Preparation Of Flower-like Hydrotalcite Materials And Its Adsorption And Recycle Behaviors Of Phosphorus In Water

Phosphorus is a kind of scarce non-renewable resource and an indispensable element in human life activities.However,every year excessive phosphorus is discharged into the water environment through agricultural runoff and wastewater,resulting in eutrophication of the water body,and causing serious harm to the life and production of human society.Therefore,the efficient removal and recovery of phosphorus from wastewater and its recycling are of great scientific significance and social value for water environment treatment and phosphorus resource utilization.In order to achieve the efficient recovery and recycling of phosphorus in wastewater,this thesis prepared the flower-like magnesia-aluminum hydrotalcite material(Mg/Al-LDO)by co-precipitation method through structural design and process control.The effects of process factors such as the amount of LDO,adsorption temperature,solution pH,contact time,and coexisting ions on the adsorption effect were investigated using kinetic and isotherm models for the adsorption behavior of phosphorus by Mg/Al-LDO.The adsorption mechanism in combination with Zeta potential,X-ray diffraction(XRD),and XPS were discussed.On this basis,in order to further improve the adsorption and recovery efficiency of phosphorus,and using co-precipitation and roasting technology to prepare calcium magnesium magnesium aluminum hydrotalcite modified biochar composite materials(Ca/Mg/Al-LDO@BC).In this paper,the interaction between the microstructure,composition and adsorption capacity of composite materials was systematically studied,and the mechanism of Ca/Mg/Al-LDO@BC composites for phosphorus adsorption was discussed.Finally,the application value of phosphorus-containing Mg/Al-LDO and Ca/Mg/Al-LDO@BC in paper flame retardant and plant fattening and efficiency enhancement were explored.The main research results are as follows:(1)The preparation of Mg-Al Hydrotalcite adsorption and recycling performance of phosphorus:Through structure design and process control,a co-precipitation method was used to prepare a magnesia-aluminum hydrotalcite material(Mg/Al-LDO)with a petal-like micromorphology,with a specific surface area as high as 200.17 m2/g.The research on the adsorption performance of phosphorus found that Mg/Al-LDO exhibited excellent phosphorus adsorption capacity,and its maximum adsorption capacity for phosphorus reached 103.8 mg P/g.At the same time,it had excellent environmental stability.Excellent adsorption effect is still maintained within the range of pH 2-9.The study of the effects of coexisting anions in water found that Mg/Al-LDO has good anti-interference ability,and the existence of low-priced anions hardly affects its adsorption effect on phosphorus.The influence order of various ions on phosphorus adsorption effect is CO32->SO42->Cl->NO3-.The adsorption behavior research found that the adsorption kinetics of phosphorus by Mg/Al-LDO conformed to the pseudo-second-order kinetic model,and the isothermal adsorption conformed to the Langmuir isothermal adsorption model.Combining the analysis of changes in Zeta potential,XRD,FTIR,and pH before and after adsorption,the adsorption mechanism analysis revealed that high-efficiency phosphate capture by Mg/Al-LDO was mainly due to the electrostatic adsorption,surface inner-sphere complexation,ligand exchange and precipitation combined process.Finally,P-LDO/Paper composite paper was obtained by mixing Mg/Al-LDO(P-LDO)with pulp after pulp adsorption and paper-making process,and the application potential of P-LDO in paper flame retardant field was investigated.The study found that when the P-LDO content in the composite paper was only 10%,the limit oxygen index(LOI)of the composite paper increased from 17.6%to 29.4%compared with ordinary paper,showing a significant paper flame retardant effect.(2)The preparation of Ca/Mg/Al-layered Hydrotalcite modified biochar composite material(Ca/Mg/Al-LDO@BC)adsorption and recycling performance of phosphorus:In order to further improve the adsorption and recovery efficiency of phosphorus,the waste calcium distillers grains were used as raw materials,and co-precipitation and roasting techniques were used to prepare the calcium magnesium magnesium aluminum hydrotalcite modified biochar composite material(Ca/Mg/Al-LDO@BC).Interactions between microstructure,composition and adsorption capacity of composite materials were researched.The study found that when the molar ratio of Ca:Mg:A1 metal ions is 1:3:1 and the amount of biochar added is 0.1 g,the prepared Ca/Mg/Al-LDO@BC has a high specific surface area is 508.97 m2/g and shows more excellent phosphorus adsorption capacity.Compared with Mg/Al-LDO,Ca/Mg/Al-LDO@BC composite reached equilibrium of phosphorus adsorption within 2 h,and its maximum adsorption capacity for phosphorus was 158.3 mg P/g,showing a higher adsorption capacity and faster adsorption removal rate.In addition,Ca/Mg/Al-LDO@BC composite materials have a wider application environment for phosphorus adsorption,and maintain a good adsorption effect in the range of pH 2-11.In particular,it exhibits more efficient adsorption and recovery capacity for low-concentration phosphorus-containing wastewater.For phosphate solutions with a concentration of 2 mg/L,the adsorption removal rates of the first 10 s and 30 s are 88.56%,93.39%,and phosphorus pollutants can be completely removed within 60 s.Phosphate fertilizer using Ca/Mg/Al-LDO@BC(P-CaMgAl-LDO@BC)after phosphorus adsorption as a plant growth promoter showed a good effect,and small greens were irrigated with experimental fertilizers showed good growth.When grown to 30 days,the greens that was irrigated with experimental fertilizer was 3.9 cm taller than the normal plants in the control group.In this paper,a flower-like hydrotalcite-like material capable of efficiently adsorbing and recovering phosphorus was successfully prepared,which solved the problems of small adsorption capacity and slow adsorption rate of traditional adsorbent.At the same time,this study clarified the phosphorus adsorption mechanism of the prepared flower-like hydrotalcite materials,and expanded its recycling potential in paper flame retardant and plant fertility,for the recovery and reuse of phosphorus in wastewater provided a new material,new technology and new theory.