Uptake, accumulation and metabolization of 1-butyl-3-methylimidazolium bromide by ryegrass from water: Prospects for phytoremediation

Abstract

The unique properties of ionic liquids make them attractive for a wide range of industrial applications, which makes it easy to be released into the environment and cause water or soil pollution. Phytoremediation of organic contaminants is a safe and important process for removing persistent pollutants from the environment. However, due to they are very chemically stable and potentially toxic to plants, whether they can be removed, assimilated and metabolized by plants remains unknown during phytoremediation process. In this study, ryegrass, Lolium perenne L., was used for imidazolium ionic liquid (1-butyl-3-methylimidazolium bromide, [C4mim]+) removal from water. The results show that [C4mim]+ could be taken up, accumulated and metabolized by plants in vivo with a high removal efficiency. Most of the [C4mim]+ was accumulated in the root tissue, with the root concentration fraction factors ranging from 4.9 to 51.5. Two hydroxylated metabolites 1-(4-hydroxybutyl)-3-methylimidazolium, and 1-(n-butyl)-3-(hydroxymethyl)-imidazolium, and two secondary metabolites were detected in the ryegrass after [C4mim]+ uptake. The metabolic mechanism was clarified using density functional theory calculations. Furthermore, [C4mim]+ at a high concentration was found to be high toxic to inhibit the growth of ryegrass markedly. In response, some oxidative stress was observed in the metabolic process, as indicated by increasing of catalase, super dismutase and peroxidase activities. Our results suggested that phytoremediation was an efficient technique for ionic liquids treatment from water.