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Comparative leaching behavior and immobilization of heavy metals in ceramic matrices derived from refinery oily sludge using TCLP and EN 12457‐2

Year: 2026

Type: article

Abstract: The increasing generation of refinery oily sludge (ROS) poses significant environmental challenges due to its high content of hazardous heavy metals, requiring effective stabilization methods. This study investigated the leaching behavior and immobilization efficiency of 31 elements in ceramic matrices incorporating ROS, comparing the toxicity characteristic leaching procedure and European standard (EN) 12457-2 protocols to evaluate environmental risk. Ceramic specimens were prepared with 0, 5, and 10 wt.% ROS and sintered at 950°C and 1050°C. Leachates were analyzed via inductively coupled plasma mass spectrometry to quantify elemental mobility. Results demonstrated high immobilization efficiency; Cu remained consistently below detection limits (<0.001 mg/kg) in all samples, while Zn concentrations remained stable across both firing temperatures and protocols. Firing temperature significantly influenced Cr mobility; in the EN 12457-2 protocol, increasing the temperature to 1050°C reduced Cr leaching from 0.529 mg/kg to undetectable levels for 5% wt. ROS content. However, specific variations were observed at higher waste loadings, with Cr reaching 4.590 mg/kg in the 10% wt. ROS samples at 1050°C, suggesting complex phase transformations. Ni was consistently immobilized below detection limits, and Pb showed minimal mobility in isolated cases. These findings confirm that ceramic processing is a viable stabilization technique for ROS, generally reducing metal mobility below regulatory limits. The study concludes that while higher sintering temperatures enhance the matrix stability for most elements through vitrification, the interaction between waste loading and temperature is non-linear, requiring precise optimization for large-scale applications.

Source: Journal of Environmental Quality

DOI: 10.1002/jeq2.70323

Authors: Dimitra Kaffe, Xenophon Spiliotis

Institution: University of Thessaly

Language: English

Topic: Recycling and utilization of industrial and municipal waste in materials production

Subfield: Building and Construction

Field: Engineering

Domain: Physical Sciences

SDG: Responsible consumption and production

Open Access status: hybrid

Estimated APC paid: $1,910