Paraquat Degradation by Biological Manganese Oxide (BioMnO x ) Catalyst Generated From Living Microalga Pediastrum duplex AARL G060.

Jakkapong Thongpitak,Chayakorn Pumas,Pamon Pumas

doi:10.3389/fmicb.2020.575361

Jakkapong Thongpitak, Chayakorn Pumas + Show 1 more

Open Access

https://doi.org/10.3389/fmicb.2020.575361

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Abstract

Paraquat is a non-selective fast-acting herbicide used to control weeds in agricultural crops. Many years of extensive use has caused environmental pollution and food toxicity. This agrochemical degrades slowly in nature, adsorbs onto clay lattices, and may require environmental remediation. Studies have shown that biosynthesized manganese oxide (BioMnOx) successfully degraded toxic synthetic compounds such as bis-phenol A and diclofenac, thus it has potential for paraquat degradation. In this experiment, P. duplex AARL G060 generated low (9.03 mg/L) and high (42.41 mg/L) concentrations of BioMnOx. The precipitated BioMnOx was observed by scanning electron microscopy (SEM), and the elemental composition was identified as Mn and O by energy-dispersive x-ray spectroscopy (EDS). The potential for BioMnOx to act as a catalyst in the degradation of paraquat was evaluated under three treatments: (1) a negative control (deionized water), (2) living alga with low BioMnOx plus hydrogen peroxide, and (3) living alga with high BioMnOx plus hydrogen peroxide. The results indicate that BioMnOx served as a catalyst in the Fenton-like reaction that could degrade more than 50% of the paraquat within 72 h. A kinetic study indicated that paraquat degradation by Fenton-like reactions using BioMnOx as a catalyst can be described by pseudo-first and pseudo-second order models. The pH level of the BioMnOx catalyst was neutral at the end of the experiment. In conclusion, BioMnOx is a viable and environmentally friendly catalyst to accelerate degradation of paraquat and other toxic chemicals.

Highlights

Non-selective herbicides, such as glyphosate and paraquat, were developed based upon their antagonistic effects on non-specific species of weeds and crops
The results show that P. duplex Algal Research Laboratory (AARL) G060 grow well in the control medium (Figure 1A)
Mn was later detected in the energy-dispersive x-ray spectroscopy (EDS) spectrum after 6 days of cultivation, and the biosynthesized manganese oxide (BioMnOx) consisted of Mn and O in the complex (Figure 3C)

Summary

Introduction

Non-selective herbicides, such as glyphosate and paraquat, were developed based upon their antagonistic effects on non-specific species of weeds and crops. Previous studies reported paraquat contamination in many countries worldwide (Huang et al, 2019). A paraquat concentration of 3.95 μg/L was reported in water samples from irrigation channels and rivers in Spain (Fernández et al, 1998). Paraquat residue in surface water in Brazil was found to be 0.279 μg/L (Veríssimo et al, 2018). Paraquat concentrations of 9.3– 87.0 μg/L were reported in surface water in Thailand (Insuwan and Rangsriwatananon, 2017). In Malaysia, 0.6–6.9 μg/L of paraquat residue was detected in water samples (Ismail et al, 2011). These contaminants accumulate in the food chain creating public health hazards for humans, animals, and the environment (Frimpong et al, 2018)

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