Construction and Mechanism Study of AC–NiO/Bi (Fe) Antibacterial Material for Bacteria Removal in Water

Although inorganic antibacterial materials that use photocatalytic technology are widely used to inhibit bacterial growth in water bodies, the external light environment limits the efficient utilization of photocatalytic antibacterial materials. The antibacterial materials are usually in powder form and are not conducive to recycling and reuse, limiting their development in practical applications. The main antibacterial ingredient (nickel oxide) was combined with Macadamia nutshell activated carbon (AC) to maintain efficient contact between bacteria and antibacterial active ingredients to apply the material for water treatment. First, different activators (H₃PO₄, ZnCl₂, and KOH) were used to prepare activated carbon (AC) from Macadamia nutshells. Among the three activators, the AC prepared with H₃PO₄ exhibited the largest specific surface area with well-dispersed pores. Then, Bi and Fe were doped to AC-NiO to improve their antibacterial and magnetic properties. After doping, the antibacterial rate increased to 95% with significantly improved magnetic properties. Moreover, AC-NiO/Bi and AC-NiO/Fe exhibited three antibacterial mechanisms: physical damage, ionic dissolution, and oxidative stress. Finally, the antibacterial test was performed on real water samples from Dianchi Lake in China. Results suggested that AC-NiO/Bi and AC-NiO/Fe could destroy microorganisms in river water samples. The material showed significant adsorption and degradation efficiency for malachite green, methylene blue, and methyl orange dyes. Since the composite material possessed excellent magnetic separation performance, it was easily recovered after use, effectively avoiding secondary pollution while reducing the material cost in practical applications.