| Nitrogen and phosphate are essential elements for animals and plants. But with the rapid development of industry and agriculture, there are thousands of tons phosphate and nitrogen releasing into surface water system. Because it enhances the growth of organisms in most ecosystems such as rivers, lakes, result in eutrophication and deterioration of water quality. Many techniques have been carried out for the removal of phosphorus and nitrogen from wastewater, for examplephysical chemistry method, biologic method, and membrane technique and constructing wetland to remove phosphate. Because of high cost and secondary pollution, they are largely limited to be applied. The application of iron sludge used as a sorbent to construct wetland is low cost and easily available. So it becomes a research hotspot and an important task. It has a large potential value to utilize iron sludge from waterworks to pure wastewater.After a detailed research, the iron sludge from waterworks is first used to remove phosphorus for its strong adsorption properties in this study. It can be applied for the deep deck of wetland soil landfill, not only can play a solid phosphorus supply to wetlands Plants, can also manage the water plant sludge reasonable consumed. A series of experiment have been carried out for the adsorption capacity to remove phosphorus, then the results showed that the pH around 5 was the best condition for phosphate adsorption.Batch adsorption studies on dried iron sludge were conducted to optimize various equilibrating conditions like the effect of contact time, initial concentration, pH, mass of sorbent, coexisting ion and so on. The results show that strong acid and strong base went against the adsorption of phosphate; while the optimal pH was around 5 and the maximal adsorption reach 24mg/g. The adsorption capacity decreased with the increase of adsorbent doze and ion strength. Simple ions had no obvious effects on adsorption. Iron sludge had good selectivity for adsorption of phosphate. Longmuir and Freundlich adsorption isotherm constants and correlation coefficients were calculated and compared. It was concluded that the adsorption data of phosphate onto iron sludge fitted to the Langmuir model more than Freundlich model.XRD, SEM, TEM, FT-IR and TG were used for the characterization of the sorbent. It is concluded that the coordination mechanism of ligand ion exchange outer surface and electrostatic adsorption were dominant. In addition, the column of iron sludge was experimnented at different column length , flux, initial concentration. The conclution suggested that the iron sluge can be used in the wetland for it chemical characteristic. |
