Identification of the Mechanism Involved in the Removal Potetial of Textile Pollutants by the Aquatic Plant Lemna gibba L.

Abstract

Some studies asserted that some aquatic plants can remove organic pollutants by degrading them into their biomass. In this work, it was aimed to examine the ability of L. gibba L. to remove two dyes, DR-89 and VB-20 and then to elucidate the mechanism of removal. For this purpose, experiments were conducted at 21±1 °C, 12h photoperiod and pH of 6.1± 0.01.  For the maximal dye concentration tolerated by the plants (50 mg L^-1), the results demonstrated that maximum dye abatement was determined to be about 53% (VB-20) and 23% (DR-89). In order to identify the mechanism of dye absorption, FT-IR, UV-vis and SEM analyses were conducted on the biomass and liquid phases. The results indicated that alcohol, alkene, phenol, and amine functions are involved in dye binding to the biomass surface without demonstrating any phytodegradation phenomenon. Additionally, the SEM analysis confirmed this result showing that the ventral lobe and the thin root of each frond (unlike the dorsal lobe) are colored via a direct interaction with the dye molecules allowing their absorption from the surrounding water. Thus, the invasive plant, L. gibba L. could remove organic dyes from contaminated mediums by accumulating them in the biomass without degrading them.