Experimental study on phosphorus removal of water by Zn/Mg/Al layered double hydroxide

Abstract

Zn/Mg/Al layered double hydroxide (Zn/Mg/Al-LDH) was prepared by co-precipitation method. The structure of Zn/Mg/Al-LDH was characterized by XRD. The results show that the samples have typical hydrotalcite structure. They were used as adsorbents to remove phosphorus from wastewater. The effects of pH value, phosphorus concentration, adsorbent dosage, oscillation intensity and reaction time on phosphorus adsorption capacity were investigated by single factor control variable method. The results show that the adsorption equilibrium of Zn/Mg/Al-LDH can be reached after 24 h. The optimal experimental conditions are as follows: stirring rate is 180 R/min, pH value is 6, and reaction temperature is 50 °C. Under above conditions, when the initial phosphorus concentration is 50mg/L, the adsorption capacity of Zn/Mg/Al-LDH for phosphorus is 54.10mg/g when the adsorption equilibrium is reached. When the initial phosphorus concentration is 200mg/L, the adsorption capacity is 69.70mg/g, and the saturated adsorption capacity is 70.37mg/g. In the simulated practical engineering application, when the discharged phosphorus meets the standard, the phosphorus adsorption capacity of Zn/Mg/Al-LDH is 37.09mg/g, and the phosphorus removal rate is as high as 99.76%.