New insight into treatment of foundry waste: porous insulating refractory based on waste foundry sand via a sacrificial fugitive route

Abstract

Waste foundry sand (WFS) accounts for the largest percentage of environmental wastes in the foundry industry and shows an alarming and continuous increase. The treatment of WFS has been investigated previously and mainly as building materials. In this work, the applicability of leaching hazardous WFS in the manufacture of porous thermal insulation material is investigated. Thermodynamic calculation and experimental investigation are performed to evaluate the crystalline composition, microstructure characteristic, strength, and heat-insulating performance, and leaching behavior. In addition to WFS, raw materials include plastic clay, kyanite, and sawdust. High addition of WFS promotes the densification and leads to the remarkable increase in compressive strength. Samples compose of 75 wt% WFS, 15 wt% plastic clay, 10 wt% kyanite, and extra 20 wt% sawdust have a maximum strength of 0.92 MPa and thermal conductivity of 0.11 W (m K)−1 at 200 °C. According to toxicity characteristic leaching procedure analysis, the target metal concentrations in porous material based on WFS are within the US EPA limits, which proves the environmentally friendly application.