Carbohydrate Polymers 115 (2015) 617–628 Contents lists available at ScienceDirect Carbohydrate Polymers j ourna l ho me page: www.elsevier.com/locate/carbpol Flocculation and adsorption properties of biodegradable gum-ghatti-grafted poly(acrylamide-co-methacrylic acid) hydrogels H. Mittal a,c,∗ , R. Jindal b , B.S. Kaith b , A. Maity c , S.S. Ray a,c,∗ a Department of Applied Chemistry, University of Johannesburg, Doornfontein, Johannesburg 2028,South Africa b Department of Chemistry, National Institute of Technology, Jalandhar 144011, Punjab, India c DST/CSIR National Centre for Nanostructured Materials, Council for Scientific and Industrial Research, Pretoria 0001, South Africa a r t i c l e i n f o Article history: Received 15 July 2014 Received in revised form 10 September 2014 Accepted 11 September 2014 Available online 23 September 2014 Keywords: Gum ghatti Hydrogel polymer Graft co-polymerization Biodegradation Flocculation Adsorption a b s t r a c t This study reports the microwave-assisted synthesis of gum-ghatti (Gg)-grafted poly(acrylamide-co- methacrylic acid) (AAm-co-MAA) hydrogels for the development of biodegradable flocculants and adsorbents. The synthesized hydrogels were characterized using TGA, FTIR and SEM. TGA studies revealed that the synthesized hydrogels were thermally more stable than pristine Gg and exhibited maximum swelling capacity of 1959% at 60 ◦ C in neutral pH. The optimal Gg-cl-P(AAm-co-MAA) hydrogel was suc- cessfully employed for the removal of saline water from various petroleum fraction–saline emulsions. The maximum flocculation efficiency was achieved in an acidic clay suspension with a 15 mg polymer dose at 40 ◦ C. Moreover, the synthesized hydrogel adsorbed 94% and 75% of Pb 2+ and Cu 2+ , respectively, from aqueous solutions. Finally, the Gg-cl-P(AAm-co-MAA) hydrogel could be degraded completely within 50 days. In summary, the Gg-cl-P(AAm-co-MAA) hydrogel was demonstrated to have potential for use as flocculants and heavy metal absorbents for industrial waste water treatment. © 2014 Elsevier Ltd. All rights reserved. 1. Introduction In the past two decades, the demand for polymer-based materi- als has increased considerably because of their user-friendly nature, low cost, ready availability and, most importantly, their proper- ties can be easily modified to suit the nature of the application. The polymer industry has undergone tremendous growth, and the polymer-based materials have found applications in various fields, such as biomedical applications, spare parts for the auto- mobile industry, food packaging and serving materials, computer hardware parts and even water purification applications (Siracusa, Ingrao, Giudice, Mbohwa, & Rosa, 2014; Srivastava, O’Connor, Pandit, & Wall, 2014; Zah, Hischier, Leão, & Braun, 2007). Gen- erally, polymer-based materials leave behind a large amount of solid waste that is not easy to recycle. Biodegradation is the process of the deterioration of the physico-chemical properties of polymers and the reduction of the matrix molecular masses ∗ Corresponding authors at: University of Johannesburg, Applied Chemistry, Neend Street, Doornfontein, Johannesburg 2028, Gauteng, South Africa. Tel.: +27 847067375; fax: +27 128412229. E-mail addresses: mittal.hemant5@gmail.com (H. Mittal), rsuprakas@csir.co.za (S.S. Ray). by converting them into CO 2 , H 2 O and CH 4 under the action of enzymes and/or the chemical decomposition associated with liv- ing organisms (bacteria, fungi, yeasts and insects) or their secretion products, and the residues that remain after biodegradation should be non-toxic in nature (Raul Mu˜ noz & Benoit Guieysse, 2006; Ashori, 2008; Nayak, 2000; Suvorova, Tyukova, & Trufanova, 2000; Wang, Yang, & Wang, 2003). In recent years, Gum polysaccha- rides biodegradable have attracted considerable attention because of their unique features, including low cost, ready availability, biocompatibility and an eco-friendly nature. The primary dis- advantage of gum polysaccharide-based polymers is their poor mechanical properties compared with those of non-biodegradable polymers. The graft co-polymerization of gum-polysaccharides with vinyl monomers is the widely studied modification technique to improve their inherent properties. (Alvarez-Mance ˜ nido, Landin, Lacik, & Martínez-Pacheco, 2008; Guo, Ge, Li, Mu, & Li, 2014; Malik, Kumar, & Ahuja, 2012; Mittal, Ballav, & Mishra, 2014; Shi & Zhang, 2007; Shi, Wang, & Wang, 2011; Xu, Luo, Lin, Zhuo, & Liang, 2009). Flocculation is a very efficient technique for the purification of domestic/industrial potable water. Flocculants can be either inor- ganic additives or macromolecular compounds. Flocculants based on macromolecular compounds are preferred over inorganic addi- tives because their molar mass, chemical structure, charge density and the nature of their functional groups can be easily modified. http://dx.doi.org/10.1016/j.carbpol.2014.09.026 0144-8617/© 2014 Elsevier Ltd. All rights reserved.