Effect of Concentration of Aminopropyl Groups on the Surface of MCM-41 on Adsorption of Cu2+

Abstract

MCM-41 synthesized at room temperature was functionalized with aminopropyltrimethoxysilane (APTMS). The functionalized MCM-41 were characterized by powder X-ray diffraction, scanning electron micrography (SEM), transmission electron-microscopy (TEM), nitrogen adsorption–desorption, and carbon, nitrogen, and hydrogen (CHN) analysis. X-ray diffraction patterns indicate that the modified materials retain the structure of MCM-41. An increase in surface concentration of aminopropyl groups (0.7 to 1.9 mmol/g) resulted in a decrease in the surface area, BJH pore size, and total pore volume. Studies on the adsorption of Cu2+ on these samples showed the Langmuir type adsorption isotherms. The value of the Langmuir monolayer capacity of Cu2+ adsorption increased linearly with an increase in the surface concentration of the amino group. The NH2/Cu2+ mole ratio increased from ∼1.5 to ∼2 when the concentration of the amino group increased from 0.71 to 1.42 mmol/g and remained almost the same for higher concentrations.