Adsorption of humic acid on acid-activated Greek bentonite

• Published in: Journal of colloid and interface science 2009-12, Vol.340 (2), p.131-141
• Main Authors: Doulia, Danae, Leodopoulos, Ch, Gimouhopoulos, K., Rigas, F.
• Format: Article
• Language: English
• Subjects: Activated; Adsorption; Algorithms; Bentonite; Bentonite - chemistry; Chemistry; Colloidal state and disperse state; Diffusion; Exact sciences and technology; General and physical chemistry; Greece; Humic acid; Humic acids; Humic Substances; Hydrogen-Ion Concentration; Isotherms; Kinetics; Mathematical models; Methylene Blue - chemistry; Microscopy, Electron, Scanning; Models, Chemical; Osmolar Concentration; Scanning electron microscopy; SEM; Sulfuric Acids - chemistry; Surface chemistry; Surface physical chemistry; Surface Properties; Temperature; Thermodynamics; X-Ray Diffraction
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2009.07.028

Kinetic, equilibrium and thermodynamic studies were conducted for the adsorption of humic acid onto bentonite activated with sulphuric acid. Morphology of untreated, activated and HA-sorbed bentonite was studied under SEM. The adsorption of humic acid on bentonite from Milos Island (Greece) acid-treated with dilute H 2SO 4 solutions over a concentration range between 0.25 and 13 M has been studied. Bentonite activated with 3 M 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 3 M H 2SO 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 (Δ H o, Δ S o, and Δ G o) of adsorption of humic acid onto acid-activated bentonite with 3 M sulfuric acid were also evaluated.