Inactivation Effects Of Phosphorus In Water And Sediment By Metal Salt Modified And Thermal Treated Attapulgite

China is a country with rich natural clay reserves,however,the effective exploitation and utilization of clay minerals are not perfect enough.In this paper,the corresponding modifications of natural attapulgite clay were carried out to prepare a new type of phosphate-fixing agent with simple production process,low cost,environmental friendliness and significant phosphorus removal effect.The experimental part consists of three chapters,the completed research work is as follows:On the basis of the round heat-modified attapulgite clay,Fe-ATP,La-ATP and Al-ATP were carried out.Their phosphorus removal effects were compared through the control effect on phosphorus pollution in water and sediment;In order to simplify the preparation process and save the production cost,the natural attapulgite clay was directly crushed into irregular particles,instead of the round attapulgite clay.The physical and chemical properties of Al-ATP were determined by relevant means and the factors affecting the adsorption of phosphorus by Al-ATP were studied;In-house culture experiments were conducted to investigate the effect of Al-ATP on phosphorus control,and with the market-oriented Phoslock for comparison.The results showed that the best modified metal salt concentration was 2 M.The corresponding total amount of the metal and the oxide content in the resulting materials increased significantly,and the carbonate impurity content was significantly reduced,which effectively improved the adsorption performance on phosphorus.Al-ATP had the best control effect on phosphorus in water;La-ATP had the best control effect on phosphorus in sediment;Fe-ATP was only suitable for phosphorous remediation in water.Overall,Al-ATP was the best material.Irregular Al-ATP and round Al-ATP had the same basic chemical compositions,physical and chemical properties,and both of them had the same phosphorus removal rate and adsorption capacity,which indicated that the process of granulation had no influence on the phosphorus removal of Al-ATP.After aluminum salt modification,the total aluminum and alumina content,BET,pore volume,porosity and pHPZC of the material were increased,thereby improving the adsorption performance of the attapulgite clay.The increase of pH value and the presence of HCO3-,and humic acid could inhibit the adsorption to phosphorus by Al-ATP.The best time for Phoslock to control phosphorus in overlying water was within one week,while the best time for Al-ATP was between 9 and 16 days;in the same dosage as Phoslock,the adsorption of Al-ATP to phosphorus in the interstitial water was stronger and the scope of phosphorus removal was wider.After the addition of Al-ATP and Phoslock,the content of mobile-P in surface sediments was significantly reduced.Material dosage was proportional to mobile-P removal rate.Thus,Al-ATP prepared by a simple method has a good control effect on phosphorus in water and sediments.