Anion Exchange Resins as Effective Sorbents for Acidic Dye Removal from Aqueous Solutions and Wastewaters

Abstract

Purification of wastewaters, particularly those containing dyes, has become increasingly important. The aim is to avoid a potential threat to the environment. Various sorbents have been used in the treatment of wastewaters contaminated by the Acid Orange 7 dye (AO7). In this article, the three anion exchange resins–weakly basic (Lewatit MonoPlus MP 62), intermediate (Lewatit MonoPlus MP 64), and strongly basic (Lewatit MonoPlus MP 500) were applied for AO7 removal from the aqueous solutions and wastewater. The most effective anion exchanger in wastewater purification proved to be Lewatit MonoPlus MP 500. AO7 sorption was not affected by the presence of Na₂SO₄ and CH₃COOH even at relatively high concentrations. The dye retentions were almost unchanged in the presence of non-ionic and anionic surfactants. AO7 sorption by Lewatit MonoPlus MP 62, MP 64, and MP 500 sharply decrease when the cationic surfactant is present in the solution. The monolayer adsorption capacity (Q₀ ) for MP 62 was found to be 79.9 mg/g at 25°C. At 45°C this value was almost ten times higher (769.5 mg/g). The increase of Q₀ values from 568.5 to 896.8 mg/g for MP 64 and from 979.0 to 1004.4 mg/g for MP 500 was observed with the rise in temperature. The optimal desorption conditions were found as follows: 1 M KSCN in 80–90% methanol for MP 62 (95–100% desorption) and MP 64 (∼88% desorption) as well as 1 M HCl in 90% methanol for MP 500 (87% desorption).

Keywords:

• anion exchangers
• Acid Orange 7
• dye sorption
• textile wastewater