Research Article Cytotoxicity, Removal of Congo Red Dye in Aqueous Solution Using Synthesized Amorphous Iron Oxide Nanoparticles from Incense Sticks Ash Waste Virendra Kumar Yadav , 1 G. Gnanamoorthy , 2 Daoud Ali, 3 Sweta Parimita Bera , 1 Arpita Roy , 4 Gokhlesh Kumar, 5 Nisha Choudhary , 6 Haresh Kalasariya, 7 and Anup Basnet 8 1 Department of Microbiology, School of Sciences, P P Savani University, Surat, 394125 Gujarat, India 2 ..Department of Inorganic Chemistry, University of Madras, Guindy Campus, -600025, T, N, Chennai, India 3 Department of Zoology, College of Science, King Saud University, PO Box 2455, Riyadh 11451, Saudi Arabia 4 Department of Biotechnology, School of Engineering & Technology, Sharda University, Greater Noida, India 5 Clinical Division of Fish Medicine, University of Veterinary Medicine, Vienna, 1210 Vienna, Austria 6 Department of Environment Sciences, School of Sciences, P P Savani University, Surat, 394125 Gujarat, India 7 Department of Microbiology, Sankalchnad Patel University, 382015 Mehsana, Gujarat, India 8 Department of Microbiology, Saint Xaviers College, Maitighar, Kathmandu 695586, Nepal Correspondence should be addressed to Anup Basnet; basnet.a@sxc.edu.np Received 13 January 2022; Revised 29 January 2022; Accepted 1 February 2022; Published 14 February 2022 Academic Editor: Palanivel Velmurugan Copyright © 2022 Virendra Kumar Yadav et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Magnetic nanoparticles have gained huge importance in the last ten years. They have found tremendous applications in the field of medicine, electronics, and environmental cleanup. The synthesis of amorphous iron oxide nanoparticles (AIONPs) is expensive making its applications highly overpriced. This research study reports the synthesis of AIONPs from waste incense sticks ash (ISA) in two steps. The first step is the recovery of ferrous fractions from ISA, followed by concentrated HCl treatment of magnetic fraction along with ultrasonication. And the second step includes treatment of ferrous-rich leachate with sodium hydroxides. The size of synthesized AIONPs varied from 40-90 nm and were highly aggregated due to the formation of large clumps. Cytotoxicity of synthesized AIONPs was determined on a normal human lung (BEAS-2B) cell line by using an MTT assay. Data showed that AIONPs induced cell toxicity in a dose-dependent manner. The particles were mainly spherical to rod-shaped and highly aggregated, it was confirmed by the microscopy analysis. The Fourier transform infrared (FT-IR) and Raman spectroscopy revealed the Fe-O, Si-O-Al as major functional groups in the AIONPs, while X-ray diffraction (XRD) revealed the amorphicity and physical property measurement system (PPMS) revealed the magnetic strength of the synthesized AIONPs. Finally, the AIONPs particles were applied for the remediation of Congo red dye from the wastewater by the adsorption method, and about 72% removal was achieved after one hour. The utilization of such ISA waste, for the synthesis of value-added minerals and their utilization for environmental cleanup, makes this whole process cost-efficient and environment-friendly. 1. Introduction Nanoparticles (NPs) and nanotechnology have drawn the attention of the whole world in the last few decades. They are known to have remarkable phenomena at the nanoscale in comparison to the bulk materials [1–4]. Out of all the NPs, magnetic NPs are extensively applied in the field of medicine [5], environmental cleanup, and research [6, 7]. The ferrous-based iron oxide nanoparticles (IONPs) have numerous advantages over other magnetic particles (Ni, Hindawi Journal of Nanomaterials Volume 2022, Article ID 5949595, 12 pages https://doi.org/10.1155/2022/5949595