Studies on degradation of glyphosate by several oxidative chemical processes: Ozonation, photolysis and heterogeneous photocatalysis

Background: removing a widely used herbicide from water

Glyphosate is one of the most widely applied herbicides in the world, sold in formulations such as Roundup. Because it is used in such large volumes, residues of glyphosate and its main breakdown product, aminomethylphosphonic acid (AMPA), can find their way into surface water and groundwater. Conventional water treatment does not always remove these compounds efficiently, so researchers have looked at advanced oxidation processes - methods that generate highly reactive hydroxyl radicals to break pollutants down. This study set out to compare several of these processes, including ozonation, to see which was most effective at degrading glyphosate in water.

Study design: comparing ozonation, photolysis and photocatalysis

This was a laboratory experiment. The researchers prepared aqueous solutions of glyphosate and treated them using several advanced oxidation processes: ozonation at two different acidity levels (pH 6.5 and pH 10), ultraviolet photolysis, and heterogeneous photocatalysis using titanium dioxide (TiO2) as a semiconductor catalyst with dissolved oxygen. For each process they tracked how quickly glyphosate broke down, measured the reaction kinetics, and monitored the formation of the degradation intermediate AMPA and the extent of mineralisation (conversion of the herbicide into simpler inorganic compounds).

Findings: ozonation at high pH broke glyphosate down fastest

Processes that generate hydroxyl radicals proved the most effective. Ozonation carried out at pH 10 produced the greatest mineralisation of glyphosate, outperforming ozonation at neutral pH, photolysis alone, and titanium dioxide photocatalysis. The degradation followed first-order kinetics, and under the O3/pH 10 conditions the half-life of glyphosate was around 1.8 minutes - a rapid breakdown over a short treatment time. The intermediate AMPA was also degraded under these conditions.

What the authors concluded

The authors concluded that advanced oxidation processes based on hydroxyl-radical formation, and ozonation at elevated pH in particular, are an effective route for degrading glyphosate and its intermediate AMPA in water. Ozonation at pH 10 gave the best mineralisation of the methods tested, achieving fast and predictable degradation.

Limitations of this study

This was a small-scale laboratory study using prepared aqueous solutions rather than real-world water sources, which contain other dissolved substances that can affect how treatment performs. It compared a limited set of processes under controlled conditions and did not assess large-scale or continuous treatment systems. The work concerns the chemistry of degrading a herbicide in water; it does not address human health outcomes and makes no claims about ozone as a therapy. It illustrates ozone's ability to oxidise and break down a persistent contaminant in water under the conditions tested.