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

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

University of South Africa

Research output: Contribution to journal › Article › peer-review

14 Citations (Scopus)

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.

Original language	English
Article number	132891
Journal	Chemosphere
Volume	291
DOIs	https://doi.org/10.1016/j.chemosphere.2021.132891
Publication status	Published - Mar 2022
Externally published	Yes

Keywords

Algae
Carbon nanomaterials
Nanocomposite
Photocatalysis
Titanium dioxide
Toxicity

ASJC Scopus subject areas

Environmental Engineering
Environmental Chemistry
General Chemistry
Pollution
Public Health, Environmental and Occupational Health
Health, Toxicology and Mutagenesis

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

Access to Document

10.1016/j.chemosphere.2021.132891

Cite this

Malatjie, T. S., Botha, T. L., Kuvarega, A. T., Madima, N., de Bruyn, K., Tekere, M., Nkambule, T. T. I., Mamba, B. B., & Msagati, T. A. M. (2022). Toxicity evaluation of TiO₂/MWCNT-CNF hybrid nanocomposites with enhanced photocatalytic activity toward freshwater microalgae: Pseudokirchneriella subcapitata. Chemosphere, 291, Article 132891. https://doi.org/10.1016/j.chemosphere.2021.132891

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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",

author = "Malatjie, {Terrence S.} and Botha, {Tarryn L.} and Kuvarega, {Alex T.} and Ntakadzeni Madima and {de Bruyn}, Karin and Memory Tekere and Nkambule, {Thabo T.I.} and Mamba, {Bhekie B.} and Msagati, {Titus A.M.}",

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T2 - Pseudokirchneriella subcapitata

AU - Malatjie, Terrence S.

AU - Botha, Tarryn L.

AU - Kuvarega, Alex T.

AU - Madima, Ntakadzeni

AU - de Bruyn, Karin

AU - Tekere, Memory

AU - Nkambule, Thabo T.I.

AU - Mamba, Bhekie B.

AU - Msagati, Titus A.M.

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AB - 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.

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KW - Nanocomposite

KW - Photocatalysis

KW - Titanium dioxide

KW - Toxicity

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