Folahan A. Adekola

Comparison of some physicochemical characterisation of columbite and tantalite samples from different locations in Nigeria

A detailed physicochemical characterization of columbite and tantalite samples from different locations in Nigeria has been undertaken. Parameters such as moisture content, loss of mass on ignition, pH, and the specific gravity of columbite and tantalite samples from different locations were determined and compared. The results showed that the moisture content of columbite samples obtained from Kwara and Plateau States are 1.0 and 0.53 %, respectively, while the percentage of moisture content of tantalite samples obtained from Kwara, Kogi, Kaduna, and Nasarawa States are 0.37, 0.30, 0.67 and 1.00 %, respectively. The percentage loss of mass on ignition of columbite samples obtained from Kwara and Plateau States and tantalite samples from Kwara, Kogi, Kaduna, and Nasarawa States are 6.1, 3.6, 7.7, 2.4, 4.4 and 4.3 %, respectively. Values of 2.40, 3.76, 3.65, 3.37, 2.07 and 1.96 were obtained as the specific gravities of columbite samples obtained from Kwara and Plateau States and tantalite samples from Kwara, Kogi, Kaduna, and Nasarawa States, respectively, and finally, the mean pH for each of columbite and tantalite samples was approximately 7.6.This study investigated the concentration ratios of dissolved nitrate: phosphate in tropical coastal waters in Mauritius (1,850 km2, 20ıS and 57ıE, Western Indian ocean) during winter 2008 and summer 2009 arising from both surface and submarine groundwater sources. Dissolved nutrients in lagoon waters were statistically compared between winter and summer periods and between urban and rural estuaries at Grand River North West (GRNW), Albion and Flic en Flac. A low ratio of 5 was computed for dissolved [nitrate]: [phosphate] for the Flic en Flac lagoon situated in a rural area, lying in the range from 2 to 15 as usually found for coastal waters globally suggesting denitrification whereas the ratio of dissolved [nitrate]: [phosphate] in lagoon waters computed for GRNW and Albion situated in urban areas were lower and less than 2 and may be attributed to possible high phosphate input. The sources of dissolved phosphate may come from the run-off of phosphate fertilisers from sugar cane plantations and submarine groundwater discharges. This high concentration of dissolved phosphate in the freshwater system can be harmful as it can cause an algal bloom. A high concentration of dissolved phosphate was recorded in September during a flood. The mean values for dissolved nitrate were 11.8 ̇ 11.0 mol/L during winter and 11.7 ̇ 5.0 mol/L during summer at Flic en Flac. Dissolved nitrate levels were observed to be abnormally high which probably were due to the lagoon water being mixed with the submarine groundwater discharge in the lagoon. In addition, a strong positive correlation was observed between phosphate and nitrate (R2D 0.74) during the period of winter 2009 to summer 2010 for all the stations at Flic en Flac. Z.B. Bissembur • J. Balgobin • A. Anjore • R.T. Ramessur • K. Boodhoo ( ) Department of Chemistry, University of Mauritius, Réduit, Mauritius e-mail: zeinabiss72@yahoo.com; j1 balgobin@yahoo.com; ramessur@uom.ac.mu; kishore.boodhoo@uom.ac.mu M.G. Bhowon et al. (eds.), Chemistry for Sustainable Development, DOI 10.1007/978-90-481-8650-1 1,

Human Exposure, Biomarkers, and Fate of Organotins in the Environment

Organotin compounds result from the addition of organic moieties to inorganic tin.Thus, one or more tin-carbon bonds exist in each organotin molecule. The organo-tin compounds are ubiquitous in the environment. Organotin compounds have many uses, including those as fungicides and stabilizers in plastics, among others in industry. The widespread use of organotins as antifouling agents in boat paints has resulted in pollution of freshwater and marine ecosystems. The presence of organotin compounds in freshwater and marine ecosystems is now understood to be a threat, because of the amounts found in water and the toxicity of some organotin compounds to aquatic organisms, and perhaps to humans as well. Organotin com-pounds are regarded by many to be global pollutants of a stature similar to biphenyl,mercury, and the polychlorinated dibenzodioxins. This stature results from the high toxicity, persistence, bioaccumulation, and endocrine disruptive features of even very low levels of selected organotin compounds.Efforts by selected governmental agencies and others have been undertaken to find a global solution to organotin pollution. France was the first country to ban the use of the organotins in 1980. This occurred before the international maritime organization (IMO) called for a global treaty to ban the application of tributyltin (TBT)-based paints. In this chapter, we review the organotin compounds with emphasis on the human exposure, fate, and distribution of them in the environment. The widespread use of the organotins and their high stability have led to contamination of some aquatic ecosystems. As a result, residues of the organotins may reach humans via food consumption. Notwithstanding the risk of human exposure, only limited data are available on the levels at which the organotins exist in foodstuffs consumed by humans. Moreover, the response of marine species to the organotins, such as TBT, has not been thoroughly investigated. Therefore, more data on the organotins and the consequences of exposure to them are needed. In particular, we believe the following areas need attention: expanded toxicity testing in aquatic species, human exposure, human body burdens, and the research to identify biomarkers for testing the toxicity of the organotins to marine invertebrates.

