Manipulating the morphology of nanoscale zero-valent iron on pumice for removal of heavy metals from wastewater

The removal of heavy metals from wastewater is one of the most important issues for the world, especially from industrial effluents. Pumice-nanoscale zero-valent iron (P-NZVI) was successfully prepared in different experimental conditions. Meanwhile, the shape, size and distribution of NZVI on P-NZVI were evaluated using a scanning electron microscope (SEM). At the optimum condition, NZVI with a mean diameter of 20.2 nm was distributed uniformly and consistently on the surface of pumice. Freundlich isotherm analysis suggested that the surface property of P-NZVI were heterogeneous. The removal of Hg (II) and Cr (VI) by P-NZVI could be well described by pseudo-first-order kinetic model. At equilibrium q(max) of Hg (II) and Cr (VI) was 107.1 and 106.9 mg/g, respectively. Thermodynamic investigation suggested that the removal of Hg (II) and Cr (VI) by P-NZVI was an endothermic and spontaneous process. The less values of Delta H-0 for Hg (II) than those for Cr (VI) demonstrated that more thermal energy was needed to remove Cr (VI) than Hg (II) at the same reaction rate. (C) 2014 Elsevier B.V. All rights reserved.