A diamino based resin modified silica composite for the selective recovery of tungsten from wastewater

A new adsorbent was developed by synthesizing 1,8-diaminonaphthalene formaldehyde resin (DANFR) and coating it over the surface of silica gels. The silica composite was then treated with HCl for the activation of binding sites (-NH3+Cl-) on its surface. The structure of DANFR and its coating over the silanols were thoroughly characterized. Further, the adsorbent was applied to remove tungsten (W) from printed circuit board recycling unit wastewater that contained various co-metal ions such as Na+, K+, Ca2+, Mg2+, Pb2+, NH4+, Zn2+, Cu2+ and Mn2+. The selective removal was achieved due to the anion exchange mechanism of Cl- with W(VI) while other cations get repelled from the surface (-NH3+) of the DANFR-silica composite. X-ray photoelectron spectroscopy studies, Raman spectra and overlay chromatograms of ion chromatography demonstrated selective separation of WO42- species from the wastewater. A removal capacity of 55.32 mg g(-1) for W(VI) was achieved from the wastewater within 45 min of reaction (pHca 6.0). Simultaneous treatment with neat aqueous solution of W brings out 63.27 mg g(-1) of W(VI) removal. Finally, recovery of WO42- ions and regeneration of the adsorbent were carried out by using alkaline solution which demonstrated successful desorption, as investigated by using ion chromatography. (c) 2016 Society of Chemical Industry