Direct Synthesis of Sulfur-Decorating PAMAM Dendrimer/Mesoporous Silica for Enhanced Hg(II) and Cd(II) Adsorption

Abstract

Water security caused by heavy metals poses a deleterious hazard to public health and the ecological system. The construction of adsorbents by polyamidoamine (PAMAM) dendrimers for efficient removal of metal ions has attracted considerable interest. However, the general method for the fabrication of these adsorbents was achieved by the surface chemical modification of the substrates with PAMAM dendrimer, which usually causes the defects of low density and uneven distribution of the dendrimer, the blocking of pores, and reducing the adsorption performance. Hence, the development of a new method for preparation of PAMAM dendrimer-based adsorbent to realize the efficient and enhanced adsorption of metal ions is still a challenge. Herein, methylisothiocyanate decorated PAMAM dendrimer/mesoporous silica composites (G0-S-1/x, G1.0-S-1/x, G2.0-S-1/x, x = 2, 4, 6, 8, 10) were synthesized by the direct sol–gel reaction of alkoxysilyl-containing functional PAMAM dendrimer. The adsorbents display enhanced adsorption property for Hg­(II) and Cd­(II) as compared with the same adsorbents which were prepared by traditional chemical modification method. Take G2.0-S-1/2 as an example, the maximum adsorption capacities are 2.41 and 0.87 mmol·g–1 for Hg­(II) and Cd­(II), respectively . Moreover, the adsorbents show excellent selective adsorption and regeneration property. G2.0-S-1/2 displays distinct selectivity for Hg­(II) with the presence of Co­(II), Pb­(II), Cd­(II), and Cu­(II). The regeneration percentage still maintains 95.2% after five adsorption–desorption cycles. The adsorption mechanism is also certified by the experimental method and theoretical calculation.

The Adsorption of Heavy Metal Ions by Poly (Amidoamine) Dendrimer-Functionalized Nanomaterials: A Review

“…According to the structure of PAMAM dendrimers, the possible binding sites for heavy metal ions included a core tertiary amine, interior amides, and terminal primary amines. To explore the potential adsorption mechanisms, X-ray photoelectron spectroscopy (XPS) [ 99 , 100 ] and density functional theory (DFT) calculations [ 50 , 101 , 102 ] were performed.…”

Poly(2-vinylpyridine)/MCM-41 Composites with Micropores and Switchable Mesopores for the Removal of Cr(VI)

“…10−12 Organics (ethylenediamine, 13 pyrene, 14 etc. ), polymers (polyethyleneimine, 15 polyamidoamine, 16 etc. ), and inorganics (single atoms, 17 metal oxide, 18 etc.)…”

Highly Efficient and Simultaneous Removal of Cr(VI) and Imidacloprid through a Ferrocene-Modified MIL-100(Fe) Composite from an Aqueous Solution

“…Mondal et al studied the chitosan biopolymer as an adsorbent to remove Pb­(II) and Zn­(II) . Luan et al synthesized sulfur-decorating PAMAM dendrimer/mesoporous silica as the adsorbent for Hg­(II) and Cd­(II) removal . Meng et al used a nitrogen-doped MoS 2 nanoflower to effectively remove Cr­(VI) .…”

“…17 Luan et al synthesized sulfur-decorating PAMAM dendrimer/mesoporous silica as the adsorbent for Hg(II) and Cd(II) removal. 18 Meng et al used a nitrogen-doped MoS 2 nanoflower to effectively remove Cr(VI). 19 defective UIO-66 to adsorb Pb(II) in wastewater.…”