International Journal of Biological Macromolecules 48 (2011) 106–111 Contents lists available at ScienceDirect International Journal of Biological Macromolecules journal homepage: www.elsevier.com/locate/ijbiomac Microwave assisted synthesis of polyacrylamide grafted starch (St-g-PAM) and its applicability as flocculant for water treatment Sumit Mishra, Ankita Mukul, Gautam Sen ∗ , Usha Jha Department of Applied Chemistry, Birla Institute of Technology, Mesra, Ranchi 835 215, Jharkhand, India article info Article history: Received 15 September 2010 Received in revised form 4 October 2010 Accepted 7 October 2010 Available online 15 October 2010 Keywords: Ceric ammonium nitrate Flocculant Microwave assisted synthesis Jar test Polyacrylamide grafted starch abstract Polyacrylamide grafted starch (St-g-PAM) was made by a novel method of synthesis, involving combi- nation of microwave radiation and a chemical free radical initiator (ceric ammonium nitrate) to initiate grafting reaction. This method (microwave assisted synthesis) is quick, highly reliable, reproducible and yields high quality product as compared to the conventional method (which uses a chemical free radical initiator alone to initiate the grafting reaction).The St-g-PAM grades synthesized were characterized by various physicochemical techniques. Further, its application as flocculant for wastewater treatment was investigated. © 2010 Elsevier B.V. All rights reserved. 1. Introduction The importance of graft copolymers in the world of polymer sci- ence is analogous to the importance of alloying in case of metals. In case of grafted polysaccharides this assumes even greater impor- tance as grafting is perhaps the most effective way of regulating the properties of polysaccharides ‘tailor-made’ according to our needs. The main problem in case of graft copolymers is the lack of com- mercial methods of synthesis. The chief methods of synthesis of grafted polysaccharides involves use of chemical free radical ini- tiator (conventional method), high energy radiations (gamma and X-ray), UV-radiation based method and microwave based methods. The conventional method of synthesis uses a chemical free rad- ical initiator (e.g. ceric ammonium nitrate or CAN) to generate free radical sites on the backbone polymer, where the monomer of the graft gets added up to form the graft chain [1–5]. This method of synthesis has low reproducibility and is not very suitable for commercial scale synthesis. A better method of graft copolymer synthesis is by use of high energy radiation (gamma rays or electron beam) as the free radical generator [6–7]. But this method is not suitable for grafted polysac- charide synthesis as the high energy radiation can cause damage to the polysaccharide backbone (radiolysis). UV rays in presence of suitable photosensitizor can also be used, but low penetration of UV-rays makes it suitable for surface grafting only. ∗ Corresponding author. Tel.: +91 9470137364. E-mail address: gsen9@hotmail.com (G. Sen). The best method of graft copolymer synthesis is by use of microwave radiation to generate the free radical sites on the back- bone polymer. Recently, the microwave based methods of graft copolymer synthesis has been classified into two types [8]: (1) Microwave initiated synthesis: uses microwave radiation alone to create free radical sites on the polysaccharide backbone, from where the graft chains grow [4,8–10]. (2) Microwave assisted synthesis: uses a combination of microwave radiation and chemical free radical initiator to create the free radical sites on the polysaccharide backbone, from where the graft chains grow. In the study reported here, we have synthesized polyacrylamide grafted starch (St-g-PAM) by ‘microwave assisted’ method, in pres- ence of ceric ammonium nitrate (CAN) as free radical initiator. Microwave assisted synthesis of grafted starch using CAN as free radical initiator, has never been reported before to the best of our knowledge. Grafted polysaccharides have diverse applications, cutting across various fields of science and technology. Some important applications are as flocculant for wastewater treatment [4,9], as matrix for controlled drug release [8,10] and rheological appli- cations. In this study, we have investigated the flocculation efficacy of polyacrylamide grafted starch (St-g-PAM) synthesized by microwave assisted process, towards its application in wastew- ater treatment. Water is the single most important resource that decides the fate of human being and for that matter any living being. The present ever increasing population and improving standard of liv- 0141-8130/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.ijbiomac.2010.10.004