Photocatalytic inactivation of harmful algae and degradation of cyanotoxins microcystin-LR using GO-based Z-scheme nanocatalysts under visible light

Abstract Three kinds of GO-based Z-scheme photocatalytic materials were synthesized to remove harmful algae and Microcystins-LR (MC-LR). The physicochemical properties of the photocatalysts were characterized. The inhibitory effects of three photocatalysts on the growth of algae under visible light were compared. The photocatalytic degradation pathways and mechanism of MC-LR by Ag2CO3-GO were proposed. The results showed that the combination modes and morphology size of GO-based Z-scheme photocatalysts had grade effects on the degradation of MC-LR. Ag2CO3-GO exhibited the best photocatalytic activity among these GO-based Z-scheme photocatalysts, which could remove nearly 100% MC-LR (0.3 mg/L) within 1 h under visible light. The degradation rate of MC-LR by Ag2CO3-GO fit well with the pseudo-first-order kinetic model and was significantly influenced by pH. The degradation of MC-LR by Ag2CO3-GO was also inhibited by the alkalinity, DOM, H2O2, and the coexistence of algae cells. The experimental results showed that ·OH and O2- played the main role in the photocatalysis of MC-LR by Ag2CO3-GO, and the Adda side chain and peptide ring in MC-LR were gradually oxidized, indicating that the biological toxicity of MC-LR was gradually lost during the degradation process. Besides, 100 mg/L of Ag2CO3-GO could obviously inhibit the growth of harmful algae, which could oxidize and damage algae cells, and further degrade their released contents under visible light, thus avoiding the secondary pollution effectively. In summary, GO-based Z-scheme photocatalysts have a promising future for the inactivation of harmful cyanobacteria and degradation of MC-LR.