Preparation Of Diatomite Adsorbent And Study On The Adsorption Characteristics Of Dyes

Abstract:A huge quantity of dye waste water is discharged by several industries including the textile dyeing, paper, plastic and leather industries every year. The dye components in waste water cause high colour intensity and are very difficult to biodegrade. In this paper, basing on the structure characteristics of diatomite, the preparation technique of diatomite adsorbent was developed with the methods of activation and combination the second composition. Hence, the study involves the preparation method, materials characterization and dye adsorption properties. The main conclusions in this work are as follows:1. It was found that the adsorption capacity of activated diatomite by450℃treatment was higher than the diatomite by acid leaching. The organic impurities were removed when the raw diatomite was calcined under high temperature conditions. The techniques of Mg(OH)2-modified diatomite, SiO2-modified diatomite and CTMAB-modified diatomite were compared, which improved the adsorption capacity for dyes. It was concluded that the SiO2-modified diatomite has the highest adsorption capacity.2. The optimum preparation of sol-gel modified diatomite was Na2SiO3(2mol/L,50mL),5g diatomite and H2SO4(3mol/L,50mL); reaction temperature50℃; reaction time1hour.3. The characterization of modified diatomite showed that the impurities contents of Al2O3, Fe2O3and CaO decreased and the SiO2content increased to91.34%. The surface area and the pore volume of modified diatomite increased and the pore size moved to the direction of decrease.4. The effects of ultrasound, dye concentration, adsorption time, adsorption temperature and pH value on the adsorption capacity of diatomite adsorbent were analyzed. It was found that Methylene blue solution decreased at ultrasound condition. The positive effect is observed for adsorption of cationic dyes. Experiments indicated that adsorption equilibrium was reached in2hours. The opposite effect is observed for increasing the adsorption temperature. The adsorption capacity increased with the increased in pH.5. The adsorption isotherms model of dyes onto RD and MD adsorbents were studied in this paper. The conclusion indicated that the Freundlich model provided higher regression coefficient for diatomite, which suggest that the diatomite has a more heterogeneous structure, the adsorption type of dyes on diatomite is multilayer adsorption, and the interaction between sorbent and adsorbate is physical. The adsorption capacity for Methylene blue was higher than that of Malachite Green on the same initial concentration.