The use of ultra filtration in trace metal speciation studies in sea water

The influence of colloids on the geochemical behavior of metals in polluted water using as an example Yongdingxin River, Tianjin, China

“…Based on the concentrations reported for the three colloidal fractions (i.e., 1-10 kDa, 10-100 kDa and 100 kDa to 0.22 lm), Mn and Fe concentrations were constant at all sites except sites F and A. Mn concentrations tended to increase with decreasing size fraction at site F, while the opposite held true for Fe at site A (Table 1), which was consistent with the result of Singhal et al (2006). They suggested that such behavior of Fe and Mn might be anticipated, as Mn ions generally occur as free cations and inorganic ion pairs and organic complexes have relatively low stability constants, while Fe precipitates and flocculates as colloidal Fe(III) hydroxide in well-oxygenated waters (Singhal et al, 2006).…”

“…They suggested that such behavior of Fe and Mn might be anticipated, as Mn ions generally occur as free cations and inorganic ion pairs and organic complexes have relatively low stability constants, while Fe precipitates and flocculates as colloidal Fe(III) hydroxide in well-oxygenated waters (Singhal et al, 2006). Consequently, it is not difficult to explain the reason for the much lower percentages of Fe in colloidal size classes 10-100 kDa and 100 kDa to 0.22 lm in poor-oxygenated waters of F (DO: 0.23 mg L À1 , Fig.…”

“…The ultrafiltration was continued until the ratio of the initial feed volume to the retentate volume (concentration factor) was about 6:1. Constant stirring above the membrane surface was done in an attempt to minimize localized concentration effects on the membrane surface (Singhal et al, 2006).…”

“…Consequently, colloid is defined as the third phase, which has an intermediate size or molecular weight. Colloids have received special attention because of their small size and large specific surface area, and thus their high reactivity toward contaminants as well as high diffusibility and mobility (Pham and Garnier, 1998;Babiarz et al, 2000;Ran et al, 2000;Wang and Guo, 2000;Guo et al, 2002;Mosley and Hunter, 2003;Baalousha et al, 2006;Singhal et al, 2006;Baalousha and Lead, 2007;Seredyń ska-Sobecka et al, 2007). The role of colloids in estuarine and marine systems has been studied extensively in recent years, whereas less is known about the polluted freshwater systems (Benoit et al, 1994;Dai et al, 1995;Guo et al, 2000;Gustafsson et al, 2000).…”

On the control of copper colloidal distribution by humic substances in the Penzé estuary

“…3. Comparison of Cu distribution over the colloidal size spectrum between the Penzé estuary (this study) and that found by Ingri et al (2004) and Singhal et al (2006) in the Ekhagen estuary (Sweden) and the Mumbai Bay (India), respectively. The Cu concentrations in each size fraction are normalized to a size range of 1 nm.…”