Highly effective nanoparticle removal in plant-based water filters

Abstract

There is emerging discussion over the advantages of nanotechnology and its prospective risks prompted by increasing reports of nanoparticle (NP) contamination of the environment and its potential impacts on human health. Water treatment facilities are a critical node for exposure to NP contamination but also offer an opportunity for their capture to minimize the exposure. Unfortunately, the typical drinking water treatment train is not suitable for the complete removal of NPs. In fact, the challenges facing the water treatment techniques with the removal of viruses (natural NPs) present a marked example of the energy-water nexus. Any upcoming regulations targeting the control of engineered and incidental NPs are bound to increase the burden on the available techniques. To address this emerging challenge, we established the feasibility of high-efficiency removal of man-made and natural NPs with a depth filter fabricated from plant-based materials. Using high-resolution analytical techniques that enable quick quantification of NP concentration, we showed that cotton fiber functionalized with cationic proteins from Moringa oleifera seeds achieve removals greater than 4 log₁₀ (99.99%) for model nano-plastics and metal nanoparticles. Our results also show that the removals achieved are consistent under a range of pH values and salinities typical to drinking water treatment. The proposed filters in this study show promise as a low-cost and sustainable solution for the capture of NP contamination at loading rates typical to conventional water treatment.