Preparation and performance of porous ceramsite for Ag+ removal in sewage treatment with total phosphorus tailings

Porous ceramsite used for the adsorption of heavy metal ions in sewage was prepared with total phosphorus tailings as raw material, which can not only reduce the environmental problems caused by the accumulation of phosphorus tailings, but also achieve the goal of “treating waste with waste”. The effects of high-silicon-phosphorus tailings addition, sintering temperature and soaking time on the properties of porous ceramsite were studied, also the mechanism of heavy metal solidification and Ag+ adsorption from sewage were revealed. The results indicated that the porous ceramsite exhibited excellent comprehensive properties after sintered at 1085 °C for 1.5 h, whose apparent porosity was 47.3%, bulk density was 1.53 g/cm3, compressive strength was 2.85 MPa, water adsorption was 27.05% and hydrochloric acid solubility was 8.5%. Furthermore, the preparation of porous ceramsite contributed to the solidification of heavy metals in phosphorous tailing due to the formation of liquid phase during the sintering. The leaching concentration of heavy metals within porous ceramsite was much lower than that in phosphorus tailings, which were far below the standard (GB 8978-1996). In addition, the numerous micropores formed by the decomposition of phosphorus tailings endowed the porous ceramsite with excellent adsorption ability. The removal efficiency of Ag+ by NaCl solution modified porous ceramsite could reach to 99.9% in the process of sewage treatment.