Effective removal of emerging dissolved cyanotoxins from water using hybrid photocatalytic composites

• Published in: Water research (Oxford) Vol. 149; no. C; pp. 421 - 431
• Main Authors: Chae, Soryong, Noeiaghaei, Tahereh, Oh, Yoontaek, Kim, In S., Park, Jin-Soo
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.02.2019; Elsevier
• Subjects: Adsorption; Cyanotoxins; Harmful algal blooms; Hybrid photocatalytic composites; Photocatalytic activity; Reactive oxygen species; Hybrid photocatalytic composites; Photocatalytic activity; Harmful algal blooms; Reactive oxygen species; Adsorption; Cyanotoxins
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2018.11.016

Harmful algal blooms are occurring more frequently in fresh water throughout the world. Certain cyanobacteria can produce and release potent toxic compounds, known as cyanotoxins, such as microcystins, cylindrospermopsin, saxitoxin, and anatoxin-a, and as such they have become a human and environmental health concern. Hybrid photocatalytic composites (HPCs) comprising carbon nanotubes on the surface of TiO2 nanotubes were designed in this study. The HPCs have a selective adsorption capacity to cyanotoxins and provide photocatalytic activity to produce reactive oxygen species for the degradation of cyanotoxins. HPCs with 5.2 mg carbon nanotubes/cm2 showed an excellent removal efficiency of microcystins-LR (>95%) at 55.6 L/m2/hr/bar. The HPCs more efficiently removed the relatively larger and more hydrophobic cyanotoxins (i.e., microcystin-LR) than the relatively smaller and more hydrophilic compounds, such as cylindrospermopsin, saxitoxin, and anatoxin-a. With a further increased in the carbon nanotube content to 8.6 mg/cm2, the adsorption capacity of the HPCs for cyanotoxins increased to 70.6% for MC-LR. However, there was significant decrease in the photocatalytic activity of the HPCs for production of reactive oxygen species, and consequently a decrease in the degradation of cyanotoxins. It is considered that this device could be used to provide complete rejection of particles and pathogens, and also to significantly reduce trace organic compounds and harmful algal toxins in emergency water supplies. [Display omitted] •Hybrid composites comprising carbon nanotubes on TiO2 nanotubes were designed.•Hybrid composites have a selective adsorption capacity to cyanotoxins.•Hybrid composites provide photocatalytic activity to produce reactive oxygen species.•Hybrid composites showed an excellent removal efficiency of microcystins-LR (>96%).•Water permeability of hybrid composites was more than 10 times that of a nanofiltration membrane.