title: Utilization of waste product (tamarind seeds) for the removal of Cr(VI) from aqueous solutions: equilibrium, kinetics, and regeneration studies.
abstract: In the present study, an adsorbent was prepared from tamarind seeds and used after activation for the removal of Cr(VI) from aqueous solutions. The tamarind seeds were activated by treating them with concentrated sulfuric acid (98% w/w) at a temperature of 150 degrees C. The adsorption of Cr(VI) was found to be maximum at low values of initial pH in the range of 1-3. The adsorption process of Cr(VI) was tested with Langmuir, Freundlich, Redlich-Peterson, Koble-Corrigan, Tempkin, Dubinin-Radushkevich and Generalized isotherm models. Application of the Langmuir isotherm to the system yielded a maximum adsorption capacity of 29.7 mg/g at an equilibrium pH value ranging from 1.12 to 1.46. The adsorption process followed second-order kinetics and the corresponding rate constants obtained were 2.605 x 10(-3), 0.818 x 10(-3), 0.557 x 10(-3) and 0.811 x 10(-3) g/mg min(-1) for 50, 200, 300 and 400 mg/L of initial Cr(VI) concentration, respectively. The regenerated activated tamarind seeds showed more than 95% Cr(VI) removal of that obtained using the fresh activated tamarind seeds. A feasible solution is proposed for the disposal of the contaminants (acid and base solutions) containing high concentrations of Cr(VI) obtained during the regeneration (desorption) process.
authors.affiliation: Chemical Engineering Group, Birla Institute of Technology and Science (BITS), Vidya Vihar Campus, Pilani 333 031, Rajasthan, India.
authors.forename: Suresh
authors.initials: S
authors.lastname: Gupta
authors.forename: B V
authors.initials: BV
authors.lastname: Babu
mesh_terms: D000327:Adsorption; D002857:Chromium / Q000737:chemistry / Q000302:isolation & purification*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D012639:Seeds / Q000737:chemistry*; D013464:Sulfuric Acids / Q000737:chemistry; D029861:Tamarindus / Q000737:chemistry*; D013696:Temperature; D018508:Water Purification / Q000379:methods*
chemical_list: D013464:Sulfuric Acids; D002857:Chromium; C033158:sulfuric acid