The surface composition and surface properties of water hyacinth (Eichhornia crassipes) root biomass were studied before and after extraction with dilute nitric acid and toluene/ethanol (2/1, v/v) followed by ethanol, using Fourier Transform Infra-red (FT-IR) spectroscopy, thermogravimetric analysis, x-ray diffraction, scanning electron microscopy. FT-IR absorption bands were obtained at 3421, 2855, 1457 and 1035 cm-1 (O-H stretch, C-H vibration, C-H asymmetric deformation, and CO stretch, respectively) and 1508, 1541 and 1559 cm-1 (all aromatic skeletal vibrations characteristic of lignin), as well as a C=O carboxylate stretch vibrational band at 1654 cm-1. Scanning electron microscopy confirmed the root biomass to be amorphous and not to have a strongly structured surface. The dilute mineral acid and organic solvent treatment increased crystallinity. Thermogravimetric analysis Studies show that the treated biomass are more thermally stable than the untreated biomass. Data are presented showing that dilute mineral acid and organic solvent treatment resulted in a decrease in the amount of lignin in the biomass. The implications of the decrease in the percentage of lignin on the adsorption of volatile polar organic solvents and non-polar n-alkane hydrocarbons is discussed.
Silver nanoparticles were synthesized using Euphorbia Confinalis stem extract which is an eco-friendly and cost effective method compared to other synthesis protocols like chemical and physical methods. Euphorbia Confinalis which is used traditionally for therapeutic uses was responsible for capping and reducing silver ions to silver nanoparticles. Silver was of a particular interest for this process due to its evocative physical and chemical properties. The silver nanoparticles synthesized were quantified and characterized using visual examination of the color changes, UV-Visible spectroscopy, Scanning Electron Microscopy, Transmission Electron Microscopy, Dynamic Light Scattering and Fourier Transform Infrared spectroscopy. The antimicrobial activity of the synthesized nanoparticles was done by agar disc diffusion method tested against Escherichia coli (Gram-Negative) and Staphylococcus aureus (Gram-Positive). The synthesis of silver nanoparticles was confirmed by color change of AgNO3 to reddish brown upon addition of the Euphorbia Confinalis stem extract. The UV-Vis spectrum showed broad absorption band at 433nm corresponding to that of Surface Plasmon Resonance of silver nanoparticles. The FTIR analysis showed the presence of aromatic, aliphatic and amines and these observations suggested the presence and binding of organic compounds with silver nanoparticles.
The synthesis of silver nanoparticles by using the stem extract and leaf extract of Sclerocarya birrea (Marula) and silver nitrate (AgNO 3) is reported. The synthesized nanoparticles were characterized using ultraviolet-visible spectroscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, dynamic light scattering, and visual inspection. The antibacterial activity of the synthesized nanoparticles was done by agar disc diffusion method and tested against Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive). The ultraviolet visible absorption spectrum showed broad absorption band at around 430 nm corresponding to that of surface plasmon resonance of silver nanoparticles. The synthesis of silver nanoparticles was also confirmed by color change of AgNO 3 to reddish brown upon addition of Sclerocarya birrea stem and leaf extracts. In addition, change in color of the solution from colorless to brown within 5 min at pH 11 showed that the rate of reduction was faster at this pH compared to lower pH. Transmission electron microscopy analysis proved that the synthesized nanoparticles were spherical in shape; energy-dispersive spectroscopy analysis confirmed the presence of silver in the synthesized nanoparticles; and dynamic light scattering confirmed that the stem nanoparticles were generally larger (36 to 58 nm) than those synthesized from leaf extracts (32 to 48 nm). These nanoparticles were found to possess potential antibacterial activity against E. coli and S. aureus.
