Browsing by Author "Mustapha, K."

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    Kinetics of the Antioxidant Activities of Solanum macrocapon and Crassocephalum rubens by DPPH Radical Scavenging Method
    (Journal of Chemical Society of Nigeria, 2020-02-11) Yusuff, K. O.; Omotosho, K.; Mustapha, K.; Abdulraheem, A. M. O.
    Solanum macrocapon (S.macrocapon) and Crassocephalum rubens (C.rubens) was investigated. The methanolic extracts of the samples were tested with 2,2-diphenyl-1-picrylhydrazyl (DPPH) at different times (30, 50, 70 and 90 minutes). UV-Visible Spectroscopy technique was employed  to evaluate the ability of the plant extracts to scavenge DPPH radicals by measuring the absorbance at the various experimental times. The concentration of sample required to inhibit 50% of the DPPH free radical (IC50) and kinetic parameter (rate constant k2) were determined from the absorbances values. S.macrocapon and C.rubens had DPPH scavenging potency with IC50 values of 2.18 x 10-2 mgml-1 and 6.27 x 10-2 mgml-1 respectively. This implied that S.macrocapon is a more potent antioxidant than C.rubens. The rate constant for the hydrogen atom abstraction by DPPH (k2) in the presence of S.macrocapon is 2.70 x 10-3 ± 0.0006 mlmg- 1min-1 with R2 value of 0.709 while for C.rubens, the rate constant is 6.89 x 10-4 ± 0.03 x 10-4 mlmg-1min-1 with R2 value of 0.987 using Pseudo-first order kinetics model. However, under second order kinetics, the rate constant, k2, for S.macrocapon is 4.73 x 10-1 ± 0.020 mM-1min-1 with R2 value of 0.993 while C.rubens has k2 value of 5.55 x 10-2 ± 0.00236 mM-1min-1 with R2 value of 0.795. Thus, the depletion of DPPH by S.macrocapon followed a second order kinetics while that of C.rubens followed a Pseudo first order kinetics. Keywords: Kinetics, DPPH, Antioxidant, UV-Vis spectroscopy, IC50Â
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    Mechanical Properties, Durability and Microstructure of Palm Kernel Shell Concrete Produced from Different Grades of Portland Limestone Cement
    (Nigerian Research Journal of Engineering and Environmental Sciences, 2024-06-30) Odeyemi, S. O.; Adegolu, E.R.; Adisa, M.O; Atoyebi, O.D; Mustapha, K.; Adeniyi, A.G.
    The need for lightweight structures and to reduce environmental waste which leads to pollution has necessitated the utilization of agro-based materials as aggregates for concrete. Notable among these wastes is the Palm Kernel Shell (PKS). This study investigated the compressive and tensile strength, durability and internal structure of PKS concrete made with 32.5N and 42.5N grades of Portland Limestone Cement (PLC). A designed mix of Grade 20 culminating into a combined ratio of 1:1:1 for cement, sand and PKS batched by volume adopting a water-cement ratio (w/c) of 0.45. The compressive and tensile strengths of the concrete were tested, the durability of the concrete was determined using a water absorption test and Scanning Electron Microscopy (SEM) was conducted to correlate the test results. The outcome of investigations showed that PKS concrete from the cement of grade 42.5N has higher compressive and tensile strengths than grade 32.5N. Microstructural images from SEM showed non-uniformly distributed voids which are higher in concrete produced from 32.5N grade cement. Hence, the PKS concrete from grade 32.5N PLC absorbed more water than the concrete made from 42.5N PLC. Therefore, cement grade affects the strength, durability and microstructure of PKS concrete.