Preparation Of Lanthanum Based Composites And Application Of Selective Phosphorus/Phosphine Removal From Water

Phosphorus（P）is an indispensable element for animals,plants and human production activities.Chinese phosphorus chemical industry provides a large number of material assets to the society,but it also produces a large number of pollutants including inorganic phosphorus/organic phosphorus.At the same time,phosphorus is also a nonrenewable resource.With the continuous development of phosphate rock,there is the pressure of the depletion of phosphate rock resources.Therefore,the efficient removal and resource recovery of inorganic phosphorus/organic phosphine pollutants in water have attracted extensive attention from scholars in recent years.At present,in the existing phosphorus removal/tadpoles,the adsorption amount of phosphorus/cricket adsorption agent is relatively low.Moreover,the concentration of phosphate in the water environment is low and there are many competitive anions.If the resource recovery of phosphorus is needed,the selectivity of phosphorus/cricket adsorption agent needs to be further improved.This paper focuses on how to improve the adsorption capacity and selectivity of phosphorus/phosphine adsorbents,to realize the efficient adsorption and separation of low concentration phosphorus/phosphine pollutants in environmental water.As a component of phosphate adsorbent,lanthanum has attracted a lot of research because of its rich,non-toxic and specific affinity for phosphate.It can react with phosphorus to form a stable lanthanum phosphate mineral（La PO₄ x H₂O）,which is no longer involved in the natural phosphorus cycle.This phosphorus removal strategy based on the La-P reaction is also recognized as the most effective means of phosphorus immobilization.However,the secondary pollutiononrecyclabilitybility of metal powder adsorbent to the water environment is an urgent problem to be solved lanthanum-basedbased metal composites are directly applied to the treatment of low concentration phosphorus/phosphine pollutants in environmental water.Based on the specific affinity of lanthanum for phospholanthanum-basedbased metal composites were immobilized on biomass and organic materials by sacrificial template method,metal ion induced synthesis,coprecipitation method,in-situ growth method and metal ion exchange method to prepare phosphate adsorbent materials.Inorganic phosphorus/organic phosphine adsorbent materials were obtained,and their selective adsorption mechanism was studied.The specific research contents and results are as follows:（1）Preparation of lanthanum doped bio-based mesoporous carbon films and their phosphate synergistic adsorption properties:lanthanum doped mesoporous carbon films（MC-La）were obtained by using Nanocrystalline Cellulose（NCC）as the guide template and tetramethoxysilane（TMOS）as the mesoporous template,one-step lanthanum doped cellulose nanocrystalline films,and then carbonizing cellulose nanocrystals under controlled conditions to remove silicon-based materials.The morphology characterization was shown that the composite membrane has a layer-by-layer self-assembly interface structure,and the composite membrane has high selectivity and adsorption capacity for phosphate.With the increase in La dosage,the specific surface area and pore volume of the composite membrane decreased,but the corresponding phosphate adsorption capacity increased significantly,and the maximum adsorption capacity was 66.16mg g^-1.The adsorption kinetics followed the quasi second-order adsorption kinetics,fitted the adsorption isotherm of phosphate,and revealed the monolayer adsorption mechanism.The results of five cycle regeneration experiments show that the adsorbent material has good recycling performance,and the adsorbent has great potential for phosphate removal in actual water.（2）Preparation of La-Ca-LDH hydrogel and its adsorption properties for phosphate in water:the preparation of sodium alginate hydrogel by La ion coordination can improve the fragility of biomass carbon membrane adsorbent material.The alginate loaded La-Ca-LDH gel（SA-La-Ca-LDH）was successfully synthesized.The adsorption results shown that the isothermal adsorption process of phosphate could be described by a quasi two level kinetic model.The maximum adsorption capacity was 62.42mg g^-1.In the p H range of 3.0-7.0,the removal efficiency of phosphate is high,and it is little affected by competitive anions such as carbonate ion,chloride ion,nitrate and sulfate.After five cycles,the phosphate adsorption capacity of the adsorbent material is still83.96%of the initial adsorption capacity.The results show that SA-La-Ca-LDH hydrogel is an economical and environmentally friendly adsorbent for phosphorus removal.（3）Preparation of La（OH）₃-PVDF foam adsorbent and its adsorption of phosphate and organic pollutants by sacrificial salt template method:to solve the mechanical properties of biomass carbon membrane and the swelling property of hydrogel adsorbent,the environmentally friendly PVDF-La（OH）₃ foam phosphate adsorbent was prepared by melting method through hard template method and water-soluble sodium chloride as sacrificial template and PVDF thermodynamic compatibility.Lamellar growth of lanthanum hydroxide in PVDF-La（OH）₃ foam pores was observed by morphology.The PVDF-La（OH）₃ foam not only has a high phosphorus adsorption capacity of 58.526 mg g^-1,but also can adsorb oil organic reagents.It is found that the adsorption capacity of the prepared foams to oil organic reagents is as high as 140-300%of their weight.After more than 10 times of organic reagents removal,the phosphate adsorption capacity still has 50%initial adsorption capacity after 7 cycles.The PVDF-La-（OH）₃ foam showed good synergistic cleaning performance of phosphate and oil-based organic pollutants.（4）Preparation of bimetallic MOF supported adsorbents and their adsorption properties for phosphate in water:in order to solve the problem of low adsorption capacity of organic adsorbent materials,multi-metals were used to adsorb phosphate.Guest metal was doped into the metal organic frameworks（MOF）by solvothermal reaction,and the lanthanide MOF compounds were loaded on the non-woven and PVDF foams respectively.After controlling the metal elements loaded on the adsorbent material,it was found that the maximum adsorption capacity after the non-woven fabric loading was 53.44mg g^-1,and the maximum adsorption capacity after PVDF foam loading was 110.47mg g^-1.It is found that the porous structure of the foam is beneficial to the direct combination of phosphate with phosphate,and promotes the diffusion of phosphate to the active binding sites.PVDF foam material has more roughness than non-woven material,and its multilayer adsorption process has a greater advantage than monolayer adsorption,showing better phosphate adsorption performance.（5）Preparation of lanthanum cobalt bimetallic mof/pvdf membrane materials and Study on the degradation of organic phosphorus and the synergistic adsorption of inorganic phosphorus in water:due to the harmful nature of organic phosphine,we use Co-based metal compounds to degrade organic phosphine and adsorb La based metal compounds for synergistic adsorption of inorganic phosphorus.Based on in-situ growth of PVDF film surface,the guest metal La doped co MOF（PVDF-La-Co）loaded with solvothermal reaction was used as the degradation adsorption of glyphosate in aqueous solution.The morphology characterization experiment proved that the PVDF film was loaded with La based MOF,and the guest metal La was successfully exchanged with the host metal co of MOF by XRD.At the same time,glyphosate degradation and adsorption experiment show that in the presence of H₂O₂ system,the degradation rate of glyphosate of PVDF-La-Co composite membrane reaches 95.5%only after 2h,the adsorption capacity of PVDF-La-Co composite membrane for inorganic phosphorus reaches 93.67mg g^-1,and the removal rate of total phosphorus reaches 93%,which is12 times shorter than that in the absence of H₂O₂,and the adsorption capacity increases to twice.The experiment shows that the degradation process promotes the adsorption process.After 10 regeneration experiments,the PVDF-La-Co composite membrane still has good glyphosate degradation efficiency and inorganic phosphorus fixation ability.