Effects Of Schwertmannite On Transport And Transformation Of Phosphorus In Aqueous Solution

In this paper,a kind of iron oxide was synthesized by slow synthesis method,and characterized by XRD,FTIR,scanning electron microscopy?SEM?and transmission electron microscopy?TEM?,show that amorphous schwertmannite was successful synthesied with high purity.The elemental analysis of the synthesized samples determined that the chemical formula of schwertmannite was Fe₈O₈?OH?_5.52(SO₄1.24),and the surface sulfate and pore sulfate content were 0.31mmol/g and 0.93 mmol,respectively.According to SEM,TEM and BET tests,schwertmannite was a spherical or elliptical particle with a diameter of about 500 nm,a specific surface area of 209 m²/g and a pore volume of 0.34 cm³/g.Static adsorptions of inorganic phosphorus and organic phosphorus in solution were carried out by using synthetic schwertmannite as adsorbent.The effects of solution pH,initial concentration and coexisting ions on adsorption performance were studied.In addition,the stability of schwertmannite after adsorption of phosphorus was also studied.The results show that schwertmannite can adsorb inorganic phosphorus and organic phosphorus,and the actual adsorption amounts are 268.08mg/g and 57.37 mg/g,respectively,which are consistent with the Langmuir isotherm adsorption model and pseudo-secondary adsorption kinetics mode.The maximum theoretical adsorption capacity of chemical adsorption is 269.3 mg/g and 56.46 mg/g,respectively,which is consistent with the actual adsorption amount.The adsorption rate constants for different forms of phosphorus indicate that the adsorption of inorganic phosphorus by schwertmannite is faster than that of organic phosphorus.Schwertmannite can also adsorb different forms of phosphorus at the same time,and the adsorption tendency is consistent with the adsorption alone,with different adsorption sites and less influence on each other.This is because the adsorption mechanism of inorganic phosphorus on the schwertmannite is mainly based on the replace sulfate ion in the hole as the form of phosphate,and the exchange of surface sulfate is supplemented.However,the adsorption of organic phosphorus on the schwertmannite is the mainly exchange of sulfateon the schwertmannite surface sulfate exchange.In the range of pH 2-6,the adsorption amount of inorganic phosphorus remained unchanged,while at pH>6,the adsorption amount decreased.The adsorption of organic phosphorus is substantially constant in the range of pH 2-10.The common three kinds of ions NO₃^-,Cl^-,SiO₄^2-have little effect on the adsorption of different forms of phosphorus by schwertmannite.Both organic phosphorus adsorption and inorganic phosphorus adsorption can inhibit the conversion of schwertmannite to goethite,broadening the stable existence of Swartmann iron ore.