XANES evidence of molybdenum adsorption onto novel fabricated nano-magnetic CuFe2O4

• A technology for preparation of CuFe2O4 is developed from industrial sludge.
• The CuFe2O4 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 CuFe2O4.
• The data implies that 0.001 N NaOH solution is sufficient for Mo desorption.
• The CuFe2O4 could be rapidly separated and recycled by a magnet in 20 s.

An efficient Molybdenum (Mo) removal technology in aqueous solutions was developed for the first time using nano-magnetic CuFe2O4 manufactured from printed circuit board (PCB) industrial sludge. This nano-magnetic CuFe2O4 adsorbent displayed a nonlinear L-type isotherm that fitted well with the Langmuir 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 oxidation species on nano-magnetic CuFe2O4 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, groundwater, and tap water. This unique Mo separation technique can also be potentially applied for geochemical investigation in various natural aqueous solutions.

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