Study On The Preparation And Property Characterization Of Organic-Montmorillonite And Their Advances In Adsorption Of Organic Pollutant

The application and sorption mechanisms of organomontmorillonites in wastewater treatment and remediation of polluted environment have been a concern in the field of environmental science and engineering.In the dissertation, we used Na+-montmorillonite as matrices to synthesize a series of organomontmorillonites by traditional aquo-phase and characterized them by X-ray powder diffraction (XRD) analysis, specific surface areas determination, and Fourier transform infrared (FTIR) spectra. Their sorption properties in aqueous solution and the purification function to food wastewater were also conducted. The main contents and results were as following:1. Sodium modification to Ca-montmorillonite has been studied by two sodium salts, NaCl and Na₂CO₃. The results show that various characters, such as expanded volume, pengrun values and cation exchange capacity (CEC) of the modified materials are improved more significantly than those of the starting material. The characteristic parameters indicate that the montmorillonite modified by NaCl is better than Na₂CO₃, which was attributed the CO₃^2- can form insoluble salt with Ca²⁺.2. Using hexadecyltrimethylammonium bromide (CTMAB) and cetyl pyridine bromide (CPB) as organo-intercalating reagents, organomontmorillonites were prepared by traditional aquo-phase method. The measurement results of XRD and FTIR show the base structure of montmorillonite does not change after intercalating by organic ions. The interlayers of pseudo-trilayer and paraffin-type monolayer arranged models simultaneously presented on both CTMAB microemulsion-Mont and CPB microemulsion-Mont.3. Sorption of o-nitrobenzoic acid and m-nitrobenzoic acid by different organomontmorillonites was performed. First, we studied o-nitrobenzoic acid sorption by homoionic Na⁺-montmorillonite and CTMAB-montmorillonites. Effects of experimental conditions, such as, sorbent concentration, ionic strength, equilibrium time and pH were also investigated systematically by orthogonal test. The order for the adsorption capacity was in the following: CTMAB microemulsion-montmorillonite > CTMAB-montmorillonite > Na+-montmorillonite. The adsorption kinetics data fitted the pseudo-second-order equation. The adsorption isotherms of o-nitrobenzoic acid fitted the Langmuir model (R2 > 0.98). Secondly, batch adsorption tests were carried out to remove m-nitrobenzoic acid from aqueous solution using organo- montmorillonites (120CPB/30SDS-montmorillonite, CPB-montmorillonite, CPB microemulsion (a)-montmorillonite and CPB microemulsion (b)-montmorillonite). The sorption kinetics data fitted the pseudo-second-order equation. The equilibrium data in aqueous solutions was well represented by the Freundlich isotherm model.4. Effect of hydroquinone on the sorption of benzoic acid onto organo-montmorillonites was studied. The concentrations of benzoic acid and hydroquinone in food waste water were determined by double wavelength K coefficient at 229 nm and 300 nm. The sorption isotherms show that the adsorption ability of organomontmorillonite for the polar organic substance in the mixed solution is higher than the organic substance in the single solution.Systematicness, scientificalness and creativeness of this dissertation1. SystematicnessTwo kinds of organomontmorillonite were synthesized: CTMAB-montmorillonites and CPB-montmorillonites. Structures of compounds were characterized roundly and the sorption behaviors of organic pollutants by these compounds were studied in the following part. The sorption suudies included either investigation of interactions between various organomontmorillonites and organic contaminant, or the interactions between organomontmorillonite and different organic contaminants.2. ScientificalnessClay mineral, which is not only the important components of soil, but also the nonmetal mineral in nature, has been widely used in industry. It is very important to study the sorption behaviors of benzoic acids and the relevant mechanisms, which may help to uphold environmental standards for complex pollutants and provide some information for their application in the pollutants removal. Structures identification of organomontmorillonites showed that the surfactant molecules had entered into the interlayer of montmorillonite. Effects of experimental conditions were investigated systematically by orthogonal test. Models of soption kinetics and isotherms were used to discuss the sorption mechanisms.3. CreativenessThe CTMAB microemulsion-montmorillonite and the CPB microemulsion montmorillonites synthesized in this article were novel compounds that had not been reported before. Properties of these products were completely studied, especially the adsorption properties provided a great deal of useful information to the development and application of organomontmorillonite compounds. The sorbents were applied in the research of interaction between montmorillonite and organic contaminants. Two systems for sorption of o-nitrobenzoic acid and m-nitrobenzoic acid were established and organomontmorillonite was applied to the removal of benzoic acid and hydroquinone in food waste water. The adsorption mechanisms of organic contaminants by montmorillonite were studied.