Crystallization of Calcium Sulfate for Mining Wastewater Treatment
This study aims to increase the particle size of the precipitate, aiming for an increasing settling speed. The effluent contains 21.88 g/L of sulfate, 526.5 mg/L of calcium, 2.9 mg/L of cadmium, 4.73 g/L of magnesium, 332.8 mg/L of manganese, and 205.8 mg/L of zinc. Based on thermodynamic simulation...
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| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-06-01
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| Series: | Metals |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2075-4701/15/7/710 |
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| Summary: | This study aims to increase the particle size of the precipitate, aiming for an increasing settling speed. The effluent contains 21.88 g/L of sulfate, 526.5 mg/L of calcium, 2.9 mg/L of cadmium, 4.73 g/L of magnesium, 332.8 mg/L of manganese, and 205.8 mg/L of zinc. Based on thermodynamic simulations, evaluating the pH increase up to 9.0, it was possible to determine that the main species are CaSO<sub>4</sub>·2H<sub>2</sub>O(s), Mg(OH)<sub>2</sub>(s), MnO<sub>2</sub>(s), ZnO(s), and Cd(OH)<sub>2</sub>(s). In the precipitation tests, it was determined that a concentration of 2.0 mol/L of Ca(OH)<sub>2</sub> resulted in a particle size of 12.2 µm. The increase of temperature has an opposite effect, decreasing 40% of the particle size at 80 °C in comparison to 25 °C. On the other hand, the reaction time increases particle size, reaching 300% of an increase from 10 min to 3 h. In the seed tests, it was found that a seed ratio of 10 g/L to 100 g/L with the CaSO<sub>4</sub> (2) seed had the greatest impact on particle size growth, resulting in a 700% increase in particle size compared to the test without seeds. In the settling tests, a sedimentation rate of 177 mL/min was achieved using seeds and flocculants, compared to 50 mL/min in the test without reagents. |
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| ISSN: | 2075-4701 |