pH Effect on Heavy Metal Release from a Polluted Sediment

Abstract

The performance of Cd, Ni, and Cu release from river sediment at different pH was investigated by a leaching test using deionised water and river water as leachants. Visual MINTEQ geochemical software was used to model the experimental results to predict heavy metal release from sediments. The distribution and speciation of heavy metals in the sediments after leaching test were analyzed by Tessier sequential extraction. Leaching test results showed that the release amounts of Cd, Ni, and Cu are in the range of 10.2–27.3 mg·kg−1, 80.5–140.1 mg·kg−1, and 6.1–30.8 mg·kg−1, respectively, with deionised water as leachant at different pH. As far as the river water was used as the leaching solution in the test, the results show similar metal leaching contents and tendencies to that of the deionised water as leaching solution. The results of Tessier sequential extraction indicate that Cd of residual fraction easily forms obvious precipitate under the acidic condition, especially in the range of pH 0–4 with the residual of Cd over 50% of the total Cd in the sediment. The exchangeable content of Ni decreases with the increase of pH under the range of 0–5. The Fe-Mn oxide fraction of Cu in the sediments changes significantly from pH 0 to pH 9. Based on the effect of pH on the leaching of Cd, Ni, and Cu from the polluted sediment in the tests, more accurate information could be obtained to assess the risk related to metal release from sediments once it is exposed to the changed acid/alkali water conditions.

Physicochemical and Bacteriological Qualities of Otamiri River Water and Sediment in South Eastern Nigeria

“…Generally, the high levels of these heavy metals in the river could be attributed to the indiscriminate dumping and subsequent burning of such solid wastes at the river bank, activities at auto-mechanic workshops at Nekede mechanic village, run-offs from Owerri urban and environs, unrestricted discharging of untreated industrial and domestic effluent into the river. In addition, the slight acidic pH recorded in the river might have also contributed to the high levels of some of these metals, as low pH has been shown to enhance the release of heavy metals from polluted sediment [24].…”

Monitoring N : P Ratio and Cd, Cu, Pb, and Zn Contents in Different Types of Anaerobic Digestates: A Six-Year Study Case

“…e high pH of the digestates also increases the risk for NH 3 volatilisation after digestion either during storage or after field application [44]. A higher soil pH also reduces plant availability of the four potentially toxic elements included in this study (Cd, Pb, Cu, and Zn) [45][46][47][48]. It is, however, debatable whether the application of digestates could influence the soil pH significantly, since the applicable amounts are usually restricted by nitrogen content.…”

Zinc Removal from ZnO Industrial Wastewater by Hydroxide Precipitation and Coagulation Methods: The Role of pH and Coagulant Dose

“…Figure 2. The solubility of metals hydroxide at different pH (Zhang et al, 2018) Figure 1 shows that the best pH for Zn precipitation occurs at pH 9.5 because it generates the lowest effluent Zn concentration of 3.71 mg/L with 95.3% removal. However, the optimum pH is 9.0, with 93.8% removal.…”

“…The solubility of metals hydroxide at deferent pH can be seen in Figure 2 in which each type of metal hydroxide is favorable to precipitate at a specific pH range (Zhang et al, 2018). Actually, the temperature differences also affects the solubility of metal hydroxide.…”