Abstract: In the present study, squid (Ommastrephes bartrami) melanin was employed to absorb Cr(VI) in aqueous solutions. Under the crushed granularity of 90 orders and fixed absorbent amount (75mg/5mL solution) conditions, the response surface methodology of Box–Behnken model, with three variables, i.e., adsorption temperature, contact time and solution pH value, was utilized to optimize the parameters for removal chromium ions. The optimized adsorption conditions were found to be 35℃ for adsorption temperature, 90 min for contact time and 5.2 for solution pH, respectively. The actual removal rate of total chromium ions reached to 64.86% under the optimized adsorption conditions. Results of scanning electron microscopy (SEM) demonstrated that the monomeric granule of squid melanin was in spherical shape, whereas, the assembled aggregates were increased after Cr(VI) adsorption. Fourier transform infrared (FT-IR) spectroscopy revealed that hydroxyl, amino and amide groups were the potential binding sites with chromium ions.

Key words: Squid ink, melanin, hexavalent chromium, removal activity, response surface methodology, scanning electron microscopy, fourier transform infrared