Multichamber Device Research Articles

Heavy metals sorption/desorption on competing clay minerals; an experimental study

The adsorption /desorption behaviour of Cd, Cu, Pb, Zn and Ni on illite, beidellite and montmorillonite was investigated using a multichamber device. This method allows one to study the adsorption/desorption rates and metal transfer reactions simultaneously on a few different solids. Sorption experiments show the highest enrichment of metal ions on smectites, but for Pb ions also on illite. The adsorbed amounts of Pb and Cu ions were very high: 80% and 70% of the total concentration of the metal ions, whereas the Zn, Ni and Cd ions were adsorbed in smaller (40–50%) amounts. A desorption experiment of metals adsorbed on clay minerals shows the following sequence of metal mobility from investigated minerals: Pb > Cd ⪢ Cu > Ni > Zn for beidellite, and Pb > Cd ≌ Cu > Ni > Zn for illite and montmorillonite. The lower metal accumulation on clay minerals after reaction with ferrous sulphate is supposed due to the premature iron hydroxide precipitation in the system, which has caused beside metals sorption their precipitation as well. Data from the sorption/desorption studies provides information regarding the different type of metal surface complexes formed with selected clay minerals and will help to predict the fate of metals in soils and sediments.

Chemical mobility and bioavailability of sediment-bound heavy metals influenced by salinity

The transfer of metals from contaminated sediments to algal cell walls (Scenedesmus quadricauda) and organisms from various trophic levels (euryhaline osmoconform hydroid Cordylophora caspia and algae Brachiomonas submarina) was studied with a multichamber device. The system consists of a central chamber which contained the mud suspension and six external chambers containing the different biological indicators. The solids in the central and external chambers are separated by 0.45 µm-diameter membranes which allow diffusion of the mobilized, dissolved metal compounds. Experiments were performed with dredged sediments at various salinities (0.5, 1.0, 1.5, and 2.0 percent, respectively) and the kinetic of re-adsorption was obtained by taking samples after different time intervals. High enrichment of Cd was found in the living alga Brachiomonas submarina, but on the other side only a weak influence of salinity on re-adsorption could be observed. Model experiments with ionic Cd showed a clear dependency on Cd-sorption on the algae, Cd-concentration in solution, and salinity. These results indicate that the transfer of metals mainly depends on the specific surface properties of the substrates and on the specific chemical form of the dissolved mobilized metal.

Studies on the transfer of heavy metals between sedimentary phases with a multi-chamber device: Combined effects of salinity and redox variation

Mobilization and transfer of heavy metals to major sediment components after changes of typical estuarine conditions (salinity, redox potential/pH) have been studied in a newly developed experimental device, consisting of a central chamber connected with six external chambers and separated by membranes of 0.45-μm pore diameter. Algal cell walls ( Scenedesmus quadricauda), bentonite, Al-oxide, Mn-oxide, quartz powder and goethite were used as model sediment components. Significant metal enrichment was found on algal cell walls, and on freshly precipitated iron hydroxide. Oxidation of anoxic mud from Hamburg harbour causes lowering of pH and remobilization of cadmium and zinc. The experiments on the effect of seawater on sediment components and dredged mud indicate the dominant role of organic substrates in the binding of metals such as cadmium and copper, suggesting that even at relatively small percentages of organic substrates these materials are primarily involved in metabolic processes and thus may constitute the major carriers by which metals are transferred within the food chain. These results demonstrate that it is particularly problematic to disperse waste materials in ecologically productive, high-energy environments such as estuaries.

Study of metal sorption/desorption processes on competing sediment components with a multichamber device

Study of metal sorption/desorption processes on competing sediment components with a multichamber device

Study of metal sorption/desorption processes on competing sediment components with a multichamber device

A new multichamber device was developed to study sorption/desorption reactions of metals on different competing sediment components and the influence of environmental factors on these reactions. The system consists of a central chamber connected with six external chambers and separated by 0.45-μm-diameter membranes.