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Distribution and speciation of Fe, Mn, Zn, Cu, Pb and P in surface sediments of Lake Mariut, Egypt

100%

Abdel-Satar A. M. , Ali M. H. , Goher M. E.

tom Vol. 46, No. 2

154--167

Lake Mariut is suffering from pollution as it receives industrial effluents and a mix of sewage from different drains, often lacking treatment systems. Sequential extraction procedures were applied for the speciation of heavy metals (Fe, Mn, Zn, Cu and Pb) and P in the lake sediment to evaluate their potential bioavailability. Total concentrations of metals had low values compared with the sediment quality guidelines. The chemical speciation data for Mn and Zn indicate a potential pollution level since the non-residual fractions contain up to 77.6 and 64.9% (respectively) of the total metal content. However, Fe, Cu and Pb are mostly linked to the inert fraction. Risk assessment of metals was carried out using the mobility factor, the contamination factor, the risk assessment code and the enrichment factor. All the analytical approaches indicated the accumulation of pollutants exceeding the adsorptive capacity of Lake Mariut sediments. The organic phosphorus fractions dominated in the sediment accounting for 51.4%, while the most abundant form of inorganic phosphorus was Ca-bound phosphorus. The rank order of P fractions was HCl-P > NaOH-P > BD-P > NH4Cl-P > Res-P. The decrease both in the dissolved oxygen level in the lake water and the Fe:P ratio in the lake sediment resulted in the high contribution of the phosphorus fractions to the overlying water.

Biosorption of some toxic metals from aqueous solution using non-living algal cells of Chlorella vulgaris

75%

Goher M. E. , Abd El-Monem A. M. , Abdel-Satar A. M. , Ali M. H. , Hussian A.-E. M. , Napiorkowska-Krzebietke A.

nr 3

Dead cells of Chlorella vulgaris were used experimentally to remove cadmium (Cd2+), copper (Cu2+) and lead (Pb2+) ions from aqueous solution under various conditions of pH, biosorbent dosage and contact time. C. vulgaris was isolated from Lake Manzala, (Egypt) and then cultivated outdoors, in growth media, maintaining pH of nearly 7.5. After cultivation, the cells were harvested by coagulation and prepared to make an experiment with different variants of pH, contact time and adsorbent dose. The adsorption specific characteristics of C. vulgaris were examined using Fourier Transformation Infrared Spectroscopy (FTR) and Scanning Electron Microscopy (SEM). The FTIR and SEM data showed vibration frequency changes for the peaks corresponding to the surface functional groups and morphological changes of C. vulgaris, respectively, after its exposure to metal ion solution. The maximum removal efficiency for copper and lead at ambient room temperature was recorded at pH 5 and 20-minute contact time, while the contact time of 120 minutes at pH 6 created the most suitable conditions for cadmium biosorption. On the other hand, 2 g dm-3 of C. vulgaris under optimum conditions was sufficient to remove 95.5%, 97.7% and 99.4% of Cd2+, Cu2+ and Pb2+, respectively, from a mixed solution of 50 mg dm-3 of each metal ion. The removal trend was in order of Pb2+ > Cu2+ > Cd2+. The results suggested that the biomass of C. vulgaris is an extremely efficient and environmentally friendly biosorbent for the removal of Cd2+, Cu2+ and Pb2 from aqueous solutions, which may be applied on a large, industrial scale.