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1 2023

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Employment of Ca2+-rich MgO nanoparticles for effective treatment of real acid mine drainage

Mothetha Matome, Kebede Kefeni, Masindi Vhahangwele, Msagati Titus

Environment Protection Engineering

2023

Vol. 49, nr 1

25--44

The efficacy of Ca2+-rich MgO nanoparticles for the effective treatment of real acid mine drainage (AMD) was evaluated. The optimized parameters include the feedstock dosage and contact time. The experimental results were underpinned using state-of-the-art analytical techniques and instruments such as FTIR, HR-FIB/SEM, EDS, XRF, and XRD. The pH REDOX equilibrium (in C language) (PHREEQC) model was also employed to complement experimental results. Optimum conditions were observed to be 45–60 min of mixing time, ≥10 000 mg/dm3 of feedstock dosage, i.e., Ca2+-rich MgO nanoparticles, and ambient temperature and pH. The metal content (Fe3+, Mn2+, Cr2+, Cu2+, Ni2+, Pb2+, Al3+, and Zn2+) embedded in AMD matrices was practically removed (≥99% removal efficacies) whilst the sulfate was also attenuated humongous (≥40%). The PHREEQC predicted metals to exist as multi-valent including carbonates and other chemical complexes. Chemical species in real AMD were predicted to precipitate as metals hydroxides, (oxy)-hydroxides, carbonates, and (oxy)-hydro-sulfates. Henceforth, the use of Ca2+-rich MgO nanoparticles was proved to be effective in the treatment of AMD from coal mining activities. However, a polishing technology will be required to further remove residual sulfates. This could be pursued to recover sulfate in valuable form and then reclaim drinking water for domestic purposes or other defined uses (end-use). This will then be the most effective closed-loop approach in the management of AMD under the circular economy (CE) concept.