Mechanisms of phosphate removal from aqueous solution by blast furnace slag and steel furnace slag
- 366 Downloads
We report the adsorption of phosphate and discuss the mechanisms of phosphate removal from aqueous solution by burst furnace slag (BFS) and steel furnace slag (SFS). The results show that the adsorption of phosphate on the slag was rapid and the majority of adsorption was completed in 5∼10 min. The adsorption capacity of phosphate by the slag was reduced dramatically by acid treatment. The relative contribution of adsorption to the total removal of phosphate was 26%∼28%. Phosphate adsorption on BFS and SFS follows the Freundlich isotherm, with the related constants of k 6.372 and 1/n 1.739 for BFS, and of k 1.705 and 1/n 1.718 for SFS. The pH and Ca2+ concentration were decreased with the addition of phosphate, suggesting the formation of calcium phosphate precipitation. At pH 2.93 and 6.93, phosphate was desorbed by about 36%∼43% and 9%∼11%, respectively. These results indicate that the P adsorption on the slag is not completely reversible and that the bond between the slag particles and adsorbed phosphate is strong. The X-ray diffraction (XRD) patterns of BFS and SFS before and after phosphate adsorption verify the formation of phosphate salts (CaHPO4·2H2O) after adsorption process. We conclude that the removal of phosphate by BFS and SFS is related to the formation of phosphate calcium precipitation and the adsorption on hydroxylated oxides. The results show that BFS and SFS removed phosphate nearly 100%, indicating they are promising adsorbents for the phosphate removal in wastewater treatment and pollution control.
Key wordsPhosphate removal Blast furnace slag (BFS) Steel furnace slag (SFS) Adsorption Precipitation
Unable to display preview. Download preview PDF.
- APHA (American Public Health Association), 1995. Standard Methods for the Examination of Water and Wastewater, 19th Ed. APHA, Washington, DC.Google Scholar
- Klute, A., 1986. Methods of Soil Analysis. Part 1. Physical and Mineralogical Methods. ASA and SSSA, Madison.Google Scholar
- Lindsay, W.L., 1979. Chemical Equilibria in Soils. John Wiley & Sons, New York.Google Scholar
- Mann, R.A., Bavor, H.J., 1993. Phosphorus removal in constructed wetlands using gravel and industrial waste substrata. Water Science & Technology, 27:107–113.Google Scholar
- Ramakrishna, K.R., Viraraghvan, T., 1997. Use of slag for dye removal. Water Management, 17(8):483–488. [doi:10.1016/S0956-053X(97)10058-7]Google Scholar
- USEPA (US Environmental Protection Agency), 1992. Toxicity Characteristics Leaching Procedure (Method 1311) in SW-846. Office of Solid Waste, Washington, DC.Google Scholar