Preparation of lightweight ceramsite by stone coal leaching slag, feldspar, and pore-forming reagents

In this study, lightweight ceramsite was prepared by stone coal leaching slag (SCLS), feldspar, and various pore-forming reagents via the roasting process, and the effect of raw meal ratio, roasting temperature, and roasting dwelling time on ceramsite features was investigated through orthogonal and single-factor experiments. The bulk density of ceramsite decreased from 900.0 to 762.0 kg/m3 when the content of Fe2O3 increased from 0 to 6 %. Under the optimal conditions (SCLS: feldspar: Fe2O3 = 65: 29: 6 and roasting at 1150 °C for 25 min), the ceramsite possessed a bulk density of 762 kg/m3 and water absorption of 2.4 %, which meet the Chinese standards for ceramsite (GB/T 17431.1–2010). The adsorption of the ceramsite was then characterized by different adsorption models and adsorption–desorption curves. The specific surface area of prepared ceramsite was 1.717 m2/g, which was suitable to produce adsorption materials. X-ray diffraction (XRD) results showed that the peak intensity of quartz and feldspar decreased and the cristobalite phase appeared with the increase in temperature, which helps to enhance the strength of sintered ceramsite. The major crystalline phases of the prepared ceramsite were quartz, feldspar, hematite, and cristobalite at 1,150 °C. The leaching concentration of heavy metals in ceramsite was far below the limited value of GB 5085.3–2007, which means that heavy metals were wrapped inside ceramsite. This study demonstrates a practical use for SCLS, potentially eliminating its damage to the environment, and provides guidance for SCLS-based ceramsite production.