Equilibrium and kinetic analysis of phosphorus adsorption from aqueous solution using waste alum sludge

• Published in: Journal of hazardous materials Vol. 184; no. 1-3; pp. 746 - 752
• Main Authors: Babatunde, A.O., Zhao, Y.Q.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 15.12.2010; Elsevier
• Subjects: Adsorption; Adsorption capacity; Adsorption kinetics; Adsorption models; Alum; Alum Compounds - chemistry; Alum sludge; Applied sciences; Byproducts; Chemical engineering; Drinking water and swimming-pool water. Desalination; Exact sciences and technology; General purification processes; Heat and mass transfer. Packings, plates; Kinetics; Mathematical models; Phosphates; Phosphorus; Phosphorus - chemistry; Pollution; Sewage; Sludge; Solutions; Waste water; Wastes; Wastewaters; Water - chemistry; Water treatment and pollution; Adsorption models; Adsorption capacity; Phosphorus; Alum sludge; Adsorption kinetics; Phosphates; Reaction product; Modeling; Mass transfer; Waste water; Eutrophication; Mass transfer coefficient; Adsorption; Batchwise; Drinking water treatment plant; Water quality; Water pollution; Kinetics; Aqueous solution; Rate constant; Diffusion; Aluminium sulfate
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2010.08.102

Excess phosphorus (P) in wastewaters promotes eutrophication in receiving waterways. A cost-effective method such as use of novel low-cost adsorbents for its adsorptive removal would significantly reduce such impacts. Using batch experiments, the intrinsic dynamics of P adsorption by waste alum sludge (an inevitable by-product of drinking water treatment plants) was examined. Different models of adsorption were used to describe equilibrium and kinetic data, calculate rate constants and determine the adsorption capacity. Results indicate that the intraparticle rate constant increased from 0.0075mgg−1min−1 at 5mgL−1 to 0.1795mgg−1min−1 at 60mgL−1 indicating that more phosphate is adsorbed per gmin at higher P concentration. Further analyses indicate involvement of film and particle diffusion mechanisms as rate controlling steps at lower and higher concentrations, respectively. Mass transfer coefficient obtained ranged from 1.7×10−6 to 1.8×10−8 indicating a rapid transportation of phosphate molecules onto the alum sludge. These results further demonstrates that alum sludge—hitherto thought of as undesirable waste, can be used as novel adsorbent for P removal from wastewater through various applications, thus offsetting a portion of the disposal costs while at the same time improving water quality in sensitive watersheds.