Direct dye biosorption by immobilized barley husk

The potential of low-cost adsorbent-barley husk to remove direct dye, namely Actarus Red BWS through biosorption process has been investigated in both continuous and batch modes. A series of experiments have been performed to evaluate the optimum biosorption conditions such as pH (2-5), biosorbent dosage (0.2-0.8g), initial dye concentration (50-200ppm), equilibrium time, and temperature (303-333K). The adsorption efficiency decreased with increase in pH and increased with increase in biomass dose. Equilibrium isotherms have been developed by applying data to Langmuir, Freundlich, and Flory-Huggins models. The highest correlation coefficient (R-2 = 0.99) related to Langmuir isotherm indicated good fitness of this model, explaining the sorption as monolayer process. The process followed pseudo-second-order kinetic model. The negative increment G degrees and positive increment H degrees values indicated the spontaneous and endothermic nature of process. The continuous mode of biosorption has been tested as the function of flow rate and bed height too.