the aqueous phase (>45 mg/L) at 45 ◦C. The positive value of _S◦ (9.67 J/mol k) exhibited an increase in the randomness at dye–SRB interface which could possibly remove some of the adsorbed water molecules from the rice biomass surface (Malkoc & Nuhoglu, 2007) leading to higher dye removal. Similar finding has been reported by Safa and Bhatti (2011) and Nasuha and Hameed (2011) where MB dye was adsorbed on rice husk and tea waste, respectively.
3.5. Scanning electron microscopy The morphology and structure of adsorbent surface are char-acterized using scanning electron microscopy (SEM). Adsorbent surface without and with adsorption of MB dye is given in Fig. 5. It is clear from these micrographs that a monolayer has adsorbed on the surface of SRB. This finding has been confirmed by the fitness of Langmuir biosorption isotherm model.