Hydrothermal Synthesis of Hierarchical Boehmite from Co-Processed Stainless Steel Dust and Aluminum Dross Residue

Stainless steel dust and aluminum dross are large-volume solid wastes in the metallurgical industry. Synergistic treatment of these wastes recovers some metals but yields an Al-rich residue (Al2O3 > 50%) that represents both a resource loss and an environmental threat if untreated. In this work, boehmite (γ-AlOOH) was synthesized via a hydrothermal route using the Al-rich residue as the aluminum source. The aim was to valorize this waste stream while comprehensively evaluating the product’s phase, morphology, pore characteristics, efficacy and underlying mechanism for Cr(VI) removal from aqueous solutions. The hydrothermal process was optimized as pH = 11.0, under which high-purity and well-crystallized γ-AlOOH was successfully prepared without harmful by-products. The product had uniform particle size distribution without obvious agglomeration, with a specific surface area of 156.7 m2/g, pore volume of 0.60 cm3/g and average pore diameter of 14.6 nm. The boehmite synthesized at pH 11.0 achieved a Cr(VI) removal efficiency of 31.28% and a maximum adsorption capacity of 15.64 mg/g. This study provides a new path for the resource utilization of high-aluminum residue, with both environmental and economic benefits and potential application value.