High removal of methylene blue dye from aqueous solution by using a novel pectin-based hydrogel

In this study, pectin/poly(methacrylic acid-co-2-acrylamido-2-methylpropane sulphonic acid) (pec/poly(MA-co-AMPS)) hydrogel was synthesised with free-radical polymerisation. The effect of the compound proportions within the pectin-based hydrogels on swelling behaviour was investigated. Confirmation of the chemical structure of the prepared hydrogel used FT-IR spectroscopy. Surface morphology assessment was performed with SEM. Cationic methylene blue (MB) dye was chosen to investigate adsorption studies using these anionic-character hydrogels. The adsorption conditions affecting performance of initial dye concentration, solution pH, adsorbent mass, contact duration and temperature were systematically investigated. Kinetics of MB adsorption abided by a pseudo-second-order model. The adsorption isotherm for hydrogels was best described by the Langmuir isotherm model and it was found to have maximum MB adsorption capacity of 448.4 mg/g at 60 min duration. Thermodynamic investigation of the adsorption process linked to temperature found the adsorption process had random, spontaneous and endothermic favourability. In conclusion, pec/poly(MA-co-AMPS) hydrogel is accepted as a promising candidate to remove MB or cationic dyes with similar features from aqueous solutions.