Crystal violet removal from aqueous media using Tragopogon dubius adsorbent

Abstract

In this study, Tragopogon dubius was used using a specific condition of adsorption to remove a cationic harmful dye (crystal violet : CV) in aqueous liquid media. Removing time, rate of adsorbent, pH of the media, initial concentration of the harmful dye, and absorbent particle size were studied to reach an optimum adsorption condition. Before and after the biosorption process of CV, the SEM micrographs and EDX spectra were obtained for Tragopogon dubius. The maximum removal efficiency of CV (90–93 %) has happened at pH=7.0, contact time of 120 min, adsorbent dose of 0.2 g/L (with particle size of 0.074 mm), temperature of 25 ○C, and pollutant rate of 50.0 mg/L. The adsorption rate of Tragopogon dubius was calculated using equilibrium models. It was also increased by water washing (30 min). The results showed that 50 % of the dye was absorbed when the adsorption time reached 50 min. Maximum adsorption (212.9 mg/g) occurred after 120 min of removing time. The results revealed the best accordance of the Tragopogon dubius adsorption with the Freundlich model (R2=0.96). A kinetic agreement was also observed between the dye adsorption and the Pseudo‐second order model. The negative value of ΔS° (−53.51 J/K mol) indicates that Tragopogon dubius removes CV during a relatively stable process with randomness in the system. The negative values of ΔG° at different temperatures indicate that the nature of CV adsorption was spontaneous.