No description available.

No description available.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, in fulfilment of the requirements for the degree of Master of Science in, Microbiology and Biotechnology 2016. / Heavy metal contamination, of natural water resources, resulting from the large amounts of toxic waste generated by industrial practices is of great environmental concern. Lead (Pb) in particular is one of the most toxic heavy metals that leads to several health deficiencies upon human exposure. The reduction of heavy metals like Pb to acceptable levels in the water therefore becomes critical for potable and agricultural use. Removal of heavy metals by conventional methods is expensive and results in secondary pollution. Bioremediation, a process that passively removes heavy metals from solution through microbial biosorption, is a much sought after alternative because it is more eco-friendly and cost-effective. Micrococcus luteus and Paenibacillus castaneae are two bacterial species reported to be highly resistant to Pb making them favourable as metal biosorbents. The present study aimed to further characterise these species as biosorbents by evaluating the influence of environmental conditions on their rate of biosorption of Pb. Each bacterial isolate was heat-killed and exposed to 0.5 mM (150 mg/L) Pb and the maximal rate of metal uptake calculated when the pH, temperature and biomass concentration were varied. Additionally, the initial metal concentration was increased from 0.005 to 1.25 mM to determine its effect on Pb uptake by each species. The influence of competing cations (Ni2+, Co2+, Mn2+ and Zn2+) on the rate of Pb uptake by each isolate was also established. Both bacterial isolates resulted in the biosorption of at least 50% of 0.5 mM Pb ions when used at a pH of 7, temperature of 25 oC, and a biomass concentration of 2 g/L. The rate of metal uptake for M. luteus at the above mentioned parameters was found to be 24.51 mg/g biomass, while the rate of metal uptake for P. castaneae was 15.63 mg/g biomass. These findings indicated that M. luteus took up more Pb at a faster rate in comparison to P. castaneae. The present study furthermore elucidated that as the metal concentration of Pb was increased, the amount of Pb biosorbed by M. luteus decreased from 84.76% to 46.10%. Similarly, P. castaneae yielded 81.39% biosorption from 0.005 mM Pb but only 34.29% of Pb was taken up when the concentration was increased to 1.25 mM. When the bacteria were exposed to various competing cations an increase in the rate of Pb biosorption was observed for P. castaneae while the opposite effect was noted for M. luteus. Findings from this study show that under high metal concentrations, both M. luteus and P. castaneae are capable of significantly reducing the level of Pb from pure solution. The results warrant further treatment of several industrial effluents using these biosorbents for subsequent application in wastewater treatment. / MT2017

