Sorption of cationic dyes onto barks and leaves of European trees

Abstract

Sorption of Methylene Blue (MB) and Malachite Green (MG) dyes onto barks and leaves of four trees was examined with a batch method. The obtained sorption isotherms are well described by the Langmuir equation. The examined barks proved to have quite different sorption capacities. The highest values were recorded for the walnut tree bark (512 and 307 mg/g towards the MB and MG dyes, respectively) and the lowest capacities were observed for the birch tree bark (68 and 22 mg/g towards the MB and MG dyes, respectively). The studied leaves proved to have rather similar sorption capacities, i.e., from 210 to 286 mg/g for the MB dye and from 152 to 189 mg/g for the MG dye. The specific surface values calculated from the MB monolayer capacity are substantially higher than those obtained by the BET method, probably because of swelling of the test materials in an aqueous medium