Study On Modification Of Natural Zeolite And Its Nitrogen And Phosphorus Removal Performance

With the continuous development of China’s social economy and the rapid improvement of urbanization level,the urban daily water consumption and sewage discharge have increased significantly,and the black and odor phenomenon of water body is increasing day by day.The common treatment methods of black and odorous water bodies have limitations such as high cost,long cycle and the need to adjust measures to local conditions.At present,there are few studies on the use of adsorbents to purify black and odorous water bodies.Due to rich sources,unique pore structure and crystal structure,and mature modification technology,natural zeolite shows excellent performance as an adsorbent.Therefore,this study proposes a practical application scheme of using natural zeolite as the carrier,preparing modified zeolite through the combination of alkali melting and lanthanum loading,and forming its ball to realize the simultaneous adsorption and removal of ammonia nitrogen and phosphate in black and odorous water,and verifies the feasibility of this scheme.The specific research results are as follows:（1）The combined modification method can make the design of zeolite more reasonable and greatly improve the performance.In this study,the modified zeolite was prepared by alkali melting and lanthanum loading.Through orthogonal experimental design,the optimal preparation conditions were determined as calcination temperature 600℃,calcination time4h,lanthanum chloride concentration 8mg/L and solid-liquid ratio 1g:30ml.Under this condition,the adsorption capacity of ammonia nitrogen is about 6.5mg/g and that of phosphate is about 0.9mgp/g.Under the optimum reaction conditions,the removal rate of ammonia nitrogen and phosphate can be more than 85%.（2）Through the characterization of materials by bet,SEM-EDS,XRD,ICP-MS and other technical means,it is confirmed that the specific surface area of natural zeolite powder increases three times after modification,and a large number of active sites are increased.Lanthanum is successfully loaded on the zeolite surface in the form of lanthanum hydroxide,which can be applied to water treatment in a wide p H range.（3）The granulation of modified zeolite powder into balls will facilitate the treatment and application of the actual black and odorous water body.The best material ratio of the main materials is:modified zeolite powder mass:bentonite mass:steel slag mass:Deionized water capacity=10g:6g:7g:6ml.Under this material ratio,the loss rate when the ball is formed is7.46%,the ammonia nitrogen removal rate reaches 78.83%,and the phosphorus removal rate reaches 82.86%,which can be reused for many times.The characterization techniques of bet,SEM-EDS,XRD,ICP-MS and FT-IR show that the modified zeolite sphere has stable forming structure,is suitable for water treatment with wide p H value,still has good adsorption and removal ability for nitrogen and phosphorus,and ammonia nitrogen and phosphate can be successfully adsorbed into the modified zeolite sphere structure.（4）From the static adsorption experiment of modified zeolite powder and sphere on the simulated water sample of black and odorous water body,it can be seen that when the optimal dosage of modified zeolite powder is 2.2g/L（5g/L for sphere）,the optimal adsorption time is4H and the optimal p H is 7.0,excluding the interference of CO₃^2-plasma,the removal rate of ammonia nitrogen is 88.5%and the removal rate of phosphate is 85.1%（83.5%for ammonia nitrogen and 86.2%for phosphate for sphere）.The maximum adsorption capacity of modified zeolite powder for ammonia nitrogen is 23.88mg/g,the maximum adsorption capacity for phosphate is 3.58mgp/g,the maximum adsorption capacity of modified zeolite sphere for ammonia nitrogen is 16.62mg/g,and the maximum adsorption capacity for phosphate is1.56mgp/g.The unit adsorption capacity of modified zeolite powder is large,while the modified zeolite sphere has higher applicability because it can be reused for many times,convenient recovery,no secondary pollution and other advantages.The modified zeolite sphere was put into the actual black and odorous water body for nitrogen and phosphorus adsorption experiment.The removal rate of ammonia nitrogen was 77.3%and that of phosphate was 75.2%.At the same time,the saturated adsorption material is also treated to achieve the purpose of treating waste with waste.