Extraction of Metals from Polluted Soils by Bioleaching in Relation to Environmental Risk Assessment

Abstract

Environmental pollution has particular implications for the whole geosystem and increases the global risk to human and ecological health. In this regard, investigations were carried out on soil samples to perform the quality status assessment by determining: pH, texture, structure and metal concentration, as well as carrying out an assessment of anthropogenic activity by determining pollution indices: Cf (contamination factor), Cd (degree of contamination), PLI (pollution load index), Er (ecological risk index) and PERI (potential ecological risk index). Analyses on soil samples showed high concentrations of metals (Cu: 113–2996 mg kg−1; Pb: 665–5466 mg kg−1; Cr: 40–187 mg kg−1; Ni: 221–1708 mg kg−1). The metal extraction experiments were carried out by bioleaching using Thiobacillus ferrooxidans, microorganisms at different amounts of bioleaching solution (20 mL and 40 mL 9K medium) and a stirring time of up to 12 h. The results on the degree of contamination, pollution loading index PLI (2.03–57.23) and potential ecological risk index PERI (165–2298) indicate that the soils in the studied area have a very high degree of pollution. The decontamination procedure by bioleaching showed a decrease, but at the end of the test (12 h), the followed indices indicate high values, suggesting that bioleaching should continue. The depollution yield after 12 h of treatment is, however, encouraging: Cu 29–76%, Pb: 10–32%, Cr: 39–72% and Ni 44–68%. The use of yield–time correlation equations allows the identification of the optimal exposure time on the bioleaching extraction process to obtain optimal results. The aim of the research is to determine the soil quality, soil environmental risk, extraction of metals from polluted soils by bioleaching and to identify influencing factors in achieving high remediation yields.

Proteomic Study of Response to Copper, Cadmium, and Chrome Ion Stress in Yarrowia lipolytica Strains Isolated from Andean Mine Tailings in Peru

“…Organisms such as plants, algae, bacteria, filamentous fungi, and yeasts are capable of removing heavy metals from different sources of water in the environment [ 29 , 30 ]. These fungi have shown tolerance to various heavy metals, including copper, chromium, lead, arsenic, cobalt, and cadmium.…”

Acidithiobacillus ferrooxidans Leaching of Silica-Sulfide Gold Ores from May-Hibey Deposits, Tigray, Ethiopia

“…pH values for leaching efects were performed in the presence of A. ferrooxidans to study the change in pH during the leaching of metal ions of iron and gold from the sulfde ore. Bacterial bioleaching takes place in an acidic environment with pH values of 1.5-2.0 where most metal ions remain in solution. Lowering the pH value rapidly decomposes the gold ore as a sulfate solution [5,21,[23][24][25]. A. ferrooxidans iron oxidants efectively oxidize sulfur and sulfdes but grow at high pH values where metal ions are not retained in solution [5,16,21,[23][24][25].…”

“…Lowering the pH value rapidly decomposes the gold ore as a sulfate solution [5,21,[23][24][25]. A. ferrooxidans iron oxidants efectively oxidize sulfur and sulfdes but grow at high pH values where metal ions are not retained in solution [5,16,21,[23][24][25]. As shown in Figure 3(a), the pH of the blank experiment (without bacteria) was nearly constant, but for the A. ferrooxidans leached sample, there was little change in pH from week 1 to 4, and this could be due to the leaching of metal ions into the sulfde ore. On the contrary, the result decreased sharply from week 11 and started to increase until week 14 in the bioleached sulfde ore (Figure 3(a)).…”

A review on the clean-up technologies for heavy metal ions contaminated soil samples

“…Sur et al, (2022) used the Thiobacillus ferrooxidans bacteria for the bioleaching of copper, lead, chromium, and nickel. It was observed that maximum bioleaching efficienciesof 76%, 32%, 72%, and 68% of copper, lead, chromium, and nickelwere achieved after 12 h of the treatment process [ 138 ].…”