The selective recovery of rhodium from wastewaters, in which the metal would be otherwise lost, would be highly profitable if the process were suitably low-cost. Current recovery processes are generally high maintenance and high-cost, whereas biological processes can be engineered to run with little external input in terms of cost and maintenance. Three emerging technologies were chosen based on their reported efficiency when removing base metals from wastewaters. The first technology screened, the sulphide-extraction membrane bioreactor (SEMB), consists of a sulphate-reducing prokaryote (SRP) anaerobic digester, in which a silicone membrane is submerged. Wastewater is passed through the membrane and metal ions are precipitated as metal sulphides by the hydrogen sulphide gas, which is capable of permeating the membrane. The second technology screened was a fluidized sand bed reactor in which metal ions are removed from solution via induction of nucleated precipitation by sodium carbonate onto the sand grains. The third, and most well established removal technology screened was a biosorption system using immobilized Saccharomyces cerevisiae biomass as the biosorbent. Experimental trials with each technology highlighted drawbacks with each; the SEMB system proved to be largely ineffective when challenged with the removal of rhodium from the wastewater as the rhodium precipitate fouled the membrane within hours, the fluidized bed system seemed unable to overcome the acidity of the wastewater and thus could not precipitate out the rhodium metal, and the efficiency of the biosorption process was hampered by the diversity of rhodium species present in the wastewater, which reduced the amount recovered. The outcomes of the trials with each technology indicated that further optimization of the technology or pretreatment of the wastewater is necessary before any of these options can be implemented. It could be concluded, however, that despite further optimization, both the SEMB and the fluidized bed system were not applicable in this case as precipitation would be non-specific, resulting in the necessity for further steps in order to purify the rhodium ions. Hence, the biosorption system was shown to be most applicable, and further optimization of the system could yield a highly efficient rhodium recovery process.

This thesis explains a method based on the homogenisation of zeta potential charges on carbon supports for the production of hierarchical structured zeolitic composites. The modification of carbons’ surface chemistry allowed zeolite particles to be fixed to the support by electrostatic interactions. In order to achieve this, the size reduction of zeolite particles was carried out by two different methods: a) ball milling and b) a synthetic route to produce zeolite colloidal dispersions. Also, the seeding method, based on hydrothermal growth was compared. The prepared materials in this work were designed to be used in the sorption of cations, and to allow vitrification and thereby reduce the final adsorbent volume. Results showed that a large pollutant amount can be trapped using a lower volume of material reducing costs and final waste disposal. The zeolites used in this work were selected based on their low density framework and low Si/Al ratio. Synthetic zeolites A, Y and clinoptilolite were successfully produced. Natural clinoptilolite was also utilised in this work. Also, zeolite A was produced at nanometre scale following the clear solutions method. All materials were successfully incorporated onto supports to produce multimodal porosity materials. The hierarchical modification of natural clinoptilolite, following a straightforward and nonexpensive methodology, is one the most significant contributions of this work. Carbons are used as supports due to their high surface area, they can be obtained from low-cost sources such as agroindustrial wastes and carbons allow volume reduction if materials are vitrified at high temperatures. In this work, carbons were produced from corn cob and husk, sugar cane bagasse, cherry stones, date stones and hazelnut shells. The prepared composite materials were tested in the removal of toxic ions from water solutions: cobalt, copper and caesium ions were effectively removed from aqueous media. Adsorption experiments showed that the distribution of supported zeolite particles improved their uptake efficiency and capacity. The kinetic studies revealed an enhanced rate constant for carbon-zeolites composites in comparison with pure zeolites. Diffusivity results suggested that mass transfer characteristics are modified by using hierarchical porous materials; results showed that particle size or support nature can modify diffusion resistances, reducing intraparticle diffusion and accelerating the overall kinetic processes. Adsorption equilibrium data was correlated using Langmuir and Freundlich models.

