ECN publication
Generic geochemical modelling approach for the leaching of elements from waste materials and soils
Published by: Publication date:
ECN Environment & Energy Engineering 7-2-2014
ECN report number: Document type:
ECN-M--14-005 Conference Paper
Number of pages: Full text:
4 Download PDF  

Geochemical modelling is increasingly being used in both scientific research and risk assessment regarding the environmental properties of contaminated materials. The performance and reliability of model predictions are strongly determined by the specific modelling approach, as well as by the applied methodologies to estimate the necessary model parameters. This resentation will give an overview of our development of a generic multi reactive surface model, including methodologies for its parameterisation and testing. The approach is being developed to describe the speciation and solid/liquid partitioning (leaching) of a wide range of elements in both soils and waste materials, on the basis of the notion that the reactive organic and mineral surfaces that are being considered in this modelling approach, play a generic and determining role in the speciation and leaching of elements in these different materials. The multi-reactive surface model relies on individual adsorption models for which generic binding parameters have been developed and published for a wide range of elements. It includes reactions for aqueous speciation and (selected) mineral solubility, in combination with sorption to organic matter (NICA-Donnan model), Fe/Al-(hydr)oxides (Generalized Two-Layer Model) and clay (Donnan model). As such, the model is fully based on published generic thermodynamic parameters for these different types of processes and used without any parameter fitting. Model parameters are obtained with standard methods for the estimation of the potentially available/reactive fraction of the elements of interest, and the available amount of the above reactive surfaces. Particular attention is given to estimation of the reactive fractions of (particulate and dissolved) organic matter, using a recently developed rapid batch fractionation procedure [1]. The performance of the model has been tested for a range of different contaminated materials, particularly by comparing measurements and model predictions of the solid/liquid partitioning of elements over a wide pH range. We have found in different studies that the binding properties of the reactive surfaces that are being considered in this modelling approach play a generic role in the speciation and leaching of elements among very different waste and soil materials. As an example, the approach has been successfully applied to different soils [2], amended soils [3], municipal incinerator bottom ash [4], steel slag [5, 6], bauxite residues [7], recycled concrete aggregate [8], and RDF incineration and gasification bottom ash [9]. We will present examples from these different model applications, illustrate similarities and differences in controlling processes and element speciation in these materials and provide an outlook on current work and ambitions to further develop and improve this generic multi-reactive surface model.

Back to List