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

•The properties of NZVI were obviously enhanced using pumice as the support.•P-NZVI was more effective to remove heavy metals from wastewater.•P-NZVI is a regenerated material.•P-NZVI was suitable for applications to in situ environmental remediation.

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 (SBET) of 32.2 m2/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 (II) 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.