Selective adsorption of cationic dye utilizing poly (methacrylic acid-co-ethylene dimethacrylate) monolith from wastewater

In this study, a poly (methacrylic acid-co-ethylene dimethacrylate (poly(MAA-co-EDMA)) monolith was prepared for the selective adsorption of acidic dye, namely, methylene blue (MB), from wastewater. The fabrication of the monolith was carried out via photoinitiation polymerization by irradiating a mixture of methacrylic acid (MAA), ethylene dimethacrylate (EDMA), porogenic solvents and an initiator. Batch adsorption assays were performed to examine the impact of monolithic dosage and initial dye concentration on the adsorption capacity and efficiency of the monolith towards MB dye molecules. This adsorption kinetic study revealed that MB adsorption on the monolith followed a pseudo-second-order model and equilibrium adsorption behavior was best modeled with the Langmuir adsorption isotherm, which indicated monolayer adsorption with a maximum adsorption capacity of 50.00 mg g^-1. Owing to the presence of negative binding sites on the monolithic surface, cationic MB molecules were selectively adsorbed in the MB/methyl orange (MO) mixture with an adsorption efficiency of 99.54% at equilibrium. Moreover, the MB-adsorbed monolith was regenerated up to four cycles, and the percentage removal efficiency of MB on the monolith dropped to 67.64 % after the fourth cycle. Finally, the monolith effectively adsorbed MB from the tap water in the presence of competing ions, and the maximum adsorptive capacity obtained was 47.62 mg g^-1 with 84.5% adsorption efficiency. Hence, the poly(MAA-co-EDMA) monolith was found to be an adequate sorbent for the treatment of cationic dyes in the presence of other dyes and competing ions from wastewater.