Biosorption of phenanthrene by pure algae and field-collected planktons and their fractions

• Algal samples were fractionated into four fractions.
• Phenanthrene sorption for the nonhydrolyzable (NHC) fractions is nonlinear and for the other fractions is linear.
• The lipid and NHC fractions have higher sorption capacities for phenanthrene than other fractions do.
• Polymethylene carbon for the NHC fraction is the higher, the greater is its sorption capacity for phenanthrene.
• The log Koc values are related to lipid contents and polarity indices for the bulk algae and their fraction samples.

The biosorption isotherms for phenanthrene (Phen) by cultured algae, field-collected plankton, and market algae samples (OSs) and their fractions (lipid-LP, lipid free carbon-LF, alkaline nonhydrolyzable carbon-ANHC, and acid nonhydrolyzable carbon-NHC) were established. All the biosorption isotherms are well fitted by the Freundlich model. The biosorption isotherms for the ANHC and NHC fractions are nonlinear and for the other fractions are linear. It was found that the NHC fractions are chemically and structurally different from other fractions by using elemental analysis and Fourier transformed infrared spectroscopy (FTIR), consisting mainly of aliphatic polymethylene carbon. The average KOC values for Phen at Ce = 0.005Sw are 10 706 ± 2768 mL g−1 and 95 843 ± 55 817 mL g−1 for the bulk market algal samples and their NHC isolates, respectively. As the NHC fraction for Porphyra contains higher polymethylene carbon than that for Seaweed or Spirulina, it exhibits higher biosorption capacity. Moreover, the log KOC values are significantly higher for the field-collected samples than for the market algae and cultured algae samples. The multivariate correlation shows that the log KOC values are positively related to the LP contents, and negatively to the C/N ratios for the original algal samples. Furthermore, the log KOC values are negatively related to the polarity indices (O/C and O + N/C) for the original samples and their fractions excluding LP fractions. These observations help to understand the role of polarity, LP and NHC fractions, and aliphatic structures in the biosorption of Phen, which requires more attention in the examination of sorption processes in the natural environment.