Browsing by Author "Kalombe, Rosicky Methode"

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    Fly ash-based geopolymer building materials for green and sustainable development
    (MPDI, 2020) Eze, Chuks Paul; Kalombe, Rosicky Methode; Ojumu, Victor Tunde
    This study reports on formulations and conditions for producing fly ash-based geopolymers with a view to showing that the compressive strength required for construction applications can be obtained without the addition of aggregates, sand, and/or cement. It was shown in a series of experiments constituting at least 73% fly ash that a compressive strength of up to 90 MPa can be obtained depending on the curing conditions. While high alkalinity resulted in stronger materials, the results showed about 40% savings in CO2 emissions without using sand and cement. Such materials are suited for construction applications with minimal environmental impact.
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    Treatment of acid mine drainage with coal fly ash in a jet loop reactor pilot plant
    (Minerals Engineering, 2020) Kalombe, Rosicky Methode
    A 1500 L batch jet loop reactor pilot plant was designed, constructed, and evaluated for performance in the treatment of acid mine drainage (AMD) using coal fly ash with a view to optimize its operation and generate performance data. Results showed that concentration of major contaminants (sulfate, Al, Fe, Ca, Mg), and minor contaminants in the treated AMD can be significantly lowered (between one and four orders of magnitude) compared to the raw AMD. It was shown that the one-step treatment process recovered at least 66.6% (728.56 kg) of treated water depending on the degree of dewatering required for slurry pumping. The energy consumption of 2.655 kW used for pumping indicated that an oversized centrifugal pump (15 kW capacity) was used for the neutralization cycle, as only a small fraction of the pump capacity was utilized. The treated water met the target water quality range (TWQR) limit for agricultural irrigation in South Africa. The analysis of the solid residue shows its suitability for backfilling of mine voids or for making geopolymer such that AMD treatment with fly ash results in a zero discharge process. The treatment process offers a cradle-to-cradle solution to acid mine drainage and coal fly ash.