Removal of aqueous Pb(II) using low-cost agricultural wastes modified by 3-aminopropyltrimethoxysilane

In order to develop the low-cost and high efficient absorbents, agricultural by-products e.g., peanut hulls, soybean shells and grapefruit peels were chemically modified with 3-aminopropyltrimethoxysilane after the saponification using 17.5% NaOH. Chemical modification was confirmed by infrared spectra and N contents. The optimum adsorption parameters for Pb(II) were around 4.5 for pH and 2 g L^-1 for ratio of solid to liquid. The kinetic adsorption fitted well with the pseudo-second order kinetic model and the isotherm adsorption fitted well with Langmuir adsorption model. The maximum absorption capacities of chemically-modified peanut hulls, soybean shells and grapefruit peels were 32.9, 75.8 and 154 mg g^-1, respectively. More than 90% Pb(II) can be desorbed from modified biosorbents using 1 mol L^-1 HCl solution. Chemically-modified grapefruit peels exhibited higher absorption capacities and can be used as potential the low-cost and high efficient absorbents for the removal of Pb(II) from wastewater.