Synthesis and characterization of FSB@Fe3O4 composites and application in removal of indigo carmine dye from industrial wastewaters.

The syntheses and characterization of fish scale biochar magnetic composites (FSB@Fe3O4) and their applications in the removal of indigo carmine dye from effluents are described. Preparation of the fish scale biochar magnetic composites, FSB@400 °C-Fe3O4, FSB@600 °C-Fe3O4, and FSB@800 °C-Fe3O4, was done following the chemical co-precipitation method. The adsorbents were characterized using peak optical absorbance, functional groups, magnetic strength, surface morphology, particle size, elemental compositions, surface charge, surface area, thermal stability, and crystalline phase, using ultraviolet-visible spectroscopy (UV-vis spec), Fourier transform infrared (FTIR) spectroscopy, vibrating sample magnetometry (VSM), transmission electron microscopy/scanning electron microscopy (TEM/SEM), energy dispersive X-ray (EDX), point of zero charge pH (pHpzc), Brunauer-Emmett-Teller (BET), thermo-gravimetric analysis (TGA), and powder x-ray diffraction (PXRD) techniques, correspondingly. The potential of magnetic composites for the abstraction of indigo carmine dye from wastewater was determined as a function of the initial concentration of indigo carmine dye, contact time, dye solution pH, adsorbent dosage, and solution temperature. The results demonstrated that the quantity (q) of indigo carmine dye adsorbed onto magnetic composites improved with a rise in initial dye concentration, adsorbent load, and solution temperature. Conversely, lower quantities of adsorbed dye were recorded at higher pH levels. The data fitted a pseudo-second-order kinetic model. The Langmuir isotherm gave the best fit (Langmuir>Freundlich>Redlich-Peterson>Toth>Hill>Sips>Temkin) suggesting a uniformly monolayer adsorption. Adsorption of environmental wastewater samples revealed that all the adsorbents can be used to effectively treat industrial wastewaters. The recycling data established that the adsorbents could be used for five consecutive cycles without significant loss of adsorption capacities.

Trace Elements in Crustaceans, Mollusks and Fish in the Kenyan Part of Lake Victoria: Bioaccumulation, Bioindication and Health Risk Analysis.

This is the first comprehensive report on the accumulation of Cr, Ni, As, and Ag in the fish species Nile tilapia Oreochromis niloticus and Nile perch Lates niloticus from Lake Victoria, complemented with recent data on Cu, Zn, Cd, and Pb. This also is the first report on Cr, Ni, As, and Ag levels in invertebrates: the shrimp Caridina nilotica, gastropod Pila ovata, and bivalve Mutela bourguignati. The study was conducted at five sites in the Kenyan part of Lake Victoria: four sites in Winam Gulf influenced by various anthropogenic pressures, including a site near Kisumu City, and one in the main lake, with lesser direct anthropogenic influence. Apart from Cu and Ag, which were highest in O. niloticus liver, the invertebrates had higher levels of trace elements than fish. Contamination of the gulf with trace elements was best mirrored by the invertebrates, whose mobility is limited; they accumulated Cr, Cd, Ag, and Pb corresponding to the levels in the surface sediment. The accumulation of trace elements in fish species and their bioindicative potential corresponded to their habitats and feeding behaviour. The tissue contents of most trace elements were higher in the inshore-dwelling, omnivorous O. niloticus compared to the pelagic, piscivorous L. niloticus. Cu (465 ± 689 mg/kg dw) and Ag (3.45 ± 1.49 mg/kg dw) in the liver of O. niloticus were up to 10 and 119 times higher than in L. niloticus, respectively. Oreochromis niloticus therefore has bioindicative potential for Cu and Ag contamination. Both the invertebrates and fish showed positive correlations between Cu and Ag concentrations, indicating similar source and/or uptake route. The target hazard quotients (THQ) show that there is no human health risk associated with the consumption of these fish. However, the levels of Zn, Cd, and Pb in P. ovata surpassed maximum food safety limits and are hence potentially unsafe for human consumption.

Distribution of arsenic, silver, cadmium, lead and other trace elements in water, sediment and macrophytes in the Kenyan part of Lake Victoria: spatial, temporal and bioindicative aspects.

This is the first detailed report on the distribution of Ni, As, Sr and Ag in water, sediments and macrophytes from Lake Victoria, complemented with recent data on the heavy metals Cr, Cu, Zn, Cd and Pb. The study was conducted over an 11-month period at five sites in the Kenyan part of Lake Victoria: four sites in the Winam Gulf influenced by various anthropogenic pressures including a site near Kisumu City, and one in the main lake, perceived to have lesser direct anthropogenic influence. Compared with the main lake site, the water in Winam Gulf had significantly higher values for electrical conductivity and concentrations of dissolved components: organic carbon and bound nitrogen, as well as major and most trace elements. This contamination is also evident in surface sediments, which contained significantly higher levels of Cr, Zn, As, Ag, Cd and Pb compared with the main lake site. The mean levels of Cr, Cu, Zn, Ag and Pb exceeded probable effect levels at least at one of the gulf sites. The sediments at the Kisumu City site were classified as severely polluted with Cu (up to 259 mg/kg dw) and Pb (up to 1188 mg/kg dw). The sediment cores showed significantly higher levels of Cu, Zn, Ag, Cd and Pb in the surface (0-3 cm) versus subsurface (22-25 cm) layer at the Kisumu City site, indicating increasing pollution by these elements within the last 15 years. This is also the first report on trace elements in the emergent water plant Vossia cuspidata and submerged plant Ceratophyllum demersum from this lake. Even though the accumulation of most elements is comparable between C. demersum (whole plant) and V. cuspidata roots, the latter shows a better bioindicative potential. Contamination of the gulf with Ni, Cu, Zn, Ag, Cd and Pb is well mirrored in V. cuspidata roots. V. cuspidata strongly restricts the acropetal transport of trace elements, and hence using the shoots as fodder does not pose a risk to livestock.

Preparation, characterization of fish scales biochar and their applications in the removal of anionic indigo carmine dye from aqueous solutions.

The preparation and applications of Tilapia (Oreochromis niloticus) fish scale biochars (FSB) as an adsorbent in the removal of indigo carmine dye (ICD) from aqueous solutions is described. The biochars were prepared through pyrolysis over a temperature range of 200 °C-800 °C and characterized for surface charge, functional groups, thermal stability, particle size and morphology, elemental composition, crystallinity, and surface area by using pHpzc, Fourier transform infrared (FTIR) spectroscopy, thermo-gravimetric analysis (TGA), transmission electron microscopy/scanning electron microscopy (TEM/SEM), energy dispersive X-ray (EDX) spectroscopy, powder X-ray diffraction (PXRD) and Brunauer-Emmett-Teller (BET) techniques, respectively. Batch experiments were carried out to determine the variation of adsorption process with initial dye concentration, contact time, initial solution pH, adsorbent load, temperature and adsorbent pyrolysis temperature on the removal of the dye. The percentage removal increased with increase in initial dye concentration and adsorbent dosage. A pH of 2 was the most appropriate for the adsorption experiments. The equilibrium data fitted pseudo-first-order kinetics and Freundlich models, while the thermodynamic parameters confirmed that the adsorption process was endothermic.