Phytodegradation of Ethanolamines by Cyperus alternifolius: Effect of Molecular Size

Abstract

Our screening of plants showed that Cyperus alternifolius (Umbrella papyrus) had the highest efficiency removal in real wastewater containing monoethanolamine—higher than Echinodorus cordifolius (Creeping Burrhead), Thalia geniculata (Alligator Flag), Acorus calamus (Sweet Flag), and Dracaena sanderiana (Lucky Bamboo). Therefore, this research studied the degradation of monoethanolamine (MEA), diethanolamine (DEA), and triethanolamine (TEA) by C. alternifolius. Plants could degrade TEA into DEA, then into MEA, and then further into acetic acid. The accumulation of ethanolamines was found mainly in plant stems, which had the highest biomass. This demonstrated that the molecular size is closely related to a diffusion coefficient that affects the removal rate through plant bodies. A smaller molecular weight—MEA (MW = 61.08 g mol−1)—was taken up the fastest, followed by DEA (MW = 105.14 g mol−1) and TEA (MW = 149.19 g mol−1), the highest molecular weight. The plants’ toxicity when exposed to ethanolamines elucidated that MEA had the highest toxicity, followed by DEA and TEA. In addition, the application of C. alternifolius in monoethanolamine-contaminated wastewater revealed that plant could completely uptake MEA at day 5 from an initial MEA concentration of 18 mM. The result indicated that C. alternifolius has the potential to remove ethanolamines and can be applied to ethanolamine-contaminated wastewater.