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Theoretical Research on Adsorption of Heavy Metal Cadmium Ion on Goethite

Author: YangYongHua
Tutor: XiaShuWei
School: Ocean University of China
Course: Marine Chemistry
Keywords: Density Functional Cadmium Goethite Plate model Chemisorption
CLC: P734
Type: Master's thesis
Year: 2008
Downloads: 157
Quote: 1
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Abstract


Using density functional theory (DFT) methods to study the heavy metals cadmium (II) hydration , hydrolysis species geometric structure , electronic structure and hydration , hydrolysis reaction of cadmium ion activity . MOPAC method using the semi-empirical study the surface of the chemical adsorption of the water molecules in the goethite (010) , and to study the Cd (II) in the goethite (010) surfaces of different chemical adsorption configuration and stability . The results are as follows : 1. Heavy metals cadmium ion hydration , water deconstruction stability order , that the stability of the Cd (II) hydrate species than hydrolysis species , of which 2 Cd ( OH ) 6 was the dominant configuration . With the deepening of the degree of hydrolysis , the inner layer gradually lose water molecules , the the Cd charge brought gradually reduced . Seen by △ G298 from Cd (II) hydration, hydrolysis reaction , the hydration reaction can be spontaneous , and Cd (II) , hydrated Cd ( OH 2) of 62 the reaction is most easily , and Cd (II) the basic hydrolysis reaction is not spontaneous . NBO analysis showed that the hydration reaction Cd passivation can hydrolysis reaction can activate Cd . Interaction of water molecules with the surface of goethite dissociative chemisorption than a combined chemical adsorption . Dissociative chemisorption occurs in the goethite (010) surface , the water molecules , the water molecules first dissociation for the combination of OH-and H of OH- and the surface of the Fe atom of the H atom bonded surface O . Molecular dynamics studies have shown that the chemical adsorption of water molecules on the surface of goethite , liquid water and goethite surface only a weak role , less impact on the surface . The 3. Cd single angle, double angle and triangle adsorbed goethite surface hydrolysis adsorption , each adsorption configuration stability order DC ( b ) gt ; SC gt ; to the TC gt ; DC (a ) . Cd (OH) 24 - the chemical adsorption is carried out the surface of the goethite , Cd (II) ion activity decreased to strengthen stability .

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CLC: > Astronomy,Earth Sciences > Oceanography > Marine basic science > Marine Chemistry
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