Efficient Adsorption of Lead(II) Ions from Artificial Wastewater by Organically Tailored vs TEOS-Doped Silica Aerogels: Synthesis, Characterization and Isotherm Studies

Abstract

In this study, two silica aerogels were synthesized and compared of their morphology and lead adsorptive behavior. One silica aerogel was aged with organic solvents, ethanol and heptane (SG-OM), while the other was doped with tetraethyl orthosilicate (TEOS) (SG-TD). Both the materials were characterized using SEM, XRD, FTIR, and BET. As per results, SG-OM showed higher surface area (312 m2/g), higher pore volume (0.85 cm3/g), and higher porosity % (85%) than SG-TD with surface area (264 m2/g), higher pore volume (0.56 cm3/g), and higher porosity % (74.9%). Both the aerogels were highly mesoporous in their structure. Moreover, when the adsorbents were investigated for lead(II) removal from synthetic wastewater, SG-OM indicated higher removal with 98.58% (pH 6), 98% (5 ppm metal concentration), and 98% (0.1 g adsorbent dose) than SG-TD with removal of 65% (pH 6), 88% (5 ppm metal concentration), and 62% (0.1 g adsorbent dose). Moreover, the highest adsorption capacity (qe) indicated by SG-OM was 15.2 mg/g and SG-TD as 11.8 mg/g. It was revealed that aging with organic solvents (ethanol and heptane) resulted in an aerogel with enhanced morphological properties and lead(II) adsorptive efficiency than aerogel doped with TEOS. Finally, the obtained results were investigated for isotherms (Langmuir and Freundlich), and it was shown that both the adsorbents best fitted Langmuir isotherm.