Adsorption Simulation Of Heavy Metal Ions By Thiourea Silica Material

Materials containing functional groups have been widely used in removing or detecting heavy metal ions in water,and their mechanism of action has been paid more and more attention.The adsorption mechanism of metal ions with thiourea and thiourea silica materials was quantitatively calculated from the molecular level.The affinity of six different oxygen-containing ligands to metal ions was discussed,which laid a theoretical foundation for the selection of functional groups.The main research contents are as follows:?1?Firstly,the active sites of thiourea with Hg²⁺,Cd²⁺ions were calculated and analyzed by DFT/B3LYP,BP86 and M06-L.It was found that thiourea and metal ions mainly coordinate with S as the active site.Subsequently,the complex formed by the substitution of different numbers of water molecules by thiourea were calculated and analyzed,and it can be known that The bond length of M-S?M=Hg,Cd?increases with the increase of the number of thiourea-substituted water molecules.The bond length of the Hg-S bond is larger than the bond length of the Cd-S bond;the wiberg bond order of the Hg-S bond is larger and the coordination bond is more stable;During the formation of complexes between thiourea and Hg²⁺,the charge transferred is more,the electron cloud overlaps more,and the effect is stronger;When thiourea replaces the same number of water molecules,And the total energy of the system is reduced more when reacting with Hg²⁺,the reaction is easier to carry out.?2?The calculation model of thiourea silica gel?TU/SiO₂?was constructed.The complex formed by TU/SiO₂ coordination with metal ions were calculated and analyzed by DFT/B3LYP method.it can be seen that when TU/SiO₂ interacts with Hg²⁺and Cd²⁺,the bond length of C-S bond increases by 0.096 and 0.084,respectively,indicating that S atom has stronger ability to interact with Hg²⁺;TU/SiO₂ transferred 0.46 and 0.35 electrons to Hg²⁺and Cd²⁺respectively,indicating that the overlap degree between TU/SiO₂ and Hg²⁺was greater and the effect was stronger.The wiberg bond order of Hg-S bond and Cd-S bond are 0.6691and 0.5468,respectively,indicating that the coordination bond formed by S atom with Hg²⁺is more stable,and the total energy of the system decreases more during the reaction between TU/SiO₂ and Hg²⁺,which makes it easier to react in thermodynamics.?3?The coordination interactions between[M?H₂O?₄]²⁺?M=Hg,Cd?and six different oxygen-containing ligands were calculated and analyzed by DFT/B3LYP method.The results show that according to the order of phosphine oxide?lactam?amide?carboxylic acid?ether and enol,the distance between metal and coordination atom increases gradually,and the interaction intensity decreases gradually;The enthalpy of ligand-substituted water molecules and the free energy of Gibbs gradually increase,and the binding capacity is gradually weakened;the transfer of ligand charge is gradually reduced?except phosphine oxide,ether?,and the binding strength decreases gradually.[M?H₂O?₄]²⁺?M=Hg,Cd?has the strongest interaction with phosphine oxide.Moreover,the binding of the metal cation to the ligand having a coordinating atom participating in the double bond is stronger than having a single bond.