Abstract
Thermodynamic equilibrium model was used to simulate the results of leaching heavy metal from cementitious wastes. Modeling results of the leached major element concentrations for samples agreed well with the leaching test using the set of pure minerals and solid solutions present in the database. The model revealed Pb and Cd were predominantly incorporated within the calcium silicate hydrate matrix while a greater portion of Cd exist as discrete particles in the cement pores. Precipitation was found to be the dominant mechanism controlling heavy metal solubility with carbonate and silicate species governing the solubility of Pb and carbonate, silicate and hydroxide species governing the solubility of Cd. In the presence of acetic acid, at low pH values Pb and Cd acetate complexes were predominant whereas, at high pH values, hydroxide species dominated. In the presence of municipal landfill leachate, Pb and Cd organic complexes dominated the heavy metal species in solution.
Highlights
There have been increased concerns regarding reusing the waste materials, as a result, an extensive array of leaching tests has been developed to assess the hazards of heavy metal-containing wastes
This study aimed at using PHREEQC to develop a model for simulating the leaching of Pb and Cd from cementations wastes and identify species governing the release of these contaminants
Establishment of geochemical simulation for metal leaching from cement: PHREEQC was used to model the leaching of contaminants from cementations wastes
Summary
There have been increased concerns regarding reusing the waste materials, as a result, an extensive array of leaching tests has been developed to assess the hazards of heavy metal-containing wastes. It is extremely important to understand the leaching behavior of the different elements. A model capable of describing contaminant leaching from wastes can assist in improving the development of management options. Many studies are available on the modeling of extraction tests for different elements considering leaching from cementbased samples (Dijkstra et al, 2006; Garrabrants et al, 2004; Astrup et al, 2006; Cornelis et al, 2006). This study aimed at using PHREEQC to develop a model for simulating the leaching of Pb and Cd from cementations wastes and identify species governing the release of these contaminants. Model outcomes were assessed by comparison with leaching profiles obtained from procedures recommended by AS 4439.3-1997.
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