, C 14 H 14 N 3 NaO 3 S, molecule weight 327.36 g mol/l, CAS 547-58-0) Fig. S1 (Supplementary information) is selected as anionic dye model. It is one of the well-known acidic/anionic dyes, and it has been widely used in textile, printing, paper, food, and pharmaceutical industries. Azo dyes are well known as carcinogenic organic substances. Like many other dyes of its class, MO do not inadvertently enter the body through ingestion, it is metabolized into aromatic amines by intesti- nal microorganisms [17]. The aim of this study is to improve the ad- sorption property of commercial coffee waste towards MO dye by us- ing two cationic surfactants. Kinetic, thermodynamic and isotherms of MO removal on this novel material were investigated. 2. Materials and methods 2.1. Chemicals All the used reagents (Na 2 CO 3 , NaHCO 3 , NaOH, HCl) were analytical-grade reagents and the chemical properties of cationic sur- factants used in this study are represented in Table S1 (Supplemen- tary information). Double distilled water was used for preparing all of the solutions and reagents. The initial pH is adjusted with 0.1 M HCl and NaOH solutions. All the adsorption experiments were carried out at room temperature (25 ± 1 °C). A sock solution of 1.0 g/l of methyl orange dye (MO, C 14 H 14 N 3 NaO 3 S, molecule weight 327.34 g mol/l, CAS 547-58-0) was prepared by dissolving the appropriate amount of dye with distilled water. http://dx.doi.org/10.1016/j.jtice.2015.06.035 1876-1070/© 2015 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved. Please cite this article as: R. Lafi, A. Hafiane, Removal of methyl orange (MO) from aqueous solution using cationic surfactants modified coffee waste (MCWs), Journal of the Taiwan Institute of Chemical Engineers (2015), http://dx.doi.org/10.1016/j.jtice.2015.06.035