Amphiphilic Calcium Alginate Carbon Aerogels: Broad-Spectrum Adsorbents for Ionic and Solvent Dyes with Multiple Functions for Decolorized Oil–Water Separation

Development of versatile, broad-spectrum adsorbents for the removal of diverse dyes from contaminated water and oil is highly desirable. In this study, a calcium alginate carbon aerogel (CCA) as an adsorbent for various types of dyes was fabricated from sodium alginate by wet spinning, cross-linking, drying, and high-temperature carbonization. The CCA carbonized at 1000 °C (CCA-1000) showed a good adsorption effect on methylene blue as a cationic dye, methyl orange as an anionic dye, oil red O as a solvent dye, and nine other dyes. Adsorption kinetics, adsorption effect of various parameters such as temperature and solution pH, regeneration performance, and adsorption mechanism were studied. The ultrahigh adsorption capacities of CCA-1000 for malachite green, crystal violet, and acid fuchsin, each with similar triphenylmethane structures, were determined to be 7059, 2390, and 6964 mg g–1, respectively. Interestingly, unlike previously reported carbon aerogels with simple oil–water separation, due to the amphiphilicity, CCA-1000 fabricated herein can be utilized to separate oil–water, surfactant-stabilized water-in-oil, and oil-in-water emulsions with simultaneous dye removal from water and oil. The present work may open up a new avenue for designing carbon aerogels with exceptional performance for broad-spectrum dye adsorption and oil–water separation from sustainable natural seaweed resources.