Investigation on the chemical bonding of copper ions on different soil samples

The mobility and bioavailability of heavy metals depend heavily on their ph ysical and chemical forms and their interactions with the different soil ph ases. Sorption capacity of different soils (brown forest, carbonaceous sand y, calcareous chernozjom) using Cu2+ as a model ion was studied. The time o f the equilibrium between solid and liquid phases was determined as 48 h. T he optimum initial pH-range was found as pH 3.5-6 and it was very much depe ndent on the soil types. From the pH changes taken place during the equilib rium process it was concluded that either protons or hydroxyl ions were rel eased into the solution. The study of effect of ion strength on the adsorpt ion of metal ions has concluded that the Na-ions showed two different effec ts, namely they decreased the adsorption of Cu2+-ions by occupying the sorp tion sites and, on the other hand, the Na-ions considerably destroyed the m ineral phases of the soils and increased the adsorption capacity. The effec t of changes of the concentration on the adsorption process was investigate d in the range of 1-10 mmol/l initial concentration using the optimum pH va lues. The linear Langmuir isotherm fitted into the initial parts of the ads orption isotherms for 1-4.5 mmol/l Cu2+-ions. (C) 2000 Elsevier Science B.V . All rights reserved.