| Eutrophication in water bodies has triggered the development of effective adsorbents to remove phosphorus from wastewater.Biomass has the advantages of wide sources,cheap and easy to get,and rich surface oxygen functional groups,making biomass become one of the materials to prepare excellent adsorbent,however,there are few unmodified biomass active sites,and the high temperature modified energy consumption is large,limiting its scope of application and adsorption capacity.Nitric acid has excellent acid and oxidation properties and plays an important role in biomass surface modification.Polyethyleneimine is a polymer water-soluble polymer include a large number of amino functional groups and has high chemical activity that can be used as an excellent modifier agent for wastewater treatment.If the polyvinyl imine is used alone,it is difficult to separate it from the aqueous solution,and it is easy to cause the secondary pollution of the water bodies.Herein,agroforestry biowaste oil-tea shell(OTS)was adopted as a precursor,through a facile two-step dipping method of nitric acid(HNO3)and polyethyleneimine(PEI),nitrogen-rich adsorbent(HNO3 modified and PEI decorated OTS,NP-OTS)was prepared at low temperature to make it an excellent adsorbent for the effective removal of phosphorus in water.In this paper,three materials: oil-tea shell(OTS),nitrate acid modified oil-tea shell(N-OTS)and nitrate acid modified oil-tea shell and loaded with Polyethyleneimine(NP-OTS)were prepared,combined with various means of characterization to characterize the adsorption materials,and apply them to the adsorption of phosphorus in the water and compare them adsorption performance,to obtain the best modification conditions,and investigate the influence of key factors on the adsorption properties,and finally analyze the adsorption mechanism.The results of this study are as follows:(1)Material characterization of the three materials(OTS,N-OTS,NP-OTS)was performed using instruments including X-ray diffraction(XRD),Fourier infrared spectroscopy(FTIR),scanning electron spectroscopy(electron microscopy(SEM),X-ray photoelectron spectroscopy(XPS)and elemental analyzer,it was found that nitrate acid modification can effectively etch the surface of the camellia shell and increase the number of aerobic functional groups;polyvinyl imine spherical particles were successfully attached to the camellia shell surface,indicating the modified load.(2)The effect of modified conditions such as nitrate modification concentration and modification time on phosphorus adsorption was systematically studied,which showed that when the nitrate acid concentration was 5 mol/L and the modification time was 8 hours,and the best modification conditions were obtained(NP-OTS).NP-OTS was also applied to phosphorus removal in water to obtain the optimal adsorption conditions.:the results showed that when the initial p H value of the solution is(3.0±0.1),the adsorbent dosage was 0.01 g,the best adsorption time is 8 hours,and the maximum adsorption amount is 97.1 mg/g,And after the five regeneration cycles of NP-OTS,its adsorption performance is still maintained above 80%.(3)Through the analysis of the adsorption kinetics,adsorption thermodynamics and adsorption isothermal models,the study shows that the phosphorus adsorption of the three materials(OTS,N-OTS,NP and N P-OTS)is more consistent with the pseudo-second-order kinetic model and Langmuir model,and the thermodynamic research shows that phosphorus adsorption is a spontaneous process.This work has certain practical significance and theoretical guiding value for the resource utilization of biological waste and phosphorus removal in wastewater. |
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