Mechanism of interactions in C.I. Acid Red 18 – Floating plants and polymeric resins systems: Kinetic, equilibrium, auxiliaries impact and column studies

Abstract

Abstract The characteristics of the removal processes of the popular textile dye C.I. Acid Red 18 (AR18) using floating plants and anion-exchange resins are presented. The use of widespread floating plants Wolffia arrhiza, Lemna minor, Spirodela polyrhiza, and Azolla caroliniana was examined. Abiotic and biological mechanisms have been identified that are important in the removal of AR18 by plants. It has been shown that only two mechanisms are responsible for the removal of AR18 from aqueous solutions: plant uptake and plant sorption. The rate constants of these processes reach 0.099 d−1 and 0.130 d−1, respectively. The most effective dye removal was registered during experiments conducting with W. arrhiza, with an efficiency of 62% on average. In the adsorption process, the weakly basic anion exchanger Amberlyst A23 (A23) and non-functinalized resin Amberlite XAD761 (XAD761) of phenol-formaldehyde matrices were used. The sorption capacities of A23 and XAD761 determined from the Langmuir isotherm model were calculated as 329.1\xa0mg/g (r2\xa0=\xa00.999) and 22.3\xa0mg/g (r2\xa0=\xa00.998), respectively. The auxiliaries presence such as 0.5–2\xa0g/L CH3COOH, 5–25\xa0g/L Na2SO4, 0.1–0.5\xa0g/L anionic or non-ionic surfactants in 500\xa0mg/L AR18 solution do not reduce AR18 uptake by A23. Kinetic data of adsorption follows pseudo-second order equation rather than pseudo-first and intraparticle diffusion ones. The working ion exchange capacity (108.3\xa0mg/mL) determined in the AR18-A23 column system confirmed a successful application of the weakly basic anion exchanger in purification adsorption step.