Adsorptive removal of cationic dyes (methylene blue and crystal violet) from aqueous solutions using anionic polyacrylamide-based monolith

In the present study, a macroporous anionic polyacrylamide-based monolith bearing negatively charged binding sites was synthesized as an adsorbent for the efficient removal of cationic dyes including methylene blue (MB) and crystal violet (CV) from aqueous solutions. The effects of various experimental parameters such as solution pH, contact time, monolith dosage, and initial dye concentration on the dyes adsorption were studied using batch experiments. Kinetic studies showed that the adsorption of MB and CV onto the monolith could be better described by the pseudo-second-order kinetic model (R2 = 1.0). The experimental equilibrium data for CV and MB were best fitted to the Langmuir isotherm model. The maximum monolayer adsorption capacity of the monolith is 120.5 mg g?1 for MB and 21.93 mg g?1 for CV at 25?C. The adsorption for MB and CV is spontaneous and exothermic. The studies reveal a significant influence of the molecular size of the dye on its percent removal. Reusability investigations indicated that the synthesized monolith could successfully adsorb MB dye after regeneration.