Preparation of bead-type biosorbent from water-soluble Spirulina platensis extracts for chromium (VI) removal

• We fabricated Spirulina platensis (water extracts) directly into beads without any polymer addition.
• A suitable preparation procedure was established for the S. platensis bead fabrication.
• High Cr(VI) removal was achieved due to compact structure of S. platensis beads.
• S. platensis beads could be regenerated by simple change of the pH of media.

A bead-shaped biosorbent for removal of Cr(VI) from industrial waste waters/aqueous media was fabricated using water soluble Spirulina platensis extract (SPE). The addition of LiCl to DMSO affected the solubility of SPE, and 1 M LiCl/DMSO was the optimal solvent system for the preparation of SPE beads. The shape of the SPE bead was determined by the concentration of SPE, and the type of coagulant affected the mechanical properties of the bead. The optimum pH for the Cr(VI) adsorption was 2.0. The maximum adsorption capacity of the SPE beads was 41.12 mg/g at pH 2.0, and the adsorption behavior of Cr(VI) on the SPE beads followed the Brunauer–Emmett–Teller (BET) isotherm. The results indicated that 0.1 M NaOH was the most effective desorption agent. The successive recycling of the adsorption–desorption process was stable for more than five cycles, and the recycling efficiency was 70%.

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