Study On The Adsorption Behavior Of Cu(Ⅱ) And Cu-EDTA Using Amino-modifled Manganese Dioxide As The Adsorbent

In view of the pollution of copper ions and its chelates, like Cu-EDTA chelates, mesoporous delta manganese dioxide （8-MnO₂） and amino-modified manganese dioxide （NH₂-MnO₂） was synthesized by chemical functionalized methods and used as adsorbents to remove the low concentration pollutants in aqueous solutions. The adsorption behaviors and the possible mechanisms of copper ions and Cu-EDTA chelates on 8-MnO₂ and NH₂-MnO₂ were investigated. The influencing factors, such as pH, ionic strength, mole ratio of EDTA and Cu（II）, temperature, etc. were also discussed.Aminopropyl functionalized mesoporous delta manganese dioxide（NH₂-MnO₂） was synthesized by grafting methods, using （3-Aminopropyl）trimethoxysilane and delta manganese dioxide（δ-MnO₂）, respectively. The BET results showed that the surface area, average pore volume and average pore size of NH₂-MnO₂ were 164.78 m2/g,0.411 cm3/g and 9.98 nm, respectively, which were smaller than δ-MnO₂.Compared to δ-MnO₂ （qmax=69.72 mg/g）, NH₂-MnO₂ （qmax=93.46 mg/g） had better removal efficiency for copper ions in aqueous solutions. Ionic strength had little effect on the adsorption of copper ions on two sorbents. The adsorption of copper ions on δ-MnO₂ was dominated by the interactions between the surface hydroxyl groups and copper ions, while the uptake of copper ions on NH₂-MnO₂ was mainly dominated by the effect of amino groups.NH₂-MnO₂ manifested high affinity and removal efficiency to Cu-EDTA chelates at pH3.5. The adsorption data of Cu-EDTA chelates were fitted well with Langmuir model, the maximum adsorption capacity of NH₂-MnO₂ （qmax=14.45 mg/g） was obviously higher than that of δ-MnO₂（qmax=5.64 mg/g） at the same conditions. The FT-IR and XPS analysis indicated that the adsorption of Cu-EDTA chelates was dominated by the interactions between the surface hydroxyl groups on δ-MnO₂ and the carboxyl groups on Cu-EDTA chelates. While, the electrostatic interactions and the hydrogen bonds between theprotonated amino groups on NH₂-MnO₂ and the carboxyl groups on Cu-EDTA chelates dominated the adsorption process.