Solar-driven semi-conductor photocatalytic water treatment (TiO2, g-C3N4, and TiO2+g-C3N4) of cyanotoxins: Proof-of-concept study with microcystin-LR

• Published in: Chemosphere (Oxford) 2023-01, Vol.310, p.136828-136828, Article 136828
• Main Authors: Pestana, Carlos J., Hui, Jianing, Camacho-Muñoz, Dolores, Edwards, Christine, Robertson, Peter K.J., Irvine, John.T.S., Lawton, Linda A.
• Format: Article
• Language: English
• Subjects: Graphitic-carbon nitride; In-reservoir treatment; Titanium dioxide; Visible light photocatalysis; Water treatment
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2022.136828

Cyanobacteria and their toxins are a threat to drinking water safety as increasingly cyanobacterial blooms (mass occurrences) occur in lakes and reservoirs all over the world. Photocatalytic removal of cyanotoxins by solar light active catalysts is a promising way to purify water at relatively low cost compared to modifying existing infrastructure. We have established a facile and low-cost method to obtain TiO2 and g-C3N4 coated floating photocatalysts using recycled glass beads. g-C3N4 coated and TiO2+g-C3N4 co-coated beads were able to completely remove microcystin-LR in artificial fresh water under both natural and simulated solar light irradiation without agitation in less than 2 h. TiO2 coated beads achieved complete removal within 8 h of irradiation. TiO2+g-C3N4 beads were more effective than g-C3N4 beads as demonstrated by the increase reaction rate with reaction constants, 0.0485 min−1 compared to 0.0264 min−1 respectively, with TiO2 alone found to be considerably slower 0.0072 min−1. g-C3N4 based photocatalysts showed a similar degradation pathway to TiO2 based photocatalysts by attacking the C6–C7 double bond on the Adda side chain. [Display omitted] •Sunlight activated g-C3N4 & TiO2+g-C3N4 removed MC-LR in less than 2 h.•TiO2+g-C3N4 removed MC-LR more rapidly than g-C3N4 alone under simulated sunlight.•LC-MS confirmed similar MC-LR degradation pathways by all three catalysts.•Facile coating method of TiO2+g–C3N4–coating allows for ready scale-up of production.•Rapid solar degradation of MC-LR by coated beads ideal for in-reservoir treatment.