Bioleaching of Zn(II) and Pb(II) from Nigerian sphalerite and galena ores by mixed culture of acidophilic bacteria

Zn(II) and Pb(II) from Nigerian sphalerite and galena ores were bioleached by a mixed culture of acidophilic bacteria. The influences of pH and ferric ion on the bioleaching rates of sphalerite and galena were examined. The result shows that pH 2.1 and 2.7 are favourable for the leaching of Zn(II) and Pb(II) from sphalerite and galena, respectively. It was observed that the use of agarose-simulated media caused cells to excrete exopolymers containing ferric ions which enhanced oxidation. The oxidation equilibrium for sphalerite and galena took 3 and 4 d, respectively. About 38.3% sphalerite and 34.2% galena were leached within 1 d and approximately 92.0% Zn(II) and 89.0% Pb(II) were recovered in 5 d, respectively. The unleached residual products were examined by X-ray diffraction for sphalerite, revealing the presence of elemental sulphur(S), zinc sulphate (ZnSO4) and few traces of calcium aluminate (Ca3Al2O6). The XRD pattern also indicates the presence of elemental sulphur (S), lead sulphate (PbSO4) and few traces of itoite (Pb(S,Ge)(O,OH)4) and cobalt lead silicate (Pb8Co(Si2O7)3) in the unleached galena ore.

Kinetics and equilibrium models for the sorption of tributyltin to nZnO activated carbon and nZnO / activated carbon composite in artificial seawater

The removal of tributyltin (TBT) from artificial seawater using nZnO, activated carbon and nZnO/activated carbon composite was systematically studied. The equilibrium and kinetics of adsorption were investigated in a batch adsorption system. Equilibrium adsorption data were analyzed using Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (D-R) isotherm models. Pseudo first- and second-order, Elovich, fractional power and intraparticle diffusion models were applied to test the kinetic data. Thermodynamic parameters such as ΔG°, ΔS° and ΔH° were also calculated to understand the mechanisms of adsorption. Optimal conditions for the adsorption of TBT from artificial seawater were then applied to TBT removal from natural seawater. A higher removal efficiency of TBT (>99%) was obtained for the nZnO/activated carbon composite material and for activated carbon but not for nZnO.

A Comparative Study of the Adsorption of Methylene Blue onto Synthesized Nanoscale Zero-Valent Iron-Bamboo and Manganese-Bamboo Composites

In this study, bamboo impregnated with nanoscale zero-valent iron (nZVI) and nanoscale manganese (nMn) were prepared by the aqueous phase borohydride reduction method and characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and PIXE analysis. The synthesized nMn-bamboo and nZVI-bamboo composites were subsequently applied to the sorption of methylene blue (MB) dye from aqueous solution. The adsorption of MB dye was investigated under various experimental conditions such as pH, contact time, initial concentration of MB dye and adsorbent dosage. The results showed that the synthesized nZVI-bamboo composite was more effective than nMn-bamboo composite in terms of higher MB dye adsorption capacity of 322.5 mg/g compared to 263.5 mg/g of nMn-bamboo composite. At a concentration of 140 mg/L MB dye, 0.02 g of nZVI-bamboo and nMn-bamboo composites resulted in 79.6% and 78.3% removal, respectively, at 165 rpm, contact time of 120 min and at a solution pH of 7.6. The equilibrium data was best represented by Freundlich isotherm model and the pseudo-second order kinetic model better explained the kinetic data for both nZVI-bamboo and nMn-bamboo composites.

Characterization of Fly Ash Generated from Matla Power Station in Mpumalanga, South Africa

In this study, fly ash was obtained from Matla power station and the physicochemical properties investigated. The fly ash was characterized by x-ray fluorescence, x-ray diffraction, scanning electron microscopy, and inductively coupled plasma mass spectrometry. Surface area, particle size, ash and carbon contents, pH, and point of zero charge were also measured. The results showed that the fly ash is alkaline and consists mainly of mullite (Al6Si2O13) and quartz (SiO2). Highly toxic metals As, Sb, Cd, Cr, and Pb as well as metals that are essential to health in trace amounts were also present. The storage and disposal of coal fly ash can thus lead to the release of leached metals into soils, surface and ground waters, find way into the ecological systems and then cause harmful effect to man and its environments.

