The sorption of uranyl onto hydrous ferric oxide (HFO) or hematite was measured by discontinuously titrating the suspensions with uranyl at pH 5.9, 6.8, and 7.8 under Pco2 = 10(-35)atm (sorption isotherms). Batch reactors were used with equilibration times up to 48 days. Sorption of 1 microM uranyl onto HFO was also measured versus pH (sorption edge). A diffuse double layer surface complexation...

nanoparticles of manganese-dioxide synthesized by mechano-chemical reaction were used foras(iii) and as(v) sorption from water environment. the influence of a milling time of manganese-dioxide on sorption was examined with batch procedure. sorption as a function of contact time was investigated. kinetic of sorption, for both as(iii) and as(v), was fast. the equilibrium condition for milled sorb...

The oxi-hydroxides, present at trace level in uranium mill tailings, are responsible of about 70% of the 226 radium sorption, half being fixed on crystallized forms. This radionuclide (half time = 1622y), present at high level (50 to 100kBq.kg), can be released in groundwater, involving a possible contamination of the food chain (actual concentration limit = 0.37Bq.l). So, it is very important ...

Reactions of heavy metals with soil are important in determining metal fates in the environment. Sorption characteristics of two heavy metals, Cd and Pb, in three tropical soils (Mollisol, Oxisol, and Ultisol) from Puerto Rico were assessed at varying metal concentrations (0 to 1.2 mM) and pH values (approximately 2 to 7). All soils sorbed more Pb than Cd. Sorption maxima were obtained for each...

The sorption of 16 ionizable organic compounds (IOCs) to an estuarine sediment was measured in synthetic estuarine water as a function of IOC concentration (1-100 microM) at fixed ionic strength (0.4 M), pH (7.6), and sediment concentration (0.018 g sediment kg(-1) suspension). Of the 16 IOCs, 11 were naphthoic acids and five were quinoline compounds. The linear sorption distribution coefficien...

The interaction of sulfonamide antimicrobial agents with smectite clay minerals and humic acid (HA)-clay complexes was investigated in batch experiments to assess the influence of adsorbed humic acid on sulfonamide sorption. Soil HA-clay complexes were produced at HA:clay ratios of 1:5, 1:50, and 1:100 (w/w). Vibrational and electronic spectroscopy indicated the preferential adsorption of polar...

The transport and fate of many contaminants in subsurface systems can be influenced by several rate-limited processes, such as rate-limited sorption, diffusional mass transfer, and transformation reactions. Identification of the controlling process in such systems is often difficult, and is confounded by the possible influence of additional factors such as nonlinear or hysteretic sorption. We p...

This article compares the sorption behaviour of 2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol, pentachlorophenol, chlorotriazine atrazine, methylthiotriazine ametryn, methoxytriazine atratone, hydroxyatrazine, and didelakylated atrazine in a topsoil and an aquifer sediment before and after removal of sorbent organic matter and in humic acid. Freundlich isotherm coefficients Kf and 1/n and fr...

The ability to predict rates of contaminant sorption and desorption in the environment is essential in order to determine contaminant bioavailability, predict contaminant fate and transport, and assess risk. In this paper, we present a new method to determine sorption-desorption time scales from the temporal moments of batch experimental data. Here, the term time scale has a precise meaning: Ti...

Heavy metals are toxic soil pollutants that are retarded in soils by sorption at the solid phase. At a small scale (of a soil sample), the sorption process can be observed and quantified using sorption isotherms. However, most environmental problems have to be treated and solved at large scales (e.g., a field scale). At the field scale, heavy metal sorption isotherms are commonly highly variabl...