Adsorption Of Humic Substances On Kaolinite And Its Effects On Sorption Of Cu(Ⅱ) To Kaolinite

The adsorption of natural organic material (NOM) such as humin acids (HA) and fulvic acids (FA) on clay minerals is an important process affecting the transportation and transformation of organic and inorganic pollutants such as heavy metals and hydrophobic organic material (HOM) in soil and aquatic environment, which might produce some potential difficulties for environmental monitoring and assessment. At the same time, the sorption behavior alters the surface physicochemical characteristics of clays and minerals, elevating or retarding the mobility of organic and nonoganic polutants, and effecting on the global carbon sequestration.FA and HA were measured by using thermal gravity analysis and FTIR spectrum. The results showed that the main peak ofweight loss of FA and HA was 300℃ and 359℃, respectively.This indicated that HA contained a larger amount of aliphatic components, while FA might have more aromatic constituents.The adsorption behavior of humic acid (HA) on kaolinite was investigated and the characteristics of HA- kaolinite complexes were studied by means of X- ray diffraction pattern, TGA and IR. According to the results obtained, when the HA- kaolin complexes wer washed six times, the HA could be stably combined with the kaolinite; the Fruendlich-type equation could describe the adsorption isotherm of HA on kaolin well, and the Kf of HA on kaolin was 0. 857; there existed apparent absorption peaks of hydrocarbon in the IR; chemical adsorption played a major role in the interaction between HA and kaolinite, and the adsorption behavior mainly took place on the hydroxyl sites of aluminum.Fulvic acids extracted from a typical rice-production region near Taihu Lake of China, were fractionated into four fractions (F4.8, F7.0, F11.0, and Feth) based on hydrophobility using XAD resin technique. Sorption between fulvic acid (FA) fractions and kaolinite were studied by batch adsorption experiments and characterizations of kaolinite before and after adsorption were investigated by fourier transform infrared (FTIR) and Scanning electron microscopy (SEM).Adsorption isotherms and those of the less alkyl group, more aromatic and phenolic group containing fractions fit the Langmuir adsorption model, whereas the fraction with high alkyl groups, low aromatic and phenolic groups exhibited a non-Langmuir multiplayer adsorption. The adsorption density of the sorbates was positively correlated with the percentage of alkyl groups, but negatively related to the aromatic and phenolic group content in each FA fraction with an order of Feth>F7.0>F11.0>F4.8. The presence of...