Butea monosperma leaf as an adsorbent of methylene blue: recovery of the dye and reuse of the adsorbent

Butea monosperma leaf powder was used as an adsorbent to remove methylene blue dye from aqueous solution. Different parameters that affect on adsorption such as dye concentration, adsorbent dose, contact time and pH of the solution were analyzed. The suitable dye concentration was found to be 100 mg/l for adsorption experiments. The adsorbent dose and optimum contact time were standardized as 0.5 g/l and 120 min, respectively. The acceptable pH of the medium for adsorption was found as pH = 8. At the standardized environment, the maximum adsorption efficiency of the adsorbent was recorded as 98.70%. The ultra-morphological structure disclosed that the adsorbent had originally rugged surface with empty spaces on it, and after adsorption of the dye, these pores and spaces were filled up with the dye. Fourier transformed infrared spectroscopy chromatogram of the adsorbent shows many downward peaks which can be attributed to the existence of functional groups like C=O, –OH and –NH, etc. The suitably studied isotherm model was the Freundlich model having the correlation coefficient (r2) value of 0.9810. The adsorbent was transferred to the acidic environment (pH 6). At the pH, about 80% adsorbed dye was exuded. The adsorbent can be used for maximum two times for removal of the dye. Therefore, it can be concluded that Butea monosperma leaf powder has potential to remove methylene blue in aqueous solution. The absorbed dye can easily be recovered from adsorbent for reuse purposes.