| This paper introduced properties and applicationthe bentonite, kaolin and modified bentonite and kaolin with dodecyl dimethyl betaine(BS-12)+Tween-80(Tw80,T), and studied the preparation of modified bentonite and kaolinite, the structure characteristics of the clay, andadsorption properties of two kinds samples to heavy metal ionsCd2+ and organic phenol.The clay modified by organism was applied to the absorption of organics and heavy metal in recent years, we modified bentonite and kaolinite with a mixture of amphoteric modifier,dodecyl dimethyl betaine(BS-12)+Tween-80(Tw80,T),The structure of modified clay were characterized by X-ray diffraction(XRD), infrared spectroscopy analysis(FTIR), the organic carbon contents(TOC), and determination of specific surface area(BET), we compared the adsorption of phenol and Cd2+ with bentonites and kaolinite modified by dodecyl dimethyl betaine(BS-12)+Tween-80(Tw80,T), we also analyzed the effects of the modifier ratios, ionic strength, temperature and pH on the adsorption of phenol and Cd2+ with the batch method of treatment, and studied the mechanism of adsorption terms of adsorption isotherms, temperature effects and thermodynamics.The results achieved in this paper are as follows:1)The organic carbon contents of modified bentonites and kaolinite showed a positive correlation with modified ratio, the specific surface area of modified bentonites and showed a negative correlation with modified ratio,and the interlamellar spacingof modified bentonites increased with modified ratio increased,but the interlamellar spacingof modified kaolinite remained unchanged with modified ratio increased.The XRD and FTIR analysis of two kinds clay showed that surface modification agent BS-12 and Tw80 intercalated into the inter layers of bentonite, and do not ntercalate into the inter layers of the kaolinite.2)The results shows that the CEC of matrix is the major factor that will have effects on the adsorption of phenol, the adsorption of phenol with bentonite is better than that with kaolinite in the same modifier ratios. Influenced by different factors, the trend of the adsorption of phenol with modified bentonites and kaolinite maintains good consistency, the adsorption capacity of bentonites and kaolinite modified by BS-12+Tw80 is obviously higher.It is found that the adsorption capacity of bentonites and kaolinite modified by 50BS+T increases with the increasing Tw80 ratios, the adsorption capacity of bentonites and kaolinite modified by 100BS+T decreases with the increasing Tw80 ratios. The adsorption of phenol decreases with the increasing temperature and pH, but increases with the increasing ionic strength. Henry model is applicable to describe the adsorption of phenol. The adsorption of phenol with bentonites modified by BS+T depends on enthalpy decreases and entropy increases, and exists a variety of forms of adsorption.The adsorption of phenol with kaolinite modified by BS+T is a hydrophobic adsorption mechanism decided by enthalpy decreases.The CEC of matrix is the decisive factor.3)The results shows that the CEC of matrix is the major factor that will have effects on the adsorption of Cd2+, the adsorption of Cd2+ with bentonite is better than that with kaolinite in the same modifier ratios.Compared with CK, modified bentonite andkaolinite had enhanced effect on the adsorption of Cd2+, but bothmodify soil sample had decreased the adsorption of Cd2+with Tw80 modified proportional increased.Langmuir model to describe the soil sample on the adsorption of Cd2+.Langmuir model is applicable to describe the adsorption of Cd2+on modified bentonite and modified kaolinite.The phenol adsorption increased with an increase of temperature and pH,but decreased with ionic strength rised. The adsorption thermodynamicparametersof Cd2+ onBS+T modified bentonites and kaoliniteshowed adsorption mechanism is the same,was a spontaneous physical adsorption processwith the characteristics of both enthalpy decrement and entropy increment.The huge difference for the adsorption of Cd2 +was determined by CEC of the matrix.4)Under the condition of Cd2+ + phenol compound,modified bentonite and kaolin soil samples for the adsorption of Cd2+ had fallen to a single adsorption Cd2+, but falling was not big, and the size order on the adsorption of Cd2+with modified bentonite and kaolinite was the same as a single adsorption. the influence ofadsorption Cd2+on compound conditions to two kindssoil samples was the same, the influence of the presence of phenol inhibited the adsorption of Cd2+to two kinds soil sample.Also under the condition of Cd2++phenol compound, except in 100 BS and 100BS+ 0.1 T modified bentonite, the rest of the soil sample for phenol adsorption was slightly lower, the existence of Cd2+ on the effect of bentonite clay samples was greater than the influence on kaolin soil samples. |
