Björn Stolpe

Asymmetrical Flow Field Flow Fractionation-Multidetection System as a Tool for Studying Metal-Alginate Interactions

The present study explores the potential use of asymmetrical flow field flow fractionation (aFlFFF) with a multidetection system for the study of metal–alginate interactions. aFlFFF, coupled on-line to a differential refractive index and seven angle laser light scattering detectors was used to provide information on the alginate size distributions. In parallel, the metal distributions of metal–alginate complexes were probed by aFlFFF–high resolution inductively coupled plasma-mass spectrometry. Average values and continuous distributions of molar masses, radiuses of gyration and hydrodynamic radiuses, which are critical for understanding the role of alginates as carriers of metal pollutants, were evaluated in presence of Pb or Cd and compared with those in metal-free solutions of alginate. The values of number average and weight average molar mass, weight average radius of gyration and shape factor for alginate were 150 and 188 kg mol−1, 53 nm and 1.7, respectively. Alginate molar mass and radius of gyration distributions were slightly shifted to higher values by the addition of micromolar concentrations of Pb or Cd. The alginate size distribution in the presence of Cd was similar to the alginate-alone control, whereas in the presence of Pb the size distribution was broader with a shift of the maximum toward higher molar masses.

Colloid-facilitated metal transport in peat filters.

The effect of colloids on metal retention in peat columns was studied, with the focus on colloids from two sources-organic matter leached from peat, and introduced organic and hydrous ferric oxide (HFO) colloids. A significant fraction of metals was found to be associated with peat-produced organic colloids; however the concentrations of organic colloids leached are low (trace concentrations) and temporal and have a limited effect on the efficiency of peat filters. In contrast, the presence of organic and HFO colloids in the input water causes a significant decrease in the performance of peat filters. Organic colloids were identified as the main vector of cadmium, copper, nickel, and zinc, while lead is transported by both organic and HFO colloids. The colloidal distribution of metals obtained in this study has important implications for the mobility of trace metals in porous media. The occurrence of colloids in the input waters and their characteristics must be considered when designing water treatment facilities.