by Tsui Wai-chu. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 161-171). / Abstracts in English and Chinese. / Acknowledgements --- p.i / Abstract --- p.ii / Abbreviations --- p.vii / Contents --- p.ix / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Literature review --- p.1 / Chapter 1.1.1 --- Metal pollution in Hong Kong --- p.1 / Chapter 1.1.2 --- Methods for removal of metal ions from industrial effluent --- p.4 / Chapter A. --- Physico-chemical methods --- p.4 / Chapter B. --- Biosorption --- p.7 / Chapter 1.1.3 --- Chitin and chitosan --- p.11 / Chapter A. --- History of chitin and chitosan --- p.11 / Chapter B. --- Structures and sources of chitin and chitosan --- p.12 / Chapter C. --- Characterization of chitin and chitosan --- p.17 / Chapter D. --- Applications of chitin and chitosan --- p.19 / Chapter 1.1.4 --- Factors affecting biosorption --- p.22 / Chapter A. --- Solution pH --- p.22 / Chapter B. --- Concentration of biosorbent --- p.24 / Chapter C. --- Retention time --- p.25 / Chapter D. --- Initial metal ion concentration --- p.26 / Chapter E. --- Presence of other cations --- p.26 / Chapter F. --- Presence of anions --- p.28 / Chapter 1.1.5 --- Regeneration of metal ion-laden biosorbent --- p.28 / Chapter 1.1.6 --- Modeling of biosorption --- p.29 / Chapter A. --- Adsorption equilibria and adsorption isotherm --- p.29 / Chapter B. --- Langmuir isotherm --- p.33 / Chapter C. --- Freundlich isotherm --- p.34 / Chapter 1.2 --- Objectives of the present study --- p.36 / Chapter 2. --- Materials and methods --- p.37 / Chapter 2.1 --- Biosorbents --- p.37 / Chapter 2.1.1 --- Production of biosorbents --- p.37 / Chapter 2.1.2 --- Pretreatment of biosorbents --- p.39 / Chapter 2.2 --- Characterization of biosorbents --- p.39 / Chapter 2.2.1 --- Chitin assay --- p.39 / Chapter 2.2.2 --- Protein assay --- p.40 / Chapter 2.2.3 --- Metal analysis --- p.41 / Chapter 2.2.4 --- Degree of N-deacetylation analysis --- p.43 / Chapter A. --- Diffuse reflectance Fourier transform infra-red spectroscopy --- p.43 / Chapter B. --- Elemental analysis --- p.43 / Chapter 2.3 --- Batch biosorption experiment --- p.44 / Chapter 2.4 --- Selection of biosorbent for metal ion removal --- p.45 / Chapter 2.4.1 --- Effects of pretreatments of biosorbents on adsorption of Cu --- p.45 / Chapter A. --- Washing --- p.45 / Chapter B. --- Pre-swelling --- p.46 / Chapter 2.4.2 --- "Comparison of Cu2+, Ni2+ and Zn2+ removal capacities among three biosorbents" --- p.46 / Chapter 2.4.3 --- Comparison of Cu2+ removal capacity of chitins with various degrees of N-deacetylation --- p.46 / Chapter 2.5 --- "Effects of physico-chemical conditions on Cu2+, Ni2+ and Zn2+ adsorption by chitin A" --- p.48 / Chapter 2.5.1 --- Solution pH and concentration of biosorbent --- p.48 / Chapter 2.5.2 --- Retention time --- p.48 / Chapter 2.5.3 --- Initial metal ion concentration --- p.49 / Chapter 2.5.4 --- Presence of other cations --- p.49 / Chapter 2.5.5 --- Presence of anions --- p.51 / Chapter 2.6 --- Optimization of Cu2+，Ni2+ and Zn2+ removal efficiencies --- p.53 / Chapter 2.7 --- "Recovery of Cu2+, Ni2+ and Zn2+ from metal ion-laden chitin A" --- p.53 / Chapter 2.7.1 --- Performances of various eluents on metal ion recovery --- p.53 / Chapter 2.7.2 --- Multiple adsorption and desorption cycle of metal ions --- p.54 / Chapter 2.8 --- Treatment of electroplating effluent by chitin A --- p.54 / Chapter 2.8.1 --- "Removal and recovery of Cu2+, Ni2+ and Zn2+ from electroplating effluent collected from rinsing baths" --- p.54 / Chapter 2.8.2 --- "Removal and recovery of Cu2+, Ni2+ and Zn2+ from electroplating effluent collected from final collecting tank" --- p.55 / Chapter 2.9 --- Data analysis --- p.56 / Chapter 3. --- Results --- p.58 / Chapter 3.1 --- Characterization of biosorbents --- p.58 / Chapter 3.1.1 --- Chitin assay --- p.58 / Chapter 3.1.2 --- Protein assay --- p.58 / Chapter 3.1.3 --- Metal analysis --- p.58 / Chapter 3.1.4 --- Degree of N-deacetylation analysis --- p.62 / Chapter A. --- Diffuse reflectance Fourier transform infra-red spectroscopy --- p.62 / Chapter B. --- Elemental analysis --- p.62 / Chapter 3.2 --- Selection of biosorbent for metal ion removal --- p.67 / Chapter 3.2.1 --- Effects of pretreatments of biosorbents on adsorption of Cu2+ --- p.67 / Chapter A. --- Washing --- p.67 / Chapter B. --- Pre-swelling --- p.67 / Chapter 3.2.2 --- "Comparison of Cu2+, Ni2+ and Zn2+ removal capacities among three biosorbents" --- p.67 / Chapter 3.2.3 --- Comparison of Cu2+ removal capacity of chitins with various degrees of N-deacetylation --- p.70 / Chapter 3.3 --- "Effects of physico-chemical conditions on Cu2+, Ni2+ and Zn2+ adsorption by chitin A" --- p.70 / Chapter 3.3.1 --- Solution pH and concentration of biosorbent --- p.70 / Chapter 3.3.2 --- Retention time --- p.78 / Chapter 3.3.3 --- Initial metal ion concentration --- p.80 / Chapter 3.3.4 --- Presence of other cations --- p.93 / Chapter 3.3.5 --- Presence of anions --- p.93 / Chapter 3.4 --- "Optimization of Cu2+, Ni2+ and Zn2+ removal efficiencies" --- p.104 / Chapter 3.5 --- "Recovery of Cu2+, Ni2+ and Zn2+ from metal ion-laden chitin A" --- p.104 / Chapter 3.5.1 --- Performances of various eluents on metal ion recovery --- p.104 / Chapter 3.5.2 --- Multiple adsorption and desorption cycle of metal ions --- p.109 / Chapter 3.6 --- Treatment of electroplating effluent by chitin A --- p.117 / Chapter 3.6.1 --- "Removal and recovery of Cu2+, Ni2+ and Zn2+ from electroplating effluent collected from rinsing baths" --- p.117 / Chapter 3.6.2 --- "Removal and recovery of Cu2+, Ni2+ and Zn2+ from electroplating effluent collected from final collecting tank" --- p.121 / Chapter 4. --- Discussion --- p.128 / Chapter 4.1 --- Characterization of biosorbents --- p.128 / Chapter 4.1.1 --- Chitin assay --- p.128 / Chapter 4.1.2 --- Protein assay --- p.129 / Chapter 4.1.3 --- Metal analysis --- p.129 / Chapter 4.1.4 --- Degree of N-deacetylation analysis --- p.130 / Chapter A. --- Diffuse reflectance Fourier transform infra-red spectroscopy --- p.130 / Chapter B. --- Elemental analysis --- p.132 / Chapter 4.2 --- Selection of biosorbent for metal ion removal --- p.133 / Chapter 4.2.1 --- Effects of pretreatments of biosorbents on adsorption of Cu2+ --- p.133 / Chapter A. --- Washing --- p.133 / Chapter B. --- Pre-swelling --- p.133 / Chapter 4.2.2 --- "Comparison of Cu2+, Ni2+ and Zn2+ removal capacities among three biosorbents" --- p.134 / Chapter 4.2.3 --- Comparison of Cu2+ removal capacity of chitins with various degrees of N-deacetylation --- p.136 / Chapter 4.3 --- "Effects of physico-chemical conditions on Cu2+, Ni2+ and Zn2+ adsorption by chitin A" --- p.137 / Chapter 4.3.1 --- Solution pH and concentration of biosorbent --- p.137 / Chapter 4.3.2 --- Retention time --- p.138 / Chapter 4.3.3 --- Initial metal ion concentration --- p.139 / Chapter 4.3.4 --- Presence of other cations --- p.141 / Chapter 4.3.5 --- Presence of anions --- p.143 / Chapter 4.4 --- "Optimization of Cu2+, Ni2+ and Zn2+ removal efficiencies" --- p.147 / Chapter 4.5 --- "Recovery of Cu2+, Ni2+and Zn2+ from metal ion-laden chitin A" --- p.148 / Chapter 4.5.1 --- Performances of various eluents on metal ion recovery --- p.148 / Chapter 4.5.2 --- Multiple adsorption and desorption cycle of metal ions --- p.149 / Chapter 4.6 --- Treatment of electroplating effluent by chitin A --- p.150 / Chapter 4.6.1 --- "Removal and recovery of Cu2+, Ni2+ and Zn2+ from electroplating effluent collected from rinsing baths" --- p.150 / Chapter 4.6.2 --- "Removal and recovery of Cu2+, Ni2+ and Zn2+ from electroplating effluent collected from final collecting tank" --- p.152 / Chapter 5. --- Conclusion --- p.154 / Chapter 6. --- Further studies --- p.156 / Chapter 7. --- Summary --- p.158 / Chapter 8. --- References --- p.161

by Sze Kwok Fung Calvin. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (leaves 118-130). / Acknowledgement --- p.i / Abstract --- p.ii / Content --- p.iv / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Literature review --- p.1 / Chapter 1.1.1 --- Heavy metals in the environment --- p.1 / Chapter 1.1.2 --- Heavy metal pollution in Hong Kong --- p.2 / Chapter 1.1.3 --- Electroplating industry in Hong Kong --- p.6 / Chapter 1.1.4 --- Chemistry and toxicity of copper in the environment --- p.7 / Chapter 1.1.5 --- Methods of removal of heavy metal from industrial effluent --- p.9 / Chapter A. --- Physico-chemical methods --- p.9 / Chapter B. --- Biological methods --- p.9 / Chapter 1.1.6 --- Methods of recovery of heavy metal from metal-loaded biosorbent --- p.17 / Chapter 1.1.7 --- The physico-chemical properties of magnetites --- p.18 / Chapter 1.1.8 --- Magnetites for water and wastewater treatment --- p.19 / Chapter 1.1.9 --- Immobilized cell technology --- p.24 / Chapter 1.1.10 --- Stirrer-tank bioreactor --- p.26 / Chapter 1.2 --- Objectives of the present study --- p.28 / Chapter 2. --- Materials and Methods --- p.30 / Chapter 2.1 --- Selection of copper-resistant bacteria --- p.30 / Chapter 2.2 --- Culture media and chemicals --- p.30 / Chapter 2.3 --- Growth of the bacterial cells --- p.32 / Chapter 2.4 --- Immobilization of the bacterial cells on magnetites --- p.32 / Chapter 2.4.1 --- Effects of physical and chemical factors on the immobilization of the bacterial cells on magnetites --- p.34 / Chapter 2.4.2 --- Effects of pH on the desorption of bacterial cells from magnetites --- p.34 / Chapter 2.5 --- Copper ion uptake experiments --- p.35 / Chapter 2.6 --- Effects of physico-chemical and operational factors on the Cu2+ removal capacity of the magnetite-immobilized bacterial cells --- p.35 / Chapter 2.7 --- Transmission electron micrograph and scanning