Effective and fast removal of crystal violet dye from aqueous solutions using Rumex acetosella: isotherm, kinetic, thermodynamic studies, and statistical analysis

In this study, the performance of Rumex acetosella leaves on the adsorptive removal of crystal violet dye from an aqueous solution was investigated. To determine the adsorption conditions, the adsorption studies were carried out under different parameters, namely contact time, temperature (0–120 min), initial pH (2–12), initial dye concentration (10–50 mg/L), and adsorbent dosage (0.2–4 g/L). Four different isotherms were applied, such as Freundlich, Langmuir, Dubinin–Radushkevich, and Harkins–Jura. From the data obtained, it was concluded that the Langmuir model was found to show the best fit for this study. The removal percentage of crystal violet reached a maximum of 94.5% at pH = 7–8 and 25℃. The adsorption capacity reached up to 434.8 mg/g in pH = 7–8 at 25℃. Kinetic studies indicated that adsorption followed the pseudo-second-order kinetic model. BET analysis and intraparticle diffusion data showed that the functional groups on the adsorbent surface were more effective than the surface area and pores in the adsorption process. Thermodynamic parameters were also investigated, and it was observed that the adsorption occurred exothermically and spontaneously. Besides, statistical analyses for isotherm models occurred. Graphical abstract