Study On Phosphorus Removal By Natural Siderite And Calcite And Their Modified Products

Phosphorus is one of the essential nutrients for plant growth,and the discharge of excessive phosphorus can easily lead to eutrophication.Adsorption method is widely used in the treatment of wastewater for its simple operation and easy operation.A number of scholars study on phosphorus removal by the natural minerals.Calcium ore and iron ore are studied the most.In this work,siderite and calcite was selected as the adsorbent for their similar structure.Study on phosphorus removal by natural siderite and calcite and the modified siderite.The main research contents and conclusions are as follows:1.The effect of particle size,dosage,initial pH and P concentration,etc on the P removal efficiency was discussed with natural siderite and calcite.Adsorption of P on natural siderite and calcite were exothermic process.Adsorption of P on natural siderite could be well fit by Freundlich model and the Pseudo-second-order equation.Howere,adsorption of P on natural siderite and calcite could be well fit by Langumuir model and the Pseudo-first-order equation.With the decrease of particle size,the increase of the dosage and the initial P concentration,the phosphorus removal efficiency of natural siderite and calcite increased.With the increase of pH,the phosphorus removal efficiency was increased first and then decreased.The phosphorus removal efficiency onto calcite decreased with the increase of pH.NO3and Cl-anion has a little influence on the phosphorus removal by siderite and calcite.HCO3-has an inhibitory effect on the phosphorus removal by siderite and calcite.SO42-also has a inhibitory effect on calcite sorption.2.Natural siderite was modified by calcination and aluminum sulfate salt.The strength of various factors which effect on the phosphorus removal efficiency of the modified siderite:calcination temperature>aluminum concentration>calcination time.By using Design-Expert and BBD method,the optimum preparation conditions were confirmed(calcination temperature of 385℃,aluminum concentration of 10.35g/L and calcination time of 115min).Through the SEM analysis,we can know that the surface texture of modified siderite is much larger than before.Some of the siderite is oxidized to hematite,which is conducive to the phosphorus removal.3.The mechanism of phosphorus removal onto siderite and calcite are investigated and the dynamics adsorption experiment was studied.Calcite is mainly deposited by precipitation.Siderite mainly produced by hydroxyl compounds ligand exchange reactions.The dynamics experimental results show that the dynamic adsorption column of siderite is not better than calcite in the recycling.