Adsorption of a basic dye Methylene Blue in aqueous solution on a bioadsorbent from agricultural waste of <i>Manihot esculenta</i> Crantz

Abstract

The objectives of present study were to prepare a bioadsorbent from Mannihot esculanta Crantz peels (MEB) and to examine its effectiveness in the removal of methylene blue (MB) dye from aqueous solution by adsorption process. The adsorption was studied in a discontinuous reactor. Effects of the following parameters were studied: dose of bioadsorbent, contact time, initial concentration and pH of MB solution. The residual concentrations of MB solution were analyzed by UV-Vis spectrophotometry. The results obtained showed that the bioadsorbent MEB has a specific surface area of 265.27 m2 g -1 and a maximum observed adsorption capacity (Qmo) of 94.12 mg g-1 . The percentage of adsorption increased with the dose of biosorbent and the time due to the availability of free sites. The adsorption was better in a basic medium, because of electrostatic interactions between negatively charged MEB surface and organic ions of MB. The dose of 800 g of bioadsorbent and a pH solution of 10 were the optimal conditions of adsorption. Pseudo-first-order model was more suitable for describing the adsorption of MB on MEB, compared with pseudo-second-order model. The Langmuir model was best for describing the adsorption of MB on MEB bioadsorbent compared to the Freundlich model. The Langmuir separation parameter RL and Freundlich parameter 1/n, less than 1, indicate that the adsorption of MB on MEB was favorable. The bioadsorbent MEB offers a high potential for adsorption of dyes in aqueous solutions.