Development of functional adsorbent from PU foam waste via radiation induced grafting I: Process parameter standardization N.K. Goel, Virendra Kumar, K.A. Dubey, Y.K. Bhardwaj n , L. Varshney Radiation Technology Development Division, Bhabha Atomic Research Centre, Trombay, Mumbai-400 085, India HIGHLIGHTS c PU foam waste inherently inert and large volume generated. c Waste converted to a hydrophilic adsorbent by radiation induced grafting of acrylic acid. c Parameters standardized to obtain adsorbent of desired grafting extent. c Grafted product show high and fast uptake of model dye. article info Article history: Received 9 February 2012 Accepted 8 September 2012 Available online 16 September 2012 Keywords: Polyurethane foam Waste Adsorbent Radiation grafting Dye uptake abstract Mutual radiation grafting process has been used to covalently link polymer chains of poly(acrylic acid) to polyurethane foam waste using 60 Co-gamma radiation source. Various experimental parameters were investigated in order to optimize the grafting process. The grafted samples have been characterized for water-uptake, surface morphology and thermal stability. Grafting extent increased with dose, dose rate and monomer concentration but decreased with increase in density of PU foam. The matrix grafted up to an extent of  90% showed uptake capacity of 220 mg/g (0.09 mol of dye/mol of acrylic acid) for a monovalent dye (basic red 29) within 3 h of contact time in a batch process. & 2012 Elsevier Ltd. All rights reserved. 1. Introduction Polyurethane foams because of their inherent properties find wide applications mainly as cushioning and insulating materials (Ashida, 2006; Benning, 1969). However, their wide application has led to it being one of the main components of municipal solid waste in the form of discarded consumer and industrial products. It is documented that by weight, approximately 1.3 million tons of waste polyurethanes are generated each year as part of the municipal solid waste stream representing 5% of all plastic waste (Frisch et al., 1999). Thus there is an immediate need to recycle or reprocess or modify PU waste particularly the foam into some suitable useful form. The graft polymerization has proven to be a powerful techni- que for designing tailored polymeric surfaces with desired prop- erties (Bhattacharya and Misra, 2004). Radiation induced grafting offers some unique advantages over the conventional chemical grafting method since it results in uniform grafting and is a room temperature process (Garnett, 1979). Radiation grafting of virgin polyurethane foam has been tried for a wide spectrum of applications like removal of heavy metal ions (Meligi, 2007; Moody and Thomas, 1979), immobilization of enzymes and cells (Romaˇ skevic ˇ et al., 2006) for designing surfaces to improve phase contacts (Braun and Farag, 1978), for bio-medical applications (Jansen, 1987; Yuan et al., 2008), for reduced protein adsorption (Fujimoto et al., 1993; Chen et al., 2008) and pre-concentration and separation (El-Shahat et al., 2010). Thus radiation grafting of virgin PU foam has been well documented however the radiation grafting of PU foam waste rarely finds mention in reported literature. Recently we have reported radiation induced grafting of different polymer wastes for designing suitable comb-type grafted vehicles for uptake of dyes from aqueous streams (Chaudhari et al., 2012; Goel et al., 2011). In the present study we explored the possibility of converting PU foam waste into a useful product for treating effluents having toxic metal ions and harmful dyes. The microcellular porous structure of PU foam was expected to provide higher surface area leading to good functionalizing efficiency and faster uptake kinetics. Mutual radiation grafting method was adopted to modify the surface of PU foam. Polyacrylic acid (PAA) was covalently Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/radphyschem Radiation Physics and Chemistry 0969-806X/$ - see front matter & 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.radphyschem.2012.09.007 n Corresponding author. Tel.: þ91 22 25590178; fax: þ91 22 25505151. E-mail address: ykbhard@barc.gov.in (Y.K. Bhardwaj). Radiation Physics and Chemistry 82 (2013) 85–91