Chemical Engineering Journal 178 (2011) 252–263 Contents lists available at SciVerse ScienceDirect Chemical Engineering Journal jo u r n al hom epage: www.elsevier.com/locate/cej Synthesis and swelling behavior of pH-sensitive semi-interpenetrating polymer network composite hydrogels based on native and modified potatoes starch as potential sorbent for cationic dyes Ecaterina Stela Dragan ∗ , Diana Felicia Apopei “Petru Poni” Institute of Macromolecular Chemistry, Aleea Grigore Ghica Voda 41 A, 700487 Iasi, Romania a r t i c l e i n f o Article history: Received 13 August 2011 Received in revised form 19 October 2011 Accepted 20 October 2011 Keywords: Polyacrylamide Potatoes starch Grafting Hydrolysis Methylene Blue Swelling ratio UV–vis a b s t r a c t Semi-interpenetrating polymer network (semi-IPN) composite hydrogels based on polyacrylamide (PAAm) as a matrix and either native potatoes starch (PS) or the hydrolyzed PS-g-PAN copolymer as entrapped polymer have been prepared using N,N-methylenebisacrylamide (BAAm) as cross-linker, ammonium persulfate as radical initiator and N,N,N ′ ,N ′ -tetramethylethylenediamine as accelerator of free-radical polymerization. The composite hydrogels have been characterized by FT-IR and swelling behavior as a function of the cross-linker ratio. The kinetics of Methylene Blue (MB) adsorption on the semi-IPN composite hydrogels has been investigated as a function of the nature of the entrapped polymer in PAAm matrix. Sorption of MB on the composite hydrogels has been well described by the pseudo-first order kinetic model, which support physisorption dominates the adsorption process. The dye adsorp- tion tests up to four adsorption/desorption cycles support the reusability of the composite hydrogels as sorbents for cationic dyes. © 2011 Elsevier B.V. All rights reserved. 1. Introduction The water pollution with dyes is becoming a huge environ- mental problem because colored wastewater has a very serious destructive impact on the environment. Release of colored wastew- aters in effluents can affect the photosynthetic activity in aquatic life, and therefore their decontamination is strongly required. Furthermore, the more stringent regulations concerning effluents require diminishing of the dye content in the water or even banning of some dyes [1]. Textile, paper, plastics, and cosmetic industries use a wide variety of cationic dyes to color their products and dis- charge large amount of effluents including dyes. The cationic dyes are more toxic than the anionic dyes as these can easily interact with negatively charged cells membrane surfaces, and can enter into cells and concentrate in cytoplasm [2,3]. The dye removal from industrial wastewaters is usually performed by processes like biological treatment, coagulation/flocculation, adsorption, and oxidation. Among these methods, adsorption is considered as an effective and economical method to remove dyes, the majority of sorbents, either synthetic or coming from renewable resources, having the advantage of the reusability [4–14]. ∗ Corresponding author. Tel.: +40 232217454; fax: +40 232211299. E-mail addresses: sdragan@icmpp.ro (E.S. Dragan), dfelicia@icmpp.ro (D.F. Apopei). Natural polymeric materials are gaining more and more interest for application as adsorbents in wastewater treatment due to their low cost, biodegradability and non-toxic nature [8,10,11,14,15]. As a functional biological polymer, starch offers an interesting set of characteristics, including biodegradability, biocompatibil- ity, and bioactivity. Native starch granules are water insoluble, containing two major components: (1) amylose, 20–30% of the starch granules, which consists in linear chains of -(1-4-linked-d- glucose) units, characterized by a molar mass ranging from 4 × 10 4 to 1 × 10 5 g mol -1 , and (2) amylopectin, which consists of branched chains of -(1-4-linked-d-glucose) units interlinked by -(1-6- linked-d-glucose) linkages, in proportion of 70–80%, characterized by a molar mass ranging from 2 × 10 5 to 1 × 10 6 g mol -1 [16]. In recent years, particular attention has been addressed to the syn- thesis of starch grafted copolymers, this being one of the most convenient ways to modify the properties of starch. Particularly, grafting of acrylonitrile (AN) on starch gives the possibility to perform further chemical reactions and to synthesize new highly added value materials for various applications, such as: soil con- ditioners, additives for paper and textiles, adhesives, enhanced oil recovery, sanitary goods, drug delivery devices, wastewaters reme- diation, etc. [17–20]. Native and modified starches have been used as raw materials in the preparation of novel sorbents such as hydro- gels [21–23]. For many applications, multicomponent hydrogels as semi- or full-interpenetrating polymer networks (IPN) show improved mechanical properties, faster response rate and diffusion of solutes [23–25]. 1385-8947/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.cej.2011.10.066