RED MUD AS AN ALTERNATIVE MATERIAL FOR THE PRODUCTION OF A GEOTECHNICAL COMPOSITE Vesna ZALAR SERJUN, Ana MLADENOVIĆ, Radmila MILAČIČ, Janez ŠČANČAR, Ana AŠLER, Nina ZUPANČIČ, Irena NIKOLIĆ, Primož OPRČKAL Athens, 7-10 May 2018, 2nd Bauxite Residue Valorisation and Best Practices Conference

INTRODUCTION INTRODUCTION RED MUD (RM) 170 million tonnes produced worldwide in 2015 environmental issues: high alkalinity, the possible presence of PTE, and their leachability efficient utilization recovery of immobilization potential due to critical raw materials high sorption capacity BR2018

INTRODUCTION INTRODUCTION CONTAMINATED SOIL (CS) 342,000 contaminated sites in the EU a legacy of the inappropriate disposal and treatment of waste, caused by industrial / mining activities After: OPRČKAL, P., Innovative approaches for sustainable remediation of contaminated waters and soils : doctoral dissertation, Ljubljana, 2018. 175 pp. PTE 34,8 % After: EEA, Progress in management of contaminated sites (CSI 015). Copenhagen: European Environment Agency, 2017 • potential routes for the migration of contaminants BR2018

INTRODUCTION INTRODUCTION IMMOBILIZATION chemical / physical mechanisms to prevent bioavailability, and to reduce the toxicity and mobility of potential toxic elements (PTE) The Best Available Technology mixing the soil with additives After OʹDay, P., Vlassopoulos, D., 2010. Mineral-Based Amendments for Remediation. Elements, 6, pp.: 375-381. BR2018

AIM OF RESEARCH AIM OF THE RESEARCH To verify: • the potential of RM to be used as an additive for the immobilization of PTE in CS • the environmental and geotechnical properties of an CS/RM composite BR2018

MATERIALS & METHODS MATERIALS & METHODS RM: Podgorica, an open disposal site (Uniprom-KAP, Montenegro) CS: one of the largest and most degraded areas in Slovenia (the 17 ha brownfield site of the Old Zinc-Works, Celje) geotechnical composite: blending the CS with 25 wt.% of RM and the optimal amount of water; compaction up to maximum dry density (according to the Modified Proctor Compaction Test) RM, CS: physical properties, chemical composition, phase composition CS/RM geotechnical composite: physical and mechanical properties, the tank leaching procedure (after 7, 28, 56 days) BR2018

BET Specific surface area (m2/g) RESULTS RESULTS RM, CS – physical properties Parameter RM CS BET Specific surface area (m2/g) 20.1 10.0 Density (Mg/m3) 3.07 2.71 RM CS BR2018

RESULTS RESULTS RM, CS – total chemical composition Parameter RM CS (%) Al2O3 17.84 9.57 CaO 20.85 7.46 Fe2O3 19.50 11.95 K2O 0.33 0.27 MgO 0.85 3.76 P2O5 0.32 5.03 SiO2 8.11 24.43 SO3 0.82 6.59 Parameter CS Critical limit values* (mg/kg) As 1790.0 55.0 Cd 166.0 12.0 Cr 78.6 380.0 Cu 1132.0 300.0 Hg 215.0 10.0 Mo 51.5 200.0 Ni 213.0 210.0 Pb 20460.0 530.0 Zn 146290.0 720.0 * According to the Decree on limit values, alert thresholds and critical levels of dangerous substances into the soil (Official Gazette of RS, Nos. 68/96, 41/04 – ZVO-1,1996. BR2018

Inertness limit values * RESULTS RESULTS RM, CS – chemical analysis of leachates Parameter RM CS Inertness limit values * (mg/kg d.m.) As 0.49 0.05 0.5 Ba <0.01 0.80 20 Cd 0.34 0.04 Cr 0.03 Cu 2.2 0.08 2 Hg 0.01 Mo 0.31 0.11 Ni 0.06 0.4 Pb 0.48 Sb Se 0.02 0.1 Zn 0.10 22.6 4 SO42- 100 10010 6000 Cl- 280 37.6 800 pH 9.0 7.4 Cond. (mS/cm) 0.3 1.45 * According to Decree on Waste Landfill (Official Gazette of RS, Nos. 36/16, 2016) BR2018

RESULTS RESULTS RM, CS - mineral composition RM CS BR2018

RESULTS RESULTS CS/RM COMPOSITE The Modified Proctor Procedure (SIST EN 13286-2, 2005) Dry density: 1.67 Mg/m3 Optimum water content: 16.1 wt.% Water permeability (after 28 days): 7.88×10-8 m/s Unconfined compressive strength (after 3, 7, 28, 56 days): 0.53 - 0.7 MPa BR2018

RESULTS RESULTS CS/RM COMPOSITE Mineral composition – no new phases! BR2018

RESULTS RESULTS CS/RM COMPOSITE Leaching test (after 7, 28, 56 days) (SIST EN 1744-3, 2002) BR2018

RESULTS RESULTS CS/RM COMPOSITE Leaching test (after 56 days) SO42- Zn Cd Pb (mg/kg d.m.) Contaminated soil 10010 22.60 0.34 0.48 CS/RM Composite 3250 0.61 0.007 0.01 Quotient 3 37 48 Limit values* 6000 4 0.04 0.5 * According to Decree on Waste Landfill (Official Gazette of RS, Nos. 36/16, 2016 BR2018

CONCLUSIONS CONCLUSIONS RM is an effective additive for the immobilization of PTE in a CS/RM geotechnical composite. Surface sorption was the main immobilization mechanism in the CS/RM composite. The CS/RM composite complies with the prescribed limit values for inert materials according to the Slovenian landfilling legislation. BR2018

CONCLUSIONS CONCLUSIONS The investigated CS/RM composite can be used for the rehabilitation of contaminated sites, as fill or for the construction of embankments. BR2018

THANK YOU FOR YOUR ATTENTION vesna.zalar@zag.si primoz.oprckal@zag.si BR2018