Phytoremediation of heavy element contaminated water using Eichhornia crassipes (water hyacinth) injected with multiwalled carbon nanotubes and titanium dioxide nanotubes – a clean environmental nanotechnology

The aquatic plant E. crassipes , injected with multi-walled carbon nanotubes (MWCNT) and titanium dioxide nanotubes (TiNT) in its aerial parts, was used for the phytoremediation of dissolved heavy-element contaminants in the water of the lake “Laguna Jovita” (Mexico). The objective was to increase plant biomass and heavy element tolerance while internally anchoring the nanoparticle to prevent secondary environmental contamination by its dispersal. The hydrophobic nanoparticles were dispersed by a natural plant surfactant ( S. saponaria ). A comprehensive experimental analysis was carried out that consisted of the physico-chemical characteristics of the water before, during and after the 12 day period of phytoremediation, the plant´s physiological characteristics, the physicochemical quantification of the plant´s cellular extracts taken from the root and the injected and non-injected aerial parts and the elemental analysis of macronutrients, micronutrients and toxic heavy-elements of these extracts using the high sensitivity technique of Total Reflection Xray Fluorescence spectrometry. The results show a notable decrease in the water´s pollutions indices, an increase of plant biomass and chlorophyll and overall, the highest micronutrient and toxic heavy-element yields of the cellular extracts from the nanoparticle injected aerial plant part. The results are discussed in terms of the adsorbability of the nanoparticles, ROS scavenging by the nanoparticles, TiNT´s photocatalytic role and the possible synergistic action of the nanoparticle in the plant´s biochemistry of heavy-element detoxification wherein low nanoparticle concentrations act as catalyst and higher ones as inhibitors. Summarising, injected nanoparticles, especially TiNTs, increase the phytoextraction efficacy of E.crassipes , demonstrating the phytoremediative power of this technology.