http://hdl.handle.net/123456789/17451 Sun, 05 Apr 2026 18:49:03 GMT 2026-04-05T18:49:03Z http://hdl.handle.net/123456789/18767 GREEN-SYNTHESIS OF SILVER NANOPARTICLES EMBEDDED INTO PVA/CNC ELECTROSPUN NANOFIBERS CO-LOADED WITH EUCALYPTUS OIL FOR BIOMEDICAL APPLICATIONS AGAINST K. pneumoniae AND S. aureus ABERE GRACE KWAMBOKA Pneumonia is the leading cause of morbidity and mortality worldwide, particularly in low- and middle-income countries. According to the World Health Organization, it accounts for 15% of deaths among children under five, exceeding 700,000 fatalities annually. In the elderly over 65 years, it causes over one million deaths each year, with rising fatality rates. Multidrug-resistant pathogens, such as Klebsiella pneumoniae and Staphylococcus aureus, intensify the crisis, outpacing the development of antibiotics. This study prepared and characterized electrospun PVA/CNC nanofibers embedded with green-synthesized silver nanoparticles and eucalyptus oil, combining natural antimicrobials, biopolymer nanofibers, and eco-friendly nanotechnology for safe, nonantibiotic therapy against pneumonia-causing pathogens. The study objectives included green-synthesis of AgNPs using ELE and characterized using FTIR, SEM, TGA, TEM and XRD; extracting essential oil (EO) from eucalyptus leaves via steam-distillation and identify the phytochemical constituents and functional groups; extracting cellulose from the ELF, synthesizing CNCs via acid hydrolysis and characterize using FTIR, SEM, TGA, TEM and XRD; fabricating and optimizing electrospun PVA/CNC nanofibers and develop composite electrospun nanofibers comprising PVA, CNCs, AgNPs, and EO (PVA/CNC/AgNPs@EO), and characterize using FTIR, SEM, TGA, and XRD; evaluating the antibacterial activity of the prepared samples against K.pneumoniae, and S. aureus, and investigate their synergistic effects in enhancing antimicrobial performance. The study's findings showed that the green-synthesized AgNPs exhibited characteristic surface plasmon resonance peaks at 420 and 422 nm, as confirmed by UV-Vis spectroscopy. FTIR analysis confirmed the involvement of O– H, C=O, and C–O functional groups in the reduction and stabilization of AgNPs. TEM micrographs revealed predominantly polydispersed spherical AgNPs with diameters ranging from 5 to 20 nm. XRD confirmed a face-centered cubic crystalline structure. Phytochemical screening of steam-distilled EO confirmed the presence of terpenoids, mainly 1,8-cineole, α-pinene, and limonene, while the FTIR established characteristic absorption peaks of monoterpenes. The isolated cellulose from ELF exhibited a crystallinity index increase from 33.88% (ELF) to 77.45% (CNCs) after alkali, bleaching, and acid hydrolysis treatments. Electrospun PVA/CNC nanofibers exhibited a bead-free morphology under SEM and demonstrated enhanced crystallinity, as confirmed by XRD. Incorporation of CNCs increased hydrogen bonding, evidenced by FTIR peak shifts, and raised the crystallinity index from 24.93% (PVA) to 54.08% (PVA/CNC). Electrospun PVA/CNC/AgNPs@EO composite nanofibers exhibited a uniform, bead-free morphology with an improved crystallinity index of 69.40%, confirming structural reinforcement. FTIR confirmed the successful incorporation of EO and AgNPs, while SEM micrographs revealed that the nanoparticles were evenly distributed within the polymer matrix without aggregation. TGA analysis demonstratedimproved stability which prevent premature degradation, ensuring sustained functional performance, with char residue increasing to 21.7% at 800 °C. Antibacterial evaluation showed inhibition zones of 10–20 mm (S. aureus) and 9–19 mm (K. pneumoniae) for 6% AgNPs, whereas EO alone recorded inhibition zones of up to 19 mm. Electrospun PVA/CNC/AgNPs@EO composite nanofibers achieved inhibition zones up to 23 mm, demonstrating synergistic enhancement compared to individual samples. The results