Digest Journal of Nanomaterials and Biostructures Vol. 17, No. 3, July - September 2022, p. 839 - 849 Lead (II) adsorption from aqueous systems using visible light activated cobalt doped zinc oxide nanoparticles M. Noman a,b , M. A. Haziq c , B. U. Safi d , S. Ullah e , G. Rukh f, , M. E. Faiq g , Z. Ullah h , S. D. Bibi h , S. Shaukat i , H. Emiliya j , Z. Rahim k , K. S. Ali l , F. Khan m , W. Can a,* a School of Environmental Science and Engineering, Tianjin University, No. 92, Weijin Road, Tianjin 300072, China b College of Environmental Science and Engineering, Donghua University, Shanghai 201620, China c Department of Water and Environmental Engineering, Kandahar University, Kandahar, Afghanistan d Department of Physics, Nangarhar University, Jalalabad, Afghanistan e Department of Water Resources and Environmental Engineering, Nangarhar University, Jalalabad 2600, Afghanistan f Department of Chemistry, Abdul Wali Khan University, Mardan 23200, Pakistan g College of Marine Biology, Ocean University of China, Qingdao, 266100, China h Department of Environmental Sciences Abdul Wali Khan University, Mardan 23200, Pakistan i Department of Chemistry, University of Swabi, Swabi, Khyber Pakhtunkhwa 23430, Pakistan j Landscape-Azerbaijan State Pedagogical University, Baku AZ1000, Azerbaijan k Department of Botany, University of Swabi, Swabi, Khyber Pakhtunkhwa 23430, Pakistan l National Centre of Excellence in Geology (NCEG), University of Peshawar, Khyber Pakhtunkhwa 25130, Pakistan m Department of Environmental Science and Engineering, University of Swabi, Swabi, Khyber Pakhtunkhwa 23430, Pakistan In this study, co-precipitation method was used to produce cobalt doped zinc oxide (Co- ZnO) nanoparticles (NPs) by reacting zinc, cobalt and hydroxide (OH − ) in methanol at 60 °C and used as an adsorbent for the removal of lead (Pb) from aqueous systems. Co-ZnO NPs were characterized by X-ray diffraction (XRD) via X-ray Diffractometer (JDX-3532, JEOL, Japan), while Transmission electron microscopy (TEM) was carried out for the shape and size of the NPs. Results shows that Co-ZnO NPs was oval in shape within the size range between 40 to 60 nm. Moreover, the Pb(II) adsorption on Co-ZnO NPs surface was carried out with respect to time, optimum dose, different pH, light effects, filtration and sonication process. The result shows that Co-ZnO NPs can remove Pb(II) efficiently from aqueous systems in the presence of sunlight, optimum dose, neutral pH, and sonication process, while the same NPs could not show effective removal of Pb(II) with respect to darkness, tube light, low and high pH respectively. Using Co-ZnO NPs, Pb(II) can be reduced up to the permissible limit set by World health organization (WHO). Co- ZnO NPs work effectively in pH range of 5.8–7.2 so therefore, no need to adjust the pH of test solution for the activation of these NPs. The synthesized Co-ZnO NPs are eco-friendly and a capable adsorbent for the removal of Pb(II) from aqueous systems. (Received April 1, 2022; Accepted July 29, 2022) Keywords: Lead, ZnO, Adsorbent, Doped nanoparticles, pH, Visible light * Corresponding authors: wangcan@tju.edu.cn https://doi.org/10.15251/DJNB.2022.173.839