Sorption Behaviors Of Phosphate On Kaoline, Humic Acid And Marine Sediment

The concentrations of nutrient elements are important for the marine environmental quality. Phosphorus is one of the main elements that can lead to eutrophication, red tide or other nutritional phenomena. Increased phosphorus concentrations in water bodies could cause excessive algae growth. It causes the water quality to worsen and seriously destroys the ecological balance of the water body. It also brings the serious harm to human"s health and the living of aquatic biology. The phosphorus adsorption on sediments in the sea can slow the process of eutrophication of water body, especially on the part of natural colloidal (clay minerals, organic matter and active metal oxide hydrate). They can affect the environment behaviors of the pollutants through a series of physical and chemical reactions, such as adsorption, complexation, coprecipitation, etc. However, phosphorus nutrients can be released from sediments under certain conditions, which may lead to eutrophication and causes second contamination. Sediments, especially clay minerals and organic matter of sediments, which plays an important roal in the eutrophication control of water bodies. Therefore, it has important significance to study the adsorption behaviour of phosphorus on sediments, clay minerals and organic matter.In this thesis, environmental factors such as temperature, salinity are studied initially on the phosphate adsorption behaviors of kaoline and humic acid through laboratory experiments. The effects of sediment characters (particle size, HC1treatment, H2O2treatment etc.) and environmental factors (the concentration of humic acid, pH, etc.) are also discussed on the phosphate sorption behaviors of a sediment sampled from the adjacent area of Yangtze Estuary.The main conclusions are as follows,(1) The pHPZNPC of kaoline was3.8, and the ionic strength had rarely effect on the PHPZNPC of kaoline. The sorption process could be described by pseudo-second-order kinetic rate equation and the sorption rate increased with the increasing temperature. The sorption isotherms fit modified Langmuir isotherm well. The sorption capability of phosphorus on kaoline increased with the decreasing salinity and the increasing temperature. Estimation of thermo dynamic parameters indicated that the sorption behavior (2)of stimation of thermodynamic parameters indicated that the sorption behavior of phosphorus was spontaneous (△(?)θ<0) and endothermic (△Hθ>0) with an increase in the degree of freedom (△Sθ>0).(3) The pHPzNpc of humic acid was in the range between3.5-5.8, affected greatly by the ionic strength. The sorption process could be described by pseudo-second-order kinetic rate equation and the sorption rate increased with the increasing temperature. The sorption isotherms fit modified Langmuir isotherm well. The sorption capability of phosphorus on humic acid increased with the decreasing salinity. The results showed that the temperature had little influence on the adsorption of phosphorus onto humic acid with the storage temperature15-25℃. The sorption capability of phosphorus on humic acid which insolubled in NSW increased compared with humic acid.(4) For the sediment, the sorption process could be described by pseudo-second-order kinetic rate equation and the sorption rate increased with the decreasing particle size and the increasing initial phosphorus concentration. The sorption isotherms fit modified Langmuir isotherm well. The sorption capability of phosphorus on the sediment increased with the decreasing particle sizes and the increasing concentration of humic acid in NSW. The sorption capability of phosphorus increased after the sediment treated by HC1and decreased after the sediment treated by H2O2. The influence of pH on the adsorption behavor was relatively complicated:When pH<5, the sorption capability of phosphorus on the sediment increased with the increasing pH; When5<pH<9, the sorption capability of phosphorus on the sediment decreased with the increasing pH; When pH>9, the sorption capability of phosphorus on the sediment increased with the increasing pH. The "stability pH range" was about7-9.