Insight into adsorption mechanism, modeling, and desirability function of crystal violet and methylene blue dyes by microalgae: Box-Behnken design application

Herein, an environmentally friendly and efficient adsorbent of microalgae (MAG) was applied for the removal of crystal violet (CV) and methylene blue (MB) dyes from aqueous solutions. Multivariate modeling and optimization of CV and MB dyes removal onto MAG via Box-Behnken design (BBD) were investigated depending on three variables i.e. MAG dosage (20–100 mg), initial pH (4–10), and adsorption time (2–6 min). The adsorption kinetics and isotherm analyses revealed that the pseudo-second-order and Langmuir models governed the adsorption of CV and MB dyes onto MAG. The maximum adsorption capacity of MAG generated from the Langmuir equation was computed to be 243.0 mg/g for CV and 297.1 mg/g for MB. The determined thermodynamic parameters denoted that the adsorption mode of CV and MB dyes by MAG was spontaneous and endothermic. Several interactions like electrostatic forces, n-π stacking, and H-bonding caused the adsorption process of CV and MB dyes on the surface of MAG. The results showed that MAG could be an effective and locally available candidate adsorbent for removing dyestuffs from contaminated industrial effluent.