Characterization of modified silica aerogel using sodium silicate precursor and its application as adsorbent of Cu2+, Cd2+, and Pb2+ ions

Sodium silicate (Na2O/SiO2 = 1:3.3) as a precursor is used to prepare silica aerogel. The prepared silica aerogel is modified by mercaptopropyl trimethoxysilane. The modified silica aerogel is characterized using Fourier transform infrared spectroscopy, Brunauer, Emmett, Teller method, and transmission electron microscopy. The adsorption and removal of Cu2+, Cd2+, and Pb2+ ions from aqueous samples using modified silica aerogel are studied. The experimental conditions such as pH of samples, initial concentration of cations, contact time, and adsorbent dose are optimized to attain the maximum adsorption capacity. The optimum values are obtained as follows: contact time = 30 min, adsorbent dose = 0.05 g for Cd2+and Pb2+ ions and 0.1 g for Cu2+ ions, pH = 6 for Cd2+ and Pb2+ ions, and pH = 4 for Cu2+ ions. The equilibrium data are fitted well by the Langmuir and Freundlich isotherm models. The adsorption capacities for Cu2+, Cd2+, and Pb2+ ions are found 90.1, 181.8, and 250.0 mg/g, respectively.