| As one of the forms of phosphorus exist in the environment, polyphosphate used in the industry for peptidization, detergent agent, plating solution and so on. These polyphosphate discharged into the environment can be hydrolyzed to orthophosphate within a certain conditions and has a certain effect on the eutrophication of water body and its bioavailability. Goethite has been used by researchers to carry out a number of studies which exists in all kinds of sediments and soils in natural systems. And it also plays an important role in the transport of polluting elements in nature. As the natural environment is complex, organic matter is used as the third party additives to study the migration and transformation mechanism of pollutants which has received more and more attention. In order to study the fate and transport behavior of polyphosphate in water body,pyrophosphte and tripolyphosphate were selected as the represent polyphosphate,adsorption process of polyphosphate on synthetic goethite which stable exist in the supergene environment have been studied systematically. The adsorption influence under different conditions(p H, electrolyte, time, temperature) was investigated. And the adsorption mechanism of goethite-organic matter-polyphosphate was also discussed in this paper.(1) For the system of goethite-organic matter-PP, results indicated that the adsorption capacity decreased from 3.00 mg/g to 0.75 mg/g with increasing p H from 6.27 to 10.99.And the lower the electrolyte concentration, the more favorable to the adsorption. The adsorption characteristic within 48 h was observed. The adsorption capacity increased rapidly within 1 h, and then reached the adsorption equilibrium. Moreover, the adsorption capacity was increased with increasing the adsorption temperature. Kinetic models and thermodynamic models were used to analyze the adsorption process, and the results showed that the adsorption were more in accord with the pseudo second-order equation and Langmuir model. Different ordering of the addition of PP, HA/FA and goethite resulted in different PP amounts being adsorbed by goethite.The presence of HA led to an increase of the amount of PP adsorbed: Goe+PP,HA?Goe+PP+HA?HA+PP, Goe >Goe+HA,PP. And the presence of FA also led to an increase of the amount of PP adsorbed:Goe+PP, FA?FA+PP, Goe >Goe+PP+FA >Goe + FA. Furthermore, combined with the characterization of materials, the adsorption mechanism may be mainly based on surface complexation and physical adsorption.(2) For the system of goethite-organic matter-TPP, Results indicated that the adsorption capacity decreased from 1.98 mg/g to 0.27 mg/g with increasing p H from 8.43 to 10.97. And the sorption of TPP on goethite increases with increasing electrolyte concentration. The adsorption of TPP on goethite increased quickly within the first 1 h and reached equilibrium within 24 h. Moreover, the adsorption capacity was increased with increasing the adsorption temperature. In order to better undersdand the biding mechanism,Kinetic models and thermodynamic models were used to analyze the adsorption process,and the results showed that the adsorption were more in accord with the pseudo second-order equation and Freundilich model. Different ordering of the addition of TPP,HA and goethite resulted in different TPP amounts being adsorbed by goethite: Goe+TPP,HA>Goe+TPP+HA>HA+TPP, Goe > Goe + HA,TPP. And the The presence of FA led to a large increase of the amount of TPP adsorbed which might attributed to the adsorption ability of goethite-FA complexes. And characterization of materials was also examined in this paper to determine the adsorption mechanism. |
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