Articles, Conference and Workshop Papers Collection

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Browsing Articles, Conference and Workshop Papers Collection by Subject "Activated carbon"

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    Adsorption kinetics of picloram on chitosan‑modified Strychnos pungens fruit shell activated carbon
    (Springer, 2025-09) Liberatus J. Mpaka; Alinanuswe J. Mwakalesi
    Activated carbon (AC) fabricated using Strychnos pungens fruit shells (biowaste) and encapsulated in a chitosan biopolymer (CHO) was applied for the removal of picloram from aqueous solutions. The synthesized activated carbon-chitosan beads (ACCHO) were characterized using Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Infrared spectroscopy (IR) and Emmett Teller (BET) surface area analysis. The findings demonstrated the successful encapsulation of AC to produce ACCHO with both crystalline and amorphous properties. The application of ACCHO for picloram removal was affected by solution pH, adsorbent dosage, and initial picloram concentration. The efficiency increased with adsorbent dosage, reaching an optimum at 40 g/L. Similarly, efficiency increased as pH increased from 2 to 6, but declined at pH 8. Optimal conditions of pH 6, 40 g/L ACCHO dosage and 50 mg/L picloram produced 88% removal efficiency. The picloram adsorption kinet- ics best fitted the pseudo-first order (PFO) model. Langmuir and Freundlich adsorp- tion isotherms provide a good description of the picloram adsorption process. The adsorption mechanism on ACCHO was postulated to involve multiple interactions caused by electrostatic and weak forces of attraction. The results of the current study suggest that ACCHO can be used as a potential adsorbent for removing picloram and similar chemicals from contaminated water.
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    Effects of phosphoric acid concentration on properties of activated carbon from Strychnos spinose fruit shells
    (Nature, 2026) John Chagu; Alinanuswe Joel Mwakalesi
    The accumulation of agricultural wastes in the environment is an emerging challenge. Their thermochemical conversion to activated carbon represents an efficient form of utilization that minimizes the secondary pollution caused by conventional treatment methods, such as incineration and landfilling. This study reports the synthesis and characterization of activated carbon from an affordable, abundant, and underutilized source of Strychnos spinosa fruit shells. The activated carbon was prepared through chemical activation using phosphoric acid of different concentrations (30%, 60%, 100%, and 150%), followed by physical activation at 500 °C for 4 h. The influence of the activating agent concentrations on the properties of activated carbon, such as yield, moisture content, ash content and iodine number, was studied. Additionally, X-ray diffraction, scanning electron microscopy, Brunauer–Emmett–Teller and Infrared spectroscopy techniques were used to study characteristics of activated carbon. The results showed that the yield of activated carbon increased from 25.33% to 29.2% as the concentration of phosphoric acid increased from 30% to 150%. The increased acid concentration also increased the moisture content, ash content and iodine number of the activated carbon. The highest iodine number of 999 mg/g was obtained for the activated carbon with the surface area of 507.373 m²/g impregnated with 150% phosphoric acid. Similarly, the SEM images revealed larger pore sizes for activated carbon produced using 150% phosphoric acid compared to those produced using 30%, 60% and 100% phosphoric acid. The findings demonstrate that phosphoric acid concentration influences the properties and performance of the Strychnos spinosa fruit shell activated carbon.
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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.