Clean water is expensive to obtain, hence the need for cheaper and effective ways of treating water. This study investigated the preparation and application/performance of affordable and effective ceramic/silver nanocomposites in the purification of water. Ceramic filters were manufactured by combining clay, flour, and broken clay pots on a weight basis. The dry mix was combined with deionized water, molded, fired, and treated with either silver nanoparticles or silver nitrate solution. Both treatments were done by submerging disks in their respective solutions. Analysis of treated water has shown that the pH of raw water was reduced by 1.08% with clay only filter, 5.20% with silver nitrate/clay filter, and finally 12% with silver nanoparticle/clay composite. Hardness decreased by 67% with nanoparticle composite while water from clay had 0.08% decrease in hardness. Biological oxygen demand fell by 50% with the clay only filter while there was 100% decrease with clay/silver composites. Nitrates decreased with clay only filters by 21.5% but increased in water treated with silver nitrate composite (84%) and clay/silver nanoparticle composite (73%). Inductively coupled plasma spectroscopy was used to estimate silver leaching from disks embedded with silver nitrate (0.024 ± 0.002mg/L) and silver nanoparticles (0.013 ± 0.002 mg/L) using 0.001 M dosage. All parameters investigated were dose-dependent.
K E Y W O R D Sceramic filters, silver nanoparticles, water purification
The adsorbent properties of dried water hyacinth root biomass towards four polar solvents (dichloromethane, ethyl acetate, diethyl ether and acetone) were studied by inverse gas chromatography between 40 and 70°C. The enthalpy of adsorption values obtained for the adsorption of the four solvents on untreated root biomass range from -51.234 kJ mol -1 for acetone, an amphoteric solvent, to -74.658 kJ mol -1 for dichloromethane, an acidic solvent. Mineral acid and organic solvent treatment led to reduction in the values of the enthalpy of adsorption for all four solvents. The Lewis acidity parameters calculated from the enthalpy of adsorption values were 0.408, 0.267 and 0.356, while the corresponding Lewis basicity parameters were 3.76, 1.80 and 2.34, respectively, for untreated, mineral acid-treated and organic solvent-treated water hyacinth root biomass. The Lewis basicity parameter-to-Lewis acidity parameter ratios for the untreated, acid-treated and organic solvent-treated biomass were found to be 9.22, 6.74 and 6.57, respectively, indicating (a) that all the surfaces of the untreated, mineral acid-treated and organic solvent-treated water hyacinth root biomass are basic in nature and (b) that for all volatile polar solvents studied, the adsorption interaction involves the lowest unoccupied molecular orbital of the solvent as the electron acceptor and the highest occupied molecular orbital of the water hyacinth root biomass surface adsorbent site as the electron donor.
The use of lignocellulosic fibres as biosorbents has both environmental and economic benefits. They are biodegradable, safe to use and most importantly renewable and less costly than synthetic fibres. The objectives of the present work were to study the performance of lignocellulosic fibres from water hyacinth (Eichhornia crassipes), a pervasive fresh water aquatic weed widely distributed in the tropics, as a biosorbent for n-alkane hydrocarbons, n-hexane to n-nonane. The free energy (G a), enthalpy (H a) and entropy (S a) for the adsorption of n-alkanes hexane to nonane on ground dried water hyacinth (E. crassipes) root biomass were studied between 40 and 70°C column temperature using inverse gas chromatography, before and after treatment of the root biomass with mineral acid and organic solvent. The free energy of adsorption (G a), enthalpy of adsorption (H a) and entropy of adsorption (S a) values of-20.42 to-35.992 kJ.mol-1 ,-21.18 to-33.704 kJK-1 mol-1 and +0.0023 to +0.0041 kJ.mol-1 respectively, were obtained for the adsorption of the n-alkane series on untreated water hyacinth root biomass. Mineral acid and organic solvent treatment leads to greater adsorption bond strength, with G a and H a values of-36.08 to-38.52 kJ.mol-1 and-34.01 to-36.33 kJK-1 mol-1 , respectively, after mineral acid treatment, and-40.98 to-46.7 kJ.mol-1 and-38.35 to-43.7 kJK-1 mol-1 , respectively, after organic solvent treatment. The results show that mineral acid and organic solvent treated water hyacinth root biomass has potential as biosorbent for the adsorption of volatile n-alkane hydrocarbons. Factors affecting the adsorbent-adsorbate interaction are discussed.
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