Toxicity and biosorption of chromium from aqueous solutions by the diatom Planothidium lanceolatum (Brébisson) Lange-Bertalot

The present study reports the ability of the diatom Planothidium lanceolatum (Brebisson) LangeBertalot (P. lanceolatum) to remove hexavalent chromium [Cr(VI)] from aqueous solutions in batch system under varying ranges of pH, contact time and initial ion concentrations by the determination Cr(VI) toxic effects and biosorption by this species. The results show a significant growth of P. lanceolatum for Cr concentrations up to 10 mg L -1 . The growth rate decreases as a function of increasing concentrations of Cr(VI). The cultures made with Tensift River water (Marrakech, Morocco) developed in the presence of Cr(VI) concentrations from 0 to 4 mg L -1 . But the culture with tannery effluent water grew with concentrations from 0 to 0.152 mg L -1 . The IC50 calculated is 8.7 mg L -1 for the artificial growth medium tested which is more than that calculated with river water (3.85 mg L -1 ) and tannery effluent water (0.075 mg L -1 ). The biosorption of Cr increases with the decrease of pH. The biosorption capacity calculated from the Langmuir isotherm was 93.45 mg Cr(VI).g diatoms -1 at an initial concentration of 0.4 g dried diatoms per liter with an initial Cr(VI) concentration of 20 mg L -1 . The wide ecological valence of this diatom to pollution parameters and the seasonal pattern of its life cycle are the main factors that make the biomonitoring of Cr(VI) by this species feasible.