Adsorption of hazardous dye Eosin Yellow from aqueous solution onto waste material De-oiled Soya: Isotherm, kinetics and bulk removal

Abstract

The main focus of this research is to develop a systematic method for the removal of a hazardous dye Eosin Yellow from its aqueous solutions by adsorption process. Eosin Yellow is an anionic halogen containing dye which belongs to Flouorescein class. During the batch studies it has been found that Eosin Yellow showed a decrease in adsorption over De-oiled Soya with increasing pH, while increase in concentration, temperature, amount of adsorbent and sieve size increased the adsorption of the dye over De-oiled Soya. The ongoing adsorption follows Langmuir, Freundlich, Tempkin and D–R adsorption isotherm models. On the basis of Langmuir constant values like Gibb's free energies at 30, 40 and 50°C have been found as 23.43, 25.15 and 25.23kJmol−1 respectively, while enthalpy and entropy of the adsorption process were calculated as 3.598kJmol−1 and 66.277 JK−1mol−1, respectively. Kinetic studies reveal that pseudo second order kinetics is operative during the adsorption process and the rate constant for the process was close to 1×10−9s·g·Mol−1 at all the temperatures. The treatment of kinetic data further reveals that the ongoing adsorption proceeds via film diffusion process and adsorption of the dye is taking place mainly on the external surface of the De-oiled Soya. The pre exponential constant (Do) and activation energy (Ea) have been found as 3.02×10−14 and 32.85kJmol−1 respectively. Under the column studies various parameters like fractional capacity of column, mass flow rate, percentage saturation of column etc. have been evaluated and their values have been found as 0.9748, 0.044mg/cm2/min and 98%, respectively. The recovery of the dye from the exhausted column was made by eluting dilute NaOH solution and almost 94% of the dye recovery was achieved.