Study On Modification Of Fly Ash For Phosphorus Removal And Its Preperation Process Of Non-sintered Ceramicite

Fly ash is the largest number of industrial solid waste discharged in China,and its emissions occupy the land and pollute the environment.The fly ash can be used in the phosphorus disposal of the rain because of its mineral composition and porous structure,but the efficiency of the fly ash was not very good,so it need to modify the fly ash and make them into granulations.With the rapid development of urbanization in our country,the problems of city water logging and water eutrophication are becoming more and more serious.The Implant retention groove is one of the important measures of LID,and its matrix is the important factors influencing the treatment effect.In the experiment,we choose fly ash ceramicite as the matrix used in the Implant retention groove to recycle the waste and protect the environment,and this technology avoided the deficiency of single matrix in the implant retention groove and poor permeability.In the experiment,we used four modifiers hydrochloric acid,sodium hydroxide,ferric chloride and rare earth ions to modify the fly ash as wet modification,and the results showed that the fly ash modified by rare earth ions could remove the phosphorus well.Then,we optimized the modification conditions of fly ash modified by rare earth ions via single factor method and response surface method,and the results showed that the best conditions of it was:dipping concentration was 0.6g/100ml,dipping pH was 9,dipping time was 16 h,and the influential effect of the factors were dipping concentration>dipping pH>dipping time and the removal rate of phosphorus in the conditions could be 97.9%.The modification mechanism of fly ash could be analyzed preliminarily by observing the change of composition and the structure features of fly ash modified or not.In our experiments,we analyzed the material of fly ash by XRD,and determined the crystal type of modified fly ash by analyzing the data through JADE software.The micro surface structure of fly ash was observed by SEM,and the surface structure change of fly ash modified or not was analyzed.The components of fly ash was detected by EDS,and analyzed the composition change of fly ash modified or not.By the analysis of XRD,we could find that new mineral phase generated only in the modification of fly ash by NaOH and are chemical modification,but others didn't,so the modifications of fly ash by hydrochloric acid,ferric chloride and rare earth ions were physical modification and the difference of the three modifications was the strength of each peak.By the analysis of SEM and EDS spectrum,the important changes of fly ash modified or not were:the surface of modified fly ash become rough compared with the fly ash material,and the particle shape are destroyed because of the corrosion degree by different modifiers.The content of each element were changed because of the modification and the iron and rare earth ions element were loaded for the modification of ferric chloride and rare earth ions so the modifier has been load in fly ash successfully and the adsorption performance of fly ash was also enhanced.In order to prepare a large specific surface area,high strength and well adsorption properties ceramicite for implant retention groove,in the experiment,we used the fly ash modified by rare earth ions as main material,NaOH and CaO as as the activities,the expanded perlite as lightweight materials and the sodium silicate as acid agent and bonding agent,and the ceramicite was manufactured by mixing,moulding and natural curing process.The preparation conditions of fly ash ceramicite were optimized by the single factor experiments and orthogonal experiments,and it was:fly ash 60%,cement 20%,lightweight materials 10%,the activities 10%,36 g water/100g material,acid agent 9g,and the influential effect of the factors were fly ash>cement>lightweight materials.The physical and chemical characteristics of the fly ash ceramicite prepared in the laboratory were determined and it was:The sum of broken rate and wear rate was 3.2%,silt content is 0.46%,hydrochloric acid soluble rate was 1.08%,void fraction was 49.5%,the specific surface area of 3.96 · 104 cm2/g.All performance indexes conform to the national standard Lightweight Aggregate Test Method(GB 2842-817)and industry standards Artificial Ceramsite Filter Material for Water Treatment(CJ/T 299-2008).The results showed that the fly ash ceramicite prepared in the laboratory has the characteristics-rough surface,specific surface area,high void ratio,well acid rain resistance,and it could be a kind of good artificial ceramsite filter material.The results of experiments for implant retention groove showed that the fly ash ceramicite filled in the implant retention groove could obviously improve the penetration rate and the phosphorus removal rate,and the phosphorus content decreased significantly when the rain water pass through it and the rate of phosphorus removal could be 87.37%.The results of dynamic simulation experiments for the adsorption of phosphorus by the implant retention groove showed that the damping trend of total phosphorus in the fly ash focus on the first grade reaction equation.