Removal mechanism of cationic dye (Safranin O) from the aqueous phase by dead macro fungus biosorbent

Abstract

Batch biosorption parametric experiments were carried out to delineate the removal mechanism of cationic dye, namely, Safranin O, from the aqueous phase using biosorbent prepared from wood rotting dead macro fungus 'Fomitopsis carnea'. Experimental data of the kinetic experiments at various temperatures (19, 27 and 35 °C) were well described using pseudo-second order kinetic models. Raising temperature from 19 to 35 °C enhanced the dye uptake potential of the biosorbent from 1,000 to 1,250 mg/g. The other variables studied were the effect of common salt (NaCl) and pH on the dye removal potential of the biosorbent. Decreased dye removal (%) efficiency at higher salt concentration suggests involvement of an ion-exchange type sorption mechanism. The pH study revealed that dye removal may occur due to the existence of an electrostatic attraction force between negatively charged biosorbent particles and dye cation. However desorption using mineral acid (H2SO4 and HCl) exhibited the highest desorption up to 76%, followed by organic acid (52%) and distilled water (not more than 2%) indicating the possibility of ion-exchange as the dominating dye sorption mechanism. Fourier transform infrared (FT-IR) spectroscopy analysis of the biosorbent, Safranin O and Safranin O loaded biosorbent also supported the possibility of ion-exchange as the dominating mechanism due to the presence of major peaks of Safranin O on the IR spectra of Safranin O loaded biosorbent, indicating that the Safranin O was present in its unaltered form on the surface of the biosorbent.