Competitive adsorption of Reactive Orange 16 and Reactive Brilliant Blue R on polyaniline/bacterial extracellular polysaccharides composite—A novel eco-friendly polymer

Highlights: ► Competitive adsorption of reactive dyes onto polyaniline/bacterial extracellular polysaccharides composite. ► The composite have functional groups of both polyaniline and bacterial extracellular polysaccharides. ► The presence of Reactive Brilliant Blue R diminished the uptake of Reactive Orange 16. ► Electrostatic interaction was identified as a major mechanism in adsorption process. ► Reactive Brilliant Blue R and Reactive Orange 16 adsorption was endothermic process. - Abstract: The performance of polyaniline/extracellular polymeric substances (Pn/EPS) composite as an adsorbent to remove the anionic reactive dyes, Reactive Brilliant Blue R (RBBR) and Reactive Orange 16 (RO), was investigated in single and binary systems. The pHpzc of Pn/EPS composite was calculated as 3.7 through potentiometric mass titration method. Electrostatic interaction between the dye anion and the nitrogen present in the polymer was identified as a major mechanism in adsorption process. Single component isotherms followed the Langmuir model with the maximum adsorption capacity of 0.5775 mmol g−1 for RBBR and 0.4748 mmol g−1 for RO. In binary system, both the reactive dye anions compete with each other and resulted in lower uptake. Binary adsorption data were interpreted well by the Sheindorf–Rehbun–Sheintuch equation as compared to extended Langmuir model with constant interaction factor. Kinetic analysis of single solute followed pseudo-first order model. Thermodynamic studies computed that RBBR and RO adsorption was endothermic, spontaneous, and feasible process.