Investigation of Pb(Ⅱ) adsorption onto pumice samples: application of optimization method based on fractional factorial design and response surface methodology

摘要

The adsorption of Pb(Ⅱ) by pumice samples collected from the Mount Ararat region, located in eastern Turkey, was investigated in a batch system. The combined and individual effects of operating parameters on adsorption were analyzed using a multi-step response surface methodology. In the first step the most effective factors, which are initial Pb(Ⅱ) concentration, pH, and temperature, were determined via fractional factorial design. Then the steepest ascent/descent followed by central composite design were used to interpret the optimum adsorption conditions for the highest Pb(Ⅱ) removal. The optimum adsorption conditions were determined to be initial Pb(Ⅱ) concentration of 84.30 mg/L, pH of 5.75, and temperature of 41.11 ℃. At optimum conditions, the adsorption capacity of pumice for Pb(Ⅱ) was found to be 7.46 mg/g according to a removal yield of 88.49 %. The obtained data agreed with a second-order rate expression and fit the Langmuir isotherm very well. The thermodynamic parameters such as ΔH°, Δ5°, and ΔG° for the Pb(Ⅱ) adsorption were calculated at four different temperatures. The present results indicate that pumice is a suitable adsorbent material for adsorption of Pb(Ⅱ) from aqueous solutions.