Chemical Engineering Journal 191 (2012) 228–235 Contents lists available at SciVerse ScienceDirect Chemical Engineering Journal jo u r n al hom epage: www.elsevier.com/locate/cej Sorption equilibrium, kinetic, thermodynamic, and desorption studies of Reactive Red 120 on Chara contraria Abuzer C ¸ elekli a,∗ , Gizem ˙ Ilgün a , Hüseyin Bozkurt b a Department of Biology, Faculty of Art and Science, University of Gaziantep, 27310 Gaziantep, Turkey b Department of Food Engineering, Faculty of Engineering, University of Gaziantep, 27310 Gaziantep, Turkey a r t i c l e i n f o Article history: Received 10 January 2012 Received in revised form 2 March 2012 Accepted 5 March 2012 Keywords: Activation energy Chara contraria Reactive Red 120 Thermodynamic Sorption a b s t r a c t Potential use of Chara contraria for sorption of Reactive Red (RR) 120 was investigated. The sorption process was highly dependent on various operating variables like particle size, adsorbent dose, pH, tem- perature, ionic strength, dye concentration, and contact time. Before and after the sorption of RR 120, adsorbent surfaces were characterized by FTIR-ATR spectroscopy. Equilibrium data was well predicted by Freundlich model. Kinetic sorption of RR 120 on C. contraria was well described by sigmoidal Logistic model. Activation parameters derived from Arrhenius and Eyring equations indicated that interaction was mainly physical sorption. Thermodynamic parameters showed that sorption process onto macro- alga was a spontaneous and endothermic nature. Low value of desorption suggested that both strong and weak binding forces could be present between dye and adsorbent. Overall, C. contraria, potentially low-cost adsorbent can be used for the removal of RR 120. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Reactive azo dyes are extensively used in dyeing processes in textile industry because of their simple dying procedures and good stability during washing process [1,2]. About 20–40% of these dyes remain in the effluents. Charges of such wastewater into receiving waters can be hazardous on exposed organisms due to their reactivity, toxicity, and stability [3]. Azo dyes constitute the largest group of mutagenic and carcinogenic xenobiotic pollutants. Disposal of these dyes and remediation of associated contami- nated sites remains a worldwide concern [3,4]. Therefore, prior to discharge of wastewaters to aquatic ecosystems, removal of recal- citrant pollutants has become a necessity for living Earth. Reactive dyes which contain one or more azo bond (–N N–), exhibit a wide range of different chemical structures, primarily based on substituted aromatic and heterocyclic groups [4,5]. Use of reactive dyes is now the most important method for dyeing of cot- ton and cellulose fibers [6]. They have high resistance to chemical, photochemical, and biological degradation and highly persistent in natural environment. Due to the complex structure and sta- bility of the dyes, conventional biological treatment methods are ineffective [2,4,7,8]. Moreover, their removal from wastewater by conventional coagulation, membrane filtration, and activated ∗ Corresponding author. Tel.: +90 3423171925; fax: +90 3423601032. E-mail addresses: celekli.a@gmail.com (A. C ¸ elekli), gizmo biyoloji@hotmail.com (G. ˙ Ilgün), hbozkurt@gantep.edu.tr (H. Bozkurt). sludge processes is difficult, since reactive dyes are highly soluble in water [1]. These processes have considerable energy requirements and thus impose high economic and environmental costs [2,9,10]. Therefore, alternative simple methods to work alongside these are sought. Sorption is known to be a promising technique, which has great importance due to ease of operation and comparable low cost of application in treating of textile dyeing effluents [8,10]. Sorption of reactive dyes has been studied in detail on various adsorbents such as bacteria, fungi, algae, aquatic plant, chitosan etc. [2,4,11]. In order to investigate sorption efficiency for remov- ing of Reactive Red (RR) 120, different adsorbents such as Lentinus sajor-caju [12], Spirogyra majuscula [7], pistachio husk [6], Hydrilla verticillata [4], chitosan [11], palm-oil industry waste [13], clay [14] were used. For this purpose, potential use of Chara contraria for removing of RR 120 has not been found in literature. However, this adsorbent had been used to remove Lanaset Red (LR) G [15,16] and to decolorize malachite green [17]. C. contraria was chosen in the present study, since it is widespread underwater meadows and so relatively cheap adsor- bent for sorption process. Besides, it was reported that this alga had considerable potential for the removal of dyes from aqueous solution [15,17]. Therefore, aim of this study was (i) to investi- gate the potential use of dried biomass of C. contraria for sorption of Reactive Red (RR) 120 from aqueous solution; (ii) to evaluate effects of particle size, adsorbent dose, pH value, temperature, ionic strength, initial dye concentration, and contact time on the sorption in the batch system; (iii) to investigate sorption kinetic models, equilibrium models, thermodynamic parameters, and 1385-8947/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.cej.2012.03.007