Adsorption Research Of Low Concentration Phosphorus From Water Onto Modified Reed Biochar

Because the excessive of nitrogen,phosphorus and other nutrient elements,the water eutrophication is the important environment problem,phosphorus is regarded as a limiting factor of eutrophication.Therefore,it is urgent to find an economical and effective method to remove the low concentration of phosphorus in wastewater and realize resource utilization for the reed.It has an important significance to human health and environmental safety.In this study,the modified reed biochar(MRB)was made by two kinds of preparation technology,studied the effects of different factors on the adsorption,and adsorption isotherms,thermodynamics and kinetics were applied to study phosphate adsorption characteristics and capacity by MRB.And then pHpzc,SEM,XRD,FTIR,element analysis were applied to study the structure features of MRB,The results showed that:(1)The MRB-2 was made by reed biochar and modified by ferric chloride,The content of iron of MRB-2 was 11.98mg·g-1,which was 44.7 times that of reed biochar.The adsorption capacity of MRB-2 was 0.658mg·g-1 at the initial concentration of 4mg·L-1,which was 34.6 times that of reed biochar.The microstructure has changed after modification.(2)The MRB-3 was made by reed straw and modified by ferric chloride,keep the quality of iron reed ratio of 0.315:1,the calcination temperature and time was 350℃ and 2h.The content of iron of MRB-3 was 115.75mg·g-1.The adsorption capacity of MRB-3 was 3.933 mg·g-1 at the initial concentration of 4mg·L-1.Iron mainly in the form of hematite load on the MRB-3,modification obviously increased O and Fe mass fractions in the biochar.The microstructure of MRB-3 has changed after modification.(3)The pHpzc of the MRB-2 and MRB-3 were 7.49 and 7.68.The adsorption effect was the best when the solution pH was 7.At the initial concentration of 4mg·L-1,the optimal dosage of MRB-2 and MRB-3 were 7g·L-1 and 0.7g·L-1.The coexisting anions has no obvious influence on phosphorus removal of MRB-3.(4)The adsorption isotherms of MRB-2 andMRB-3 were fitted well with Langmiur equation,which indicates the adsorption is monolayer adsorption and chemical adsorption.(5)ΔGθ<0,ΔHθ>0 and ΔSθ>0 indicate that the adsorption of MRB-2 and MRB-3 were a spontaneous,entropy increasing and endothermic process.(6)The kinetic experimental data of the adsorption of MRB-2 and MRB-3 fitted well the pseudo-second-order equation,the adsorption is mainly controlled by intraparticle diffusion.(7)The residual concentration of phosphorus was not a obvious differents with the experiment control group.Adsorption of phosphorus in river water,the optimal dosage of MRB-3 were 0.15g·L-1,when adsorption time reached 6h,residual phosphorus concentrations in river water has reached the《surface environment quality standard》(GB3838-2002)of the national Ⅱ(≦0.1mg·L-1)water quality standards.The research will provide basic data for MRB used for deep removal of low concentration phosphorus from sewage treatment plant and water body.