Adsorption Of Phosphates By Wetland Plant Thalia Dealbata

With the development of social economy,the problem of environmental pollution becomes more and more serious.The treatment of environmental pollution and the reuse of resources has become a hot issue of social concern.Eutrophication is one of the main causes of water environment and the key nutrient element is phosphorus.Leaching of phosphorus not only causes great loss to production,but also brings potential threat to ecological environment.Therefore,the removal of phosphate is of great significance for water purification.Constructed wetland is a new ecological technology to deal with water pollution.A large number of wetland plants will be produced in the wetland system every year.If these wetland plants are not well utilized,they will easily cause environmental pollution and resource waste.Therefore,it is of great significance in economic and resource utilization to seek effective measures to utilize wetland plants and make them "turn waste into treasure".In this paper,using wetland plants thalia dealbata as materials,reforced straw biochar(BH,200BH,350BH,500BH and 650BH at different carbonization temperatures)at different carbonization temperatures were prepared by high-tem,perature oxygen-limiting method.BH represents the reforced peanut material,and the number after BH represents the carbonization temperature)to conduct characterization analysis of biomass and biochar.The modified carbon was prepared by soaking 50g of FeSO4·7H2O in 500mL 1.0mol/L and modifying the biochar with loaded iron(BHFeBH,200FeBH,350FeBH,500FeBH and 650FeBH).Using potassium dihydrogen phosphate to simulate phosphate in water,determine the biochar with the optimal adsorption amount of potassium dihydrogen phosphate by BH,200BH,350BH,500BH and 650BH.The optimal biochar was mixed with the constructed wetland matrix soil in different proportions(soil sample,1%200FeBH,2%200FeBH,5%200FeBH and 10%200FeBH)to prepare soil samples with different proportions of added carbon.The optimal ratio was found out through adsorption kinetics experiment and adsorption isotherm experiment.The effects of pH,reaction time,initial concentration and temperature on phosphate adsorption were analyzed.The soil sample with the optimal ratio was added with carbon into the constructed wetland pilot system.The water sample in the constructed wetland pilot system was collected and the content of phosphorus in the water was determined by AA3 flow analyzer.The main conclusions are as follows:(1)with the increase of carbonization temperature,the yield of regenerated straw biochar decreases gradually,the ash content increases gradually,and the specific surface area and micropore volume increase with the increase of carbonization temperature.(2)The phosphate adsorption data measured by biochar yield,ash content and pre-experiment show that the best biochar is the biochar modified by ferric divalent,which has economic value and ideal adsorption effect.(3)The quasi-second-order kinetic model is more suitable for fitting soil samples and the phosphate adsorption process of soil samples with the addition of carbon,and R2 is closer to 1 when it is above 0.95,which is a rapid reaction chemical process.Langmuir isothermal adsorption model can better fit the phosphate adsorption by adding carbon,and R2 is close to 1,indicating that it is the chemical adsorption process of the single molecular layer on the solid surface.The 5%and 10%carbon content are close to each other in adsorption capacity,and the 5%carbon content should be popularized from the economic point of view.(4)Different pH values can affect the surface charge of biochar and its interaction with surface functional groups,thus affecting the phosphate adsorption process.With the increase of pH value,the adsorption of modified carbon to phosphate showed a tendency of increasing first and then decreasing.There was a relatively large adsorption capacity between pH6.0 and 10.0,and the corresponding optimal adsorption capacity was 1.05mg/g,1.4mg/g and 1.5mg/g,respectively.25? was the optimal reaction temperature of the solution,and the comparison of adsorption capacity data was the largest.(5)The optimal carbon(200FeBH biochar)and wetland soil samples were applied to the wetland substrate at the ratio of 5%to determine the phosphorus content of wetland water quality.Wetland matrix with 5%200FeBH biochar was observed for a month,and water samples were collected once a week for a total of 5 times.The phosphorus adsorption capacity was determined to be 30.39,23.52,32.87,40.96 and 42.70 times of that without carbon.