Surface Silanization Of Alkali-avtivated Montmorillonite And Its Remove Methylene Blue From Aqueous Solution

Montmorillonite mineral has abundant natural reserves,low price and good adsorption performance.However,it is easy to agglomerate in the organi c polymer matrix.This problem can be effectively solved by modifying the su rface of montmorillonite by organosilane modification,because the modification can promote the surface of montmorillonite from hydrophilic to hydrophobi c.The dispersity of montmorillonite in organic polymer matrix was improved.In this paper,based on Zhejiang Sanding montmorillonite,the surface modifica tion ofγ-aminopropyl triethoxysilane（APTES）was successfully prepared by 2mol/L sodium hydroxide activation treatment.X-ray diffraction（XRD）,Fourie r transform infrared spectroscopy（FTIR）,synchronous thermal analysis（TG/DT G）and solid state nuclear magnetic ~1H spectroscopy（~1H NMR）were used to analyze the composition,microstructure and surface group distribution of the m aterials during the preparation process.The adsorption properties,process and mechanism of modified montmorillonite material for methylene blue were inves tigated through batch experiments.The main results of this study are summariz ed as follows:（1）At room temperature,montmorillonite was activated with 2 mol/Lsodium hydroxide for different periods of time,and the inner montmorillonite still retained intact lamellar structure for 10 days;Si dissolution reached steady state on the 6th day of alkali treatment.The impurities contained in montmor illonite ore sample are dissolved by alkali treatment.The hydroxyl content of montmorillonite was the highest after 8 days of alkali activation treatment,whi ch concentrated on the surface of montmorillonite in the form of Si-OH.Alkal i activation had a directional regulation effect on the distribution of surface hy droxyl.（2）A comparative study showed that alkaline activation pretreatment effectively increased the loading capacity of organosilane on montmorillonite;I n the non-polar solvent（toluene）system,the organosilane only condenses with the hydroxyl groups on the outer surface of montmorillonite and at the edge o f"fracture".Condensates with hydroxyl groups in the interlayer of montmorillo nite,on the outer surface and at the edge of"fracture"in the ethanol/aqueous solvent system.The loading capacity of organosilane in montmorillonite increas ed with the increase of water content in the reaction system.In the presence of ethanol/water solvent,the organosilanes are loaded between montmorillonite layers in a"double arrangement"mode.The loading of organosilane on mont morillonite surface involves grafting reaction and oligomerization reaction.The samples activated by alkali for 8 days had the best modification effect in all s olvents（silane loading was the best）.（3）The adsorption of methylene blue by modified montmorillonite is significantly affected by p H,and the maximum adsorption capacity is 369.5 m g/g at the optimum p H of 12 at room temperature.The adsorption kinetics ac cords with the quasi-second-order model,and the adsorption mechanism mainly involves chemical adsorption caused by electrostatic adsorption.The intramole cular diffusion model shows that adsorption is not controlled by a single intra molecular diffusion.The adsorption isotherm is more consistent with Langmuir equation.The calculation of thermodynamic parameters shows that the spontane ous endothermic reaction of the suction attachment;The presence of backgroun d cation inhibits adsorption,while background anion promotes adsorption.The material has good reusability.