Investigation of biosorption of Gemazol Turquise Blue-G reactive dye by dried Rhizopus arrhizus in batch and continuous systems

Abstract

Gemazol Turquise Blue-G, a vinyl sulfone mono-azo type reactive dye, containing copper-phtlalocyanine as cromofor group, was removed from its aqueous solution in batch and continuous packed bed sorption systems by using dried Rhizopus arrhizus as a biosorbent. Operating variables studied were temperature, initial pH, initial dye concentration and sorbent dosage in the batch stirred system and flow rate and inlet dye concentration in the continuous packed bed. In the batch system, the fungal biomass exhibited the highest dye uptake as 773.0 mg g −1 at 45 °C, at an initial pH value of 2.0, at an initial dye concentration of 812.6 mg l −1 for a biomass dosage of 0.5 g l −1. The Freundlich, Langmuir and Redlich–Peterson adsorption models were used for the mathematical description of the biosorption equilibrium and isotherm constants were evaluated at different temperatures. Equilibrium data fitted well the Langmuir model in the studied concentration (100–800 mg l −1) and temperature (25–45 °C) ranges. Sorption data were fitted to pseudo first-order, pseudo second-order and saturation type kinetic models assuming that the external mas transfer limitations in the system can be neglected. The dye uptake process was found to follow pseudo second-order and saturation type kinetics. The thermodynamic parameters calculated showed that the adsorption process is feasible and has an endothermic character. The effect of operating parameters on the sorption characteristics of R. arrhizus in the continuous packed bed was investigated at pH 2.0 and at 25 °C. Data confirmed that the total amount of sorbed dye and column sorption capacity decreased with increasing flow rate and increased with increasing inlet dye concentration. The maximum column biosorption capacity of dried R. arrhizus cells was 823.8 mg g −1 at the highest inlet dye concentration of 776.3 mg l −1 at the minimum flow rate of 0.8 ml min −1. Thomas model was applied to experimental column data to determine the characteristic parameters of column useful for process design and to predict the breakthrough curves. The model was found suitable for describing the whole part of dynamic behavior of the column with respect to flow rate and inlet dye concentration.