Removal of Phosphorus from Aqueous Solutions by Adsorption Using Dewatered Alum Sludge

摘要

This study explored the feasibility of using dewatered alum sludge as absorbent for the removal of phosphorus.Phosphorus adsorption isotherm and its kinetics were examined and effects of adsorbent particle size,initial phosphorus concentration and temperature were investigated.The result shows that both Langmuir isotherm and Freundlich isotherm are found to fit the date of phosphorus adsorption onto dewatered alum sludge well,however,the Langmuir isotherm yields a better fit than the Freundlich isotherm while its saturation adsorption capacity is 1.11 × 104 mg/kg.The adsorption is influenced by particle size and initial phosphorus concentration but slightly affected by temperature.The capacity of phosphorus adsorption reduces from 1847.44 mg/kg to 1045.23 mg/kg when the adsorbent particle size changes from smaller than 0.25 mm to 1.0-2.0 mm,while the capacity of phosphorus increases from 857.55 mg/kg when the initial phosphorus concentration is 5 mg/L to 2395.72 mg/kg when the initial phosphorus concentration is 15 mg/L.Moreover,when temperature was 25℃,30℃,35℃,the capacity of phosphorus adsorption was 1806.98 mg/L,1854.18 mg/L,1847.44 mg/L respectively.The change of phosphorus concentration with time can be described by the pseudo second-order kinetics with correlation coefficient of 0.95.Accordingly,amounts of phosphorus adsorbed at equilibrium can be calculated with error around 15％.