Adsorption of chromium(VI) and nickel(II) ions on acid‐ and heat‐activated deoiled spent bleaching clay

• Published in: Journal of the American Oil Chemists' Society Vol. 78; no. 8; pp. 831 - 835
• Main Authors: Seng, C. E., Lee, C. G., Liew, K. Y.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.08.2001; Springer
• Subjects: Adsorption; Biological and medical sciences; chromium(VI); Fundamental and applied biological sciences. Psychology; Molecular biophysics; nickel(II); spent bleaching clay; Surface properties. Adsorption; Clay; Acids; Adsorption; Efficiency; Chemical treatment; Thermal activation; Freundlich isotherm; Chromium; Nickel; Bleaching agent; Langmuir isotherm; Heavy metal
• ISSN: 0003-021X; 1558-9331
• DOI: 10.1007/s11746-001-0351-7

De‐oiled spent bleaching clay was activated either by acid treatment followed by heat activation or by heat activation alone at temperatures between 200 and 800°C. The surface area of the heat‐activated clay attained a maximal value of ≈120 m2 g−1 at temperatures between 400 and 500°C while the acid‐heat‐treated clay attained maximal surface area of ≈140 m2 g−1. The adsorption capacities of chromium [Cr(VI)] for both series studied increased as the activation temperature increased until 300°C and decreased again at higher temperatures. At lower pH, more than 95% of the Cr(VI) was absorbed in a solution with initial concentration of 1 mg L−1 per gram of adsorbent activated at 300°C. The adsorption patterns followed Freudlich's isotherms. Two maximal values of adsorption capacities of nickel [Ni(II)] were observed at activation temperatures of 200 and 500°C for acid‐treated samples, whereas these were at 200 and 700°C for the nonacid‐treated samples. The amount of Ni(II) adsorbed increased with the pH of the solution for all samples studied. The maximal adsorption capacities of the adsorbents in solution containing initial Ni(II) concentration of 5 mg L−1 per 0.5 g of adsorbent and at pH 6 were found to be 44 and 42%, respectively, for the acid‐treated sample activated at 500°C and for the nonacid‐treated sample activated at 700°C. They all obeyed both the Langmuir's and Freundlich's isotherms.