Decontamination of metal-contaminated waste foundry sands using an EDTA–NaOH–NH3 washing solution

Abstract

Waste foundry sand (WFS), which is a hazardous byproduct from the foundry industry, is often contaminated with potentially toxic elements (PTEs), such as Cu, Pb and Zn, and widely re-utilized as a construction material. Therefore, the depollution of WFS has been suggested due to its environment friendly reprocessing to avoid potential long-term hazardous impacts. In the current study, a unique chemically induced technique has been proposed for the removal of PTEs from WFS. EDTA, NaOH and NH 3 were used as extractants in combination or in succession. The optimum removal of PTEs was accomplished using a solid (WFS) to solution (50 mmol L-1 EDTA) ratio of 10 under strongly basic pH conditions, which was achieved with NaOH addition. The washing efficiency was further enhanced with the addition of NH 3 to the solution. The complete process cycle duration was adjusted to 9 h with a washing sequence that was repeated three times for 3 h each. The ultimate efficiencies (%) for the removal of PTEs were as follows: Cu, 98; Pb, 81; Sn, 83; and Zn, 50. The leaching of residual PTEs (%) from the decontaminated WFS was also in compliance with the regulatory levels that are defined by the monitoring authorities.

Recovery of phosphorus from incinerated sewage sludge ash by combined two-step extraction and selective precipitation

“…Similar results were found by Sawai et al [45] that, under acidic conditions, even though the apparent stability constant of Cu-EDTA was greater than that of the corresponding Zn complex under the same pH conditions, the Zn-EDTA was dominant. In order to ensure the cost-effective use of EDTA, it is important to assess the efficacy of metal(loid) removal under different conditions.…”

“…The most logical explanation for such a difference must be linked to the continued presence of residual EDTA in the two-step extract. Additionally, the stability constants of metal-EDTA varied with the solution pH, which can be confirmed by a the previous research result that Cu-EDTA complexes was a more dominant species than Zn-EDTA in the alkaline pH region [45]. This is an advantage for the two-step process because it means that incorporation of Cu and Zn into the P-precipitate by isomorphic substitution is greatly reduced [48].…”

Chemical mixtures and fluorescence in situ hybridization analysis of natural microbial community in the Tiber river

“…A general low concentration of pesticides, corrosion inhibitors and PAHs was found in the agricultural area indicating a scarce pollution of the river at this point due to agricultural practices. Nevertheless, the relatively high levels of metals such as Ba, Al and Fe indicated a source of industrial contamination (Sawai et al, 2016). In fact, because there is a foundry close to this point, the occurrence of these metals can be ascribed to releases from it.…”

Mechanical Properties of Natural Rubber Filled with Foundry Waste Derived Fillers

“…There are more than 20,000 foundries in China, generating 20–30 million tons of foundry waste annually [4]. It was reported that foundry wastes have some application areas, such as fine and/or coarse fillers in concrete, cement production, bricks, embankment material and road bases [5,6,7,8]. However, no more than 15% of foundry waste has been reused in these areas [9].…”