The efficiency of phytoremediation using Panicum maximum and TiO2 nanoparticles

Abstract

This study focused on the application of Panicum maximum (guinea grass) for evaluating the phytoremediation of titanium dioxide nanoparticles (nTiO2). This study was done to explore the ability of Panicum maximum Jacq as a hyperaccumulator for phytoremediation of nTiO2. Titanium dioxide has steadily become more abundant in our environment over the years due to human activities, and this could potentially harm the environment. Panicum maximum (guinea grass) is a non-vascular plant with a short life cycle. It is well adapted to a wide variety of conditions. It originated from Africa but is presently found and cultivated in almost all parts of the world with tropical climates. It is loosely to densely tufted, with short rhizomous rooting at the lower nodes. Leaf blades are linear to narrowly lanceolate. Plant to metal oxide nanoparticle interaction was investigated by germination of seeds in the presence of titanium dioxide nanoparticles (nTiO2). The uptake of nTiO2 by Panicum maximum Jacq was evaluated after treatment of the seedlings with nTiO2. The synthesized nTiO2 was characterized, using Transmission Electron Microscope, Scanning Electron Microscope. Energy Dispersive Spectroscopy (EDX), and X-ray Diffraction (XRD). The average mean particle distribution was analyzed using Image J. The Image J analysis showed that the average particle distribution of nTiO2 was 9 nm. The TEM and SEM results revealed that the particles in the nTiO2 were spherical in shape. The XRD analysis revealed that the nTiO2 was predominantly 67.1% and 32.9% of anatase and rutile forms, respectively. Metal uptake was analyzed using the Inductively Coupled Plasma – Optical Emission Spectrometer method (ICP-OES) after the plants were digested using the wet digestion and microwave digestion methods. The ability of the plants to translocate the metals to the aerial parts of the plants (Translocation Factor - TF) was evaluated for the metal using concentration ranging from 5 ppm to 50 ppm. It was observed that the root had the highest concentration of nTiO2 while the lowest uptake was found in the leaf. The TF was highest for the 5 ppm sample. The roots with the shortest length, which indicated stress/toxicity were that of the plants which were treated with 50 ppm of nTiO2. These also had the highest accumulated nanoparticles which suggested that these plants were negatively impacted by a higher concentration of nTiO2. The standard with 5 ppm treatment showed the highest value of the translocation factor which suggested that at this concentration the nanomaterial aided and catalyzed the movement of nanoparticles to the aerial parts of the plant. The results suggested that seed treated with nanoparticles before planting for phytoremediation purposes could increase the metal uptake selectivity.