Abstract: Reactive dyes are extremely toxic and harmful to the environment even present at very low concentration. In this study, sodium alginate based reusable hydrogels was prepared for the removal of methylene blue from waste water. pH-tunable hydrogels was prepared by the introduction of ionic pendant functionalities on sodium alginate (SA) by the utilization of ethylene glycol and acrylic acid through condensation followed by free radical polymerization. The structure, formation and thermal stability of hydrogel was identified by Fourier transform infra red spectroscopy and thermogravimetric analysis respectively. Swelling nature at different pH ranges and the humidity contents of both dried and dye adsorbed hydrogels was investigated. The morphology of the dry and dye adsorbed hydrogel was also studied using scanning electron microscopy. The swelling studies infer that pronounced swelling obtained at higher pH than at lower pH. The surface morphology of plain hydrogel before and after adsorption of methylene blue (MB) was examined by SEA analysis. The adsorption tendency of the SEA hydrogel in MB was steadily investigated at different pH, contact time, concentration dye and adsorbent dosage. All prepared hydrogels were performed well in the removal of MB from waste water up to 80–98%. Recycling of hydrogels has a vital role for waste water treatment and it can be done by desorption studies which shows that 0.1 N HCl revealed higher elution efficiency i.e. 90.00%. Furthermore, adsorption–desorption studies suggested that SA based hydrogels contributes to enhance the removal efficacy, which renders the hydrogels well-designed for the efficient removal of cationic dyes (MB). However, polyol based hydrogels have been chosen for an adsorbent because of low-cost, ecofriendly, biocompatible and efficient biosorbents. Graphical Abstract: [Figure not available: see fulltext.]. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.