Sequential extraction of trace metals and particle size distribution studies of Kainji Lake sediment, Nigeria

Abstract Sequential extraction was carried out to determine the concentrations of some trace metals (Mn, Cu, Fe, Pb and Cd) in the Kainji lake sediments from seven different locations in four fractions: exchangeable, bound to iron and manganese oxide, bound to organic matters and residual. This was to undertaken to assess the environmental fate of these trace metals. The BCR technique, a modified form of the Tessier method of sequential extraction was used. The proportion of the mean metal concentrations of the bioavailable metals follows the order Fe>Cu>Pb>Mn>Cd. Generally, Fe was most abundant metal in the sediment and about 40% was found in its bioavailable form. Although Cd contributed least to the bioavailable content, a greater percentage (~60%) was found in the bioavailable fraction. This suggests that Cd is highly mobile and, since it is known to be toxic, its concentration in the bioavailable form constitutes an environmental threat. The contribution of metals bound to organic matter was found to be high and of the same magnitude as those bound to oxides and constitutes about 70% of the non-bioavailable metal contents. The petrological analysis of the sediments revealed that the sediments were predominantly quartz and rock clays with percussion marks and indentations.

Determination of concentration of heavy metals in two common fish species from asa river, ilorin, nigeria

Concentrations of some heavy metals in Tilapia zilli (Tilapia) and Synodontis membrane (Catfish), the two common fishes from Asa River Ilorin, Nigeria have been determined. Manganese, zinc, iron, and lead, were present at appreciable concentrations in the tissues of the two species while cadmium, mercury, and nickel, were found to be less than 0.01 ppm. Concentrations of metals were highest downstream than at upstream locations. Mean concentrations of Mn in Tilapia, ranged between 0.56 ppm at the upstream end and 2.69 mg/kg of fresh weight at the downstream end. Pb, Zn, and Cr ranged between 4.05 and 5.59 mg/kg of fresh weight, 0.09 and 1.16 ppm, 5.62 and 11.15 ppm, and 0.09 and 0.13 ppm respectively. In the Catfish, Mn, Fe, Zn, and Cr ranged between 0.62 and 0.78 ppm, 3.79 and 8.79 ppm, 0.78 and 1.57 ppm, 7.30 and 15.15, and 0.23 and 0.35 ppm respectively. Heavy metals except lead did not pose any health risks in human since the calculated probable amounts being ingested by an average adult (50 kg average weight) per day were lower than WHO maximum recommended value of intake. However, the level of lead was higher than WHO limit and this could render inedible the fishes from this catchment river.

Characterization and kinetic study on ammonia leaching of complex copper ore

Abstract Ammonia leaching kinetics of a complex Cu-ore assaying 8.8% Cu and 36.1% Fe was examined. Mineralogical characterization indicated that the major phase of the ore was siderite with chalcopyrite as the major sulfide mineral. The effects of parameters such as agitation, temperature, NH 3 concentration, particle size and oxygen partial pressure ( p O2 ) were investigated. Under the standard leaching conditions of 125–212 µm particle size, 120 °C, 1.29 mol/L NH 3 and 202 kPa of p O2 , about 83% Cu could be selectively extracted in 2.5 h. However, when using higher NH 3 concentration and lower particle size, more than 95% extraction was achieved. The leaching process was found to be surface reaction controlling. The estimated activation energy was (37.6±1.9) kJ/mol and empirical orders of reaction with respect to p O2 and [NH 3 ] were about 0.2 and 1, respectively.

Kinetics and Equilibrium Models for Sorption of Cu(II) onto a Novel Manganese Nano-adsorbent

Abstract The studies of kinetics and equilibrium sorption of Cu(II) were undertaken using nanoscale zerovalent manganese (nZVMn) synthesized by chemical reduction in a single pot system. nZVMn was characterized using scanning electron microscopy, energy dispersive x-ray, and surface area determined by Brunauer–Emmett–Teller. The effect of pH, contact time, adsorbent dose, agitation speed, initial Cu(II) concentrations, temperature, and ionic strength on the sorption of Cu(II) onto nZVMn were investigated in a batch system. The kinetic data followed pseudo-second-order. The mechanism was governed by pore diffusion. The equilibrium sorption data were tested by Freundlich, Langmuir, Temkin, Dubinin–Kaganer–Raduskevich, and Halsey isotherm models. The Langmuir monolayer adsorption capacity (Qmax = 181.818 mg/g) is much greater compared to other nano-adsorbents used in sorption of Cu(II). The thermodynamic parameters (ΔH0, ΔS0, ΔG0) revealed a feasible, spontaneous, and endothermic adsorption process. nZVMn has a great potential for effective removal of copper (II) in aqueous solution. GRAPHICAL ABSTRACT