| Bentonite is a kind of a montmorillonite as the main clay mineral rocks,with adsorption and ion exchange properties.But natural bentonite was low in organic carbon content and weak in the adsorption capacity of organic compounds.Therefore,some aspects like its modified methods,techniques and applications need to be studied.In this paper,the anion-cation organobentonites were prepared by incorporating both cationic surfactant bromide cetyltrimethylammonium(CTMAB) and anionic surfactant sodium dodecyl sulfate(SDS) to bentonite.Systematically studied the influencing of the amount of CTMAB,the amount of SDS,bentonite / water(solid-liquid ratio),the pH Value, the reaction time and the reaction temperature to the modification.Based on the single factor experiments,Center Complex design(CCD) of The Response Surface Methodology (RSM) was used to optimize the synthesis process conditions,which are 123%of the amount of CTMAB,13.45%of the amount of SDS,5.15%of bentonite / water,8.45 of the pH Value,74 min of the response time and reaction under the room temperature.It discussed the absorption performance of the anion-cation organobentonites to the direct dye - Methyl orange and acid dyes - Acid red 3R.The results showed that the anion-cation organobentonites had higher adsorption capacity than the Na-bentonite.Its decolorization rate to Acid red 3R could reach to 99.97%;the decolorization rate to the methyl orange could reach to 95.35%,which were higher than that of activated carbon.On the basis,it studied the adsorption mechanism of the anion-cation organobentonites to the dye molecules.The adsorption isotherm of the anion-cation organobentonites to Methyl orange and Acid red 3R on higher concentrations was to be a linear.A two-phase model was used to describe the acts the organic compounds between organobentonite / water interface,and with the two mechanisms of distribution and surface adsorption to describe the adsorption of organobentonite to organic compounds in water.when the concentration is high,surface adsorption reached saturation,and then the adsorption role to Methyl orange and Acid red 3R is mainly the partition role.Compared 123CTMAB/13.45SDS-Bt with 123CTMAB-Bt Bt,its saturated surface adsorption(N) of Acid red 3R reduced 11.2691 mg/g,distribution coefficient(K_d) increased by 0.0048,and the biggest amount of saturated adsorption increased by 17.0550 mg/g, which showed that the addition of anion and cation surfactants in modification reduced the saturated surface adsorption,but its bigger distribution coefficient makes saturation adsorption capacity greater.Then we can consider the main reason of causing synergy is that the increased amount of distribution is larger than the decreased amount of surface adsorption,the distribution rate of distribution role in the total adsorption increased. |
