Adsorption of humic acid on acid-activated Greek bentonite.
The adsorption of humic acid on bentonite from Milos Island (Greece) acid-treated with dilute H(2)SO(4) solutions over a concentration range between 0.25 and 13M has been studied. Bentonite activated with 3M sulfuric acid (AAS) showed a higher efficiency in removing humic acid from aqueous solutions and was selected for further investigation. The specific surface area of acid-activated bentonite was estimated using the methylene blue adsorption method. The morphology of untreated, activated, and HA-sorbed bentonite was studied under scanning electron microscope (SEM). The effects of contact time, adsorbate concentration, adsorbent dose, and temperature on the adsorption of humic acid onto bentonite activated with 3M H(2)SO(4) were studied using a batch adsorption technique. Acidic pH and high ionic strength proved to be favorable for the adsorption efficiency. Pseudo-first-order, pseudo-second-order, and intraparticle diffusion models were used to describe the kinetic data and the rate constants were evaluated. The experimental isotherm data were analyzed using Langmuir, Freundlich, and Temkin equations and the isotherm constants were determined. Thermodynamic parameters (DeltaH(o), DeltaS(o), and DeltaG(o)) of adsorption of humic acid onto acid-activated bentonite with 3M sulfuric acid were also evaluated.
Laboratory of Organic Chemical Technology, School of Chemical Engineering, National Technical University of Athens, Zografou Campus, 9 Iroon Politechniou, GR-15780 Athens, Greece. ddoulia@chemeng.ntua.gr
Danae
D
Doulia
Ch
Ch
Leodopoulos
K
K
Gimouhopoulos
F
F
Rigas
D000327:Adsorption; D000465:Algorithms; D001546:Bentonite / Q000737:chemistry*; D004058:Diffusion; D006115:Greece; D006812:Humic Substances; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008751:Methylene Blue / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D008956:Models, Chemical; D009994:Osmolar Concentration; D013464:Sulfuric Acids / Q000737:chemistry*; D013499:Surface Properties; D013696:Temperature; D013816:Thermodynamics; D014961:X-Ray Diffraction
D006812:Humic Substances; D013464:Sulfuric Acids; D001546:Bentonite; C033158:sulfuric acid; D008751:Methylene Blue