| The eutrophication was caused by the excessive phosphate enter the water body with the development of human society.In this paper,we mainly used the anhydrite ore and magnesite ore as raw material to prepare anhydrite-brucite-periclase composite material?ABPM?.We used the Flue gas desulfurization gypsum?FGD gypsum?as raw material to prepare Nano-FGD gypsum as well.And the performance and mechanism of phosphate removal of two material would be investigated.The mineral composition,chemical composition and morphology of selected mineral were characterized by XRD,XRF,TG/DTG,SEM and TEM,etc.The performance of phosphorus removal of ABPM and FGD gypsum was studied through the static experiments and the mechanism of phosphorus removal was investigated by characterization of the sample after phosphorus removal.At the same time,selecting the ABPM as the dynamic column packing to study the performance of actual phosphorus removal.Concluded as follow:?1?The anhydrite ore was mainly composed of anhydrite and a small amount of dolomite,and the anhydrite with a dense and smooth surface has prismatic morphology.The Magnesite ore was mainly composed of magnesite and a small amount of dolomite,and the magnesite had flake morphology,the magnesite was decomposed and newly-form the nano-periclase after heat treatment.The periclase had ellipsoid morphology and hole structure.?2?The results of static experiments showed that the optimum mixing ratio of anhydrite and BPM was 5:1,the maximum phosphorus removal by ABPM was26.14 mg·g-1?35°C?,and the acidic environment was favorable for the removal of phosphorus.When initial concentration of phosphorus is 10 mg·L-1,the removal rate of phosphorus can reach 98%,and the phosphorus concentration in solution is less than 0.1 mg·L-1 at the equilibrium adsorption.The NO3-,Cl-,humic acid has little effect on the phosphorus removal,while HCO3-has inhibiting effect on phosphorus removal.Finally,the phosphorus in solution was immobilized in the form of an amorphous calcium-phosphorus compound?Ca3?PO4?2·nH2O?after the process of adsorption and precipitation.The BPM plays a key role in the process of phosphorus removal,such as synergistic release,sustained release,adsorption sites and alkaline environment.?3?The ABPM material can be used as dynamic column packing to removal of phosphorus(1 mg·L-1)for more than 200 days and the removal rate is over 80%.The P concentration of effluent can reach the standard of surface water environmental quality?(0.2 mg·L-1),so the ABPM can be used as a low-concentration phosphorus wastewater treatment filler.?4?the FGD gypsum mainly consists of gypsum and a small amount of dolomite and quartz,which has a columnar structure.The diameter of the FGD gypsum is approximately 1-2 um,which is smaller than natural anhydrite.The thermally treatment can promote the dehydration of gypsum step by step and newly form the nano-structured anhydrite.?5?The static experimental results showed that the capacity of phosphorus removal would increase with the increase of the temperature of thermally treatment.The FGD gypsum has the maximum capacity(22.82 mg·g-1)of phosphorus removal at thermally treatment at 600°C.The phosphorus was immobilized in the form of hydroxyapatite,which can be proved by the XPS,FTIR and TEM.The Calcined FGD gypsum has excellent capacity for phosphate removal for three reasons:an enhance content of active Ca by calcination,a novel nanoscale prismatic structurewith a high specific surface area,and a favorable reactivity and alkaline environment produced by the decomposition of magnesite,dolomite and calcite. |
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