Competitive biosorption of Yellow 2G and Reactive Brilliant Red K-2G onto inactive aerobic granules: Simultaneous determination of two dyes by first-order derivative spectrophotometry and isotherm studies

This study focused on the competitive biosorption of Yellow 2G (Y2G) and Reactive Brilliant Red K-2G (RBR) by inactive aerobic granules in binary solutions. A first-order derivative spectrophotometric method for the simultaneous determination of Y2G and RBR in binary solutions was developed. Dubinin–Raduskevich (D–R) isotherm successfully predicted the biosorption of Y2G and RBR in both single and binary solutions. However, none of the tested binary adsorption isotherms could realistically represent the biosorption equilibrium data. Maximum biosorption capacity calculated from D–R isotherm for Y2G and RBR in single solution was 58.50 and 66.18 mg g−1, respectively; in binary solutions, for Y2G it decreased to 40.38 mg g−1, but for RBR it increased to 171.21 mg g−1, showing their synergism and antagonistic interactions. The FTIR results indicated the main functional groups on aerobic granules for biosorption of Y2G and RBR would be amine, hydroxyl, carboxyl and either.