Production of high-value-added lightweight glass ceramics based on phosphorus tailings and coal gangue

Solid waste-based lightweight glass ceramics aroused a great deal of attention with the introduction of green building materials. This material demonstrated high performance while alleviating the pressure of waste accumulation. Lightweight glass ceramic was fabricated from phosphorus tailings and coal gangue as raw materials in this work. The effects of phosphorus tailing ratios (50 wt% - 100 wt%) and heat-treatment temperatures (1130 °C–1170 °C) on the pore morphology, properties and toxicity evaluation of lightweight glass ceramics were investigated. Differential Scanning Calorimetry (DSC), and Thermogravimetric mass spectrometry (TG-MS) tests were performed to characterize the sintering behavior of lightweight glass ceramics. The research found that Fe2O3 in the phosphorus tailings and C and FeS2 within the coal gangue achieve in-situ foaming by creating the gas at elevated temperatures. Results revealed that increasing the proportion of phosphorus tailings facilitated the generation of the molten glassy phase, which favored the formation of bubbles and the expansion of pores. The average pore size of lightweight glass ceramics enlarged from 15.33 μm to 75.02 μm upon increasing the amount of phosphorus tailings from 50 wt% to 100 wt%. Increasing the amount of the glassy phase could be achieved by adjusting the heat-treatment temperature. This not only formed a protective film preventing water penetration into the interior of the lightweight glass ceramics but also effectively protected them from corrosion by acidic and alkaline solutions. The water absorption dropped dramatically from 16.44 % to 3.63 % and the corrosion resistance was greater than 98 % when the temperature rose from 1130 °C to 1170 °C. From the toxicity evaluation, the leaching toxicity of Cr, Cu, Pb and Zn in lightweight glass ceramics was 4 orders of magnitude below the limiting value and an extremely low potential ecological risk index (RI = 3.32) was obtained. The optimal preparation parameters were phosphorus tailings addition of 80 wt% and a heat-treatment temperature of 1160 °C. The corresponding porosity, bulk density, compressive strength, water absorption, acid resistance and alkali resistance were 51.29 %, 1.38 g/cm3, 10.62 MPa, 4.81 %, 98.63 % and 99.96 %. The findings of the research offered a feasible solution for the development of novel green building materials, simultaneously reducing the environmental hazards of solid wastes.