Removal of crystal violet dye from aqueous solutions using <i>Robinia pseudoacacia</i> L. (Fabaceae) Fruits biosorbent

Synthetic dyes are a major source of environmental pollution. In this regard, biosorption is an important treatment method for the removal and detoxification of synthetic dyes from aqueous solutions. Accordingly, the present study was conducted to investigate the potential of <i>Robinia pseudoacacia</i> L. biosorbent (RPF) in the removal of crystal violet (CV) dye from aqueous solutions. To this end, biosorption parameters, including zero charge point, pH, initial dye concentration, biosorbent dose, stirring speed, and temperature, were investigated. Variations in the treated and untreated biosorbent surfaces were characterized using FTIR spectroscopy. The results showed that the RPF biosorbent removed 77% of CV under optimal conditions: pH of 6, initial dye concentration of 10 mg/L, biosorbent dose of 1 g, contact time of 30 min, stirring speed of 150 rpm, and temperature of 298 K. The Dubinin-Radushkevich isotherm (R²= 0.976) and pseudo-second-order kinetic (R² = 0.995) models were well fitted according to isotherm and kinetic studies. Thermodynamic studies revealed that the process was endothermic according to the ΔG values. Moreover, the phytotoxicity of treated CV solutions was significantly reduced. Thus, the RPF biosorbent was determined to be a low-cost, sustainable, and ecofriendly material for the removal and detoxification of synthetic dyes from aqueous solutions.