Facile preparation of three-dimensional graphene oxide/ $${\iota}$$-carrageenan composite aerogel and its efficient ability for selective adsorption of methylene blue

A three-dimensional graphene oxide/ $${\iota}$$ -carrageenan composite aerogel (GO/ $${\iota}$$ -Car) has been facilely manufactured in a benign approach and characterized in detail. The adsorption ability of the GO/ $${\iota}$$ -Car aerogel was also investigated on the methylene blue (MB) removal from synthesized solutions. It was found that the adsorption process followed the pseudo-second-order kinetic model. The Langmuir maximum adsorption capacity of MB on the GO/ $${\iota}$$ -Car aerogel was calculated to be 245.28 mg g−1. Thermodynamic calculations proved that the adsorption was a spontaneous, exothermic process with the enthalpy change of −10.36 kJ mol−1 and the entropy change of 54.64 J mol−1 K−1. Furthermore, adsorption selectivity studies showed that the GO/ $${\iota}$$ -Car aerogel could selectively adsorb the cationic MB in the presence of anionic dye methyl orange, which was mainly attributed to the electrostatic attraction between the negatively charged aerogel and the positively charged MB. In addition, the MB removal rate by the GO/ $${\iota}$$ -Car aerogel could still reach 91.9% after three desorption–adsorption cycles. Overall, the GO/ $${\iota}$$ -Car aerogel prepared in this study could be a green, cost-effective, reusable and promising selective adsorbent for cationic dye removal from water.