Synthesis And Adsorptive Property Of Double Imine Bridged Mesoporous Silica

The heavy metal pollution of water became one of the serious problems at present in China, it has the characteristics of enrichment and difficult to purify compared with the water pollution by organic substances. For this reason, developing a highly efficient green adsorbent of heavy metals is of great significance in the field of water resources protection.Mesoporous silica is a kind of efficient adsorbent emerging in recent years.It has become the hot research topic for water purification due to its many advantages, such as large specific surface area, excellent thermal stability etc. To increase the active site of the materials, it is general to carry the method of post-synthesis for preparing modified silica-based materials. Obviously, the method exists lots of disadvantages. The organic group lead to smaller surface area and lower-ordered by pore plugging. In order to obtain more efficient mesoporous silica adsorption materials, the article devoted itself to synthesis and characterize a novel kind of double imine bridged mesoporous silica desorption materials. and then they were applied to adsorb three kinds of heavy metal ions of Cu(II),Cd(II), Cr(VI). The main contents in this paper as follows:1. CTAB/PAANa/PMOS materials were synthesized by hydrothermal method, using DIOS as organic silicon source, TEOS as inorganic silicon source, CTAB/PAANa as mixed template under alkaline conditions, The effect of addition of PAANa on the structure and morphology of materials were studied. When the adding amount of PAANa is 0.01 %, the specific surface area was 1022 m2 g-1. The channel of the materials are arranged ordered and the grain is relatively uniform. When the content of PAANa is more than 0.1%, the material of spheroidal particles was broken, and the order was reduced.2. The selective adsorption of samples CTAB/PAANa/PMOS were examined for heavy metal ion Cu(II), Cd(II) and Cr(VI). Among the results, the adsorption performance of CTAB/PAANa/PMOS0.01 was the best. When reacting with Cu(II) and Cd(II), the optimum condition of pH is 9, adsorbent dosage is 2.5 mg/mg, adsorption time for 8 h;When the reacting with Cr(VI), the optimum condition of pH is 4, adsorbent dosage is 2.5mg/mg,, adsorption time for 8 h. Thermodynamic model fitting obtained the biggest theory of adsorption capacity for Cd(II),Cu(II) and Cr(VI) were 421.94 mg/g,436.68 mg/g and434.78 mg/g with CTAB/PAANa/PMOS0.01. Pseudo-second-order kinetic model can be a very good evaluation for Cu(II), Cd(II) and Cr(VI) in adsorption process, showed that the reaction between adsorbent and adsorbate mainly for electrostatic forces and cooperate with the reaction. To reuse 8 times for Cd(II), the adsorption effect remains unchanged, to reusethe Cu(II) and Cr(VI), the adsorption effect weakened.3. Under alkaline conditions, a series of sample DDA/PMOS were prepared with different mole ratio of TEOS to DIOS. In the reaction system, DDA acted as template with DIOS as organic silicon and TEOS as inorganic silicon source. The double imine group was confirmed that it corporate itself into silica structures of DDA/PMOS sucessfully. And the channel of DDA/PMOS showed hexagonal ordered arrangement with the increase of proportion of organic silicon source, the morphology of samples changed from irregular paticles to rodlike particles. Although the integrity of mesoporous structure reduced, the sample still present mesoporous structure.4. This paper discussed the DDA/PMOS transistor adsorption process for heavy metal ion Cu(II), Cd(II) and Cr(VI), among the results, the materials of DDA/PMOS0.3 was better adsorption for the metals. The materials of DDA/PMOS0.3, the reaction pH is 9, adsorbent dosage is 2.5 mg/mg, adsorption time is 4 h, the results of Cu(II)、Cd(II) was the best;Optimal pH for Cr(VI) is 3, adsorbent dosage is 2.5 mg/mg, adsorption time for Cu(II) is 4h and the adsorption time for Cd(II) is 8 h,the results of Cr(VI) was best. Langmuir model to calculate the maximum theoretical adsorption capacity of 427.35 mg/g,675.68 mg/g and709.22 mg/g, greatly influenced by the initial concentration of the heavy metal adsorption process. Pseudo-second-order kinetic model could be a very good evaluation DDA/PMOS0.3 of these three kinds of ion adsorption process, show that the reaction between adsorbent and adsorbate mainly for electrostatic forces and cooperate with the reaction.Two kinds of adsorbent to reuse 8 times for Cd(II), basically remain unchanged,the adsorption effect to reuse for Cu(II), Cr(VI), the adsorption effect weakened.