Toxicity evaluation of TiO2/MWCNT-CNF hybrid nanocomposites with enhanced photocatalytic activity toward freshwater microalgae: Pseudokirchneriella subcapitata

Terrence S Malatjie; Tarryn L Botha; Alex T Kuvarega; Ntakadzeni Madima; Karin de Bruyn; Memory Tekere; Thabo T I Nkambule; Bhekie B Mamba; Titus A M Msagati

doi:10.1016/j.chemosphere.2021.132891

Toxicity evaluation of TiO₂/MWCNT-CNF hybrid nanocomposites with enhanced photocatalytic activity toward freshwater microalgae: Pseudokirchneriella subcapitata

Chemosphere. 2022 Mar;291(Pt 2):132891. doi: 10.1016/j.chemosphere.2021.132891. Epub 2021 Nov 17.

Authors

Terrence S Malatjie¹, Tarryn L Botha¹, Alex T Kuvarega¹, Ntakadzeni Madima¹, Karin de Bruyn², Memory Tekere³, Thabo T I Nkambule¹, Bhekie B Mamba¹, Titus A M Msagati⁴

Affiliations

¹ Institute for Nanotechnology and Water Sustainability, College of Science, Engineering and Technology, University of South Africa, Florida Science Campus, P/Bag X6, Roodepoort, 1709, South Africa.
² College of Agriculture and Environmental Sciences Laboratories, University of South Africa, Science Campus, Florida, Johannesburg, 1710, South Africa.
³ Department of Environmental Sciences, College of Agriculture & Environmental Sciences, University of South Africa, Florida Science Campus, P/Bag X6, Roodepoort, 1709, South Africa.
⁴ Institute for Nanotechnology and Water Sustainability, College of Science, Engineering and Technology, University of South Africa, Florida Science Campus, P/Bag X6, Roodepoort, 1709, South Africa. Electronic address: msagatam@unisa.ac.za.

PMID: 34800499
DOI: 10.1016/j.chemosphere.2021.132891

Abstract

A wide range of semiconductor-assisted photocatalytic nanomaterials (NMs) are currently being considered and investigated as potential photocatalysts in water treatment. The applications of nanocomposites composed of nano-structured titania (nano-TiO₂) and multi-walled carbon nanotubes (MWCNTs) nanocomposites is growing markedly on account of enhanced photocatalytic efficiency. However, concurrent with the increasing production and application comes a serious concern of these emerging nanosystems about their potential risks in aquatic systems, and thereby potentially threatening aquatic organisms via toxic mechanisms that are, at present, poorly understood. In the present study, the lethal toxic effect and oxidative stress induced by TiO₂/MWCNT-CNF nanocomposite in freshwater Pseudokirchneriella subcapitata were assessed. The growth inhibition and sublethal oxidative stress produced by the nanocomposites were evaluated on green microalgae P. subcapitata after 3 days of exposure at 24 h intervals. Moreover, the nanocomposites were physicochemically characterized using a combination of analytical techniques (XRD, SEM/EDS, HRTEM, TGA, UV-Visible spectroscopy). Evaluation of the hybrid for the photocatalytic degradation of Acid Violet 7 dye indicated an enhanced dye removal performance for TiO₂/MWCNT-CNF (96.2%) compared to TiO₂ (75.2%) after 2 h of visible light irradiation. While the nanocomposite showed good potential for the degradation of the azo dye, overall, the findings herein indicated that acute exposure of P. subcapitata to various concentrations of TiO₂/MWCNT-CNF nanocomposite may cause algal growth inhibition including undesirable sublethal oxidative stress effects. The findings of this study contribute to a better understanding of the potential hazards of the developing nanocomposites materials towards the nano-bioremediation materials to treat wastewaters.

Keywords: Algae; Carbon nanomaterials; Nanocomposite; Photocatalysis; Titanium dioxide; Toxicity.

MeSH terms

Catalysis
Fresh Water
Microalgae*
Nanocomposites* / toxicity
Nanotubes, Carbon* / toxicity
Titanium / toxicity

Substances

Nanotubes, Carbon
titanium dioxide
Titanium