Relevance of anionic dye properties on water decolorization performance using bone char: Adsorption kinetics, isotherms and breakthrough curves

This manuscript reports the performance of bone char for decolorization of aqueous solutions containing anionic dyes with different molecular properties. Kinetics, isotherms and breakthrough curves for the adsorption of acid blue 25 (AB25), acid blue 74 (AB74) and reactive blue 4 (RB4) on bone char have been determined and used for the assessment of the process performance where the impact and relevance of dye properties have been studied. An artificial neural network-based analysis was used to understand the relevance and impact of dye molecule properties on the adsorption behavior of bone char. Dye adsorption and intra-particle diffusion rates, adsorption capacities, equilibrium constants, enthalpies and breakthrough-curve parameters were calculated and correlated with the dye molecular properties. Results showed that these adsorption parameters were highly dependent on the properties of anionic dye molecules where the dimension of dye molecules is relevant during kinetics and breakthrough curves, while dye molecular weight has more impact on adsorption isotherms. These findings suggested that steric factors may govern the dye removal mainly in dynamic adsorption experiments. Experimental findings and FTIR characterization of bone char supported an anionic dye removal mechanism based on electrostatic interactions. In summary, the results of this study highlight the impact of anionic dye properties on the efficacy of batch and dynamic adsorption processes using bone char and provide new insights in water decolorization using this adsorbent.