Efficient carbon interlayed magnetic chitosan adsorbent for anionic dye removal: Synthesis, characterization and adsorption study Bahareh Tanhaei a, ⁎, Ali Ayati a, ⁎, Evgenia Iakovleva b , Mika Sillanpää c,d,e a Department of Chemical Engineering, Quchan University of Technology, Quchan, Iran b Kärsa Ltd, A.I.Virtasen aukio, 00560 Helsinki, Finland c Institute of Research and Development, Duy Tan University, Da Nang 550000, Viet Nam d Faculty of Environment and Chemical Engineering, Duy Tan University, Da Nang 550000, Viet Nam e School of Civil Engineering and Surveying, Faculty of Health, Engineering and Sciences, University of Southern Queensland, West Street, Toowoomba, 4350, QLD, Australia abstract article info Article history: Received 10 July 2020 Received in revised form 22 August 2020 Accepted 27 August 2020 Available online 29 August 2020 Keywords: Magnetic chitosan Carbon Adsorbent Kinetic Isotherm Methyl orange The present paper describes the synthesis of a novel magnetic chitosan (CCF), in which the carbon-Fe 3 O 4 core- shell nanoparticles play the role of magnetic part. The structure, property and morphology of the magnetic CCF were characterized by FT-IR, XRD, EDAX, SEM and BET techniques. Its adsorption performance was investigated for the removal of methyl orange from aqueous solutions by varying experimental conditions. The results showed the fast adsorption of methyl orange in wide pH range of 3–11 and the maximum adsorption capacity was found to be 425 mg g -1 at 45 °C. The results of adsorption kinetics indicated that the adsorption mechanism was better described by the pseudo-second-order equation, whereas pore diffusion is the rate-controlling of ad- sorption kinetics. Furthermore, among different isotherm models, Langmuir and Sips isotherm models fitted well the equilibrium experimental data at different temperatures revealing the surface heterogeneity of the adsor- bents. The adsorbent exhibited high adsorption performance, compared to the some other chitosan adsorbents reported in literatures. © 2020 Elsevier B.V. All rights reserved. 1. Introduction In last two decades, the water pollution has been a worldwide con- cern, especially in developing countries, and the contaminant species detection and removal from the wastewater, surface and ground water is a significant global challenge [1–4]. In this regard, adsorption method has received significant attention and it is considered as preva- lent separation technique, owning to its simplicity of design and opera- tion, low initial cost and high removal efficiency even from dilute solutions [5–7]. Among the wide range of low cost adsorbents, chitosan and its derivatives attracted significant interest for the organic and inor- ganic contaminant removal from the aqueous solutions [8–11]. Chitosan, as a natural polysaccharide biosorbent extracted from the N-deacetylation of chitin biopolymer, is an effective and low cost adsor- bent compared to activated carbon and due to the miraculous number of free amino and hydroxyl groups, has outstanding chelation behavior to tightly bind several pollutants [12–15]. One of the most important drawbacks of chitosan adsorbents is their difficult separation from the treated aqueous solutions using the traditional separation techniques, such as filtration or sedimentation, because of filter blockage or adsor- bent lost [16,17]. In order to overcome this problem, recent studies have been focused on employing magnetic separation technology, by cross-linking of the chitosan to the magnetic materials surface, in which the sorbent can be easily and quickly separated by an external magnet after the process with producing no contaminants [17–19]. Among the magnetic materials, iron oxides, including magnetite (Fe 3 O 4 ) and maghemite (Fe 2 O 3 ), have been studied intensively, due to their strong super-paramagnetic activity, facile preparation, high ther- mal stability and low toxicity [3,20]. These magnetic particles are sensi- tive to acid conditions, which can reduce their magnetic separability [18]. Coating the surface of iron oxide particles with inert layers is an ef- fective strategy to protect them and enhance attenuation performance [21]. Silica and alumina are two recently introduced materials which have been used as coating layer of iron oxides particles in the magnetic chitosan composites adsorbents [22–25]. They improve the nanoparti- cles' chemical stability, prevent oxidation and also add new specific functionalities to chitosan for pollutants adsorption [16]. According to the significant synergistic behavior between Fe 3 O 4 and carbon [26], carbon was extensively considered as one of the most promising materials for coating on iron oxides particles, due to its non-toxicity, high chemical inertness, low magnetic susceptibility and noteworthy compatibility [27,28]. It can effectively keep the magnetic core from environmental oxidation and facilitate the linkage of func- tional groups to their surface [29]. For the first time, the C/Fe 3 O 4 core- shell (CF) particles have been used as core for the synthesis of magnetic International Journal of Biological Macromolecules 164 (2020) 3621–3631 ⁎ Corresponding authors. E-mail addresses: b.tanhaei@qiet.ac.ir (B. Tanhaei), a.ayati@qiet.ac.ir (A. Ayati). https://doi.org/10.1016/j.ijbiomac.2020.08.207 0141-8130/© 2020 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect International Journal of Biological Macromolecules journal homepage: http://www.elsevier.com/locate/ijbiomac