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Browsing by Author "Gachanja, Anthony N."

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    Adsorption of selected heavy metals on modified nano cellulose
    (2016) Madivoli, Edwin S.; Kareru, Patrick G.; Gachanja, Anthony N.; Mugo, Samuel; Murigi, Martin K.; Kairigo, P. K.; Kipyegon, Cheruiyot; Mutembei, Jackson K.; Njonge, Francis K.
    Cellulose is an inexpensive, renewable, bio-based and an abundant raw material suitable for the development of filter membranes for water purification. This is because it has numerous functional groups that afford ease of modification to create active surfaces upon chemical modification. In this study, cellulose was isolated from two abundant biomasses, namely, Eichhornia crassipes and Cyperus papyrus using the soda process followed by bleaching with peracetic acid. The percent yield of cellulose nanofibrils (CNF) obtained from E. crassipes and C. papyrus was found to be 31.64 ± 1.46% and 29.55 ± 0.64% respectively. The degree of crystallinity and crystal sizes were calculated to be 71.42% and 0.059 nm for E. crassipes and 46.15% and 0.068 nm for C. papyrus respectively. The FT-IR absorption of the carbonyl functional group of an ester indicated that effective esterification of cellulose using citric acid was obtained when cellulose nanofibrils to citric acid ratio was 1:1. From batch adsorption studies, the capacity for citric acid modified cellulose to remove heavy metals was determined to be 8.36 mg/g Zn2+, 18.06 mg/g Cu2+, 42.69 mg/g Cd2+ and 21.64 mg/g Pb2+. In comparison to the % adsorption using unmodified cellulose of less than 5%, the heavy metals adsorption using modified nanocellulose materials were 86.47% Pb2+, 85.20% Cd2+, 77.40% Cu2+, and 70.04% Zn2+. From these results, it was concluded that modified cellulose could be used as a low cost adsorbent for removal of heavy metals and that development of household water filtration units using modified cellulose could be exploited.
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    Antibiotic residues in milk from Juja and Githurai markets in Kenya by liquid chromatography-tandem mass spectrometry
    (2021) Ouma, Josephine; Gachanja, Anthony N.; Mugo, Samuel; Gikunju, Joseph
    The use of antibiotics in livestock production can potentially generate drug residues in animal products, leading to adverse health effects for consumers. This study was carried out to assess the presence and quantify the levels of antibiotic residues in milk sold in Juja and Githurai markets in Kenya. A total of 65 milk samples, comprising raw milk purchased from shops (32 samples), milk purchased from automated vending machines (23 samples) and packet milk (10 samples) were analyzed for the presence of amoxicillin, cloxacillin, tetracycline, sulfamethoxazole and trimethoprim residues. A single aqueous extraction was performed and the extracts were analyzed using liquid chromatography-tandem mass spectrometry. The prevalence of antibiotic residues in raw milk samples purchased from shops and milk dispensed from automated vending machines was 46.9% and 26.1%, respectively. No antibiotic residues were detected in packet milk samples. The prevalence of antibiotic residues was higher in milk from Githurai market compared to Juja market (52% vs. 25%, P value = 0.0137). Overall, 10.8% of samples tested positive for at least one antibiotic residue above the maximum residue limits established by the Codex Alimentarius Commission and the European Union, while 20% of samples had detectable antibiotic residues at concentrations below the maximum residue limits. The mean concentrations were 6.7 µg/L, 53.3 µg/L, 30.6 µg/L, 5.0 µg/L and 6.2 µg/L for amoxicillin, cloxacillin, tetracycline, sulfamethoxazole and trimethoprim, respectively. These results suggest frequent occurrence of antibiotic residues in some milk from the selected markets, which may be posing a public health risk to consumers.
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    Synthesis and characterization of dialdehyde cellulose nanofibers from O. sativa husks
    (2019) Madivoli, Edwin S.; Kareru, Patrick G.; Gachanja, Anthony N.; Mugo, Samuel; Makhanu, David Sujee
    Periodate oxidation of cellulose breaks the C2–C3 bond of the glucose repeating units forming two vicinal aldehyde groups that are amenable to further reactions. In this article, effects of reaction conditions during the oxidation such as reaction time, oxidant concentration, and temperature on the aldehyde content were investigated and an optimized reaction condition identified. The synthesis of 2,3-dialdehyde cellulose (DAC) was confirmed by scanning electron microscopy, transmission electron microscopy (TEM), Fourier-transform infra-red spectroscopy (FT-IR), differential scanning calorimetry, thermal gravimetric analysis and wide-angle X-ray diffractometer (WXRD). Formation of dialdehyde cellulose (DAC) was confirmed by the appearance of carbonyl peak in FT-IR spectra while a decrease in crystallinity of the fibers as a result of oxidation was confirmed by WXRD. Morphological changes during oxidation were observed using SEM while the size of the fibers was confirmed by TEM, which showed the average length of the fibers decreased after oxidation as compared to native cellulose. Thermal degradation studies revealed that oxidation of cellulose decreased the thermal stability of the polymer as compared to native cellulose and was dependent on the aldehyde content. In conclusion, oxidation of native cellulose to dialdehyde cellulose had a profound effect on the thermal stability, degree of crystallinity, size and morphology of the polymer.