The Equilibrium Characteristic of Ferric Sludge Adsorption Phosphate

With the rapid development of industry and agriculture, there are thousands of tons phosphate and nitrogen releasing into surface water. Phosphate becomes the main reason for eutrophication, resulting in deterioration of water quality. Ferric sludge from drinking waterworks was found to possess potential efficiency to remove phosphate ions from aqueous solutions. The maximum phosphate ions adsorption capacity was about 15.5 mg/g at pH around 5 and contact time above 4 hours in the batch system by newly dewatered sludge. Column experiments showed that higher concentration of the solution was in favor of fast equilibration. Adsorption characteristic studies have been carried out by Langmuir, Freundlich, Temkin and Dubinin-Radushkevick (D-R) isotherms. The results showed that the experimental data fitted better to Freundlich and Dubinin-Radushkevick (D-R) isotherms. Above studies suggested that the mechanism of phosphate ions removal followed inner-sphere complexes.