electron micrograph of Pseudomonas putida 5-X loaded with Cu2+ --- p.36 / Chapter 2.7.1 --- Transmission electron micrograph --- p.36 / Chapter 2.7.2 --- Scanning electron micrograph --- p.37 / Chapter 2.8 --- Copper ion adsorption isotherm of the magnetite-immobilized cells of Pseudomonas putida 5-X --- p.37 / Chapter 2.9 --- Recovery of adsorbed Cu2+ from the magnetite-immobilized cells of Pseudomonas putida 5-X --- p.38 / Chapter 2.9.1 --- Effects of eluents on the Cu2+ removal and recovery capacity of the magnetite-immobilized cells --- p.38 / Chapter 2.9.2 --- Batch type multiple adsorption-desorption cycles of Cu2+ using ethylenediaminetetra-acetic acid (EDTA) --- p.39 / Chapter 2.10 --- Removal and recovery of Cu2+ from the electroplating effluent by a bioreactor --- p.39 / Chapter 2.10.1 --- Batch type multiple adsorption-desorption cycles using the copper solution and electroplating effluent --- p.39 / Chapter 2.10.2 --- Continuous type bioreactor to remove and recover Cu2+ from copper solution and electroplating effluent --- p.40 / Chapter 2.11 --- Statistical analysis of data --- p.43 / Chapter 3. --- Results --- p.44 / Chapter 3.1 --- Effects of physical and chemical factors on the immobilization of the bacterial cells on magnetites --- p.44 / Chapter 3.1.1 --- Effects of cells to magnetites ratio --- p.44 / Chapter 3.1.2 --- Effects of pH --- p.44 / Chapter 3.1.3 --- Effects of temperature --- p.44 / Chapter 3.2 --- Effects of pH on the desorption of bacterial cells from magnetites --- p.49 / Chapter 3.3 --- Copper ion uptake experiments --- p.49 / Chapter 3.4 --- Effects of physico-chemical and operational factors on the Cu2+ removal capacity of the magnetite-immobilized bacterial cells --- p.49 / Chapter 3.4.1 --- Effects of pH --- p.49 / Chapter 3.4.2 --- Effects of temperature --- p.53 / Chapter 3.4.3 --- Effects of retention time --- p.53 / Chapter 3.4.4 --- Effects of cations --- p.53 / Chapter 3.4.5 --- Effects of anions --- p.57 / Chapter 3.5 --- Transmission electron micrograph of Pseudomonas putida 5-X loaded with Cu2+ --- p.62 / Chapter 3.6 --- Scanning electron micrograph of Pseudomonas putida 5-X loaded with Cu2+ --- p.62 / Chapter 3.7 --- Copper ion adsorption isotherm of the magnetite-immobilized cells of Pseudomonas putida 5-X --- p.68 / Chapter 3.8 --- Recovery of adsorbed Cu2+ from the magnetite-immobilized cells of Pseudomonas putida 5-X --- p.68 / Chapter 3.8.1 --- Effects of eluents on the Cu2+ removal and recovery capacity of the magnetite-immobilized cells --- p.68 / Chapter 3.8.2 --- Batch type multiple adsorption-desorption cycles of Cu2+ using ethylenediaminetetra-acetic acid (EDTA) --- p.74 / Chapter 3.9 --- Removal and recovery of Cu2+ from the electroplating effluent by a bioreactor --- p.74 / Chapter 3.9.1 --- Batch type multiple adsorption-desorption cycles using the copper solution and electroplating effluent --- p.74 / Chapter 3.9.2 --- Continuous type bioreactor to remove and recover Cu2+ from copper solution and electroplating effluent --- p.81 / Chapter 4. --- Discussion --- p.89 / Chapter 4.1 --- Selection of copper-resistant bacteria --- p.89 / Chapter 4.2 --- Effects of physical and chemical factors on the immobilization of the bacterial cells on magnetites --- p.89 / Chapter 4.2.1 --- Effects of cells to magnetites ratio --- p.89 / Chapter 4.2.2 --- Effects of pH --- p.90 / Chapter 4.2.3 --- Effects of temperature --- p.91 / Chapter 4.2.4 --- Effects of pH on the desorption of bacterial cells from magnetites --- p.92 / Chapter 4.3 --- Copper ion uptake experiments --- p.93 / Chapter 4.4 --- Effects of physico-chemical and operational factors on the Cu2+ removal capacity of the magnetite-immobilized bacterial cells --- p.94 / Chapter 4.4.1 --- Effects of pH --- p.95 / Chapter 4.4.2 --- Effects of temperature --- p.96 / Chapter 4.4.3 --- Effects of retention time --- p.97 / Chapter 4.4.4 --- Effects of cations --- p.98 / Chapter 4.4.5 --- Effects of anions --- p.101 / Chapter 4.5 --- Transmission electron micrograph of Pseudomonas putida 5-X loaded with Cu2+ --- p.101 / Chapter 4.6 --- Scanning electron micrograph of Pseudomonas putida 5-X loaded with Cu2+ --- p.102 / Chapter 4.7 --- Copper ion adsorption isotherm of the magnetite-immobilized cells of Pseudomonas putida 5-X --- p.103 / Chapter 4.8 --- Recovery of adsorbed Cu2+ from the magnetite-immobilized cells of Pseudomonas putida 5-X --- p.104 / Chapter 4.8.1 --- Effects of eluents on the Cu2+ removal and recovery capacity of the magnetite-immobilized cells --- p.104 / Chapter 4.8.2 --- Batch type multiple adsorption-desorption cycles of Cu2+ using ethylenediaminetetra-acetic acid (EDTA) --- p.105 / Chapter 4.9 --- Removal and recovery of Cu2+ from the electroplating effluent by a bioreactor --- p.107 / Chapter 4.9.1 --- Batch type multiple adsorption-desorption cycles using the copper solution and electroplating effluent --- p.107 / Chapter 4.9.2 --- Continuous type bioreactor to remove and recover Cu2+ from copper solution and electroplating effluent --- p.108 / Chapter 5. --- Conclusion --- p.110 / Chapter 6. --- Summary --- p.112 / Chapter 7. --- References --- p.115

by Lau Tsz Chun. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 134-143). / Abstracts in English and Chinese. / Acknowledgements --- p.i / Abstract --- p.ii / Contents --- p.vi / List of Figures --- p.xi / List of Tables --- p.xv / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Reviews --- p.1 / Chapter 1.1.1 --- Heavy metals in the environment --- p.1 / Chapter 1.1.2 --- Heavy metal pollution in Hong Kong --- p.3 / Chapter 1.1.3 --- Electroplating industries in Hong Kong --- p.7 / Chapter 1.1.4 --- "Chemistry, biochemistry and toxicity of selected metal ions: copper, nickel and zinc" --- p.8 / Chapter a. --- Copper --- p.10 / Chapter b. --- Nickel --- p.11 / Chapter c. --- Zinc --- p.12 / Chapter 1.1.5 --- Conventional physico-chemical methods of metal ions removal from industrial effluent --- p.13 / Chapter a. --- Ion exchange --- p.14 / Chapter b. --- Precipitation --- p.14 / Chapter 1.1.6 --- Alternative for metal ions removal from industrial effluent: biosorption --- p.15 / Chapter a. --- Definition of biosorption --- p.15 / Chapter b. --- Mechanisms involved in biosorption of metal ions --- p.17 / Chapter c. --- Criteria for a good metal sorption process and advantages of biosorption for removal of heavy metal ions --- p.19 / Chapter d. --- Selection of potential biosorbent for metal ions removal --- p.20 / Chapter 