42 Int. J. Nanoparticles, Vol. 13, No. 1, 2021 Copyright © 2021 Inderscience Enterprises Ltd. Heavy metal removal from polluted water by Nopal cactus biopolymer-based magnetic nanocomposites Nghia T. Bui Institute of Environmental Science, Engineering and Management, Industrial University of Ho Chi Minh City, 12 Nguyen Van Bao, Ward 4, Go Vap District, Ho Chi Minh City, Vietnam Email: btnghia109@gmail.com Loan T.B. Duong Petrovietnam Camau Fertilizer Joint Stock Company, Ca Mau Province, Vietnam Email: duongbichloan18061995@gmail.com Thach T.C. Nguyen Faculty of Chemical Engineering, Industrial University of Ho Chi Minh City, 12 Nguyen Van Bao, Ward 4, Go Vap District, Ho Chi Minh City, Vietnam Email: camthachiuh@gmail.com Ngoc T.T. Tran* Research Institute for Sustainable Development, Ho Chi Minh City University of Natural Resources and Environment, 236B Le Van Sy Street, Ward 1, Tan Binh District, Ho Chi Minh City, Vietnam Email: tttngoc@hcmunre.edu.vn *Corresponding author Abstract: In the present study, Nopal cactus biopolymer-based magnetic nanocomposites were generated by a two-step process in which cobalt superparamagnetic (CoFe2O4) nanoparticles were firstly synthesised following a co-precipitation method with the aid of surfactants. Then, the composite materials with the nanoparticles dispersed in the matrix of biopolymer, which was extracted from Nopal cactus, were achieved with the support of ultrasonication. The obtained black nanocomposites were fully characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM) and Fourier transform infrared (FT-IR). The nanocomposites as novel nano-adsorbents were used for removal of heavy metal ions from the aqueous solution. In addition, the nanocomposites were strongly attracted by a permanent magnet due to superparamagnetism, making it easy to completely isolate them from water and is exhibiting good reusability.