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Nanocelluloses with fiber diameter of ∼ 5 nm were extracted facilely from seasonal defoliation of ginkgo leaves by combined TEMPO-mediated oxidation/mechanical treatment and were used as adsorbents to remove charged contaminants from water. The chemical composition of nanocellulose was determined by solid-state 13C NMR and elemental analysis, whereas the morphology was characterized by TEM and POM techniques. The adsorption capacity of ginkgo nanocellulose against cationic dye molecules and heavy metal ions (e.g., cupric ions) were investigated in a static adsorption study. The results verified that nanocelluloses extracted from biomass waste, such as ginkgo leaves, could be used as efficient adsorption media for remediation of contaminated water.
In Northern Tanzania, high levels of fluoride in community drinking water supply is recognized as one of the major public health concern, the problem is further ameliorated by presence Escherichia coli and fecal coliform bacteria in surface water and shallow wells. Efforts to decontaminate the water involve mostly the use of low efficient bone char for fluoride removal without disinfecting the pathogens. To address this problem, a robust adsorbent which is capable of removing fluoride and microbes simultaneously with minimal diverse impact on the treated water is necessary. Here we highlight development of composite material developed from recycling of crustacean biomass waste from sea food industry. Chitosan polymer, isolated from prawns shell was composited with crab shell derived brushite (CaHPO4.2H2O) to form chitosan-hydroxyapatite composite. XRD and FT-IR analysis confirmed transformation of brushite phases into hydroxyapatite and formation hybrid composite. Fluoride adsorption tests were performed in batch mode to evaluate effectiveness. Defluoridation capacity of up to 6.4 mg/g in field water containing fluoride concentration of 5-70 mg/L was achieved. The best performance was observed with fluoride concentration of 10 mg/L and below. Apart from fluoride removal, the composite also reduced color tint and microbes from surface water samples. The pH of the treated water in most samples remained around 6.5-8.5, which is acceptable for drinking water.
Zeolite and cellulose-acetate nanocomposites were fabricated in this study using a combination of melt blending and solution mixing. The nanocomposites were optimized for heavy metal adsorption using spiked lead and cadmium solutions. Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy and Powder X-Ray diffraction crystallography were used for physical characterization. Fourier Transform Infrared spectra showed a reduction of the hydroxyl peak for cellulose acetate and that of the residual silanol group for zeolites symbolizing bonding during nanocomposite formation. Scanning Electron Microscope results showed an increase in voids with zeolite loading in the nanocomposites, a useful characteristic of good adsorbents. Powder X-ray diffraction crystallography results showed a reduction in 2 theta values for the nanocomposites due to penetration of the polymer into the silicate lattice e.g. zeolite 2 theta peak at 7.44° reduced to 7.09° in the nanocomposites signifying an increase in crystal lattice d- spacing from 1.188 nm to 1.247 nm. The nanocomposites adsorbed a maximum of 97.20% lead ions and 85.06% cadmium ions from solution.
Fluoride levels in drinking water exceeding 1.5 mg/L especially underground water can be detrimental to health. Various defluoridation technologies exist such as reverse osmosis, adsorption and ion exchange. However, adsorption has been preferred over the other due to its low cost and ease of operation. In this study, a novel adsorbent nanomaterial was prepared to remove fluoride from drinking water. The influence of different parameters such as pH, contact time, co-existing ions and dosage were investigated in order to understand the sorption behaviour of the adsorbent under varying conditions. The adsorption process best fitted with the Langmuir model with a maximum adsorption capacity of 62.5 mg/g. The adsorbent can be used under normal water pH=7. Anions and cations had no influence on the sorption capacity except for chlorides, carbonates and bicarbonates. The adsorbent reduced fluoride concentration from 10 ppm to approximately 1.5 ppm per 50 mg nanocomposite loading as recommended by World Health Organization. The synthesized nanocomposite can be used for defluoridation of water with high fluoride concentrations beyond recommended limit.
Clinoptilolite modified with polypyrrole and iron oxide nanoparticles (Cln-PPy-Fe3O4) nanocomposite as a potential adsorbent for V (V) ions was prepared via polymerization of pyrrole monomer using FeCl3 oxidant in aqueous medium in which clinoptilolite-Fe3O4 nanoparticles were suspended. The structure and morphology of the prepared adsorbent was analysed with the Fourier transform infrared (FTIR) spectrometer, field-emission scanning electron microscope (FE-SEM), energy dispersive X-ray spectroscopy (EDX) and high-resolution transmission electron microscope (HR-TEM). Column fixed bed studies were performed to test the ability of the adsorbent to remove V (V) ions from aqueous solution. Low values of adsorbent exhaustion rate (AER) and large bed volumes were observed at lower metal ion concentration, higher bed mass and lower flow rate for V(V) removal indicating good performance. The volume of treated water processed at breakthrough point were found to be 0.09; 0.63 and 1.26 L for bed mass of 1, 2.5; and 5 g, respectively. The Yoon–Nelson and Thomas models appropriately described the breakthrough curves.
Chlorophenols are among the priority listed water contaminants due to their estrogenic, mutagenic or carcinogenic health effects. The Ag/ZnO nanocomposites (NCs) were synthesized, characterized and tested for photacatalytic degradation of chlorophenols in water. The synthesis was done using zinc nitrate hexahydrate (ZnNO3. 6H2O) precursor and sodium hydroxide (NaOH). Silver nitrate (AgNO3) was added to ZnO and reduced with sodium brohydride to produce the silver nanoparticles (NPs) within the ZnO structure. The silver content was varied from 1, 3 and 5wt% for optimisation. The nanocomposites were characterised using ultraviolet - visible spectroscopy (UV-Vis), photolumniscence (PL), x-ray diffraction (XRD), and scanning transmission electron microscopy (STEM). The nanocomposites were tested for their photocatalytic properties on 2- chlorophenol (CP), 2- chlorophenol (CP) and 2,4- dichlorophenol (DCP) in water. The UV-Vis results showed that, as the amount of silver was increased a gradual slight red shift was observed. The XRD patterns for Ag/ZnO exhibited peaks that were characteristic of the hexagonal wurzite structure and peaks characteristic for Ag appeared at 38.24o, 44.37o, 64.67o and 77.58o corresponding to (111), (200), (220) and (311) reflection planes. STEM results showed the presence of Ag in ZnO with ZnO appearing as rods shapes. The EDX elemental analysis confirmed the presence of Ag in the Ag/ZnO nanocomposites with no contaminants peaks. On testing the nanocomposites for phohotocatalytic degradation of chlorophenols, addition of Ag to ZnO improved degradation of the chlorophenols compared to the pristine ZnO.
Much of the global agricultural by products go waste, especially in developing nations where much of their revenues depend on the exports of raw agricultural products. Such waste streams, if converted to “value added” products could serve as additional source of revenue while simultaneously having a positive impact on the socio-economic well being of the people. We present a preliminary investigation on utilizing chemical activation technique and ball milling to convert agricultural waste streams such as cocoa pod, coconut husk, palm midrib and calabash commonly found in Ghana into ultra-high surface area activated carbon. Such activated carbons are suitable for myriads of applications in environmental remediation, climate management, energy storage and conversion systems (batteries and supercapacitors), and improving crop productivity. We achieved BET surface area as high as ∼ 3000 m2/g.