Magnetite graphene oxide (MGO) has gained attention as a potential adsorbent in wastewater treatment. In this study, incorporation of MGO into biopolymer matrix and dried by supercritical CO2 to improve the adsorption efficiency is presented. Alginate/MGO aerogel was prepared by blending the MGO with alginate and formed hydrogel by ionic crosslinking through external gelation. The blend ratio of MGO and alginate studied are comprised of 2 and 3 wt%, respectively. The hydrogel was dried by supercritical CO2 at 110 ± 5 bar and 40 °C in 4h. The physical-chemical properties of alginate/MGO adsorbent and its adsorption efficiency via removal of methylene blue (MB) are studied. The sharp curve for 30% weight loss for both types of adsorbents has been shown around 200 °C in TGA correspond to the exothermic peak form in DSC analysis. Alginate/GO and alginate/MGO are stable over temperatures of 300 and 700 °C, respectively. Alginate/GO successfully adsorbed 90% of MB concentration meanwhile the alginate/MGO had removed up to 84% of MB. Another highlighted technique is supercritical CO2 drying which considered as one of the most promising techniques to preserve the structure of aerogel with minimal shrinkage as low as 15% in comparison to ambient drying (50%).