Investigation Of Preparation And Phosphorus Removal Effect Of Calcium Silicate Hydrate Modified By Lanthanum

Excessive phosphorus concentration is one of the important causes of water pollution,so it is urgent to reduce the phosphorus concentration in water to reduce the risk of eutrophication.At present,the main methods of phosphorus removal are chemical precipitation method,biological method,ion exchange method,electrochemical method and adsorption method.Compared with other phosphorus removal methods,adsorption method has the advantages of low cost,high efficiency,easy operation and is widely used.Calcium silicate hydrated material has better phosphorus removal performance,is a certain strength of porous structure material,developed pore structure,with a good interception ability.The raw materials are widely sourced and the production cost is low.However,the adsorption capacity of phosphate is small,and there are many problems in practical application,such as large dosage and high mud yield.In order to improve its adsorption capacity of phosphate,the method of modifying calcium silicate hydrate with lanthanum was studied according to the characteristics of lanthanum modified adsorption materials with fast adsorption speed and strong adsorption capacity.The main conclusions are as follows:（1）when the initial Ca/Si ratio increases,the adsorption capacity of phosphorus removal first increases and then decreases,reaching the maximum adsorption capacity of19mg P/g at 1.8.Moreover,the long-term phosphorus removal experiment shows that the adsorption capacity of phosphate by CSH is stable and has certain anti-interference ability.It was found by XRD that with the increase of initial Ca/Si,CSH changed from crystal phase to gel state to crystal phase.（2）Langmuir model,Sips model and Temkin model can all describe the phosphate adsorption process of La-CSH well.The maximum theoretical adsorption capacity is144.03mg P/g.The number of layers formed by phosphate on the surface of La-CSH is between single layer and multiple layers,but still close to single layer.The phosphorus removal process of La-CSH is closer to the quasi-second-order kinetics,and the adsorption equilibrium is basically reached after 1440min.The adsorption process is an endothermic entropy increasing reaction,and the reaction is a spontaneous process.At p H of 4-9,the removal effect was better.The adsorption effect of CO₃^2-on La-CSH was slightly inhibited,while the dephosphorization effect of F^-on La-CSH was significantly inhibited.Ca²⁺in the coexisting cation promoted the dephosphorization of La-CSH,while Mg²⁺showed a slight inhibition.La-CSH was analyzed by means of SEM-EDS,Mapping,XRD,FTIR and XPS,and the phosphorus removal mechanism of La-CSH was explored.It was found that La-CSH mainly formed inner layer complexation through the ligand exchange between phosphate and the hydroxyl group of La（OH）₃ to remove phosphate in water.（3）under the conditions of actual water application,La-CSH only has the adsorption effect on orthophosphates in water,but has no removal effect on granular TP and dissolved organophosphorus.Humus in water reduces the adsorption capacity of La-CSH.