| The release, migration and the biological effectiveness of phosphorus in the surface environment mainly depends on the adsorption and desorption physicochemical process of phosphorus in soil, sediment and water. The iron-bound phosphorus(Fe-P) is a specially important component of various forms of inorganic phosphorus in soil,sediment and water. it is more lively influenced by the external conditions change and with great potential for the release. Humic acid is an important component of natural organic matter and goethite is the widespread presence of iron oxide in the surface environment, they are present at the same time and may interact with each other. This mutual interaction may effect the role of mineral surfaces as reactive surfaces in natural environments, because their chemical properties-such as surface change, colloidal stability and the adsorption capacity may be significantly altered. Therefore, this study through different factors(the concentration of phosphate, pH and ionic strengh) and adding the different sources of HA on goethite adsorped phosphate. Combined with related representation studied the mechanism of humic acid influence the adsorption of phosphate on goethite, provided important scientific support about the use of phosphorus in soil,the migration and transformation of phosphorus in the lake and eutrophication of lake..Papers obtained the following conclusions:(1) The adsorption isotherms of phosphates was in closed agree with the Langmuir adsorption isotherm.The maximum adsorption amount(Qm) at pH=4.5is4737mg/kg, Qm at pH=7is4113mg/kg.the adsorption capacity at pH=7is below at pH=4.5.and it’s Qm decreased by13.2%compared with pH=4.5.the adsorption of phosphorus on goethite decreased with increasing pH or decreasing ionic strength.(2) The addition of sigma HA and soil HA all can significantly reduce the amount of phosphate adsorption,which were up to26.6%and25.6%by addition of100mg/L and40mg/L of sigma HA respectively at pH=4.5, while the reduction were26.8%and23.1%at pH=7.The soil HA experimental group were up to31.8%、30.8%by addition of100mg/L and40mg/L of soil HA respectively at pH=4.5, while the reduction were27.1%、25.3%at pH=7. Different order of addition of phosphate and HA could result in different phosphate amounts adsorbed by goethite:prior addition of phosphate>simultaneous addition> prior addition of HA. The equilibrium data of phosphate adsorption agree well with the Langmuir adsorption isotherm in both conditions. the adsorption of phosphorus on goethite decreased with increasing pH or decreasing ionic strength. The results of total organic carbon and infrared spectral features indicated that HA and phosphate compete for the goethite surface, and hydroxyl on the surface of goethite played a certain role in the process of adsorption of phosphate and HA.(3) Different sources of HA have different inhibition of phosphorus sorption on goethite, inhibition of soil HA is stronger than sigma HA,which may be because there have different in Molecular weight, elemental composition, element ratio, functional groups such as hydroxyl, carboxyl and aromatic degrees, fat degrees.The result of total organic carbon indicated the adsorption of soil HA at the surface of goethite is stronger than the Sigma HA. The result of elemental analysis, uv-visible spectrum,the three-dimensional fluorescence spectroscopy, infrared spectroscopy and nuclear magnetic resonance spectral characteristics indicated that:molecular weight, polarity, degree of humification, aliphatic, aliphatic with oxygen content, carbon content of hydroxyl and carboxyl, oxygen function groups and the content of aromatic carbon of soil HA is relatively larger than sigma HA,which may be the main reasons of soil HA have stronger inhibition of phosphorus sorption on goethite than sigma HA. |
PDF Full Text Request