Production of green, low-cost and high-performance anorthite-based ceramics from reduced copper slag

Abstract

Waste slags are promising sources of ceramic materials, but slag-derived ceramics also show inferior whiteness and quite different constituents compared to commercial products due to the introduction of impurity elements. To solve this issue, in this work, reduced copper slag after iron and copper extraction was used as a new raw material to prepare novel anorthite-based ceramics. The role of slag addition in the sintering, microstructure, physical and mechanical properties, leaching behavior, and color quality was investigatedby using different characterization techniques such as DSC-TG, XRD, SEM, spectrophotometer, Archimedes method, 3-point bending method, and acetic acid buffer solution method. The results show that the ceramics are more effective in liquid generation with the slag addition, significantly enhancing the sintering and reducing the porosity. The slag also favors the development of anorthite grains as it is an Al2O3-SiO2-CaO-based system. As a result, a dense and well-bonded structure with few impurity phases and fine rounded pores is produced with 40 wt% of slag addition. These effects contribute to a remarkable improvement in flexural strength (87.6 MPa) and good maintenance of whiteness (∼90). Moreover, its leaching toxicity is ∼ 3 orders of magnitude lower than the thresholds. The high strength, appearance quality and cleanliness are the competitive advantages of the designed ceramics compared to other slag-derived ceramics. However, limited densification and severe blisters and bloating appear after introducing more than 50 wt% of slag, leading to a much inferior mechanical and color performance.