Study On Preparation Of Modified Fly Ash Adsorbent And Its Control Of Internal Source Pollution Of Water Sediment

The problem of water eutrophication is one of the main environmental governance problems facing the world today.The main cause of water eutrophication is the excess of nutrients in the water body.The excess of nutrients in the water body will cause the excessive reproduction of aquatic plants and reduce the dissolved oxygen in the water.So as to induce the eutrophication of the water body,the control of the nutrients in the water body is an important means to control the eutrophication of the water body.In view of this problem,this study intends to produce a new,efficient and economical adsorption material for the treatment of water eutrophication.First,fly ash is used as a carrier to load lanthanum which has a high-efficiency adsorption effect on phosphorus,and then granulate it to make its shape more stable at the mud-water interface,and it is not easy to be disturbed and float up.When the phosphate in the bottom mud is released into the overlying water,it will first be adsorbed by the modified fly ash particles,and at the same time,it will also adsorb the phosphate present in the floating water to inhibit the release of endogenous phosphorus and control the eutrophication of the water.purpose.The main research conclusions are as follows:(1)Study on modification of fly ash:Study the removal effect of three kinds of modified fly ash adsorbents on phosphate radical.Compared with acid modified fly ash and alkali modified fly ash,the adsorption efficiency of lanthanum modified fly ash is increased by 34.%And 40%.Through the dosage test,the optimal dosage ratio is determined to be 0.3 g/L.Through the XRD analysis of different modified fly ash,it can be known that the elements of Fe,Al,Ca,etc.,have been reduced to a certain extent in the acid-modified and allkali-modified fly ash,and these elements have a certain effect on phosphate.Adsorption can be combined with phosphorus to form compounds.XRF analysis shows that after combining 4.7%of lanthanum,the adsorption effect of lanthanum-modified fly ash on phosphate is significantly improved,indicating that lanthanum effectively adheres to the modified fly ash.On the surface,lanthanum can form stable compounds with phosphate.Lanthanum-modified fly ash adsorbs phosphorus in the water body,which is affected by pH,and has a better effect under neutral and alkaline conditions.The adsorption isotherm model of modified fly ash is closer to the Langmuir adsorption model,which is in line with the characteristics of monolayer adsorption.The adsorption process is chemical adsorption and physical adsorption at the same time.(2)Fly ash granulation research:the powdered lanthanum modified fly ash was added with clay materials and binders for granulation research.After determining the auxiliary materials,the adsorption effect of fly ash pellets was studied through orthogonal experiments.Using different proportions of fly ash montmorillonite,under the conditions of 4:6,5:5,6:4,and 7:3,the green fly ash pellets were prepared at the temperature of 600℃,700 Calcination was performed at 800℃,and 900℃,and the calcination time was controlled at 1 h,2 h,3 h,4 h,and pellets with particle sizes of 3 mm,5 mm,8 mm,and 11 mm were prepared.Analyzing the ball formation effect and adsorption performance of fly ash pellets,it is concluded that the best synthesis conditions for fly ash pellets are:the ratio of fly ash/montmorillonite is 7/3,the roasting temperature is 900℃,and the roasting time 4 h,the particle size is less than 3 mm.The adsorption behavior of modified fly ash pellets for phosphates fits well with the Langmuir adsorption isotherm model,and the maximum adsorption capacity is 6.3 mg/g.(3)Research on the modified fly ash pellets to control the release of endogenous phosphorus at the mud-water interface:By putting fly ash pellets into eutrophic water,the effect of controlling the release of endogenous phosphorus is studied.The results show that the modified fly ash The pellets have a good control effect on the release of endogenous phosphorus at the mud-water interface.Observation of phosphorus release from sediments at 60 days showed that active phosphorus in the sediments gradually transformed into a relatively stable form of phosphorus.After 60 days,the stable calcium and phosphorus in the sediments accounted for 70%of the total inorganic phosphorus.The sediments released phosphorus from the overlying water.Ability is significantly weakened.At the same time,the removal rate of total phosphorus in the overlying water is more than 40%,and the removal of orthophosphate is more than 60%,and the phosphorus control effect is obvious.After material characterization of fly ash pellets after adsorption of phosphate,it is found that phosphorus is uniformly adsorbed on the surface of the material.The modified fly ash pellets have a better ability to control the source pollution of eutrophic water.