(562bc) In Situ Treatment of Cyanotoxins in Water Sources Using Fiber-Immobilized TiO2/Fe Nanoparticle Catalysts

Due
to climate change, nutrient runoff from agriculture, and worsening
eutrophication of water sources, harmful algal blooms (HABs) are globally increasing
in frequency and distribution.^1,2 HABs are cyanobacteria that
accumulate biomass and produce cyanotoxins such as microcystin-LR; 25 to 75% of
HABs are estimated to be toxic.^3,4 Cyanotoxins,
like microcystin-LR, are highly toxic and have a median lethal dose (LD₅₀)
of about 50 µg/kg of body weight, which is equivalent to that of sarin gas.⁴ Because of
nutrient pollution, cyanobacteria and cyanotoxins are becoming more prevalent
and are severely damage ecosystems; cyanobacteria have negative impacts on
ecosystem functions, such as organism relationship disturbances, biodiversity
changes, light conditions, and oxygen concentrations.⁴ Several
animal studies have shown evidence of microcystins exhibiting tumor promoting
properties.⁴ Cyanobacteria
and cyanotoxins adversely impact human health and promote negative health
effects like liver damage, immunotoxicity, and neurotoxicity.⁵ Annually, the
U.S. alone spends $2.2-4.6B on methods, including filtration, flocculation,
coagulation, or sedimentation, to battle the effects of HABs.^1,3,6 However, these methods are only
temporary solutions, and key disadvantages associated with these techniques
include detrimental environmental impacts and inefficiency.¹

Currently,
there is no known method that adequately mitigates both HABs and cyanotoxins
present in water sources. Studies have shown that both titanium dioxide (TiO₂)
and iron nanoparticles can effectively inactivate cyanobacteria while also
reducing available nutrients for algal bloom formation.^1,7 For
cyanotoxin degradation, iron and titanium dioxide nanoparticles have primarily
been studied. Although studies have not focused on cyanotoxin degradation by
the combination of iron and TiO₂, research has shown synergistic
effects between iron and TiO₂ for photocatalytic degradation of
organic pollutants such as methylene blue and hydroquinone.^8–10 One
concern is freely-dispersed nanoparticles in water sources and the effects on
aquatic organisms. While freely-dispersed TiO₂ can cause harmful
effects on some desirable aquatic species, iron nanoparticles have minimal
toxicity effects towards beneficial organisms.^1,7 Therefore,
a novel in situ treatment approach could be the immobilization of TiO₂/Fe
nanoparticle catalyst on a retrievable fiber, which would allow light
activation of nanoparticle catalyst for the deactivation of cyanobacteria and
degradation of cyanotoxin.

This study will focus on the
degradation of cyanotoxins. Continued work for the following will be discussed
specifically: testing commercially available and experimentally synthesized TiO₂
and Fe nanoparticles for cyanotoxin degradation, immobilizing nanoparticles on
fiber, and the evaluation of in situ fiber treatment of cyanotoxins.

References

1.        Marsalek, B. et al. Multimodal action and
selective toxicity of zerovalent iron nanoparticles against cyanobacteria. Environ.
Sci. Technol. 46, 2316–2323 (2012).

2.        He, X. et
al. Toxic cyanobacteria and drinking water: Impacts, detection, and
treatment. Harmful Algae 54, 174–193 (2016).

3.        Meng, X.,
Savage, P. E. & Deng, D. Trash to Treasure: From Harmful Algal Blooms to
High-Performance Electrodes for Sodium-Ion Batteries. Environ. Sci. Technol.
49, 12543–12550 (2015).

4.        Bláha,
L., Babica, P., Maršálek, B. & Luděk Bláha, A. Toxins produced in
cyanobacterial water blooms-toxicity and risks. Interdisc Toxicol 2,
36–41 (2009).

5.        Tucek, J.
& Zboril, R. Multimodal Action and Selective Toxicity of Zerovalent Iron
Nanoparticles against Cyanobacteria. (2012).

6.        Meglič,
A., Pecman, A., Rozina, T., Leštan, D. & Sedmak, B. Electrochemical
inactivation of cyanobacteria and microcystin degradation using a boron-doped
diamond anode — A potential tool for cyanobacterial bloom control. J.
Environ. Sci. (China) 53, 248–261 (2017).

7.        Bessa Da
Silva, M., Abrantes, N., Nogueira, V., Gonç Alves, F. & Pereira, R. TiO 2
nanoparticles for the remediation of eutrophic shallow freshwater systems:
Efficiency and impacts on aquatic biota under a microcosm experiment. Aquat.
Toxicol. 178, 58–71 (2016).

8.        Mazille,
F., Schoettl, T. & Pulgarin, C. Synergistic effect of TiO2 and iron oxide
supported on fluorocarbon films. Part 1: Effect of preparation parameters on
photocatalytic degradation of organic pollutant at neutral pH. Appl. Catal.
B Environ. 89, 635–644 (2009).

9.        Wang, Q.,
Xu, S. & Shen, F. Preparation and characterization of TiO2 photocatalysts
co-doped with iron (III) and lanthanum for the degradation of organic
pollutants. Appl. Surf. Sci. 257, 7671–7677 (2011).

10.      Wang, X.,
Tang, Y., Leiw, M. Y. & Lim, T. T. Solvothermal synthesis of Fe-C codoped
TiO2 nanoparticles for visible-light photocatalytic removal of emerging organic
contaminants in water. Appl. Catal. A Gen. 409–410, 257–266
(2011).