Amine-modified silica-cellulose acetate nanofiber membranes for effective removal of hardness and heavy metals in drinking water Senuri Kumarage 1 , Imalka Munaweera 1 , Laksiri Weerasinghe 1 , Chanaka Sandaruwan 2 , Nilwala Kottegoda 1 1 Department of Chemistry, Faculty of Applied Sciences, University of Sri Jayewardenepura, Gangodawila, Nugegoda, Sri Lanka, 2 Sri Lanka Institute of Nanotechnology (SLINTEC), Nanotechnology and Science Park, Mahenwatte, Pitipana, Homagama, Sri Lanka With the increasing urbanisation and population growth, the water scarcity is a global challenge. Water hardness and heavy metal pollution are important factors that influence water quality. Contributing to the UN's 6 th sustainable goal of clean water and sanitation, this work involves the development of efficient and convenient approach of water purification by integrating amine-functionalized silica nanoparticles (AMS NPs) into cellulose acetate (CA) electrospun nanofiber membranes. AMS NPs were synthesized using tetraethyl orthosilicate (TEOS) and N-[3(Trimethoxysilyl) propyl] ethylenediamine(TMSPED) as precursors, via micro-wave assisted sol-gel method. These AMS NPs were incorporated into the CA nanofibers by electrospinning. The synthesized AMS NPs and the CA/AMS membranes were characterized using Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, Transmission Electron Microscopy, Energy Dispersive Spectroscopic elemental mappingand X-ray Photoelectron Spectroscopyto confirm the successful synthesis of nanoparticles, nanofiber formation and incorporation of AMS NPs into the membranes.The removal of hardness (Ca(II) and Mg(II)) from water samples was studied using Atomic Absorption Spectroscopy (AAS), whilst heavy metals removal was studied using Inductively Coupled Plasma Mass spectrometry (ICP-MS). The hardness removal efficiency of membranes was optimized by changing the loading amount of AMS NPs, the amine content of the synthesized AMS NPs, and the membrane dosage. The amine content of the AMS NPs was changed by altering the ratio between TEOS and TMSPED. The optimised membrane was made up of 40% AMS NPs synthesised at a TEOS: TMPSED molar ratio of 3.8:2.2 and a membrane dose of 12 g/L. The membrane was saturated in 8 hours, removing around 50% of the total hardness from synthetic water (500 ppm), and the removal effectiveness dropped as the initial hardness increased. The optimised membrane was then employed for heavy metal removal, and it removed more than 90% of As(V), Cd(II), and Pb(II) in 4 hours (from an initial concentration of 150 ppb). Both hardness and heavy metal removal followed pseudo-second-order kinetics and Freundlich isotherm. By washing with food-grade vinegar and 0.1N HCl, the membrane demonstrated a good regeneration capacity. The findings demonstrated that AMS/ CA nanocomposite membranes had a high potential for water softening and heavy metal removal in contaminated water. References 1. Boretti, A.; Rosa, L., Reassessing the projections of the world water developmentreport. NPJ Clean Water 2019, 2 (1), 1-6. 2. Munaweera, I.; Koneru, B.; Patel, A.; Dang, M.; Balkus Jr, K.; Di Pasqua, A., Nitric oxide-and Cisplatin-releasing amine- modified mesoporous silica nanoparticles for the treatment of non-small cell lung cancer. 2016 .
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