Adsorption of textile dye Reactive Red 120 by the chitosan–Fe(III)-crosslinked: Batch and ﬁxed-bed studies Carla Albertina Demarchi, Mayara Campos, Clo ´ vis Antonio Rodrigues * Nu ´cleo de Investigac ¸o ˜es Quı´mico-Farmaceˆuticas (NIQFAR), Universidade do Vale do Itajaı´(UNIVALI), Itajaı´88302-202, Santa Catarina, Brazil Introduction Many industries, such as the textiles, leather, cosmetics, paper, printing and plastics industries, use synthetic dyes as part of their production processes. Efﬂuents from these industries therefore contain various kinds of synthetic dye stuffs [1]. Dye contamina- tion in aqueous wastewater from industries is a serious problem because dyes are not biodegradable, and tend to suppress photosynthetic activity in aquatic habitats by preventing the penetration of sunlight [2]. Moreover, most of these dyes can cause allergy, dermatitis, and skin irritation [3], and can also lead to genetic mutations in humans [4]. Compared to traditional methods of decontamination of efﬂuents containing dyes, the adsorption method is the best alternative, and has been widely used to remove pollutants from efﬂuents [5], due to its low cost, simplicity of design, availability and ability to treat dyes in more concentrated form [6,7]. Most commercial systems use activated carbon as adsorbent to remove dyes in water, because of its great adsorption capacity. However, its widespread use is restricted due to its cost. In order to decrease the cost of treatment, some attempts have been made to ﬁnd low- cost alternative adsorbents [1]. Chitosan is derived from a natural polysaccharide, chitin, which is the second most abundant polysaccharide in nature. It is relatively cheap and exhibits higher dye adsorption capacities [8,9]. Absorbents containing iron have received a great deal of attention, due to their chemical stability and high absorption capacity [10–13]. Chitosan–iron complex has been used to remove oxyanions, such as, Cr (VI) [14,15], As(III) [16] and As (V) [17] from aqueous solutions, however the uses of chitosan–iron complex for adsorption dyes have not been reported. A great number of publications related to adsorption of textile dyes by magnetic chitosan and its derivatives have recently been reported in the literature [10,18–22]. However, the use of magnetic particles is restricted to the separation process using the batch method, and it is not appropriate for ﬁxed-bed process. Another disadvantage of magnetic particles, as compared with the chitosan–iron complex, is related to the fact that their synthesis involves many steps. On the other hand, the iron–chitosan complex is easily synthesized. This paper presents a study of the use of chitosan–iron(III) crosslinked with glutaraldehyde (Ch-Fe), as an adsorbent for the textile anionic dye Reactive Red 120 (RR120). This work involves studies of equilibrium and kinetics of adsorption in different conditions of pH and temperature, study of recovery and reuse of the adsorbent, and also factorial design in batch studies, and ﬁxed- bed studies to predict adsorption on an industrial scale. Experimental Materials The chitosan (viscosimetric molecular weight of 2.5  10 5 g/ mol, and desacetylation degree of 85%) was obtained from Purifarma (Sa ˜o Paulo). The dye Reactive Red 120 (Procion Red HE-3B; MF: C 44 H 24 Cl 2 N 14 O 20 S 6 Na 6 ; MW: 1469.98) was kindly Journal of Environmental Chemical Engineering 1 (2013) 1350–1358 ARTICLE INFO Article history: Received 16 August 2013 Received in revised form 7 October 2013 Accepted 8 October 2013 Keywords: Reactive Red 120 Chitosan–iron(III) Textile wastewater Factorial design ABSTRACT This paper presents a study of the use of chitosan–iron(III) crosslinked with glutaraldehyde (Ch-Fe) as an adsorbent for the textile anionic dye Reactive Red 120 (RR120) in batch and ﬁxed-bed systems. The maximum adsorption capacity was calculated from the adsorption isotherms, and well ﬁtted by the Langumir–Freudlich isotherm model. The process followed the kinetic model of pseudo-second-order. In ﬁxed-bed studies, the Thomas, Adams-Bahort and Clark models were applied to the breakthrough curves. The thermodynamic parameters showed that the adsorption process is spontaneous and favorable. The adsorbent can be easily regenerated and reused. The adsorption of the RR120 was optimized using a 3 3 factorial design, and the initial pH of the dye solution had a signiﬁcant effect. ß 2013 Elsevier Ltd. All rights reserved. * Corresponding author at: Universidade do Vale do Itajaı ´, Itajaı ´ CEP 88302-202, SC, Brazil. Tel.: +55 47 3341 7664; fax: +55 47 3341 7600. E-mail address: crodrigues@univali.br (C.A. Rodrigues). Contents lists available at ScienceDirect Journal of Environmental Chemical Engineering journal homepage: www.elsevier.com/locate/jece 2213-3437/$ – see front matter ß 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jece.2013.10.005