Physicochemical and instrumental characterization of rice husk and its potential use as a low cost adsorbent for mutagenic dye bromophenol blue

In this study fine powder of rice husk were used as novel adsorbent for the removal of bromophenol dye. Different conventional physicochemical analysis and instrumental techniques were used to characterize the adsorbent. The surface area of the adsorbent was found to be 160.6 m2/g with bulk density of 1.139 g/dm3. Proximate and ultimate analysis showed that the selected material is a rich source of carbon with the advantage of not having Sulphur contents. FTIR and SEM analysis confirmed the surface modification via aqua regia in comparison to parental material (that have enhanced its surface porosity). The maximum uptake capacity (0.8 mg/g) of dye was reached at pH 3, 20 ppm of adsorbate concentration, and 0.5 g of treated rice husk dosage at room temperature and 60 min of equilibrium time. The equilibrium adsorption data was best explained by Freundlich adsorption isotherm with R 2 value of 0.998. Kinetic studies revealed that adsorption follows pseudo second order kinetic model with R 2 value of 0.997, K 2 equal to 0.831 (g/mg min), and q e value of 0.97 mg/g. The thermodynamic parameters (∆S° = 6.78 J/mol, ∆H° = 1501 J/mol, ∆G° −1.50, 0.5, 0.621 and 0.0787 kJ/mol corresponding to 293, 303, 313 and 333 K) pointed towards the endothermic and spontaneous nature of the process.