Preparation And Application Of Diatomite-based Composite Absorbent For Phosphorus Removal Of Eutrophication

Diatomite was adopted as basic material to develop two novel diatomite-based compositeabsorbents (diatomite-based fly ash complex, DFC and diatomite-based steel slag complex,DSC) by combining fly ash and steel slag, respectively. Phosphorus removal and stability ofDFC and DSC was investigated using preparation parameters such as material ratio,calcination temperature and calcination time to determine the optimum preparationtechnology.The phosphorus removal performance of the prepared DFC and DSC was conductedunder static adsorption experiments. The influence of absorbent dosage, adsorption time,temperature, pH value and interfering ions on the effect of phosphorus removal wasinvestigated. Different models of adsorption kinetics and adsorption isotherm were selected tofit the adsorption behavior of phosphorus onto DFC and DSC, respectively, and thephosphorus sorption mechanism of DFC and DSC was studied.The experimental results showed that the best phosphorus removal of DFC was achievedwhen absorbent dosage was40g/L, contact time was240min, pH value was4, temperaturewas20℃, while absorbent dosage was2g/L, contact time was480min, pHvalue was from6to8, temperature was30℃, the phosphorus removal of DSC maintained the relatively highlevel. The presence of anions in the wastewater would decrease the removal of phosphoruswhile cations existing in the wastewater could enhance the phosphorus adsorption. Evaluationof the experimental data in terms of adsorption kinetics revealed that the adsorption ofphosphorus onto DFC and DSC followed well the pseudo-second-order kinetic model.Freundlich and Redlich-Prterson isotherm equations could better describe the adsorption ofphosphorus onto DFC and DSC. The calculated thermodynamic parameters (△G~o＜0，△H~o＞0，△S~o＞0) indicated that the adsorption of phosphorus onto DFC and DSC wasendothermic, and elevating temperature was beneficial to spontaneity of adsorption. Theadsorption process of phosphorus onto DFC and DSC was fairly stable, and the quality ofeffluent water was safe. The adsorption of phosphorus onto DFC was physically carried outwhile the phosphorus adsorption onto DSC was predominant of a chemical nature, coupledwith physisorption.Phosphorus-containing wastewater sample in East Lake was treated using DFC and DSC,indicating that the application of DSC in removing phosphorus of actual eutrophication waterbody was more feasible than that of DFC.