Preparation Of The Bentonite Modified With The Cationic Gemini Surfactants And Its Application On Environmental Remediation

At present, atmosphere, water, soil, and other biological environment have been polluted by chemicals in a certain extent, which has a strong impact on ecological environment and human health. Hence, environmental pollution control and remediation are the most important issues around the world, which need to be solved in environmental science and engineering fields. So we need to explore new materials, new methods and new techniques in environmental pollution control and remediation. In this project, cation Gemini surfactant is used as intercalation agent to prepare the organic bentonite, and its surface properties is quantitatively characterized using the inverse gas chromatography(IGC). Moreover, the printing and dyeing wastewater with methyl orange solution is simulated and the adsorption properties of cation Gemini surfactant modified benonites is studied. At the same time, a lot of effort is made to determinate the adsorption thermodynamic functions of three different cationic Gemini modified bentonite to19volatile organic compounds(VOCs). The main academic contribution of this work contains the following aspects:1. The organic bentonite is prepared using a class of cationic Gemini surfactant (Gm-n-m) as intercalation agent.When Gm-n-m enters the layers of bentonite, the hydrophobic ability is improved, the lamellar distance is increased from1.51nm to3.91nm, and the organic content reaches to23.53%. The lamellar distance and organic content of Gm-n-m modified benonite are significantly improved than that of DTAB (dodecyltrimethyl ammonium bromide) modified benonite.The reaction temperature, reaction time, stirring speed and the amount of intercalation agent significantly effect on the lamellar distance and organic content of Gm-n-m modified benonite. The optimized preparation conditions were:the intercalation agent to sodium benonite ratio of40%, the reaction temperature of70℃, reaction time of3h, and the stirring speed of205r/min.2. The printing and dyeing wastewater with methyl orange solution is simulated and the adsorption properties of Gm-n-m modified benonite is studied. The effect of adsorption time, the quantity of Gm-n-m modified benonite, the pH value and the salinity of methyl orange solution on the adsorptive capacity of organic bentonite are also investigated. It is found that the surface of Gm-n-m modified benonite is positively charged., which means that the modified benonite is in favor of adsorption of methyl orange anion. Most methyl orange anion are adsorbed on the surface of organic bentonite, and only a few dissolved in the organic layer of the interlayer space, and the removal rate of methyl orange on Gm-n-m modified bentonite is visibly higher than the DTAB modified bentonite. The adsorption behaviors were well fitted to the liner Freundlich adsorption model. And the adsorption process is in the nature of heat adsorption. Moreover, through the dynamics model calculation it is found that the adsorptive action fits well with Ho-second-order rate equation. This is suggested that the adsorption is controlled by chemical adsorption.3. IGC is used to study the surface energy, the acidity and the basicity of Gm_n_m modified bentonite. Results show that:(1)The disperse component of surface free energy of modified benonite decreases with increase in temperature. The influences of the length of the carbon chain of Gemini surfactan on the disperse component of surface free energy are not visible. The surface of modified benonite shows strong basicity.The longer the carbon chain of Gemini surfactant, the more obvious the basicity of surface;(2)Adsorption of VOCs on the organic benonite is physical adsorption. And the organic benonite has strong adsorption selectivity to VOCs. The absorbability of the organic benonite to VOCs are affected by the chemical and physical properties of the VOCs such as molecular weight, molecular structure, boil points, polarity and so on. The longer the carbon chain of Gemini surfactant for modifying, the stronger the adsorption capability. The higher the temperature, the poorer the adsorption capability.