A comparative study on the adsorption of toxic cationic dyes by Judas tree (Cercis siliquastrum) seeds

Abstract

Cercis siliquastrum seeds were used for the adsorption of the basic dyes namely basic blue 9 and basic green 4 from the wastewater. Adsorption experiments were conducted under various conditions including different temperatures (25, 35, and 45 degrees C), pH (2-12), contact time (0-180 min), adsorbent amount (0.2-4.0 g/L), and concentration (10-50 mg/L). The adsorption processes were applied to various isotherms such as Freundlich, Langmuir, Dubinin-Radushkevich, and Harkins-Jura. Furthermore, different adsorption kinetic models including pseudo-first-order, pseudo-second-order, Boyd, and intraparticle diffusion were studied to comprehend the mechanism of the adsorption of the dyes. The results illustrated that the adsorption was best described by the Langmuir (r(2) = 0.9949 for basic blue 9 dye and r(2) = 0.9939 for basic green 4 dye at 25 degrees C). From the Langmuir isotherm, the q(m) value of basic blue 9 was found as 500.0 mg/g whereas those of basic green 4 was found as 243.9 mg/g at 25 degrees C. According to the thermodynamic parameters, it was determined that the adsorption process occurred endothermically and spontaneously for basic blue 9 and basic green 4 dyes. Considering the capacity of adsorption for both dyes, this study suggests that Cercis siliquastrum seeds are low-cost and environmentally friendly materials for the effective adsorption of basic dyes.