Design of Nanostructured Tamarind Seed Kernel Polysaccharide-Silica Hybrids for Mercury (II) Removal

Abstract

Tamarind (Tamarindus indica L.) seed kernel polysaccharide-silica (TKP-Si) nanohybrids have been fabricated in a base catalyzed sol-gel reaction where tetraethylorthosilicate (TEOS) and tamarind kernel polysaccharide were used as silica precursor and template respectively. The nanohybrids were found to be photoluminescent and efficient in Hg(II) removal from the synthetic aqueous solution. The synthesized nanohybrids were characterized using Fourier Transform Infra-red spectroscopy (FTIR), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), Differential Thermal Analysis (DTA), and Photoluminescence (PL) analysis. For obtaining the most efficient sample in terms of mercury (II) binding, various ratios of reactants (Polysaccharide: TEOS: H₂O: EtOH) were used and the optimum sample thus obtained was calcined at 200°C (in air) to further enhance its binding performance. A mechanism for the sorption of Hg(II) by the optimum hybrid sample (TH₁) has been proposed and to understand its sorption behavior, kinetics and isotherm studies have also been performed. Regeneration studies indicated that the loaded Hg(II) from the used hybrid can be easily desorbed and can be successfully reused for eight consecutive adsorption-desorption cycles.

Keywords:

• Hg(II)adsoption
• nanohybrid
• sol-gel
• tamarind polysaccharide
• TEOS

ACKNOWLEDGEMENTS

Authors are indebted to Department of Science and Technology, India for financial support and to Prof. R. Chandra (Director, IIC, IIT, Roorkee, India) and Dr. T. Alam (Jamia Milia Islamia, New Delhi, India) for XRD and thermal analysis respectively.

Notes

†Permanent Address: Department of Chemistry, IET, M.J.P. Rohilkhand University, Bareilly 243 006, India.