Browsing by Author "Emmy Solomon Lema"

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    Efficient and reusable activated carbon from aframomum angustifolium fruits’ shells for removal of ceftriaxone from aqueous solution: adsorption isotherms, kinetics, and thermodynamics studies
    (Indonesian Journal of Chemistry, 2025-11) Baraka Alfaksad Kasazi; Alinanuswe Joel Mwakalesi; Emmy Solomon Lema
    The accumulation of ceftriaxone antibiotics in aquatic systems is a growing global concern due to their potential risks to human and ecological health. The current study investigates the synthesis, characterization, and application of activated carbon (AC-FPAA-H3PO4) made from the shells of Aframomum angustifolium fruits. AC- FPAA-H3PO4 was synthesized using chemical activation (H3PO4, 4 M) followed by pyrolysis at 600 °C for 1 h and characterized using BET, FTIR, and SEM-EDX. AC-FPAA-H3PO4 exhibited a surface area of 1895.6 m2/g, which allowed for its reuse in 5 consecutive cycles without requiring active site regeneration. The optimal removal efficiency (97.8%) was achieved at pH 2, 298.15 K, 100 rpm, 20 g/L adsorbent dosage, and 200 mg/L ceftriaxone concentration. The adsorption process was described by Langmuir (R2 = 0.9862) and Freundlich (R2 = 0.9833) isotherms, and the kinetics were fitted to the pseudo-second- order model. The adsorption was spontaneous (ΔG = −6.80 kJ/mol) and exothermic (ΔH = −4.43 kJ/mol), with increased randomness at the solid-solution interface (ΔS = 7.69 J/mol K). The adsorbent demonstrated high efficiency in removing ceftriaxone from real water samples, including river water (99.36%) and well water (96.92%). The findings suggest AC-FPAA-H3PO4 is a promising adsorbent for removing ceftriaxone from an aqueous environment.
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    KOH-activated carbon from Aframomum angustifolium fruit shells for caffeine removal from aqueous solution
    (Springer, 2025-12) Baraka Alfaksad Kasazi; Alinanuswe Joel Mwakalesi; Emmy Solomon Lema
    This study reports on the preparation of activated carbon using Aframomum angustifolium fruit shells (FPAA) and its application for the removal of caffeine from aqueous solution. The activated carbon was prepared using KOH activation in a 1:2 ratio, followed by pyrolysis at 500 °C for 1 h. The activated carbon (AC-K) was characterized using the point of zero charge of potential of hydrogen (pHpzc), N2 adsorption–desorption analysis, scanning electron microscopy–energy-dis- persive X-ray spectroscopy (SEM–EDX), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The surface of AC-K exhibited a mesoporous structure with an increased BET surface area from 335 to 407.6 m2/g. The classical method and response surface methodology (RSM) using Box–Bohnken design (BBD) were used to optimize the performance of AC-K to remove caeine from aqueous solutions. The results indicated that the adsorption aligned best with the Langmuir model (R2 = 0.996 and RMSE = 0.3531), indicating the formation of a monolayer film. In addition, the adsorption was described by the pseudo-second-order model (R2 = 0.995 and RMSE = 0.017). The highest caffeine removal eciencies were 78.67 and 90.40% as determined using classical and BBD methods, respectively. Therefore, the prepara- tion and use of an eco-friendly and previously unexplored precursor for activated carbon preparation is demonstrated in the current study. This study contributes to sustainable waste valorization while oering a promising alternative material for the removal of emerging contaminants such as caffeine from water systems.