Leaching and geochemical modelling of a metallurgical slag heap

1. Leachingandgeochemical modelling of a metallurgicalslagheap Dr. Mojca Loncnar (mojca.loncnar@acroni.si) Dr. Hans A. van der Sloot, Hans van der Sloot Consultancy, The Netherlands Assist. Prof.Dr. Marija Zupančič, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Slovenia Assist. Prof.Dr. Ana Mladenovič, Slovenian National Building and Civil Engineering Institute, Slovenia 03/04/2017 Fifth International Slag Valorisation Symposium │ Loncnar M, van der Sloot H.A., Zupančič M., Mladenovič A.

2. Outline: • Casestudy: Metallurgicalslagheap Javornik, Slovenia • Materials • Sampling of heap samples • Groundwater monitoring • Data comparison and geochemical modelling • ResultsandDiscussion • Batch data • pH dependent data (compositesample) • Geochemical modelling • Comparisonbatch data, GW data and pH dependent data • Conclusions Fifth International Slag Valorisation Symposium │ Loncnar M, van der Sloot H.A., Zupančič M., Mladenovič A. 03/04/2017

3. Case study: Metallurgical slag heap Javornik • near the town of Jesenice in NW Slovenia approx. 3 ha large Landfill area 2 ha approx. 400 000 t metallurgical wastes Operationstarted in 1987 2009 landfilling stopped • 73 % slags from carbon and stainless steel production • 19 % EAF and VOD dust • 8 % refractory material • other wastes 50 m Source: www.google.si/maps Fifth International Slag Valorisation Symposium │ Loncnar M, van der Sloot H.A., Zupančič M., Mladenovič A. 03/04/2017

4. Sampling of heap samples • 11 locations on the metallurgical heap (batch extraction tests + pH dependence test (on composite sample) Sampled at thedepthofaround 6m belowthelandfillsurface Sampled at thedepthofaround 20-30 cm belowthelandfillsurface L1 L9 L7 L4 L8 L5 L2 L10 L6 L3 L11 Source: www.google.si/maps Fifth International Slag Valorisation Symposium │ Loncnar M, van der Sloot H.A., Zupančič M., Mladenovič A. 03/04/2017

5. Groundwater monitoring (years 2011 – 2015) 7 piezometers Twiceannually spring, autumn P1 P1 and P2: reference piezometers P4 P2 P3 P7 P5 P6 Fifth International Slag Valorisation Symposium │ Loncnar M, van der Sloot H.A., Zupančič M., Mladenovič A. 03/04/2017

6. Data comparisonandGeochemical modelling • Thedatabase / expertsystem LeachXSTM1: • Management of data (the pH dependentleaching data, thebatch data, the GW data) andvizualizationofthecalculatedandmeasuredresults (in MS Excel) • Geochemical speciation and chemical reaction/transport modelling: • Modelling environment ORCHESTRA Thegeochemicalmodelling: • Mineral sorption (extended MINTEQ database) • Sorption on Fe-oxides (Dzombak & Morel) • Sorption on Al-oxide, dissolved organic carbon (DOC) and particular organic carbon (POM) (interaction according to NICA-DONNAN) • Multi-element modellingtakingintotheaccountall (33) measuredelements Fifth International Slag Valorisation Symposium │ Loncnar M, van der Sloot H.A., Zupančič M., Mladenovič A. 03/04/2017

7. Total chemicalcomposition • Chemicalcompositionofthecompositelandfillsample • Chemical composition of the individual landfill samples Sampled at thedepthofaround 20-30 cm belowthelandfillsurface Sampled at thedepthofaround 6m belowthelandfillsurface Fifth International Slag Valorisation Symposium │ Loncnar M, van der Sloot H.A., Zupančič M., Mladenovič A. 03/04/2017

8. Mineralogy(XRD analysis: thecompositelandfillsample) Fifth International Slag Valorisation Symposium │ Loncnar M, van der Sloot H.A., Zupančič M., Mladenovič A. 03/04/2017

