Synthesis and characterization of a new starch/SnO2 nanocomposite for efficient adsorption of toxic Hg2+ metal ion

• Starch based nanocomposite (starch/SnO2) was synthesized by sol–gel method.
• Starch/SnO2 nanocomposite was used for the removal of Hg2+ from aqueous medium.
• The maximum adsorption capacity was found to be 333 mg g−1 at 25 °C.
• The adsorbed Hg2+ metal ion could be successfully desorbed using 0.1 M HCl solution.

In this study, starch based nanocomposite (starch/SnO2) was synthesized and used as an effective adsorbent for the removal of Hg2+ from aqueous medium. The as-prepared starch/SnO2 nanocomposite was characterized by means of the XPS, XRD, BET, FTIR, SEM and TEM analyses. The effects of contact time, pH, initial Hg2+ concentration and temperature on the adsorption performance of starch/SnO2 nanocomposite were investigated thoroughly. The experimental results showed that starch/SnO2 nanocomposite had high ability to remove Hg2+ ion from aqueous medium. The adsorption of Hg2+ was maximum at the pH 6 and equilibrium was achieved within 60 min. The pseudo-second-order equation represented the adsorption kinetics with high correlation coefficient (>0.998) and the Freundlich isotherm model fitted the adsorption data better than the Langmuir. The maximum adsorption capacity was found to be 192 mg g−1 at 25 °C which was increased with the temperature, indicated the endothermic adsorption. The feasibility of Hg2+ adsorption onto starch/SnO2 nanocomposite was also studied thermodynamically and the results showed that the adsorption was spontaneous and chemical in nature. The adsorption capacity of the regenerated adsorbents could still be maintained at 94% by the fourth adsorption–desorption cycle.

Figure optionsDownload as PowerPoint slide