Journal of Hazardous Materials 280 (2014) 514–523 Contents lists available at ScienceDirect Journal of Hazardous Materials jo ur nal ho me p ag e: www.elsevier.com/locate/jhazmat n-Benzoyl-n-phenylhydroxylamine impregnated Amberlite XAD-4 beads for selective removal of thorium S. Chandramouleeswaran, Jayshree Ramkumar ∗ Analytical Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, India h i g h l i g h t s • XAD-4 was impregnated with a commonly used gravimetric agent n-benzoyl-n-phenylhydroxylamine. • Sorbent characterized by different techniques to understand the pore filling of XAD-4. • Sorption of Th was fast (30 min) and unaffected by initial solution pH. • Selectivity achieved by tuning the conditions of the mixture solution. a r t i c l e i n f o Article history: Received 16 January 2014 Received in revised form 7 August 2014 Accepted 9 August 2014 Available online 3 September 2014 Keywords: Impregnation Sorption Selective Thorium a b s t r a c t n-Benzoyl-n-phenylhydroxylamine impregnated Amberlite XAD-4 beads were used for the removal of Th(IV) from a mixture of ions. The impregnated XAD was characterized using different techniques like weight and colour change, IR spectra, surface area and pore size measurements to confirm the presence of n-BPHA within the macroreticular resin structure. The experimental conditions were optimized to make the separation fast and selective. It was seen that the maximum sorption was achieved in the pH range of 3–7.5 and uptake was nearly complete within half an hour. The results obtained in the present study were subjected to extensive modelling in order to get a complete understanding of the sorption process. It is seen that the maximum uptake was calculated to be 500 mg/g and has very fast kinetics it was seen that the process is chemisorption. It was further deduced from the modelling that the overall sorption process was controlled dominantly by external mass transfer. Considering the simplicity this procedure, the present study has a possible application for the removal of thorium from different mixtures. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Thorium is a very important element in various fields like geol- ogy [1,2] and medicine [3] and is present in low levels in the aqueous waste stream from mining nuclear materials. Due to the various applications, there is a need for development of separa- tion procedures. It is reported that thorium can be released into the atmosphere from both natural and anthropogenic sources and the concentration in volcanic ash, soil etc. are in the range of 0.5–7.3 g/g but it is less than 1 ng/g in ground water system [4,5]. Sorption using simple and cheap adsorbents is gaining lot of importance [6–12] and there is ongoing research for the devel- opment of newer cheap and easily available sorbents thus avoid regeneration. ∗ Corresponding author. Tel.: +91 22 2559 2224; fax: +91 22 2550 5151. E-mail address: jrk@barc.gov.in (J. Ramkumar). Modification of sorbents to enhance selectivity has been reported in literature [13]. In this study, the selective uptake of thorium has been studied using the organic resin Amberlite XAD-4, modified with a ligand n-benzoyl-n-phenylhydroxylamine (n-BPHA) that has used extensively in analytical chemistry as a chromophore and for separation prior to analysis. There are various reports of the use of n-benzoyl-n-phenylhydroxylamine (n-BPHA) as an analytical reagent in solvent extraction [14–16], gravime- try [17–19], spectrophotometry [20], titrimetry [21]. The use of n-BPHA for removal of metal ions prior to their analysis has also been reported [22–24]. The use of n-BPHA for the extraction- chromatographic study to obtain carrier-free 234 Th(UX1) from uranyl nitrate and 233 Pa from irradiated thorium has been reported [25]. There are various reports on the use of XAD-4 for dif- ferent applications [26–28]. Hence it was of great interest to evaluate the sorption efficiency of a neutral resin XAD-4 impreg- nated with n-BPHA. Various experimental factors which could affect sorption were varied and optimized to get maximum uptake. http://dx.doi.org/10.1016/j.jhazmat.2014.08.047 0304-3894/© 2014 Elsevier B.V. All rights reserved.