Removal of lead(II) ions from aqueous solutions using cashew nut shell liquid-templated thiol-silica materials

Abstract

A range of thiol-silica composites were prepared using cashew nut shell liquid (CNSL) or one of its phenolic constituents, cardanol, as templates. The procedure involved formation of a CNSL or cardanol emulsion in a water-ethanol system into which (3-mercaptopropyl)-trimethoxysilane and tetraethyl orthosilicate were simultaneously added at various ratios. The reaction mixture was aged at room temperature for 18 h followed by a Soxhlet extraction of the template and drying. The materials were characterized by diffuse reflectance Fourier transform infrared, nitrogen physisorption, scanning electron microscopy and acid titration. Results indicated that indeed the thiol-silica composites were successfully prepared, with thiol group loadings ranging from 1.6-2.5 mmol/g. The materials were tested for lead(II) adsorption, and results showed that they had maximum adsorption capacities up to 66.7 mg/g, depending on the thiol group loading and type of template used in preparing the adsorbent.

KEY WORDS: Thiol-silica materials, Cashew nut shell liquid, Lead(II) adsorption

Bull. Chem. Soc. Ethiop. 2014, 28(3), 363-372.

DOI: http://dx.doi.org/10.4314/bcse.v28i3.5