Preparation And Performance Study Of Red Mud-based Phosphorus Removal Material

In order to improve the phosphorus removal efficiency of red mud in water and endow it with magnetic recovery performance,this study uses the Bayer process alumina industrial solid waste red mud（RM）as the raw material,and the brewing industry waste Spirit-based distillers’grains（SDG）as the reducing agent.Magnetized red mud material（MRM）was obtained by reducing and roasting red mud,and then impregnated with lanthanum chloride to prepare lanthanum-loaded magnetized red mud material（La-MRM）.MRM and La-MRM are used for phosphorus removal in both low-phosphorus and high-phosphorus waters.Besides,the adsorption performance and mechanism of MRM and La-MRM have been explored.This work provides new ideas and theoretical support for the resource utilization of red mud and distiller’s grains.This specific work includes the following three aspects:（1）The RM was subjected to reduction roasting and lanthanum loading modification,and the structures and properties of RM,MRM and La-MRM were analyzed by XRD,FTIR,SEM,BET,VSM and XPS.After roasting,the non-magnetic hematite in RM has been successfully reduced to magnetite,and the saturation magnetization and specific surface area of MRM increased by 9.21 times and 3.64 times compared with RM,which increased the adsorption sites of MRM and possessed magnetic properties.Furthermore,the metal ion-lanthanum with high adsorption activity for phosphorus has been successfully loaded on the surface of the MRM and the adsorption active sites increased to achieve the purpose of modification.（2）The adsorption behavior of RM and MRM on low-concentration phosphorus in water has been studied:when the initial concentration of phosphorus solution is 5mg·L^-1,p H value is 6,T=25°C,the removal rate of phosphorus in water by MRM is93.1%,which is 4.97 times of RM.The treated water can meet the national first-class discharge standard（GB 8978-1996）,indicating that MRM has good selectivity for the adsorption of phosphorus in water.Besides,MRM can be recycled through magnetic separation,with regeneration efficiency up to 94.92%.The adsorption process of phosphorus in water by MRM conforms to the Langmuir adsorption isotherm model and pseudo-second-order kinetic equation,and is a monolayer chemisorption controlled process with spontaneous endothermic entropy increase.The adsorption mechanism study shows that MRM mainly achieves the phosphorus removal through chemical precipitation,coordination exchange,physical adsorption and electrostatic attraction.（3）RM and La-MRM are applied to phosphorus removal in high phosphorus water.When the amount of adsorbent is 4 g·L^-1,the initial concentration of phosphorus solution is 50 mg·L^-1,p H value is 5,T=25℃,the removal rate of phosphorus in water by La-MRM reaches 98.48%,which is 6.62 times that of RM,and the treated water body can reach the secondary discharge standard.The adsorption isotherm studies show that the adsorption of phosphorus in water by RM is affected by a variety of mechanisms.The La-MRM adsorption process is more in line with the Langmuir isotherm adsorption model and belongs to the surface monolayer adsorption;The kinetic model and thermodynamic studies show that the adsorption of phosphorus by La-MRM can be described by a quasi-second-order kinetic model,which is a spontaneous process of endothermic entropy increase,and the spontaneous limit is stronger than RM,which confirms that the modification of lanthanum loading benefits the phosphorus removal.The adsorption mechanism study shows that La-MRM mainly removes phosphorus through electrostatic attraction and ligand exchange in high phosphorus water.