Removal of acid, direct and reactive dyes on thepolyacrylic anion exchanger

In the present studythe polyacrylic anion exchanger Amberlite IRA 478 (IRA 478) was used forremoval of textile dyes such as C.I. Acid Red 18 (AR18), C.I. Reactive Blue 21 (RB21) and C.I. Direct Yellow 142 (DY142) from aqueous solutions. Sorption of the above-mentioned dyes was carried out by the static and dynamic methods. The obtained results were analyzed by determining the adsorption isothermparameters using the Langmuir and Freundlichmodels. Kinetic parameters of dyessorption were calculated from the pseudo-first order, pseudo-second order and intraparticle diffusion models. The monolayer sorption capacities of IRA 478 determined from the Langmuir isotherm were found to be 1098.5 mg/g for AR18 (R²=0.994), 46.8 mg/g for DY142 (R²=0.820) and 23.5 mg/g for RB21 (R²=0.987).Kinetic studies revealed that effectiveness of AR18, DY142 and RB21 uptakeincreases with increasing phase contact time and initial dyesconcentration.The kinetics of the dyessorption process on the anion exchanger is best described by the pseudo-second order model (PSO) due to the high values of the determination coefficients R² (linearity condition of the plot t/q_t vs.t). The rate constantsof the pseudo-second order kinetics k₂are reduced from 0.1001 to 0.0008 g/mg·min for AR18, from 0.0147 to 0.0112 g/mg·min for DY142 and 0.0489 to 0.0072 g/mg·min for RB21 with an increase of initial concentration of dyes.The presence of salts and surfactants had an impact on the retention of direct and reactive dyes.