Resourceful reuse and performance evaluation of modified electrolytic aluminum spent cathode carbon block material as cement admixture

In order to address the environmental hazards and sustainable recycling of spent cathode carbon block (SCCB), this study designed a one-step strategy of "breaking cyanide-sinking fluoride-polydopamine wrapping" and a secondary modification of nanoscale SiO2 grafting. The impact of modified SCCB on cement was also investigated. The results showed that, after harmless treatment, the fluoride and cyanide concentrations of SCCB decreased to 7.3 mg/L (<10 mg/L) and 0.024 mg/L (<1 mg/L), respectively, thereby effectively treating harmful ions. In addition, based on the excellent mechanical properties of highly graphitized carbon blocks in SCCB and the volcanic ash effect of nanoscale SiO2, the dispersibility of SCCB in cement was enhanced, which consequently strengthened mechanical interlocking ability between SCCB and cement. This slightly improved the mechanical properties of cement mortar. These findings concurrently provide a safe and practical approach for the disposal of SCCB and a novel additive material for construction and building materials.