Efficient continuous adsorption of anionic dyes by polyethyleneimine resin: Optimization and mechanistic study

Given the widespread use of anionic dyes in industry, removing these dyes from industrial effluents is necessary due to their hazardous nature. Herein, we report the synthesis of polyethylimine-based functionalized cross-linked resin (PEI–MA) for the adsorptive removal of these dyes in a batch as well as on a fixed-bed for their simultaneous removal from a multicomponent system. The thermally stable PEI-MA (T_d = 366 °C) exhibited high adsorption efficiencies for Alizarin Yellow (AY), Congo Red (CR), and Eriochrome Black T (EBT), with adsorption capacities of 274.2, 273.2, and 153.1 mg/g, respectively. The highest adsorption efficiency was achieved at pH 5.6, with an adsorbent dosage of 2 g/L. The optimization of the adsorption process was studied by RSM, which exhibited less than 1 % of SSE from the predicted values. Moreover, DFT simulations were performed to explore the molecular recognition and affinities of resin-dye complexes. The computational study revealed that the formation of resin–dye complexes was a favorable and spontaneous binding process, which was driven by substantial enthalpic contributions from hydrogen bonds and electrostatic interactions. Likewise, isotherm, kinetic, and thermodynamic models displayed that the adsorption process fitted well with the Langmuir and Temkin models and adsorption was exothermic in nature. Moreover, PEI–MA exhibited excellent adsorptive performance for the simultaneous removal of the studied anionic dyes from a multicomponent system in a continuous operation for more than 10 h.