Removal of mercury (II) and chromium (VI) from wastewater using a new and effective composite: Pumice-supported nanoscale zero-valent iron

Nanoscale zero-valent iron successfully supported on pumice (P-NZVI) was used to remove heavy metals from wastewater with a higher removal capacity and efficiency. NZVI particles with a mean diameter of 30.6 nm are distributed uniformly on the surface of P-NZVI. The thermal stability and mechanical strength of P-NZVI were also obviously enhanced. P-NZVI with a 7.7% NZVI mass fraction had a specific surface area (S-BET) of 32.2 m(2)/g. The removal capacity of Hg (II) and Cr (VI) by P-NZVI was 332.4 mg Hg/g Fe and 306.6 mg Cr/g Fe, respectively. As an increase of pH, the removal rates of Hg (II) increased but those of Cr (VI) decreased gradually. P-NZVI is a regenerated material. The X-ray photoelectron spectroscope analysis (XPS) results indicated that Hg (If) and Cr (VI) were removed by a rapid physical adsorption in the first 0.5 min and predominantly by reduction. In terms of the efficiency and speed, P-NZVI was a promising candidate for applications to in situ environmental remediation, especially to the heavy metals pollution incidents with an extremely high concentration of heavy metals. (C) 2014 Elsevier B.V. All rights reserved.