Objective
The aim of the research project is to select the most effective washing methodologies to solve the problem of remediation of coke oven plant sites contaminated with heavy metals (As, Zn, Pb in particular).
The results show that the extraction efficiencies of the acid leachings (HCI or HNO3) are closely correlated with the pH of the medium.
Two leachings in series, the first EDTA and the second by an acid solution are very efficient and improve the solubilisation of Zn and Cu.
Taking into account the variations of the heavy metals contents and their different behaviours, it seems necessary to carry out in each case preliminary laboratory trials to optimize the parameters (pH, concentration percentage of dry matter) of any leaching treatment.
Various studies carried out at industrial sites have highlighted the possible contamination of soil at coke oven sites by certain heavy metals and similar metalloids. The results of research have shown that As, Zn and Pb contents in soil from coke oven plants can be considerable in relation to the reference values for contaminated soil laid down in the Netherlands.
The problems of contaminated site remediation are becoming more urgent each year throughout Europe.
The work of the CRM will be directed towards assessing the effectiveness of the various methods of soil washing in order to eliminate heavy metals and similar metalloids (chiefly Zn, Pb and As). This work is currently being undertaken on coke oven sites but the results could also be extended to the treatment of other steel-related sites.
Tests will deal specifically with the examination of soil from actual coke oven sites.
Two types of reactors are envisaged for the mixing of soils and leaching agents:
- mixed laboratory reactor, in which the soil is treated in the form of slurry for three types of substrates; if necessary, this will be done after separation of the coarse and fine fractions (the latter generally being more contaminated), with a view to reducing the amounts to be treated;
- in a column representing as accurately as possible the layered structure of soil. This type of test is only feasible in the case of permeable soils in order to verify the suitability of treatment in situ.
The leaching agents used might be acidic solutions, chelating solutions or surfactants, for example. Optimum conditions and the concentrations of leachates to be used per unit of soil mass will be examined for the decontamination of the substrates in question. Wherever possible, preference will be given to those substances which are least harmful to the soil structure.
At the same time, an analytical programme will be carried out for each test in order to determine the efficiency of decontamination.
Topic(s)
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4000 LIEGE
Belgium