Recovery and reutilization of high-quality boron carbide from sapphire wafer grinding-waste

Considerable amounts of high-quality boron carbide (B4C) are discarded as J240 sapphire-wafer grinding waste (J240-W), which can be mostly recovered and reutilized after purification for environmental protection. This paper has developed a feasibility method that simultaneously removes the alumina (Al2O3) and iron (Fe) impurities from J240-W with microwave-assisted acid leaching strategy. The influence factors on the Al2O3 leaching ratio, such as leaching temperature, sulfuric acid concentration, liquid-solid ratio and time, have been investigated and optimized. For comparison, the leaching of Al2O3 with conventional and ultrasound-assisted methods has also been performed. The result indicates that the Al2O3 leaching ratio at 80 °C with microwave assistance is 68.95%, much higher than that of conventional (23.66%) and ultrasound (53.13%) methods. Attributed to the unique heating mode of microwave, the Al2O3 leaching ratio can rise to 95.28% at optimum condition, while the content of purified B4C can reach to 98.22% with the residual Al2O3 and Fe fall to 0.26% and 0.12%, respectively. The recovered B4C with high purity and suitable particle size can be reutilized to manufacture W5 abrasive and W0.5 armor material, which is beneficial for environmental protection and resources reutilization.