Poly(amidoamine) dendrimer immobilized on mesoporous silica foam (MSF) and fibrous nano-silica KCC-1 for Gd3+ adsorption in water.

High performance adsorption of Gd3+ by the second generation poly(amidoamine) dendrimer immobilized on mesoporous silica foam (MSF) and fibrous nano-silica KCC-1. • Poly(amidoamine) dendrimer was grafted on mesoporous silica foam and fibrous silica KCC-1. • The prepared adsorbents were extensively characterized after each preparation step. • Gd3+ adsorption over the adsorbents was examined under various experimental conditions. • Mesoporous silica foam was more effective as a host than KCC-1 for the dendrimer. • High adsorption capacity and recyclability with good selectivity were confirmed. Separation and recovery of low concentration rare earth elements (REEs) from aqueous environment need to be considered to meet their growing demand for high-technology devices. In this work, the second-generation poly(amidoamine) dendrimers immobilized on a mesoporous silica foam (MSF) or a fibrous nano-silica KCC-1 (PAMAM@GTA-NH 2 -MSF and PAMAM@GTA-NH 2 -KCC-1, respectively) were prepared after systematic grafting of 3-aminopropyltriethoxysilane and glutaraldehyde (GTA) as a cross-linking spacer. These were investigated for recovery of gadolinium ions (Gd3+) in water via adsorption. The prepared adsorbents were extensively characterized in each preparation step by various analytical instruments, and successful attachment of the organic groups on the silica supports was confirmed. The Gd3+ adsorption over the functionalized materials was examined under different conditions of the solution pH, initial Gd3+ concentrations, and adsorption time. PAMAM@GTA-NH 2 -MSF performed better than PAMAM@GTA-NH 2 -KCC-1, with exceptionally high adsorption capacity (ca. 132 mg/g) and recyclability with reasonable selectivity for potential commercial use. Gd3+ selectivity against competing ions could be further enhanced to ca. 86% by successive functionalization with N-(phosphonomethyl) iminodiacetic acid on PAMAM@GTA-NH 2 -MSF. [ABSTRACT FROM AUTHOR]