Resource utilization of high aluminum alkaline waste solution to prepare active alumina carrier

The recycling of precious metals from spent aluminum-based catalysts generates a large amount of high-Al alkaline waste solutions, which not only cause a serious waste of aluminum resources, but also may have a negative impact on the environment due to their strong alkalinity. At present, there are few researches on the resource utilization of these high-Al alkaline waste solutions, an investigation into the re-preparation of active alumina carrier from a high-Al alkaline waste solution ([Al] 6.594 g/L, pH 14) of spent Pd-Al₂O₃ catalysts by the carbonating-roasting process was performed in this paper. First, the carbonating method was adopted to treat the waste solution, converting the Al therein to pseudo-boehmite; then, the pseudo-boehmite underwent roasting to re-make alumina carrier. Experimental results showed that the P content of 2% ~3% and the caustic ratio (i.e., [Na₂O] to [Al₂O₃] ratio) of 1.5 in the waste solutions are conducive to the significant increase in the specific surface area and dispersion index for the pseudo-boehmite products. In addition, the pseudo-boehmite, after performing, was subjected to roasting under the conditions of temperature 450 ℃, holding time 3.5 h, and heating rate 100 ℃/h, which successfully obtained γ-Al₂O₃ catalyst carrier that meet the product quality index. This process can achieve the high-efficient resource reuse of high-Al alkaline waste solutions with eco-friendliness and without generation of the three wastes, thus making it promising for industrial application.