Abstract
Mine wastewater (MW) is often rich in heavy metals that can have measurable effects on humans. The storage and treatment of MW remains a challenge for most mining companies. Iron (Fe) in MW was removed by using extracts from Eucalyptus globulus (EG); Callistemon viminalis (CV); and Persea americana (AS). Fe was removed from MW samples with an initial concentration of 5.53 mg Fe mL−1; 4.63 mg Fe mL−1 and 4.40 mg Fe mL−1 using EG leaves, CV flowers and AS seed extracts, respectively. Conditions of the MW decontamination were studied by varying the dosage of the plant extracts, the temperature of the medium and the contact time between the MW and the plant extracts. Undiluted plant extracts—which were mixed with the MW and heated at 45 °C for 3 h—gave the highest Fe-removal efficiency for CV (70%) and AS (53%) extracts, respectively. Similarly, EG extracts, albeit heated at 25 °C, showed a higher Fe-removal efficiency (85%) than the CV and AS extracts at low to high temperatures. The residual Fe concentration in the MW was 0.83 mg Fe mL−1, 1.39 mg Fe mL−1 and 2.07 mg Fe mL−1 for EG, CV and AS extracts, respectively. Residue solid-phase deposits from the precipitation reaction of the MW with the plant extracts were collected and analyzed. Fe was among the byproducts detected in the deposited material. The characterization of the annealed solid-phase deposits revealed Fe precipitates as maghemite-C (Fe2O3) and magnetite (FeFe2O4) nanoparticles. Therefore, the MW quality and form were improved, making it reusable for other purposes.
Highlights
Mining has been an economically important anthropogenic activity since the 16th century [1].Precious metals such as gold (Au) and other minerals, including iron (Fe), are extracted from ore-richMinerals 2020, 10, 859; doi:10.3390/min10100859 www.mdpi.com/journal/mineralsMinerals 2020, 10, 859 deposits
The industrial mineral extraction processes used for mining activity are more developed in South Africa; studies have revealed that more than 12 million people in Sub-Saharan Africa depend on artisanal mining [7,8,9,10,11]
Minimal variation was observed among the triplicate measurements, confirming the efficiency of the measurement method
Summary
Mining has been an economically important anthropogenic activity since the 16th century [1].Precious metals such as gold (Au) and other minerals, including iron (Fe), are extracted from ore-richMinerals 2020, 10, 859; doi:10.3390/min10100859 www.mdpi.com/journal/mineralsMinerals 2020, 10, 859 deposits. Mining has been an economically important anthropogenic activity since the 16th century [1]. Precious metals such as gold (Au) and other minerals, including iron (Fe), are extracted from ore-rich. Sub-Saharan African countries, Burkina Faso [3], Nigeria [4], Ghana [5], Mali, Tanzania, South Africa, Zambia and Zimbabwe are the primary suppliers of the beneficial precious metals [6]. The industrial mineral extraction processes used for mining activity are more developed in South Africa; studies have revealed that more than 12 million people in Sub-Saharan Africa depend on artisanal mining [7,8,9,10,11]
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