The Structural And Adsorptive Characteristics Of Surfactant And Polymer Modified Bentonite

Organobentonites are widely used in environmental protection involved with hydrophobic organic compounds (HOCs) due to their excellent sorption capacity. In recent years, enhancing sorption capacity of organobentonites and applying them to wastewater treatment have drawn great. At present, the bentonite is mainly modified by surfactants, so the sorption capacity of organobentonites is dependent on the conformation and arrangement model of surfactants within the organobentonites interlayers. As thus, the sorption capacity and wastewater treatment efficiency might be improved by controlling the arrangement model of surfactants, which could further reduce the application cost of organobentonite.In the first part of this dissertation, The previous investigations about the structural characteristics, sorptive characteristics and applications of organobentonites are systematically reviewed, and then it is noted that some problems need to be further resolved before the organobentonites can be widely applied in wastewater treatment, such as improving their sorption capacities, synthesizing novel efficient organobentonites and reducing the costs of the wastewater treatment. To resolve these problems, it is necessary to understand the correlation between structural and sorptive capacities of organobentonites and their sorptive mechanism. In this dissertation, series of organobentonites are synthesized by simultaneously controlling the loading amounts of cations surfactant and polymer on bentonites. Then structural characteristics of the resulting composite organobentonites are characterized with various methods. Sorption capacities of the organobentonites toward organic compounds are investigated. The feasibility of using surfactant and polymer modified bentonites for simultaneous sorption of organic compounds and heavy metals from water are also examined. The main original conclusions of this work are as follows:(1) A series of composite-bentonites with high sorption capacity towards HOCs were synthesized by modifying bentonite simultaneously with surfactant and polymer. The sorption capacity of composite-bentonites was better than that of traditional organobentonites. The sorbed amounts of phenol and nitrobenzene on composite-bentonites were enhanced by 18.5%~44.9% and 9.1%~24.3%, respectively, compared with those on traditional organobentonites, and Koc values were increased significantly. For example, Koc values of several composite organobentonites including 60C/4%P-Bt, 80C/4%P-Bt, 60C/6%D-Bt and 80C/4%D-Bt were larger than that of lOOC-Bt, and Koc value of 60C/4%T-Bt was close to that of lOOC-Bt. Furthermore, the optimum packing density, 1.00-1.27CEC, was observed when composite-bentonites reached the maximum sorbed amounts. (2) The potential mechanisms for the enhanced sorption of HOCs on the compositebentonites were proposed. The conformation and arrangement model of organic cation within the composite -bentonites interlayers was affected by polymer. With the increase of intercalation capacity of the cationic polymer, the basal spacing values of composite-bentonites increased gradually. The CTMA+ configuration evolved into tran/gauche, which led to the formation of organic phase with better affinity to the organic compounds.(3) Novel composite bentonites that could simultaneously remove HOCs and heavy metals from water were synthesized by intercalating bentonite with both CTMAB and CTS . The sorption toward organic compounds was enhanced due to organic phase with stronger affinity to the organic compounds was formed within the organobentonites interlayers, while heavy metals were captured by their chelation with CTS.