No abstract

The present study reports the ability of the diatom Planothidium lanceolatum (Brébisson) Lange-Bertalot (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.

No abstract

Various biomaterials have shown promise as sorbents to remove heavy metals from polluted waters at lower cost than conventional wastewater treatment technologies. The aim of this study is to characterize the ability of the freshwater diatom Navicula subminuscula Manguin to biosorb cadmium, copper and zinc from aqueous solutions. Our results indicate that the biosorption of metals by N. subminuscula increased as the initial concentration of metal ions increased in the medium until a concentration of 100-130 mg L -1 . Biosorption equilibrium was established in 30 minutes. The maximum metal ions biosorbed was found to be 42, 90 and 127 for 16 10 8 diatoms per liter for Cd, Cu and Zn, respectively. The maximum uptake of metals was obtained at pH 6.0 for Cu and at pH 8.0 for Cd and Zn. An increase in the biosorption of P. lanceolatum was observed with an increase in temperature from 15 to 25°C. The biosorption of all three metal ions followed the Langmuir isotherm. Competitive biosorption of cadmium, copper and zinc ions was also achieved. The FTIR (Fourier Transformed Infra Red spectroscopy) results of algal biomass revealed the different functional groups at the diatom surface that are able to react with metals in the medium. The results all together suggest that N. subminusculacan be used as a biosorbent for an efficient removal of heavy metals from aqueous solutions which temperature and pH values could be close to the mean ones of the Tensiftriver.