Hierarchically assembled mesoporous ZnO nanorods for the removal of lead and cadmium by using differential pulse anodic stripping voltammetric method

Mesoporous hierarchical ZnO nanorods (ZnOs) with specific surface areas of 15.75 m(2) g(-1), and pore volumes of 0.038 cm(3) g(-1) were successfully synthesized by hydrothermal method. The ZnOs were characterized by XRD, SEM, TEM, SAED, BET surface area analyze and EDX. The ZnOs were investigated as adsorbents for the removal of Pb(II) and Cd(II) from aqueous solutions. Batch experiments were conducted under different adsorbate concentrations, contact times, adsorbent dosages, pHs and temperature conditions. Equilibrium data were best fitted with the Langmuir and Freundlich isotherm models and maximum adsorption capacities of Pb(II) and Cd(II) were determined to be 160.7 and 147.25 mg g(-1) respectively. Adsorption kinetics of both metal ions followed the pseudo-second-order model. The ZnOs remained effective for heavy metal ion adsorption after regeneration by an acid wash. Pb(II) and Cd(II) loading capacities of the recycled ZnOs have an average two-thirds that of the original capacities. The metal ion adsorption capacity and reusability of ZnOs make them promising adsorbents for wastewater cleanup. (C) 2013 Elsevier B.V. All rights reserved.