The Preparation Of Dual Metal Locking Phosphorus Sorbent And The Study Of Its Use Effect For Lake Internal Loading Control

Lake eutrophication is a serious environmental problem and the results of a lot of studies indicated that phosphorus is the main limiting nutrient for lake eutrophication.Studies indicated that even though the external phosphorus loading of the lake has been effectively controlled,lake eutrophication still can persist for several decades.Consequently,the control of internal phosphorus releasing from sediments is necessary for lake eutrophication control.In this study,the abundant kind of clay-attapulgite was used as the modified material to prepare a phosphorus-locking material with simple process,environmental friendliness and excellent phosphorus removal effect.The experimental part consists of three chapters,the completed research work is as follows:Dual metal locking phosphorus sorbent?LA@TCAP?was prepared by treatment with a double metal salt solution on the basis of aluminum salt modification,the physical and chemical properties of LA@TCAP were then examined in detail.The total amount of metal and metal oxide content in the prepared LA@TCAP increased significantly after modification.The content of carbonate impurities decreased and the specific surface area of TCAP increased from 29.15 m²/g to 69.92 m²/g for LA@TCAP.The maximum adsorption capacity of TCAP increased from 4.06 mg/g to 10.62 mg/g for LA@TCAP.The kinetic adsorption experiments showed that the adsorption of LA@TCAP could be better fitted with the pseudo-second-order kinetics model,and the correlation coefficients of the fitting curves at different phosphorus concentrations were all more than 0.9591.The pH and the presence of Cl^-,SO₄^2-,NO₃^-,HCO₃^-ions had little effect on the adsorption of phosphate by LA@TCAP.The effects of LA@TCAP addition on sediment phosphorus were investigated under long-term aerobic and anaerobic conditions in a long-term laboratory simulation experiments.Both under aerobic and anaerobic conditions,LA@TCAP could control the phosphorus concentrations in overlying water.The removal efficiency of phosphate in overlying water in aerobic period was 61.40%-94.17%in Chaohu Lake and 58.06%-85.98%in Taihu Lake;the removal efficiency of phosphate in overlying water in anaerobic period was 49.46%-55.97%in Chaohu Lake and 48.18%-62.55%in Taihu Lake.The material could not only control the phosphorus in the overlying water,but also control the phosphorus in the interstitial water.The more the amount of the material,the better the control effect on the phosphorus in the interstitial water could obtain.Meanwhile,the material addition did not cause elevation of the forms of nitrogen studied in overlying water and interstitial water.The content of Mobile-P in the surface sediment could be effectively reduced and the percentage of Mobile-P removal was nearly correlated with the doage of the material added.The control effect of LA@TCAP on sediment internal phosphorus was studied under the disturbance of various wind and the various pH values,and the phosphorus control mechanism of the material was analyzed.The results of wind and wave disturbance studies showed that aluminum salt and LA@TCAP could reduce the content of suspended solids,phosphate and total phosphorus in the simulated disturbing action.However,the control efficiency of LA@TCAP was better than aluminum salts.The content of SS concentration in the overlying water from the LA@TCAP treated sediment was 15%and 14%of the control group under moderate and large wind conditions;the content of phosphate concentration was 4%and 5%of the control group under moderate and large wind conditions;and the content of total phosphorus concentration was 11%and 16%of the control group under moderate and large wind conditions.The pH of the overlying water increased,The amount of phosphate released into the overlying water increased with the increase of pH value in overlying water.The phosphate content of the overlying water was only 1.16-1.63 times that of neutral at the pH in the range of 8-10,and the phosphate content did not change much.LA@TCAP could transform Mobile-P in the sediment into more stable Ca-P and Al-P.Thus,LA@TCAP prepared by a simple method has a good control effect on the phosphorus in the water and sediment.