Adsorption And Application Of Surface Modified Ecological Brick To Urban Non-point Source Pollutant Nitrogen And Phosphorus

The problem of urban black-odor water bodies pollution causing adverse effects on the urban water environment quality has become increasingly serious and has attracted people's attention.The sources of pollution include: urban domestic sewage,large amounts of industrial wastewater,and urban non-point source pollution.Among them,urban non-point source pollution has become a major source of pollution causing black and foul odors in urban water due to its uncertainty,wide distribution of pollutants and difficulty in treatment.On the other hand,The use of traditional hard materials for water slope protection caused a certain visual pollution to the coordination of coastal landscapes during use.With the growing awareness of the concept of ecological governance,the drawbacks of this type of slope protection are increasingly prominent.Therefore,it is particularly important to research and develop new types of ecological slope protection materials and apply them to urban river banks in order to retain the adsorption of non-point source pollutants and improve the visual environment.This project selected the highly effective adsorption of nitrogen and phosphorus materials on the surface of concrete to make a modified ecological brick,and studied the effects of loading capacity,nitrogen and phosphorus concentration,and adsorption time on the adsorption of nitrogen and phosphorus.At the same time,the adsorption model was used to fit the experimental results and XRD technique was used to characterize the modified ecological bricks to explore the adsorption mechanism of nitrogen and phosphorus on the modified ecological bricks.Finally,the alkali-reducing effects of several alkali-reducing methods on modified eco-brick and the absorption of phosphorus on the surface of eco-brick were explored in order to provide a theoretical basis for applying it as a slope protection material for urban river banks in practical projects.The results of material screening tests showed that after 3 h of adsorption reaction,the removal rate of ammonia on zeolite was the highest,which was 28.38%.The adsorption process of ammonia nitrogen conforms to the pseudo-second-order kinetics model and the Freundlich empirical formula,mainly for multi-layer adsorption;After 3 h,fly ash had the highest removal rate of phosphorus,which was 90.36%.The adsorption process of phosphorus is in accordance with the pseudo-second-order kinetics model and the Langmuir equation and the Freundlich empirical equation.It is mainly between monolayer adsorption and multilayer adsorption,and the surface is not uniform.The removal rate of ammonia nitrogen by zeolite modified eco-brick increases with the increase of zeolite loading.With the best loading capacity of 60 mg/cm2,the ammonia removal rate was 8.34%.The adsorption process of ammonia nitrogen conforms to the pseudo-second-order kinetic model,Langmuir equation and Freundlich empirical formula,and is mainly between single-layer adsorption and multi-layer adsorption with uneven surface.The removal rate of phosphorus from fly ash modified ecological bricks showed a trend of increasing first and then decreasing with the increase of fly ash loading capacity.Under the best loading capacity of 36 mg/cm2,the phosphorus removal rate was 66.19%.The adsorption process of phosphorus is in accordance with the double-constant rate equation,the intragranular diffusion equation and the Freundlich empirical equation,and is mainly multi-layer adsorption,which is controlled by the intragranular diffusion process.The alfalfa absorption test showed that in the environment of phosphorus deficiency,with the increase of time,the alfalfa root can continuously excrete citric acid to activate the calcium phosphate on the surface of the modified ecological brick.Increase the available phosphorus in the solution,and then absorb and use it.The reduction of available phosphorus further promotes the secretion of citric acid.As a result,the phosphorus in the surface of the modified eco-brick is continuously transferred into the alfalfa plant.After 15 days,the proportions of phosphorus absorbed by the alfalfa modified fly ash modified eco-brick and zeolite modified eco-brick were 38.40% and 42.57%,respectively.The increase in the number of alfalfa plants promoted the secretion of citric acid from root exudates and the further absorption of phosphorus from plants on the modified eco-brick surface.However,the uptake of phosphorus by alfalfa per plant decreased.Taking into account the environmental conditions of alfalfa growth and the absorption of phosphorus on the surface of ecological bricks,the optimum number of alfalfa plants should be three.Compared with fly ash modified ecological bricks,phosphorus on the surface of zeolite modified ecological bricks is more easily absorbed by plants,which is beneficial to the growth of alfalfa.Therefore,it is more appropriate to use it as a slope protection material for urban river banks in practical projects.