Preparation Of Lanthanum Phoslock Supported By Volcanic Ash And Its Inhibitory Effect On Phosphorus Release In Jiuli Lake Sediment

Lake eutrophication is a global water environment problem.Lake ecological restoration is a systematic project,which needs to be started from two aspects:controlling and cutting off external pollution and removing internal pollution.On the basis of the prevention and control of pollution from point sources,non-point sources and surface runoff around lakes,we should focus on the dredging of lake bottom mud and the control of endogenous pollution.In the 1990 s,Australia’s Commonwealth and Industrial Research Organization(CSIRO)developed Phoslock,which can effectively remove orthophosphate from water.When it precipitates to the sediment interface,it can also passivate the phosphorus at the water and soil interface and control the release of endogenous phosphorus.In this thesis,Jiuli Lake collapsed wetland was taken as the research object.Firstly,natural volcanic ash was acidified and Na OH coprecipitating method was used to prepare Naoh-La modified phosphorus-locking agent of volcanic ash loaded with lanthanum.Secondly,the adsorption experiment of new phosphoruslocking agent was carried out in the laboratory.Finally,samples of raw water and sediment of Jiuli Lake collapsed wetland were collected to simulate the inhibition effect and mechanism of new phosphorus locking agent on phosphorus release of Jiuli Lake sediment.The main conclusions of this thesis are as follows:(1)After acidification of volcanic ash,Na OH-La modified phosphorous lock agent loaded with lanthanum was prepared by Na OH coprecipitate method.SEM analysis results show that acidizing treatment can improve the roughness and porosity of volcanic ash surface,increase its specific surface area,and provide more adsorption sites.The results of EDS analysis showed that lanthanum was successfully loaded on the modified volcanic ash surface,and the distribution was uniform.(2)The adsorption results of Na OH-La modified pozzolash phosphorus lock agent show that the adsorption capacity is low when p H is too high or too low,and the adsorption capacity is the highest when p H=7.0±0.5.The larger the ionic strength of solution,the less the adsorption capacity and the shorter the adsorption equilibrium time of Na OH-La modified pozzolash phosphor-locking agent.(3)The test results of Na OH-La modified Pozzolanic phosphorus-locking agent on phosphorus inhibition of Jiuli Lake sediment showed that: The removal rates of TP and SRP in overlying water were 68.75%-74.99% and 99.11%-99.56%,respectively,after 25 d of theoretical dosage of phosphorus lock agent,and the phosphorus release in sediment was-5.9643±0.3451mg/m2.The results show that the phosphorus locking agent can effectively adsorb phosphorus from overlying water,and after it sinks to the surface of the sediment,the covering layer formed can inhibit the release of phosphorus from the sediment and promote the transfer of phosphorus from the water to the covering layer.4)The SMT method was used to extract the phosphorus form in the sediment.Before adding phosphorus lock agent,phosphorus mainly existed in the form of IP and HCLP in the sediment.After phosphorus locking agent was added,NAIP content in sediment decreased significantly,while CHLP content increased,indicating that NAIP easily released in sediment transformed into CHLP which was difficult to dissolve in water and not easy to release.The research results have guiding value for controlling phosphorus pollution in Jiuli Lake sediment.