Removal of Cr(VI) from aqueous solution on seeds ofArtimisia absinthium(novel plant material)

Abstract

A B S T R A C TArtimisia absinthium, a medicinal plant material, showed excellent adsorption in removing mutagenic Cr(VI) from aqueous solution along with Cu(II), Ni(II), and Zn(II). Various parameters like effect of pH, contact time, temperature, and initial concentration were investigated using batch process to optimize conditions for maximum adsorption. A. absinthium was characterized using scanning electron microscopy (SEM). Adsorption of Cr(VI) was favorable at pH 2 as 96% of Cr(VI) could be removed from aqueous solution. However, adsorption of Cr(VI) decreased to 73% in presence of electrolyte (0.1 N KNO 3 ) at pH 2. The point of zero charge of A. absinthium was 3.9 in double distilled water. The adsorption data were analyzed using Langmuir, Freundlich, Temkin, Hasley, and Dubinin-Redushkeuich isotherm models at 30, 40, and 50˚C. The maximum monolayer adsorption capacity towards Cr(VI) was found to be 46.99 mg g −1 at 30˚C which was relatively large compared to some other similar adsorbents reported earlier. The kinetic data showed that pseudo-second-order rate equation was better obeyed than pseudo-first-order. The intra-particle diffusion model showed that Cr(VI) adsorption involved three different stages. The breakthrough and exhaustive capacities of the adsorbent were found to be 35 and 45 mg g −1 , respectively, at pH 2. Desorption study showed that 93.05% Cr(VI) could be desorbed by column operation with 0.01 N NaOH solution.

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