Preparation And Properties Of Lantanum-modified Adsorbents For Phosphorus Removal

Excessive phosphorus discharged into natural water will speed up eutrophication.That will cause serious water pollution problems and even make the destruction of water ecosystems.Therefore,phosphorus removal has become one of the key research directions in wastewater treatment,and many effective dephosphorization methods have been gradually develope.Among them,the adsorption method is considered to be one of the effective and convenient methods and the adsorbent is the key to achieving a good phosphorus removal effect.This thesis has carried out the research of lanthanum-modified absorbents for phosphorus removal in wastewater.The details are as follows:(1)Three kinds of lanthanum-modified absorbents were prepared by impregnation acidification,ion-exchanged and lanthanum precipitation methods,respectively.Their phosphates-removal properties were compared.The saturated phosphorus adsorption capacity of the original bentonite is only 6.7 mg/g.The above said values of the corresponding La-modified bentonites are improved to 12.7 mg/g,7.3 mg/g and 24.9 mg/g,respectively.The absorbent prepared by precipitation method has the best removal ability,which is nearly 4 times that of the unmodified sample.(2)The La-modified biomass carbon absorbents for phosphorus removal were prepared by the impregnation-calcination method by using the solid waste of traditional Chinese medicines as raw materials,such as Lianhua Qingwen.The effects of the calcination temperature and activator on the phosphorus removal performance were studied.The La-modified biomass carbon obtained by adding an activator and calcined at 400℃ has the best dephosphorization performance.Its saturated adsorption capacity reaches to 123.6 mg/g,while the corresponding value of the pure biomass carbon is only 96.3 mg/g.(3)Using graphene oxide(GO) as a structural regulator,the GO and La contained metal organic framework material(GO-La-MOF)was prepared by solvent synthesis,and corresponding GO-La-MOF-based carbon composite material was also prepared by calcination.Their phosphorus removal performances were studied.The calcined modified material(GO-La-MOF-650)has the highest saturated adsorption capacity,which is about 75.9 mg/g,while the corresponding values of La-MOF and GO-La-MOF are just 68.9 mg/g and 71.5 mg/g,respectively.(4)The three types of La-modified adsorbents were characterized by XRD,SEM,EDX,and N2 adsorption to analyzed the crystal structure,microstructure,surface chemical composition and pore structure of the samples and compared their phosphates-removal properties.It was found that the preparation process successfully loaded lanthanum on the adsorbent in the form of various compounds.The best phosphates-removal temperature for them is about 30℃,and a weak acidic condition is conducive to phosphate removal.The phosphorus adsorptions of the three kinds of adsorbents conform to the Langmuir adsorption isotherm model and the pseudo-secondary adsorption kinetic model.The adsorption process has chemical adsorption is involved.