Experimental Study on Adsorption of Phosphate Simulated Wastewater by Different Iron Oxides
Phosphorus is one of the necessary nutrients for plant growth,but excessive phosphate in water is easy to cause eutrophication and affect the water ecological balance.Iron,on the other hand,is one of the most abundant metallic elements in the Earth's crust and exists in the environment mainly in the form of iron oxides.Iron oxides are commonly found in nature in two types:nanocubs(HNCs)and nanocrystals(HNPs).Different types of iron oxides have different atomic arrangement structure and different interface characteristics,which leads to different adsorption mechanisms of phosphate in water.In this paper,the adsorption properties of synthetic iron oxides(HNCs and HNPs)on phosphate simulated wastewater were studied.The results show that in the first 15 minutes of the reaction,the adsorption rates of the two iron oxides on the simulated phosphate wastewater are very fast,and the adsorption equilibrium is basically reached at 30 minutes of the reaction.The adsorption process of HNCs and HNPs on the phosphate in the simulated wastewater is controlled by physical adsorption and chemical adsorption.With the increase of the initial concentration of phosphate,the removal rate of phosphate by two iron oxides,HNCs and HNPs,increased continuously.With the increase of reaction temperature,the removal rate of phosphate from wastewater by HNCs and HNPs also increased,indicating that the adsorption process of phosphate by iron oxides was endothermic.Under the same conditions,HNCs has better adsorption effect on phosphate in simulated wastewater than HNPs.With the increase of coexisting salt ion concentration,the phosphate removal rate continued to increase.The effect of coexisting salt ions on phosphate adsorption by HNCs is slightly worse than that by HNPs,indicating that the adsorption of phosphate by HNCs and HNPs is mainly surface complexation and electrostatic interaction.
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