Evaluation of eco-label properties and heavy metal leachability in fired clay bricks incorporating ceramic sludge

Large-scale industrial production generates significant amounts of semi-solid waste containing heavy metals. Ceramic industrial sludges, in particular, are potentially hazardous because these metals are toxic and must be disposed of in conventional landfills and the environment within certain limits. Although previous studies have investigated the incorporation of various sludge types into fired clay bricks, these studies have generally reported leachability or physical performance in isolation, without linking the results to formal eco-label criteria. Consequently, limited research has focused on the environmental safety of ceramic sludge, particularly its compliance with both regulatory and eco-label requirements. Therefore, the objective of this research is to use ceramic sludges from the ceramic industry and perform an evaluation to determine the appropriate proportions or ratios of ceramic sludges in fired clay brick to determine the leaching behaviour of heavy metals and whether they meet the requirements of the standard and the eco-label requirements. Six different ratios (0, 1, 5, 10, 20, and 30%) of ceramic sludge were mixed into fired clay brick and fired at 1050 °C in an observed furnace. The sludge element composition was determined by XRF, and the leaching behaviour of the sludge was evaluated by the TCLP procedure method. The result showed that before and after mixing the raw materials, the pattern decreased for all metals, especially zinc (Zn) and lead (Pb). Although some metals showed marginally lower leaching at higher substitution levels (10-30%), 5% is recommended as the optimum ratio because it achieves full compliance with USEPA and eco-label limits for all measured metals while incorporating the least sludge, offering the most practical and economical balance between waste valorization and environmental safety. In addition, 5% has the lowest value for Cu with 0.187 mg L^-1 and As with 0.032 mg L^-1 compared to the other percentage mixture for Zn, Pb, Al, K and Fe the data are not in the highest values. The novelty of the present study investigates ceramic sludge and provides a comprehensive environmental assessment by integrating TCLP analysis with eco-label compliance evaluation based on USEPA limits and SIRIM ECO 023:2016 criteria.