Carbohydrate Polymers 89 (2012) 275–281 Contents lists available at SciVerse ScienceDirect Carbohydrate Polymers jo u rn al hom epa ge: www.elsevier.com/locate/carbpol Microwave assisted synthesis of polyacrylamide grafted gum ghatti and its application as flocculant Priti Rani, Gautam Sen ∗ , Sumit Mishra ∗∗ , Usha Jha Department of Applied Chemistry, Birla Institute of Technology, Mesra, Ranchi 835 215, Jharkhand, India a r t i c l e i n f o Article history: Received 8 January 2012 Received in revised form 20 February 2012 Accepted 1 March 2012 Available online 8 March 2012 Keywords: Gum ghatti Flocculant Microwave assisted synthesis Graft co polymer Wastewater treatment a b s t r a c t Polyacrylamide chains (PAM) were grafted onto the backbone of gum ghatti by microwave assisted method. The grafting of the PAM chains on the polysaccharide backbone was confirmed through intrinsic viscos- ity study, FTIR spectroscopy, elemental analysis (C, H & N) and SEM morphology study. The intrinsic viscosity of gum ghatti appreciably improved on grafting of PAM chains, thus resulting grafted product with potential application as superior viscosifier. Further, flocculation efficacy of the graft copolymer was studied initially in kaolin suspension and then in municipal wastewater through ‘Jar test’ procedure, toward possible application as flocculant for wastewater treatment. © 2012 Elsevier Ltd. All rights reserved. 1. Introduction Gum ghatti is one of the oldest form of gum commercially avail- able since the dawn of civilization. The name ghatti came from the word ghat or the mountain passes which were the trade routes of India. Gum ghatti continues to be a cheap and abundant polysaccha- ride, cultivated and exported from Indian subcontinent. In this investigation, we have attempted to modify the properties of this cheap polysaccharide, toward its transformation into customized superior material with potential applications as viscosifier and as flocculant for wastewater treatment. Grafting with a synthetic polymer seems to be the most effective way of modification of a polysaccharide. In that case, precise modulation of properties in accordance with the intended application is possible (Mishra, Mukul, Sen, & Jha, 2011; Mishra, Sen, Rani, & Sinha, 2011; Sen & Pal, 2009b; Sen, Mishra, Jha, & Pal, 2010; Sen, Singh, & Pal, 2010). Gum ghatti is an amorphous, translucent exudate of the Anogeis- sus Latifolia tree of the Combretaceae family. The tree is quite large and is found abundantly in the dry, deciduous forests of India. Gum ghatti occurs in the form of calcium–magnesium salt. It is a composition of l-arabinose, d-galactose, d-mannose, d- xylose, and d-glucuronic acid in a molar ratio of 10:6:2:1:2 and ∗ Corresponding author. Tel.: +91 9740137364. ∗∗ Corresponding author. Tel.: +91 9431337645. E-mail addresses: gsen9@hotmail.com (G. Sen), sumitmishra1@gmail.com (S. Mishra). trace of 6-deoxyhexose below 1%. Partial hydrolysis gives two aldobiouronic acids, namely 6-O-(beta-d-glucopyranosyluronic acid)-d-galactose and 2-O-(beta d-glucopyranosyluronic acid)-d- mannose. Acid labile side chains are attached to the backbone through l-arabinofuranose resides (Whistler & Bemiller, 1973). Graft copolymers by definition, consists of a long sequence of one polymer (backbone polymer) with one or more branches (grafts) of another (chemically different) polymer (Gowariker, Viswanathan, & Sreedhar, 1986, chap. 12; Odian, 2002). The pro- cess of graft copolymer synthesis starts with a preformed polymer (polysaccharide in this case). An external agent is used to create free radical sites on this preformed polymer. The agent should be effec- tive enough to create the required free radical sites, at the same time should not be too drastic to rupture the structural integrity of the preformed polymer chain. Once the free radical sites are formed on the polymer back- bone (i.e. preformed polymer), the monomer (i.e. vinyl or acrylic compound) can get added up through the chain propagation step, leading to the formation of grafted chains. The various methods of graft copolymer synthesis actually differ in the ways of generation of the free radical sites on this preformed polymer. The most contemporary technique in graft copolymer synthe- sis involves the use of microwave radiations to initiate the grafting reactions. Superiority of this technique over others has been well discussed in earlier studies (Mishra & Sen, 2011; Mishra, Mukul, et al., 2011; Mishra, Sen, et al., 2011; Mishra, Rani, & Sen, 2012; Pal, Ghorai, Dash, Ghosh, & Udayabhanu, 2011; Pal, Sen, Ghosh, & Singh, 2012; Sen & Pal, 2009b; Sen, Kumar, Ghosh, & Pal, 2009; Sen, Mishra, et al., 2010; Sen, Singh, et al., 2010; Sen, Ghosh, Jha, & 0144-8617/$ – see front matter © 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.carbpol.2012.03.009