Preparation And Application Of Complex Pillared Montmorillonite Composites

With the development of industry and agriculture, water pollution, water shortages and water ecological environment deterioration and other issues, have become the main problems which restrict the sustainable development of society. Among them, the dyeing wastewater pollution is one of the most serious environmental problems. Montmorillonite is cheap, abundance in nature and an effective adsorbent, which can be used in the treatment of wastewater and has been favored by many researchers. However, natural montmorillonite can not meet the requirements in the process of using, in order to expand the application fields of montmorillonite, natural montmorillonite must be modified. In this paper, three types of complexes pillared montmorillonite composites were prepared by using the different complex modification agent, and its effect on the decoloring of cationic dye, absorption and desorption mechanism were explored, which may be used to provide valuable experimental data and process basis for the treatment of dyes wastewater and the development of montmorillonite mineral resources.The main research works and achievements were as follows:（1） By ion exchange and coordination synthesis, the salieylidene-β-lactamic acid metal complex had been encapsulated in montmorillonite（[M（Ⅱ）-L₁/MMT]（M=Cu,Zn,Ni） for short）, the 5,5’- methylenedisalicylic acid metal complex had been encapsulated in montmorillonite（[M（Ⅱ）-L₂/MMT]（M=Zn,Cd,Pb） for short）. the salieylidene-2-aminopyridine metal complex had been encapsulated in montmorillonite（[M（III）-L₃/MMT]（M=La,Er,Y） for short）, and the structures were characterized by the methods of XRD, FT-IR, and TGA-DTA. The results showed that montmorillonite composites had been successfully prepared.（2） This paper focused on the decoloration effect and influence factors of crystal violet（CV） on [Cu（Ⅱ）-L₁/MMT], methylene blue（MB） on [Zn（Ⅱ）-L₂/MMT] and rhodamine B（RB） on [La（III）-L₃/MMT]. The results showed that the removal rate of CV on [Cu（Ⅱ）-L₁/MMT] was 99.60%, RB on [Zn（Ⅱ）-L₂/MMT] was 99.90% and MB on [La（III）-L₃/MMT] was 97.70%, which had a good bleaching effect. Compared with the Na-MMT, the adsorption capacity of the CV increased from 285.6 mg·g^-1 to 444.4 mg·g^-1, the adsorption capacity of the RB increased from 240.2 mg·g^-1 to 312.1 mg·g^-1, the adsorption capacity of the MB increased from 285.0 mg·g^-1 to 421.2 mg·g^-1.（3） By the fitting means of adsorption isotherms and adsorption kinetics, the results showed that the adsorption isotherm of crystal violet（CV） on [Cu（Ⅱ）-L₁/MMT], methylene blue（MB） on [Zn（Ⅱ）-L₂/MMT] and rhodamine B（RB） on [La（III）-L₃/MMT] followed Langmuir adsorption model, the adsorption behavior were followed pseudo second order kinetic model. Thermodynamic analysis shows that, CV on [Cu（Ⅱ）-L₁/MMT] and RB on [Zn（Ⅱ）-L₂/MMT] is a spontaneous endothermic process, and MB on [La（III）-L₃/MMT] is a spontaneous and exothermic process.（4） The adsorption of Crystal violet（CV）, Rhodamin B（RB） and Methylene blue（MB） onto the composites [Cu（Ⅱ）-L₁/MMT], [Zn（Ⅱ）-L₂/MMT] and [La（III）-L₃/MMT] from binary mixture systems was studied. The experimental results show that the three composites is an excellent adsorbent for the cationic dyes used. Under our experimental conditions, the removal rate of each dye is more than 96%. In binary mixture systems, there is competition between the dyes. when the dosage of adsorbent is insufficient, the dye which has a strong affinity with adsorbent can be preferentially adsorbed.