Thermodynamic study of the acid-induced decontamination of waste green sand generated in a brass foundry.

Waste foundry sand (WFS) from the brass and bronze casting and molding process include various potentially toxic elements (PTEs), such as copper, zinc, tin, and lead. Hence, the utilization of WFS in construction and geotechnical applications evokes environmental concerns due to the rain-induced leaching of PTEs into the groundwater system. The present study investigated the extractive decontamination of WFS using mineral acids, e.g., HCl, H2SO4, or HNO3. Favorable extraction efficiency was achieved with HCl as compared to the other mineral acids, which was further enhanced at high temperatures and increased acid concentrations. The thermodynamic analysis indicated that ≥ 4 mol L-1 of HCl and ≤ 100 °C temperature ensured maximum extraction of PTEs due to the endothermic interactions between the HCl and PTEs. The HCl-treated WFS needed to be rinsed with water to restrict the after treatment elution of PTEs. The hazardous environmental impact of acid-treated WFS was evaluated following the standard leaching test and comparison with legislative recommendations for PTEs, which showed the water-assisted leaching rate of all the PTEs are within the regulatory limits.

Does open-beach ship-breaking affect the mineralogical composition of soil more adversely than typical industrial activities?

In Bangladesh, India, and Pakistan the ship breaking (SB) sector dismantles end-of-life ships on open beaches, exposing the environment to the resulting pollution, especially the soil and water. Because SB occurs in the vicinity of other poorly-regulated activities in industrial zones (IZ) in these countries, there is some ambiguity concerning the relative roles played by SB and IZ in the accumulation of hazardous materials in the soil. In the absence of comparative studies, this study investigated the relative levels of soil contamination due to SB or IZ in the same geographic region by taking soil samples from SB and unrelated IZs in Chittagong, Bangladesh. The technogenic input of sixty-four chemical elements into the soil at the SB or IZ were compared with off-site reference values or the natural content of these elements in the Earth's crust and surface. The magnitude of soil contamination by ecotoxic elements, the corresponding bioavailability, and the ecological risks were assessed based on the regulatory reference values (RRVs) and with other approaches using data aggregation. Among the different potentially toxic elements, Cr, Cu, Ni, Pb, and Zn were found to be above the maximum allowable concentration (p < 0.05) in both SB and IZ. Moderate-to-high soil contamination from SB and moderate-to-considerable soil contamination in the IZ were observed. However, the element-bioavailability as ascertained via solid-phase speciation or weak-acid induced leaching, and the evaluation of associated ecological risk both indicated a low hazard quotient for soils from both SB and IZ. The outcome of the current research marked both SB and IZ soils as contaminated but not polluted, yet remediation is suggested. The level of contamination in SB soils was relatively higher than that of IZ. The comparative results presented in this study for the first time will hopefully be useful as a reference for future ecological and geochemical studies concerning the environmental contamination associated with both ship recycling on open beaches and other typical industrial activities.