Olushola S. Ayanda

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.

Application of Cyanex® extractant in cobalt/nickel separation process by solvent extraction

This study presents a detailed review on the advanced hydrometallurgical treatment involving the extraction and separation of Cobalt (Co) and Nickel (Ni) by Cyanex® extractants. The structures, properties and applications of various Cyanex® extractants such as Cyanex®272, Cyanex®301, Cyanex®921, Cyanex®923 and Cyanex®421X were discussed and compared. Cyanex®272 thus proved to be the most appropriate solvent extractant for the separation of Co and Nickel from sulphate and chloride media due to its stability to common oxidant, better physicochemical properties and its ability to avoid gypsum crystallization in stripping-electrowinning circuit. Finally, various solvent extraction (SX) techniques for the extraction and separation of Co and Ni using Cyanex® extractants were discussed as well as newer processes of extraction and separation.

Use of mobile phones and cancer risk.

Mobile phones work by transmitting and receiving radio frequency microwave radiation. The radio frequency (RF) emitted by mobile phones is stronger than FM radio signal which are known to cause cancer. Though research and evidence available on the risk of cancer by mobile phones does not provide a clear and direct support that mobile phones cause cancers. Evidence does not also support an association between exposure to radio frequency and microwave radiation from mobile phones and direct effects on health. It is however clear that lack of available evidence of cancer as regards the use of mobile phone should not be interpreted as proof of absence of cancer risk, so that excessive use of mobile phones should be taken very seriously and with caution to prevent cancer.

Activated carbon-fly ash-nanometal oxide composite materials : preparation, characterization, and tributyltin removal efficiency

The physicochemical properties, nature, and morphology of composite materials involving activated carbon, fly ash, nFe3O4, nSiO2, and nZnO were investigated and compared. Nature and morphology characterizations were carried out by means of scanning electron and transmission electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. Other physicochemical characterizations undertaken were CNH analysis, ash content, pH, point of zero charge, and surface area and porosity determination by BET. Experimental results obtained revealed that activated carbon, nSiO2, activated carbon-fly ash, activated carbon-fly ash-nFe3O4, activated carbon-fly ash-nSiO2, and activated carbon-fly ash-nZnO composite materials exhibited net negative charge on their surfaces while fly ash, nFe3O4, and nZnO possessed net positive charge on their surfaces. Relatively higher removal efficiency (>99%) of TBT was obtained for all the composite materials compared to their respective precursors except for activated carbon. These composite materials therefore offer great potential for the remediation of TBT in wastewaters.

Application of black walnut (Juglans nigra) husk for the removal of lead (II) ion from aqueous solution

The biosorption characteristics of Pb (II) ions from aqueous solution using black walnut (Juglans nigra) seed husk (WSH) biomass were investigated using batch adsorption techniques. The effects of pH, contact time, initial Pb (II) ion concentration, and temperature were studied. The Langmuir, Freundlich and Temkin isotherms were used to analyze the equilibrium data. It was found that the adsorption of Pb (II) ions onto WSH was best described by the Freundlich adsorption model. Biosorption kinetics data were tested using the pseudo-first order and pseudo-second order models, and it was observed that the kinetics data fitted the pseudo-second order model. Thermodynamic parameters such as standard Gibbs free energy change (ΔG0), standard enthalpy change (ΔH0) and standard entropy change (ΔS0) were evaluated. The result showed that biosorption of Pb (II) ions onto WSH was spontaneous and endothermic in nature. The FTIR study showed that the following functional groups: O-H, C = O, C-O, C-H and N-H were involved in binding Pb (II) ions to the biomass.

Phenols, flame retardants and phthalates in water and wastewater – a global problem

Organic pollutants in water and wastewater have been causing serious environmental problems. The arbitrary discharge of wastewater by industries, and handling, use, and disposal constitute a means by which phenols, flame retardants (FRs), phthalates (PAEs) and other toxic organic pollutants enter the ecosystem. Moreover, these organic pollutants are not completely removed during treatment processes and might be degraded into highly toxic derivatives, which has led to their occurrence in the environment. Phenols, FRs and PAEs are thus highly toxic, carcinogenic and mutagenic, and are capable of disrupting the endocrine system. Therefore, investigation to understand the sources, pathways, behavior, toxicity and exposure to phenols, FRs and PAEs in the environment is necessary. Formation of different by-products makes it difficult to compare the efficacy of the treatment processes, most especially when other organic matters are present. Hence, high levels of phenols, FRs and PAEs removal could be attained with in-line combined treatment processes.

Biological wastewater treatment: Microbiology, chemistry, and diversity measurement of ammonia oxidizing bacteria

Nitrification is an important biological process in nitrogen cycling and has a significant effect on effluent quality in wastewater treatment. Nitrification occurs in two steps by two types of chemoautotrophic bacteria, the ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB). The ammonia oxidizing bacteria is responsible for the oxidation of ammonia with oxygen into nitrite and is often the rate-limiting step in nitrification in wastewater treatment plants. Hence, a better understanding of the ecology, microbiology and chemistry of ammonia oxidizing bacteria in biological wastewater treatment systems is necessary in order to enhance treatment performance and control. A detailed review of various biological wastewater treatment processes, ammonia oxidizing bacteria and archaea; economic importance, problems, various molecular techniques for the investigation of the diversity and community structure, as well as the isolation of ammonia oxidizing bacteria were discussed.

Kinetics, isotherm and thermodynamics of tributyltin removal by adsorption onto activated carbon, silica and composite material of silica and activated carbon

AbstractActivated carbon, silica, and composite material of silica and activated carbon were used as adsorbents to remove tributyltin (TBT) from artificial seawater, and the adsorption efficiencies for the precursors and the composite were compared. The composite presented higher TBT adsorption efficiency than the precursors. The adsorption of TBT onto these materials as a function of adsorbent amount, contact time, pH, stirring speed, initial adsorbate concentration, and temperature was investigated. Maximum TBT adsorption was recorded within the pH range of normal saline water (pH 8). The adsorption kinetics of TBT onto the adsorbents followed a pseudo-second-order kinetic model and the equilibrium adsorption data of TBT onto the precursors and composite were well represented by the Freundlich models. The calculated thermodynamic parameters indicated that TBT adsorption onto the precursor and the composite was spontaneous and endothermic. Optimal conditions for the adsorption of TBT from artificial seaw...

Sediment-associated trace and major metals in the headwaters of a tropical reservoir

ABSTRACT Bed sediment samples of the two headwaters of a tropical reservoir in Southwestern Nigeria were analysed for some metal concentrations using ICP-OES for a period of one year. Sediment samples were collected bi-monthly from both the lower and upper reaches of the streams from May 2013 to March 2014. Sediment samples were microwave-digested and analysed using ICP-OES. Concentrations of metals were higher in the lower reach than in the upper reach, and wet season concentrations were higher than in the dry season with the exception of Fe and Mn. The annual mean metal concentrations were as follows: Fe (121.72 ± 6.82 µg/g); Mn (9.34 ± 2.57 µg/g); Na (6.20 ± 2.29 µg/g); K (0.65 ± 0.57 µg/g); Mg (8.07 ± 1.36 µg/g); Ca (13.92 ± 2.85 µg/g); Ba (0.17 ± 0.17 µg/g); Al (106.54 ± 5.55 µg/g); and Se (0.6 ± 0.19 µg/g). These values were lower in comparison with the baseline concentrations of elements on the earth’s crust. Contamination assessment of all the metals investigated in this study showed that metals in the bed sediments of the two headstreams had not reached pollution status with the exception of Se.