Anion-Exchange Resins for C.I. Direct Blue 71 Removal from Aqueous Solutions and Wastewaters: Effects of Basicity and Matrix Composition and Structure

In this work, eight ion exchangers with different functional groups and various polymeric matrixes (Amberlite IRA 67, Lewatit MonoPlus MP 62, Lewatit MonoPlus MP 64, Amberlite IRA 458, Amberlite IRA 900, Amberlite IRA 958, Lewatit MonoPlus MP 500, and Lewatit MonoPlus M 500) were used for the removal of C.I. Direct Blue 71 textile dye from aqueous solutions and wastewaters. For comparison, the sorption parameters of the low-cost sorbent prepared from orange peel were also measured. The sorption process of the dye was investigated by the column and batch sorption methods. High values of the monolayer sorption capacity (1630.6 mg/g), working ion-exchange capacity (13 mg/mL), and total ion-exchange capacity (128 mg/mL) were obtained for the macroporous anion exchanger Amberlite IRA 958 with quaternary ammonium functionalities. The amount of C.I. Direct Blue 71 retained by Amberlite IRA 958 was found to be dependent on the initial dye concentration and the phase contact time. The solution pH and salt (NaCl and Na₂SO₄) and anionic surfactant (SDS) concentrations do not influence the anion-exchange resin performance, whereas the presence of the cationic surfactant (CTAB) decreased the dye sorption on Amberlite IRA 958 significantly. Desorption of the dye occurred with 85.4% yield using 1 M NaOH in methanol. The results obtained in the purification of raw wastewaters confirmed that Amberlite IRA 958 can be a promising adsorbent for the removal of textile dyes from wastewaters of different types.