Moringa oleifera iron nanoparticles for nitrate removal in surface water

Abstract

The availability of clean potable water is a life threatening problem in South Africa, especially in rural areas. They rely on surface and groundwater as the main sources of water for drinking and other domestic purposes without any pre-treatment. The quality of these sources, however, becomes worse every day due to contaminants from industrial effluent, agricultural runoffs and other human activities. The main aim of this study was to fabricate iron nanoparticles (FeNPs) using Moringa oleifera, and also to investigate their effectiveness in nitrate (NO3-) removal from surface water and ground water. The importance of fabricating nanoparticles using plant extracts is being emphasized globally because traditional methods are costly, toxic and not eco-friendly. The green synthesis of FeNPs using extracts of Moringa oleifera seeds and leaves were prepared by mixing different ratios of plant extracts with iron chloride solution, and characterized using Dynamic light scattering, UV-visible spectroscopy (UV-vis), X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). FTIR revealed the presence of functional groups such as OH, CH and CO in both plant materials and green synthesized FeNPs. The UV-vis spectrum of Moringa oleifera leaves (MOL) based FeNPs and Moringa oleifera seed (MOS) based FeNPs showed absorption peaks at 210 and 240 nm respectively. The HRTEM of MOSFeNPs showed the particle size in the range of 2.6 -6.2 nm and 3.4-7.4 nm for MOL- . FeNPs which varied from the DLS results; MOS-FeNPs(151-224 nm) and MOL- · FeNPs (250-474nm). In addition, an adsorption study of NO3- ion removal from surface water was also investigated. Batch adsorption experiments showed that 43% and 48% of nitrate was removed by Moringa oleifera extracts (seeds and leaves) compared to the 85% and 26% using MOS-FeNPs and MOL-FeNPs, respectively. Furthermore, the antibacterial activity studies using disc method illustrated that the maximum zone of inhibition against Escherichia coli was observed by MOS-FeNPs (17 mm) and followed by MOL-FeNPs (15 mm). The results of the study revealed these nanoparticles as a possible alternative method to nitrate removal in surface water and that they have dual properties as coagulant and antibacterial agents.