Study On Adsorption Characteristics Of Phosphorus And Ammonia Nitrogen By The Modified Attapulgite

Excessive emission of nitrogen and phosphorus will cause eutrophication of the water body.Adsorption and removal of nitrogen and phosphorus were not only effective measures to reduce nitrogen and phosphorus pollution,but also a feasible method for recycling nitrogen and phosphorus.In this paper,metal oxide modified attapulgite was used as an adsorbent to explore the adsorption characteristics of modified attapulgite for phosphorus and ammonia nitrogen,and to clarify its adsorption mechanism.The study of the characteristics of phosphorus absorption by zirconium modified attapulgite showed that compared with the original attapulgite,the adsorption efficiency of zirconium-modified attapulgite for phosphorus increased by 76.85%;the change of p H has little effect on the removal of phosphorus by the zirconium-modified adsorbent;coexisting ions HCO₃^-,CH₃COO^-,Ca²⁺and Mg²⁺will reduce the efficiency of phosphorus removal,while Fe³⁺ion had little effect.The theoretical maximum adsorption capacity of modified adsorbent was 17.04 mg/g.Quasi-second order kinetics better described the phosphorus removal process of the modified adsorbent,that was,the chemical reaction was the rate control step.FT-IR and XRD characterization,phosphorus leaching morphological analysis and average adsorption energy analysis showed that the main mechanism of phosphorus removal by zirconium-modified attapulgite was electrostatic interaction and coordination exchange.The study of the characteristics of phosphorus absorption by calcium hydroxide modified attapulgite showed that compared with the original attapulgite,the adsorption efficiency of calcium-modified attapulgite for phosphorus increased by 68.17%;the change of p H has little effect on the removal of phosphorus by the calcium-modified adsorbent;coexisting ions HCO₃^-,NH₄⁺,CH₃COO^-and Fe³⁺will reduce the efficiency of phosphorus removal,and Ca²⁺will promote the phosphorus removal efficiency of calcium modified adsorbent,Mg²⁺cation less affected.The theoretical maximum adsorption capacity of modified adsorbent was 23.87 mg/g.Quasi-second order kinetics better described the phosphorus removal process of the modified adsorbent,that was,the chemical reaction was the rate control step.Phosphorus leaching morphological analysis and average adsorption energy analysis showed that the main mechanism of phosphorus removal by calcium-modified attapulgite was electrostatic action and surface precipitation.The study of the characteristics of phosphorus and ammonia nitrogen absorption by zirconium modified attapulgite showed that compared with the original attapulgite,the adsorption efficiency of zirconium-modified attapulgite for phosphorus increased by76.39%;the adsorption efficiency of zirconium-modified attapulgite for ammonia nitrogen increased by 86.27%;the adsorbent had the best adsorption of nitrogen and phosphorus under neutral conditions;coexisting ions HCO₃^-and NO₃^-anions reduced the ammonia nitrogen removal efficiency of the adsorbent,and it was found that K⁺and Na⁺cation will significantly reduce the ammonia nitrogen removal efficiency of the adsorbent,while Mg²⁺cation had less effect.The theoretical maximum phosphorus adsorption capacity of modified adsorbent was 23.87 mg/g and the maximum ammonia nitrogen adsorption capacity was 52.08 mg/g.The quasi-second-order kinetics better described the nitrogen and phosphorus adsorption process of zirconium-modified attapulgite,that was,the chemical reaction was the rate control step.The average adsorption energy analysis showed that the main mechanism for the removal of nitrogen and phosphorus by zirconium-modified attapulgite was chemical adsorption.The modification of zirconium and calcium hydroxide significantly improved the adsorption performance of attapulgite,and the adsorption mechanism was mainly electrostatic interaction and coordination exchange,which had certain theoretical value.Therefore,the two modified attapulgite clays in this study were expected to become a new type of high-efficiency adsorption materials.