of this research establish a synergistic interplay among the samples, highlighting the potential of the developed nanofibers in biomedical applications such as pneumonia causing pathogens, implant coatings, and respiratory healthcare masks. Wed, 01 Jan 2025 00:00:00 GMT http://hdl.handle.net/123456789/18767 2025-01-01T00:00:00Z http://hdl.handle.net/123456789/17464 BIO-SORPTION STUDIES OF POLYCYCLIC AROMATIC HYDROCARBONS AND PESTICIDES FROM SELECTED SURFACE WATERS IN NAROK AND BOMET COUNTIES, KENYA USING LOCALLY AVAILABLE BIOCHAR ADSORBENTS Abdallah Bakari Chaka Narok and Bomet Counties of Kenya rely on surface waters mainly from rivers for domestic use, livestock and plant farming. Increased anthropogenic activities such as charcoal burning and agrochemical practices near riparian areas in the two Counties have led to environmental and ecotoxicological concerns of people and animals that rely on these waters. This study aimed to determine the presence and levels of polycyclic aromatic hydrocarbons (PAHs) and pesticide residues in surface waters from Narok and Bomet Counties; and further explore the bio-sorption of these pollutants using locally available biochar adsorbents. The surface waters of the two Counties were sampled via a two-factorial design based on geographical distribution and proximity to point-source pollutants during both wet and dry seasons. PAHs and pesticides were extracted by solid-phase extraction and analyzed by gas chromatography hyphenated to mass spectrometry (GC-MS) and GC- time of flight mass spectrometry (GC-ToFMS) respectively. Biochar adsorbents were prepared from cow dung (CDB) and sugarcane bagasse (SBB) and characterized. Adsorption studies of the prevalent PAHs and pesticides were conducted using the two adsorbents. Various adsorption optimization studies were conducted to determine the optimal adsorption conditions. There were 38 different types of pesticides detected in the two Counties. The pesticides chlorpyrifos, cypermethrin, cyfluthrin and cyhalothrin were more prevalent in Narok County while triazine, semicarbazone and epinephrine were more prevalent in Bomet County. There were significantly more pesticides detected during the wet season (p ≤ 0.05). Four of these posed serious ecotoxicology concerns with risk quotients above 1.0 (high risk). Seven United States Environmental Protection Agency (US EPA) priority PAHs were detected in concentrations of up to 31.42 µgL-1 (dibenzo[a,h]anthracene). The surface waters were significantly polluted with dibenzo[a,h]anthracene with risk quotients above 1.0 in the surface waters and were found to be hazardous, with hazard quotients above 10.0, thus indicating potential environmental risks. The biochar findings indicated the SBB sample to have a smoother morphology with a higher C/H/O ratio compared to the CDB which had more mineral oxides composition. The XRD diffractograms indicated the samples were largely amorphous while the TGA and DTG thermograms showed CDB to be more thermal resilient than SBB. The adsorption studies indicated high adsorption efficacies of between 78 to 90 % under optimal conditions of: 10 – 15 °C, pH of 4 – 8, 30 min sorption time, sorbate concentration of 4.0 ppb and adsorbent dosage of 2.0 g/Lsorbate. Temkins adsorption model was most favored model while the adsorption processes were feasible and spontaneous under room temperature conditions. The adsorbents were found to be regenerated with an adsorption capacity of 63 – 80 % for the third adsorption cycle. The study indicated pesticide and PAH pollution in the surface waters of Bomet and Narok Counties thus there is a need for more government policy interventions in deterring farming near riparian lands and in training of famers regarding best practice for pesticide applications. The study also recommends fabrication of biochar-based filters from locally available materials for removal of pesticides