Capture And Reuse Of Phosphorus In Eutrophic Water By Iron-Impregnated Biochar

With the continuous development of city and industry,as well as a large number of agricultural fertilizer and phosphorus detergent,the eutrophication phenomenon of lake has become increasingly serious.However,phosphorus is a kind of non renewable resources which can not be replaced.Therefore,the best way to alleviate the contradiction between the increasingly serious eutrophication problem and the lack of phosphorus resources is to realize phosphorus recovery in wastewater treatment.In this study,water hyacinth was used as raw material to prepare iron-impregnated biochar?MW450?.Through the adsorption kinetics,adsorption isotherms,p H impact experiments,the coexistence of anion competition experiments,the actual eutrophic water of Dianchi adsorption and penetration experiments,the trapping ability of phosphorus was studied.Combined with XRD,SEM-EDS,XPS and other technicals,the mechanism of adsorption was analyzed.According to the part of experimental results,the saturated adsorption MW450phosphate-solubilizing and recycle ability were studied.Based on this,the solution of phosphorus removal from MW450 was applied to arsenic contaminated rice pot experiment in different ways,and the effects of As,Fe and P accumulation in different parts of rice were studied.The main results are as follow:1.The MW pyrolyzed at 450^oC?MW450?exhibited the most prominent phosphate sorption capacity,which was estimated to be 5.07mg g^-1 based on Langmuir-Freundlich model.2.For the initial concentration of 1,5,15 mg P l^-1,pH value of 2-9solution,MW450 can remove more than 90%of the P.Anionic Sb?OH?₆^-,NO₃^-and SO₄^2-had little effect on the adsorption of P by MW450.3.Through the use of MW450 for the actual eutrophic water(initial P concentration of 0.71-0.94 mg l^-1)to explore the efficiency of its adsorption of P,the results show that about 96%of the P can be removed.4.According to XRD,Fe₃O₄ and Fe₂O₃ were found on the surface of MW450.Hysteresis loop results show that the saturation magnetization is45.8 emu g^-1,so magnetic separation technology can be used for the recovery of P.According to the results of XPS,the mechanism of adsorption of MW450 by P is mainly surface complexation and ligand exchange.5.The desorption of MW450 was carried out using 30 mmol l^-1NaOH solution,and the desorption rate could reach 90.34%.The results of adsorption desorption cycles showed that the desorption capacity of P was decreased obviously after 1 cycle,and the desorption amount reached a stable state after 3 cycles.But the maximum number of cycles was more than 11 times,and the desorption rate was still maintained at about 51%.6.Phosphorus solution which is desorbed from the saturated adsorption of MW450 is applied to the rice pot experiment with As contaminated.The result proves the state of low phosphorus soil can promote the formation of iron plaque on root surface of rice,and applying phosphorus solution in different forms can inhibite the formation of iron plaque on rice root and promote the accumulation of As in rice root,reduce the content of As accelerating in the roots,stem,chaff and unpolished rice.According to the above results,the iron-impregnated biochar?MW450?is of great potential for the collection and recovery of P in Wastewater,and the application of different forms of phosphorus solution has an effect on the accumulation of As in rice.