| The adsorption of phosphorus by iron minerals affects the Biogeochemistry cycle of phosphorus.However,traditional research focuses more on the adsorption of inorganic phosphorus by iron minerals,while ignoring the adsorption process of organic phosphorus.In addition,organic matter is widely present,and it is easy for iron minerals to form complexes,which in turn affects the phosphorus adsorption process.Therefore,in this study,based on the prepared iron minerals and their organic matter complexes(FeO-HA),the adsorption characteristics of Goethite,ferrihydrite and their organic matter complexes for organic phosphorus were studied,the adsorption behavior of phosphorus on ferruginous water and its complex during the aging process was discussed,and the effect of organic matter on the adsorption capacity of phosphorus in natural soil was studied.The main findings are as follows:(1)Powder X-ray diffraction analysis shows that goethite has good crystallinity,while ferrihydrite has no obvious characteristic peaks,and the crystallinity is poor.Form exists,with irregular morphology,with conchoidal fractures,indicating its amorphous form.The BET analysis results show that the specific surface area of ferrihydrite is significantly higher than that of goethite.The combination of HA and Fe O did not change the crystal structure of FH.The specific surface area of goethite was 90.2507 m~2/g,the specific surface area of goethite complex was 72.2468 m~2/g;ferrihydrite was 214.672 m~2/g,water The iron ore complex is 196.908 m~2/g,which is lower than the elemental minerals.The humic acid-loaded complexes reduced the adsorption sites on the mineral surface.The infrared spectra showed that there were hydroxyl absorption peaks on the surface of the complexes,and the complexes were mainly composed of didentate and dinuclear complexes.(2)The results of adsorption isotherms showed that the iron oxide component was the main contributor to the adsorption of phosphorus on the surface,but the adsorption capacity of the two iron ore complexes was lower than that of the original minerals;the iron minerals and humus in the synthesized complexes were in the form of ligand exchange Exist;the size of the molecular spatial structure of phosphorus and the competition with organic matter will affect its adsorption on ferrihydrite;under natural conditions,the adsorption of humus and phosphorus in pure minerals has a competitive relationship,which inhibits the adsorption of phosphorus and reduces the adsorption of Fe O-HA complexes.(3)XRD results show that under natural conditions,weakly crystalline ferrihydrite transforms to a crystalline structure at a slow rate for 30 days,and humus inhibits the transformation of ferrihydrite;BET results show that the specific surface area of the four minerals after transformation is uniform.reduce.The decrease rate of the specific surface area of the composite is lower than that of the elemental minerals,indicating that the composite structure is more stable under natural conditions;Langmuir adsorption isotherm results show that the adsorption capacity of the four minerals decreased after 30 days,and the adsorption of inorganic phosphorus by ferrihydrite decreased the most.Under natural conditions,the adsorption of humic substances by pure minerals competes with phosphorus,and the adsorption of iron minerals by organic matter affects the transformation of their forms,which in turn affects the fate of phosphorus.(4)The effect of organic matter on the adsorption of organic phosphorus in different soils was studied by equilibrium adsorption method.The results showed that organic matter was one of the important factors affecting the adsorption of organic phosphorus in natural soil.There was a positive correlation between soil organic matter content and soil adsorption capacity.After removal of organic matter,the adsorption capacity of organic phosphorus on Xianning soil,Shaanxi Xihe soil,Hainan brick red soil and Hailun black soil decreased by 13.20%,44.51%,14.22%and 35.81%,respectively.It was found that the ability of adsorbing inorganic phosphorus in four kinds of soils decreased after removing organic matter,which was consistent with the result of organic phosphorus.Therefore,organic matter is an important factor affecting the adsorption of organic phosphorus in soil. |
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