Heavy Metal Accumulation and Plant-Mediated Nanoparticle Synthesis in Euphorbia tirucalli: A Sustainable Remediation Strategy

Abstract

Terrestrial environments are continuously threatened by heavy metal contamination, which can cause both environmental and health concerns. The researchers investigated the possibility of using Euphorbia tirucalli, Salvia officinalis, Senna auriculata, and Gliricidia sepium plants, which naturally occur in the Tumati Hills in Karnataka, India. All testing was done for bioaccumulation factor (BAF), bioconcentration factor (BCF), metal enrichment factor (MEF), and metal translocation factor (MTF) and rhizospheric microbial diversity. E. tirucalli outperformed the other species, showing better capacity to store iron and manganese, higher MEF and MTF, and strong interactions with catalase- and urease-producing microbes, such as Bacillus sp., Actinomycetes, and Brevibacillus sp. The hyperaccumulation properties of E. tirucalli made it a good candidate for green synthesis of iron oxide (Fe₂O₃) and lead oxide (PbO) nanoparticles using extracts from its roots and stems. Absorbance peaks seen in the UV–visible spectrum were characteristic of metal oxides, showing that nanoparticles formed. Analysis using scanning electron microscopy (SEM) and energy X-ray-dispersive spectroscopy (EDS) demonstrated that the nanoparticles are rounded and well-distributed, containing only small amounts of impurities. Fourier transform infrared spectroscopy (FTIR) identified functional groups involved in nanoparticle stabilization, while X-ray diffraction (XRD) confirmed the crystalline phases of α-Fe₂O₃ and orthorhombic PbO. The integrated methodology combining phytoremediation profiling, microbial characterization, and plant-mediated nanomaterial synthesis demonstrates a novel and sustainable approach to reclaiming heavy metal-contaminated soils. This work positions E. tirucalli as a multifunctional species with both environmental remediation and bionanotechnological applications, opening new avenues for low-cost, eco-friendly nanoparticle production.