and PAHs in waste waters. Mon, 01 Jan 2024 00:00:00 GMT http://hdl.handle.net/123456789/17464 2024-01-01T00:00:00Z http://hdl.handle.net/123456789/17452 SYNTHESIS AND CHARACTERIZATION OF β- CYCLODEXTRINE CAPPED MAGNETIC NANOPARTICLES ANCHORED ON CELLULOSIC MATRIX FOR REMOVAL OF HEXAVALENT CHROMIUM FROM MIMICKED WASTEWATER LYNDA SAMATO MESOPPIRR Water is one of the most abundant features on Earth covering up to 70% of Earth's crust but only less than 1% of this water is fit for human consumption. Water can be polluted by both organic and inorganic matter. Hexavalent chromium (Cr(VI)) one of the inorganic pollutant is an important component in many industrial process finds its way into water bodies posing health problems which include lung cancer and inhibition of DNA and RNA in biological systems. This study thus focused on the preparation, characterization, and application of a novel nanocomposite adsorbent, CNC-Fe3O4NP CD, for the removal of Cr(VI) from aqueous solutions. The cellulose used in this research was extracted from Typha angustifolia and hydrolized to cellulose nanocrystals (CNCs) using 32% H2SO4. The prepared and characterized cellulose nanocrystals, were incorporate onto iron oxide nanoparticles using co-precipitation method and functionalized with β-cyclodextrin by shear homogenization. Fourier Transform Infrared Spectroscopy (FTIR) identified the characteristic peaks of cellulose functional groups, including O-H stretching at 3309 cm⁻¹, C-H stretching at 2892 cm⁻¹, and C-O-C stretching at 1034 cm⁻¹. Transmission Electron Microscopy (TEM) revealed that the CNCs had nano-scale dimensions, with an average particle size of 98.57 ± 2.54 nm. X ray Diffraction (XRD) analysis confirmed the successful conversion to crystalline form, with a crystallinity index of 77.41%. The characterization of the nanocomposite (CNC Fe3O4NP) with Scanning Electron Microscopy (SEM) and TEM analyses showed a uniform distribution of Fe3O4 nanoparticles, with an average particle size of 16.82 nm. The nanocomposite exhibited strong magnetic properties, as evidenced by Vibrating Sample Magnetometer (VSM) analysis, which recorded a magnetization value of 64.56 emu/g. Batch adsorption studies were conducted under varying conditions, including pH, adsorbent dosage, initial Cr(VI) concentration, contact time, and temperature. The optimal conditions for Cr(VI) removal were determined to be a pH of 2, an adsorbent dosage of 1.0 g, an initial Cr(VI) concentration of 20 mg/L, a contact time of 35 minutes at room temperature. Under these conditions, CNC-Fe3O4NP-CD achieved a maximum Cr(VI) removal efficiency of 97.45%. In the presence of competing ions such as Cu²⁺, Zn²⁺, and Pb²⁺ at a concentration of 20 mg/L, the Cr(VI) removal efficiency of CNC Fe3O4NP-CD decreased to 30.22%, 30.22%, and 40.49% respectively. Regeneration studies demonstrated that CNC-Fe3O4NP-CD could be reused effectively over multiple adsorption-desorption cycles. Based on kinetic study, the experimental data fitted best with the pseudo-second-order kinetic model, which exhibited high linear regression coefficients (R² > 0.98) across all tested conditions. Equilibrium isotherm studies fitted well with the Langmuir isotherm model, indicating monolayer adsorption on a homogeneous adsorbent surface. The Freundlich and Temkin isotherms fitted to the experimental data. Thermodynamic studies revealed that the adsorption process was spontaneous, as indicated by negative Gibbs free energy (ΔG°) values. The enthalpy change (ΔH°) was also negative, suggesting that the adsorption process was exothermic. The positive entropy change (ΔS°) indicated an increase in randomness at the solid-liquid interface during adsorption. From the study, CNC-Fe3O4NP-CD presented a highly effective, sustainable, and reusable adsorbent for Cr(VI) Mon, 01 Jan 2024 00:00:00 GMT http://hdl.handle.net/123456789/17452 2024-01-01T00:00:00Z