Sorption Kinetic Profiles and Equilibrium Thermodynamics of Chromium(VI) Ion Sequestration Using Modified Rice Husk

International Journal of Chemistry | Vol. 2, No. 5, May 2011 | pp. 60–67

DOI: 10.46882/2011/IJC/000032

Article Type: Original Research Paper

Title: Sorption Kinetic Profiles and Equilibrium Thermodynamics of Chromium(VI) Ion Sequestration Using Modified Rice Husk

Names of Authors: E. N. Chidi¹, O. P. Ejike¹*

Authors’ Affiliations:
¹Department of Pure and Industrial Chemistry, Nnamdi Azikiwe University, Awka, Nigeria.

Abstract: Industrial electroplating and leather processing release toxic hexavalent chromium [Cr(VI)] into aquatic channels, presenting heavy mutational and carcinogenic hazards. This investigation explores the utilization of chemically modified rice husk (CMRH) prepared via nitric acid oxidation for the adsorptive removal of Cr(VI) ions from simulated effluents. The surface chemistry and porosity of the adsorbent were studied using scanning electron microscopy (SEM) and FT-IR spectroscopy. Batch extraction experiments evaluated parameters of solution pH, contact time, adsorbent dosage, and initial metal ions concentration. Maximum Cr(VI) sorption occurred at an acidic pH of 2.0, with an equilibrium contact period of 120 minutes. Equilibrium data matched the Langmuir isotherm expressions, indicating a maximum monolayer adsorption capacity of 38.46 mg/g at 298 K. Sorption kinetics followed the pseudo-second-order kinetic model with a correlation coefficient (R²) greater than 0.99, indicating a chemisorption process. Thermodynamic constants, including enthalpy (delta H° = 14.2 kJ/mol) and entropy (delta S° = 56.4 J/mol K), confirmed that the phase transformation was endothermic and spontaneous. Desorption trials using 0.1 M NaOH showed high recovery metrics, presenting CMRH as a cost-effective choice for industrial water treatment.

Keywords: Rice husk; Acid modification; Hexavalent chromium; Adsorption kinetics; Chemisorption; Wastewater treatment

Manuscript Timeline: Received: January 15, 2011; Revised: February 22, 2011; Accepted: March 12, 2011; Published: May 04, 2011.

Citation: Chidi, E. N., & Ejike, O. P. (2011). Sorption Kinetic Profiles and Equilibrium Thermodynamics of Chromium(VI) Ion Sequestration Using Modified Rice Husk. International Journal of Chemistry, 2(5), 60–67.

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