Synthesis And Performance Testing Of Vermiculite-based Hydrogels

Hydrogel is a kind of polymer materials which has highly swelling in the solvent. It has a three-dimensional network structure formed by the monomers material by the appropriate physical and chemical crosslinking. The hydrogel has sense stimulation change outside(e.g., temperature, p H solution, ionic strength, electric field, etc.) and is responsed to volume changes. As a result, they are widely used in medicine, pharmacy, agriculture, forestry and gardening, environmental and biological engineering, and other fields.In recent years, the research of hydrogel is toward to high-performance, multi-functional and environmentally friendly direction. Based on this, the preparation of inorganic/organic composite hydrogel, especially the clay base hydrogel is concerned widely, this is because the clay-based hydrogel is combined with the characteristics of the hydrogel and mineral materials, which has a low cost, large amount of water absorption and high resistance to salt, biodegradable, etc. In past ten years, clay matrix composite hydrogel study, based on the attapulgite, montmorillonite, bentonite, diatomite composite materials are more, and the study of vermiculite is relatively less. Vermiculite is a kind of natural clay minerals, it is a kind of layered magnesium(or aluminum) silicate minerals, its structural unit layer is 2:1 type, interlayer has a large number of exchangeable cation and water molecules. Therefore, we can make use of the excellent properties of the structure contains a lot of activity-OH groups, grafting it onto the monomer which contains double bonds and induce polymerization reaction to form inorganic/organic copolymer.Commonly method of preparation of hydrogels are mainly chemical method, radiation method, plasma method. Among them, the glow discharge electrolysis plasma(GDEP) is more and more attentioned because of the mild conditions(without N2 protection), reaction control(control the discharge voltage and discharge time), no need adding chemical initiator, no secondary pollution, and the advantages of environmentally friendly. Moreover, through the study we found that GDEP has super Faraday characteristics, namely, in the process of GDEP, each with 1 mol electronic through, will be generated 12 mol HO· in liquid phase reaction area. In the reaction process, the HO·groups can add to the polymer chains leading to water hydrogels performance better.This paper adopts the GDEP to synthesis of a series of vermiculite based hydrogel. We mainly examine the swelling properties in water and the dye adsorption performance of the vermiculite based hydrogels. The results can lay theoretical basis for the hydrogel used in agriculture, forestry and gardening, water absorption, water purification, sewage treatment and environmental field. This paper is divided into four chapters:Chapter 1 The concept of hydrogel, classification method, the treatment methods and research progress of the vermiculite materials were reviewed, put forward glow discharge electrolysis plasma to preparation VMT groundmass hydrogel, expounded the effective, scientific and advanced nature of GDEP, and pointed out the deficiency in the research process of VMT based hydrogel.Chapter 2 The materials, instruments preparation, characterization and research content are introduced.Chapter 3-5 In aqueous solution, the glow discharge electrolysis plasma(GDEP) is used to synthesize VMT/P(AMPS- co – AA、VMT/PEG/AA and VMT/PVP/AA hydrogels. The structure of hydrogels are characterized by FT- IR, XRD, SEM and TG.The effect of discharge voltage, discharge time, the dosage of vermiculite and amount of crosslinking agent on water/dyes absorption swelling properties of the hydrogel were studied, The possible polymerization mechanism was also discussed. The hydrogels swelling kinetics in distilled water and the water swelling behavior in different p H solution and salt solution were studied. The adsorption performance and usability of hydrogel were studied for common dye at the same time. The results show that the swelling process is fast, adsorption efficiency is high. The hydrogels has p H sensitivity and salt sensitivity. The dye adsorption behavior follows the pseudo-second dynamic model and the material has usability. The hydrogels has excellent swelling and adsorption of dyes.