Removal of Pb(II) from water samples using surface modified core/shell CdZnS/ZnS QDs as adsorbents: Characterization, adsorption, kinetic and thermodynamic studies

This research presents aqueous colloidal method to synthesize CdZnS/ZnS surface mod-ified core/shell quantum dots (QDs) with capping agents 2-mercaptoacetic acid and 3-mercaptopropanoic acid. The QDs were characterized by the different analytical techniques. Using Plackett-Burman and Central composite designs, optimum conditions for the removal of Pb(II) from aqueous medium were developed: QDs (0.013 g) at pH 6.9, time of adsorption and desorption (20 min), temperature (61.1 & DEG;C) and dilution on 100 ppb standard solutions. Moreover, Freundlich models suggested that Pb(II) adsorption was favorable on the heterogeneous surface of QDs. The values of DG? and DH " (-59.26 KJ/mol.K) suggested the process was spontaneous and exothermic. The negative DS' (-0.16 KJ/mol.K) indicates that the Pb(II) chemisorb on QDs. While, system follows the pseudo-second order rate equation which indicates that rate limiting step involves chem-ical reaction and could be influenced by the intraparticle/pore diffusion of Pb(II) ions with QDs. By using atomic absorption spectrophotometer, developed method was tested for Pb(II) removal from tap and ground water samples taken from the different districts of Karachi City. The % recovery for Pb(II) was found to be 96.4 % (tap water) and 94.8 % (ground water) with LOD = 0.1 ng mL?1 and LOQ = 0.90 ng mL?1.(c) 2022 The Authors. Published by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).