Fabrication of NiO coated SiO2 and SiO2 coated NiO for the removal of Pb2+ ions

We have prepared silica, SiO2 coated NiO and NiO coated SiO2 by sol-gel method. The physicochemical properties of the desired materials were investigated by surface charge properties, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, surface area measurements and X-ray diffraction (XRD) analyses. The point of zero charge (PZC) of the solid was determined by the salt addition method. In coated materials, two PZC values were noted representing the surface charge of their counterparts. The SEM image of SiO2 coated NiO displays a uniform coating of silica on the surface of NiO, whereas in case of NiO coated SiO2, a honeycomb like appearance was observed with highly porous structures. In the diffractograms of NiO, the characteristic peaks were suppressed in NiO coated silica, however, no diffraction peak could be seen in SiO2 coated NiO. Batch adsorption technique was applied for the removal of Pb2+ ions from aqueous solution. The sorption trend for Pb2+ ions was observed in the order of NiO coated SiO2 > SiO2 coated NiO > NiO > SiO2. This trend confirms that the coated materials have more sorption capacities than their parent counterparts.

Graphical abstractNiO coated silica was synthesized by the sol–gel method. Due to the porous nature and high surface area, the coated material removes more Pb2+ ions from the aqueous solution than the rest of the adsorbents prepared in the present work.Figure optionsDownload full-size imageDownload as PowerPoint slide