title: Synthesis of silica gel supported salicylaldehyde modified PAMAM dendrimers for the effective removal of Hg(II) from aqueous solution.
abstract: A series of silica gel supported salicylaldehyde modified PAMAM dendrimers (SiO2-G0-SA ∼ SiO2-G2.0-SA) were synthesized and their structures were characterized by FTIR, XRD, SEM, TGA, and porous structure analysis. The feasibility of these adsorbents for the removal of Hg(II) from aqueous solution was first described and the adsorption mechanism was proposed. The adsorption was found to depend on solution pH, the generation number of salicylaldehyde modified PAMAM dendrimers, contact time, temperature, and initial concentration. Results showed that the optimal pH was about 6 and the adsorption capacity increased with the increasing of generation number. Density functional theory (DFT) method was used to investigate the coordination geometries and the chelating mechanism. Adsorption kinetics was found to follow the pseudo-second-order model with film diffusion process as rate controlling step. Adsorption isotherms revealed that adsorption capacities increased with the increasing of temperature. Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models were employed to analyze the equilibrium data. The adsorption can be well described by Langmuir isotherm model and took place by chemical mechanism. The thermodynamics properties indicated the adsorption processes were spontaneous and endothermic nature. The maximum adsorption capacity of SiO2-G0-SA, SiO2-G1.0-SA, and SiO2-G2.0-SA were 0.91, 1.52, and 1.81 mmol g(-1), respectively. The considerable higher adsorption capacity compared with other adsorbents indicates SiO2-G0-SA ∼ SiO2-G2.0-SA are favorable and useful for the uptake of Hg (II), and can be potentially used as promising adsorbents for the effective removal of Hg(II) from aqueous solution.
authors: School of Chemistry and Materials Science, Ludong University, Yantai 264025, PR China. Electronic address: niuyuzhong@126.com.
authors: Yuzhong
authors: Y
authors: Niu
authors: School of Chemistry and Materials Science, Ludong University, Yantai 264025, PR China. Electronic address: rongjunqu@sohu.com.
authors: Rongjun
authors: R
authors: Qu
authors: School of Chemistry and Materials Science, Ludong University, Yantai 264025, PR China.
authors: Hou
authors: H
authors: Chen
authors: School of Chemistry and Materials Science, Ludong University, Yantai 264025, PR China.
authors: Lei
authors: L
authors: Mu
authors: School of Chemistry and Materials Science, Ludong University, Yantai 264025, PR China.
authors: Xiguang
authors: X
authors: Liu
authors: School of Chemistry and Materials Science, Ludong University, Yantai 264025, PR China.
authors: Ting
authors: T
authors: Wang
authors: School of Chemistry and Materials Science, Ludong University, Yantai 264025, PR China.
authors: Yue
authors: Y
authors: Zhang
authors: School of Chemistry and Materials Science, Ludong University, Yantai 264025, PR China.
authors: Changmei
authors: C
authors: Sun
mesh_terms: D000327:Adsorption; D000447:Aldehydes / Q000737:chemistry*; D050091:Dendrimers / Q000737:chemistry*; D008628:Mercury / Q000737:chemistry*; D058428:Silica Gel / Q000737:chemistry*; D012996:Solutions; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification / Q000379:methods
chemical_list: D000447:Aldehydes; D050091:Dendrimers; C104700:PAMAM Starburst; D012996:Solutions; D014874:Water Pollutants, Chemical; C013243:salicylaldehyde; D058428:Silica Gel; D008628:Mercury
keywords: Adsorption; Hg(II); PAMAM dendrimers; Salicylaldehyde; Silica gel; Synthesis