Biosynthesized silica-based zinc oxide nanocomposites for the sequestration of heavy metal ions from aqueous solutions

Abstract

In the present study, biosynthesized silica-based zinc oxide nanocomposites (nano-SZO) have been explored as nanoadsorbent for sequestrating heavy metal ions viz. Ni2+, Cd2+and Cu2+ from synthetic medium. The nanocomposites have been obtained by utilization of agricultural waste by means of green synthetic approach with an average particle size of 30.52 nm and a pH at zero-point charge as 4.8. The process has been optimized at a pH equal to 5.0 for Ni2+ and 6.0 for Cu2+ and Cd2+. Adsorption was best described by Langmuir isotherm and the highest value of maximum adsorption capacity, qm of nano-SZO was obtained for Cu2+ (32.53 mg/g), Ni2+ (32.10 mg/g), and Cd2+ (30.98 mg/g). The studied heavy metal ions are considerably adsorbed by the nano-SZO through chemisorption by active binding with polyhy- droxy functionalities attached at the surface of the nanoadsorbent confirming the utilization of biosyn- thesized nano-SZO as eco-friendly and efficient nano adsorbents for the sequestration of heavy metal ions.