XANES evidence of molybdenum adsorption onto novel fabricated nano-magnetic CuFe 2 O 4 Yao-Jen Tu a,⇑ , Chen-Feng You a,b,⇑ , Chien-Kuei Chang c , Ting-Shan Chan d , Sheng-Hsien Li b a Earth Dynamic System Research Center, National Cheng-Kung University, No 1, University Road, Tainan City 701, Taiwan, ROC b Department of Earth Sciences, National Cheng-Kung University, No 1, University Road, Tainan City 701, Taiwan, ROC c Department of Chemical and Materials Engineering, National Kaohsiung University of Applied Science, No 415, Chien Kung Road, Kaohsiung 807, Taiwan, ROC d National Synchrotron Radiation Research Center (NSRRC), No 101, Hsin-Ann Road, Hsincho 30076, Taiwan, ROC highlights  A technology for preparation of CuFe 2 O 4 is developed from industrial sludge.  The CuFe 2 O 4 is effective in removing Mo from wastewater, groundwater and tap water.  The K-edge XANES spectra show that Mo(VI) was the dominant species on CuFe 2 O 4 .  The data implies that 0.001 N NaOH solution is sufficient for Mo desorption.  The CuFe 2 O 4 could be rapidly separated and recycled by a magnet in 20 s. graphical abstract Nano-magnetic CuFe2O4 Industrial Cu Sludge Acid leaching reactor Chemical exchange reactor Ferrite process reactor Adsorbent recovery Magnet 19980 20000 20020 20040 20060 0.00 0.25 0.50 0.75 1.00 1.25 MoO2(Mo4+) MoO3(Mo6+) CuFe2O4-Mo (pH=2.75) Mo K-edge Normalized absorption Energy (eV) article info Article history: Received 2 December 2013 Received in revised form 24 January 2014 Accepted 25 January 2014 Available online 2 February 2014 Keywords: Molybdenum Mo K-edge XANES Adsorption Industrial sludge Nano-magnetic CuFe 2 O 4 abstract An efficient Molybdenum (Mo) removal technology in aqueous solutions was developed for the first time using nano-magnetic CuFe 2 O 4 manufactured from printed circuit board (PCB) industrial sludge. This nano-magnetic CuFe 2 O 4 adsorbent displayed a nonlinear L-type isotherm that fitted well with the Lang- muir isotherm, suggested limited adsorption sites and monolayer sorption on surface. The K-edge X-ray absorption near-edge structure (XANES) spectra demonstrated that Mo(VI) was the predominant oxida- tion species on nano-magnetic CuFe 2 O 4 and the maximum adsorption capacity was found to be 30.58 mg g 1 at pH 2.75. When pH became higher, more negative charges would occur at the surface of adsorbent and lead to more electric repulsion. Consequently, Mo adsorption was sharply reduced in alkaline condition. Importantly, these adsorbed Mo anions were replaced easily by OH  ions in NaOH solution and showed huge potential for removal/concentration of Mo in industrial wastewater, ground- water, and tap water. This unique Mo separation technique can also be potentially applied for geochem- ical investigation in various natural aqueous solutions. Ó 2014 Elsevier B.V. All rights reserved. 1. Introduction Molybdenum (Mo) is a trace element which presents widely in nature and is required by the human body for many important bio- logical and physiological processes [1–3]. The estimated daily http://dx.doi.org/10.1016/j.cej.2014.01.084 1385-8947/Ó 2014 Elsevier B.V. All rights reserved. ⇑ Corresponding authors at: Earth Dynamic System Research Center, National Cheng-Kung University, No 1, University Road, Tainan City 701, Taiwan, ROC. Tel./fax: +886 6 2758682 (Y.-J. Tu). E-mail addresses: todojen@gmail.com (Y.-J. Tu), cfy20@mail.ncku.edu.tw (C.-F. You). Chemical Engineering Journal 244 (2014) 343–349 Contents lists available at ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej