Adsorption of Polycyclic Aromatic Hydrocarbons from aqueous solution by Organic Montmorillonite Sodium Alginate Nanocomposites.

The adsorption method is generally considered a promising technique to remove inorganic and organic contaminants in an economically and environmentally friendly superior manner. In this study, organic montmorillonite sodium alginate composites were prepared, in which, montmorillonite and cationic surfactant (cetyltrimethylammonium bromide, CTAB) in different added amounts were coagulated with sodium alginate using CaCl2 as the crosslinking agent. The morphological properties of the composites were characterized thoroughly and employed in three typical target pollutants of polycyclic aromatic hydrocarbons (PAHs) (acenaphthene, fluorene, and phenanthrene) by batch adsorption experiments from aqueous solution. The composites provide an efficient alternative for PAHs removals. The composites could be stably separated and regenerated with methyl alcohol. Furthermore, the adsorption kinetic and isotherm data were well described by the Elovich kinetic and the Freundlich isotherm model, respectively. According to these, the adsorption process occurred via multilayer adsorption on the composite's energetically heterogeneous surface. Moreover, pore diffusion and hydrophobicity played a dominant role in the adsorption mechanism. Overall, our study offers a developed adsorbent that has the advantage of being recyclable, low cost, biodegradable and biocompatible for effectively removing PAHs from aqueous solution.

Natural and anthropogenic lead in soils and vegetables around Guiyang city, southwest China: a Pb isotopic approach.

Soils, vegetables and rainwaters from three vegetable production bases in the Guiyang area, southwest China, were analyzed for Pb concentrations and isotope compositions to trace its sources in the vegetables and soils. Lead isotopic compositions were not distinguishable between yellow soils and calcareous soils, but distinguishable among sampling sites. The highest (207)Pb/(206)Pb and (208)Pb/(206)Pb ratios were found for rainwaters (0.8547-0.8593 and 2.098-2.109, respectively), and the lowest for soils (0.7173-0.8246 and 1.766-2.048, respectively). The (207)Pb/(206)Pb and (208)Pb/(206)Pb ratios increased in vegetables in the order of roots

[Sulfur isotopic ratios indicating sulfur cycling in slope soils of karst areas].

Sequential extraction methods for soil sulfur were used to determine delta34 S ratios and sulfur contents of total sulfur, organic sulfur, SO4(21) and FeS2 in slope soils of karst areas. In general, FeS2 has the lowest delta34 S ratios, ranging from -6.86% per hundred to -4.229% per hundred, followed in ascending order by SO4(2-) (-2.64% per hundred - -1.34% per hundred), total sulfur (-3.25% per hundred - -1.03% per hundred) and organic sulfur (-1.63% per hundred -0.50% per hundred) in surface soils of profiles, and delta34 S ratios in different sulfur forms all show increasing trend with profiles deepening. Covariations of delta34 S ratios of SO4(2-) and FeS2 with increasing depth are related to SO4(2-) dissimilatory reduction, while the increase in parallel of delta34 S ratios of total sulfur and organic sulfur could be resulted from organic sulfur cycling. delta34 S ratios have been extensively used to indicate sulfur sources, moreover, SO4(2-) dissimilatory reduction and organic sulfur mineralization result in significant sulfur isotopic fractionation, and sulfides oxidation and SO4(2-) assimilation have no isotopic fractionation occurred, the vertical variations of delta34 S ratios in different sulfur forms can therefore be good records for depth-dependant sulfur cycling processes. Furthermore, by comparing depth distributions of sulfur contents and delta34 S ratios in different sulfur forms, it is easily to discuss the migration of SO4(-1) and organic sulfur fractions in soil profiles.