Kinetic and thermodynamic investigations of adsorption of fluoride onto activated Aloe verα carbon

Tamil Nadu Water Supply and Drainage Board, District Water Testing Laboratory, Theni-625 531, Tamilnadu, India

Department of Chemistry, Gandhigram Rural University, Gandhigram-624 302, Tamilnadu, India

E-mail : drkpelango@rediffmail.com

Manuscript received 7 December 2006, revised 8 August 2007, accepted 10 August 2007

Batch sorption system using activated Aloe verα carbon as an adsorbent was investigated to remove fluoride ions from aqueous solutions. The system variables studied include initial concentration of the sorbate, agitation time, pH, co-ions and temperature. The experimental data fitted well to the Freundlich and Langmuir isotherms. Thermodynamic parameters such as ∆H°, ∆S° and ∆G° were calculated indicating that the adsorption was spontaneous and endothermic. A mechanism involving intra particle diffusion and surface adsorption has been proposed for the adsorption of F^- onto the adsorbent. XRD patterns of the adsorbent were recorded to get a better in sight into the mechanism of adsorption process.