Evaluation of the encapsulation of nickel, chromium and lead-rich wastes in cement matrices by TCLP test

Abstract

This study focuses on the characterisation of industrial waste coming from an Algerian factory of cutlery and the feasibility of its solidification/stabilisation (S/S) using hydraulic binders. Toxicity characteristic leaching procedure (TCLP) test, XRD and SEM–EDX analyses performed on the raw waste show that the latter has a high potential pollutant due to the presence of heavy metals such as “nickel, trivalent chromium, hexavalent chromium and lead” in high concentrations. Therefore, its S/S by cement seems to be a solution of its storage. For the study of its feasibility, two types of mix design were used with different waste/cement ratios. The initial and final setting times were evaluated for cement pastes. The mechanical strengths were evaluated at 7 and 28 days. Solidified/stabilised materials were submitted to TCLP test after 7 and 28 days. The leachates were analysed by flame atomic absorption spectrophotometry. XRD and SEM–EDX analyses were used to characterise the solidified/stabilised materials compounds. TCLP results highlight the efficiency of S/S treatment by reducing the pollutant potential of the waste. TCLP results show that mortars have a better efficiency in encapsulation pollutants compared to cement pastes, due to the difference in microstructure network between the two materials and the particle size of the waste.