University of Macau / Institute of Chinese Medical Sciences

by Kwok Shu Cheung, Eric. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1990. / Bibliography: leaves 89-106. / Acknowledgement --- p.i / Abstract --- p.ii / Introduction / Chapter A. --- Objective --- p.1 / Chapter B. --- Literature Review / Chapter 1. --- Electroplating industry in Hong Kong and its impact on the environment --- p.7 / Chapter 2. --- Physical and chemical methods for removing heavy metals from electroplating effluent --- p.11 / Chapter 3. --- Removal of heavy metals by conventional activated sludge process --- p.16 / Chapter 4. --- Acclimation of wastewater bacteria to heavy metals --- p.26 / Chapter 5. --- Biosorbent and its role in metal detoxification --- p.28 / Materials and Methods / Chapter A. --- Isolation and selection of nickel-resistant bacteria --- p.32 / Chapter B. --- Culture medium and solution --- p.33 / Chapter C. --- Growth of organism --- p.33 / Chapter D. --- Immobilization of bacterial cells --- p.36 / Chapter E. --- Effect of growth conditions on nickel removal capacity of immobilized Enterobacter sp. cells --- p.37 / Chapter F. --- Effect of bioreactor operational conditions on the Ni2+ removal capacity of immobilized bacterial cells --- p.38 / Chapter G. --- Optimization of nickel removal efficiency of bioreactor --- p.39 / Chapter H. --- Determination of Ni2+ adsorption isotherm of immobilized cells of Enterobacter sp. --- p.39 / Chapter I. --- Recovery of nickel from the bioreactor --- p.40 / Chapter J. --- Activity of the regenerated bioreactor --- p.41 / Chapter K. --- Removal of Ni2+ from synthetic effluent by bioreactor --- p.41 / Chapter L. --- Removal of Ni2+ from electroplating effluent by bioreactor. --- p.41 / Chapter M. --- Production of immobilized bacterial cells by replacement of D-glucose by molasses in the growth medium --- p.42 / Results / Chapter A. --- Isolation and selection of nickel resistant bacteria --- p.44 / Chapter B. --- Effect of growth conditions on nickel removal capacity of immobilized Enterobacter sp. cells / Chapter 1. --- Nutrient limitation --- p.44 / Chapter 2. --- D-glucose concentration --- p.45 / Chapter 3. --- Incubation temperature and incubation time --- p.45 / Chapter C. --- Heavy metal removal capacity of immobilized cells of Enterobacter sp. --- p.50 / Chapter D. --- Effect of bioreactor operational conditions on Ni2+ removal capacity of the immobilized bacterial cells --- p.50 / Chapter E. --- Optimization of nickel removal efficiency of bioreactor --- p.55 / Chapter F. --- Determination of Ni2+ adsorption isotherm of immobilized cells of Enterobacter --- p.57 / Chapter G. --- Recovery of nickel from the bioreactor and activity of regenerated bioreactor against a fresh nickel flow --- p.61 / Chapter H. --- Removal of Ni2+ from synthetic effluent by bioreactor --- p.61 / Chapter I. --- Removal of Ni2+ from electroplating effluent by bioreactor. --- p.64 / Chapter J. --- Production of immobilized bacterial cells by replacement of D-glucose by molasses in the growth medium --- p.68 / Discussions / Chapter A. --- Effect of growth conditions on nickel removal capacity of immobilized Enterobacter sp. cells --- p.70 / Chapter B. --- Heavy metal removal capacity of immobilized cells of Enterobacter sp. --- p.73 / Chapter C. --- Effect of bioreactor operational conditions on Ni2+ removal capacity of the immobilized bacterial cells --- p.74 / Chapter D. --- Optimization of nickel removal efficiency of bioreactor --- p.74 / Chapter E. --- Determination of Ni2+ adsorption isotherm of immobilized cells of Enterobacter sp. --- p.76 / Chapter F. --- Recovery of nickel from the bioreactor and activity of the regenerated bioreactor against a fresh nickel flow --- p.77 / Chapter G. --- Removal of Ni2+ from synthetic effluent by bioreactor --- p.78 / Chapter H. --- Removal of Ni2+ from electroplating effluent by bioreactor --- p.79 / Chapter I. --- Production of immobilized bacterial cells by replacement of D-glucose by molasses in the growth medium --- p.82 / Chapter J. --- Further considerations of applicability of immobilized Enterobacter sp. cells to treatment of electroplating effluent --- p.83 / Conclusions --- p.86 / References --- p.89

No description available.

Thesis (Ph. D.)--University of Hong Kong, 2009. / Includes bibliographical references (p. 167-180). Also available online.

Thesis (Ph. D.)--University of Hong Kong, 2009. / Includes bibliographical references (p. 167-180). Also available in print.

The technique of extraction with supercritical carbon dioxide (SC-CO$ sb2$), which is now used routinely for the recovery of non-polar analytes from a variety of liquid and semipermeable solid media, was extended to the efficient extraction of metal ions. Measurements of the solubilities in SC-CO$ sb2$ corroborated the hypothesis that the non-polar character of a series of tetraalkylammoniun dialkyldithiocarbamates ion pairs was influenced (i) primarily by the chain length of the alkyl substituent(s) on the carbamate nitrogen and (ii) to a lesser extent, by the chain length of the alkyl substituent(s) on the ammonium counter ion. In operation, analyte metal(s) in aqueous medium was derivatized by in situ complexation with the dithiocarbamate complexing reagent and the product complex(es) was partitioned into the SC-CO$ sb2$ mobile phase then purged from the extractor by replacing the headspace with fresh solvent. A novel silica flame-in-tube interface was developed for the sensitive detection, by atomic absorption spectrometry (AAS), of As, Cd, Cu, Mn, Pb, Se, or Zn in SC-CO$ sb2$ extractor eluate. For different analyte elements, the limits of detection (LODs) ranged from sub-nanogram to low picogram if standard was flow injected into the mobile phase. These sensitivities permitted differences in the rates of mobilization of different forms of the analyte metal from various media to be explored as a technique for probing the interaction of the analyte metal with the matrix. A portion of the Zn burden in fresh bovine liver was mobilized rapidly in the absence of complexing agent and the remainder was solubilized more rapidly than the Zn in a freeze-dried reference material of this tissue. The nebulizer assembly of a conventional flame-AAS was modified to extend the range of metals amenable to on-line detection. Supplemental heating of the inlet air to 200$ sp circ$C resulted in an on line detector which provided approximately a ten-fold improvement over convention

No description available.