| Steel slag is a waste, which mainly contents the oxide of calcium, iron, aluminum, silicon, magnesium, manganese, phosphorus and other elements, with the characteristics of porous and large surface area. This paper investigates the adsorption of steel slag as a adsorbent on phosphorus, discusses the adsorption-desorption characteristics of phosphorus in the solution with the steel slag as the adsorbent with the particle size of 0.25mm and 0.08mm. On the base, we also study the effects of temperature, pH, solid to liquid ratio and time on phosphorus adsorption-desorption, reveal the adsorption-desorption rules of phosphorus with steel slag.The results showed that the steel slag with the diameter sizes of 0.25 mm and 0.08mm were both in accordance with Freundlich equation when adsorbing phosphorus in the solution, and consistent with its parameters n, non-concessional Adsorption. The parameter k of the adsorption equation of steel slag with the diameter of 0.08mm,was 5.68 times larger than that with the diameter of 0.25mm.The purification ability to phosphorus in the solution of the former was better than that of the latter. With the increase of the initial mass concentration of phosphorus in the solution, The removal ability difference of the steel slag with the diameters of 0.08mm and 0.25mm to the phosphorus in the solution decreased gradually. It was the best model to use Elovich equation to fit the apparent rate equations of the steel slag, followed by the two-constant equation and kinetic equation. In the expression of Elovich equation, the parameter a in the equation of the steel slag on phosphorus adsorption with the size of 0.08 mm was greater than that of 0.25 mm, while the parameterβwas the contrary. The initial adsorption rate of the steel slag with the diameter of 0.08 mm was larger, and the adsorption speed was lower. With the decreases of the particle size of the steel slag, the ability of phosphorus adsorption using the steel slag increased. With the increase of initial concentration of phosphorus solution, with the increase of the initial mass concentration of phosphorus in the solution, The removal ability difference of the steel slag to the phosphorus in the solution decreased gradually. With the increase of solution pH values, the adsorption removal rate of the steel slag to phosphorus in the solution decreased. The adsorption removal rate of the steel slag to phosphorus in the solution increased with the temperature rising, and higher temperature favored the removal of phosphorus in the solution. The result indicated that the optimal solid-liquid ratio in the phosphorus adsorption with steel slag was 1:20, and the adsorption rate of the milling steel slag was significantly higher than the original steel slag, and the pH value after adsorption with steel slag of the solution increased.In the isothermal desorption experiment, the desorption rate of phosphorus with steel slag increased with the initial concentration of solution. The desorption amount of phosphorus increased gradually with time moving. The desorption rate of phosphorus was only 14.52% when arrived at adsorption-desorption equilibrium. It could be seen that the phosphorus which adsorbed by the steel slag was most associated with it in a more stable way. As the pH value of the desorption agent increased, the desorption rate of phosphorus increased, indicating that the process of phosphorus desorption is the process of consuming OH- or releasing proton, also indicating that there was ligand exchange in the process of phosphorus adsorption-desorption. With the increase of solution temperature, the phosphorus content in liquid increased, indicating that the amount of phosphorus content released by steel slag increased. Therefore, the temperature played a significant role on the phosphorus adsorption, that is, with the increase of temperature, the adsorption capacity significantly increased, and the temperature also played a significant role on the phosphorus desorption rate, indicating the reaction of phosphorus desorption with steel slag was endothermic.Use of steel slag adsorption of phosphorus removal from wastewater, It not only solved the problem of using waste steel slag, but also provided raw materials for the development of adsorbent to the purpose of using the waste (waste steel slag) to administer waste (phosphorus waste water), which offered a new idea to achieve the cycle economic and environment protection, provided a theoretical basis for the development of steel slag adsorbent.
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