9. Mineralogy(SEM-EDS: themicrographoftheprehydratedcalcium aluminate grain) Reaction rim is composed of C-A-H phase, with the typical microstructure of (prismatic) hexagonal cross section Fifth International Slag Valorisation Symposium │ Loncnar M, van der Sloot H.A., Zupančič M., Mladenovič A. 03/04/2017

10. One-stage batch test (CEN 12457) Legend: Inert limit forwaste Non-hazardous limit forwaste Fifth International Slag Valorisation Symposium │ Loncnar M, van der Sloot H.A., Zupančič M., Mladenovič A. 03/04/2017

11. Modelling of pH dependent data • Multi-element modellingtakingintotheaccountall (33) measuredelements • Chemicalspeciationfingerprint (CFS) used forthespeciationmodellingofmetallurgicalslagheap Fifth International Slag Valorisation Symposium │ Loncnar M, van der Sloot H.A., Zupančič M., Mladenovič A. 03/04/2017

12. Modelling of pH dependent data: major elements Legend: pH-dep. data model pred. L/S = 10 model pred. L/S = 0.3 • Major elements dictate the leaching conditions (pH, Eh, conductivity) • In the case of many elements the measured conc. at L/S = 10 correspond well with the model prediction Fifth International Slag Valorisation Symposium │ Loncnar M, van der Sloot H.A., Zupančič M., Mladenovič A. 03/04/2017

13. Modelling of pH dependence data: parameters of environmental concern Legend: pH-dep. data model pred. L/S = 10 model pred. L/S = 0.3 Fifth International Slag Valorisation Symposium │ Loncnar M, van der Sloot H.A., Zupančič M., Mladenovič A. 03/04/2017

14. Geochemicalmodelling • Calculated speciation in the liquid and solid phases • Leaching of CALCIUM at pH > 12 was adequate describe by portlandite, calcite, CSH and CAH c Fifth International Slag Valorisation Symposium │ Loncnar M, van der Sloot H.A., Zupančič M., Mladenovič A. 03/04/2017

15. Geochemicalmodelling • Calculated speciation in the liquid and solid phases • Leaching of CHROMIUM at alkaline pH controlled by Cr substitution as a solid solution in ettringite Fifth International Slag Valorisation Symposium │ Loncnar M, van der Sloot H.A., Zupančič M., Mladenovič A. 03/04/2017

16. Comparison of the batch and pH dependent data • The batch data plot along the pH dependent leaching curve • The same solubility controlling phases control leachability • In some samples, Ca is affectedbycarbonation Legend: pH-dependent data batch data (L1-6) batch data (L7-11) Fifth International Slag Valorisation Symposium │ Loncnar M, van der Sloot H.A., Zupančič M., Mladenovič A. 03/04/2017

17. Comparison of GW data and pH dependent data • The GW data showedlowerconc. orfallright on the pH dependentcurve • Not big differences in the conc. between the reference piezometers and other piezometers indicating limited influence of the landfill area on the GW data Legend: pH-dependent data reference piezometers (P1, P2) piezometers 3-7 Fifth International Slag Valorisation Symposium │ Loncnar M, van der Sloot H.A., Zupančič M., Mladenovič A. 03/04/2017

18. Comparison of the batch, GW data and pH dependent data • The main differences between the batch and pH-dependent data, on the one hand, and GW data, on the other hand, is the contact with the landfill material (solubility control), which is absent in the case of GW monitoring Legend: pH-dependent data reference piezometers (P1, P2) piezometers 3-7 batch data (L1-L6) batch data (L7-L11) Fifth International Slag Valorisation Symposium │ Loncnar M, van der Sloot H.A., Zupančič M., Mladenovič A. 03/04/2017

19. Conclusion • The modelling approach used in this study provides benefits for understanding the observed leaching behaviour, which is needed in the case of decisions about future management of waste heap. • It can thus form the basis for the projection of the long-term leachate qualityof the landfill under changing exposure conditions such as carbonation and oxidation. • Bringing together data from various laboratory leaching tests - in particular pH dependence- , field data, and geochemical modelling results, provides a much more complete picture of the release controlling factors in a landfill than can be provided by any single one of these data sources. Fifth International Slag Valorisation Symposium │ Loncnar M, van der Sloot H.A., Zupančič M., Mladenovič A. 03/04/2017

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