Synthesis of seawater based geopolymer: Characterization and adsorption capacity of methylene blue from wastewater

•A mesoporous seawater-based geopolymer (SW-GP) was developed by using industrial by-products.•The seawater-based geopolymer was synthesized at ambient temperature using seawater.•A seawater-based geopolymer (SW-GP) is a promising adsorbent to remove methylene blue (MB) from aqueous solutions.•The adsorption capacity of the seawater-based geopolymer was 59.52 mg/g.