1.1.7 --- Procedures of biosorption --- p.23 / Chapter a. --- Basic study --- p.23 / Chapter b. --- Pilot-scale study --- p.25 / Chapter c. --- Examples of commercial biosorbent --- p.27 / Chapter 1.1.8 --- Seaweed as a potential biosorbent for heavy metal ions --- p.27 / Chapter 1.2 --- Objectives of study --- p.30 / Chapter 2. --- Materials and Methods --- p.33 / Chapter 2.1 --- Collection of seaweed samples --- p.33 / Chapter 2.2 --- Processing of seaweed biomass --- p.33 / Chapter 2.3 --- Chemicals --- p.33 / Chapter 2.4 --- Characterization of seaweed biomass --- p.39 / Chapter 2.4.1 --- Moisture content of seaweed biomass --- p.39 / Chapter 2.4.2 --- Metal ions content of seaweed biomass --- p.39 / Chapter 2.5 --- Characterization of metal ions biosorption by seaweed --- p.39 / Chapter 2.5.1 --- Effect of biomass weight and selection of biomass --- p.39 / Chapter 2.5.2 --- Effect of pH --- p.40 / Chapter 2.5.3 --- Effect of retention time --- p.41 / Chapter 2.5.4 --- Effect of metal ions concentration --- p.41 / Chapter 2.5.5 --- Effect of mix-cations and mix-anions on the removal capacity of selected metal ions by Ulva lactuca --- p.43 / Chapter 2.5.6 --- Recovery of adsorbed metal ions from Ulva lactuca (I): screening for suitable desorbing agents --- p.44 / Chapter 2.5.7 --- Recovery of adsorbed metal ions from Ulva lactuca (II): multiple adsorption-desorption cycles of selected metal ions --- p.45 / Chapter 2.5.8 --- Removal and recovery of selected metal ions from electroplating effluent by Ulva lactuca --- p.45 / Chapter 2.6 --- Statistical analysis of data --- p.46 / Chapter 3. --- Results --- p.47 / Chapter 3.1 --- Effect of biomass weight and selection of biomass --- p.47 / Chapter 3.1.1 --- Effect of biomass weight --- p.47 / Chapter 3.1.2 --- Selection of biomass --- p.58 / Chapter 3.2 --- Effect of pH --- p.58 / Chapter 3.2.1 --- Cu2+ --- p.58 / Chapter 3.2.2 --- Ni2+ --- p.61 / Chapter 3.2.3 --- Zn2+ --- p.61 / Chapter 3.2.4 --- Determination of optimal condition for biosorption of Cu2+ ，Ni2+ and Zn2+ by Ulva lactuca --- p.67 / Chapter 3.3 --- Effect of retention time --- p.67 / Chapter 3.4 --- Effect of metal ions concentration --- p.73 / Chapter 3.4.1 --- Relationship of removal capacity with initial concentration of metal ions --- p.73 / Chapter 3.4.2 --- Langmuir adsorption isotherm --- p.73 / Chapter 3.4.3 --- Freundlich adsorption isotherm --- p.77 / Chapter 3.5 --- Effect of mix-cations and mix-anions on the removal capacity of selected metal ions by Ulva lactuca --- p.81 / Chapter 3.5.1 --- Effect of mix-cations --- p.81 / Chapter 3.5.2 --- Effect of mix-anions --- p.85 / Chapter 3.6 --- Recovery of adsorbed metal ions from Ulva lactuca (I): screening of suitable desorbing agents --- p.91 / Chapter 3.6.1 --- Cu2+ --- p.91 / Chapter 3.6.2 --- Ni2+ --- p.91 / Chapter 3.6.3 --- Zn2+ --- p.91 / Chapter 3.7 --- Recovery of adsorbed metal ions from Ulva lactuca (II): multiple adsorption-desorption cycles of selected metal ions --- p.94 / Chapter 3.8 --- Removal and recovery of selected metal ions from electroplating effluent by Ulva lactuca --- p.97 / Chapter 4. --- Discussion --- p.106 / Chapter 4.1 --- Effect of biomass weight and selection of biomass --- p.106 / Chapter 4.1.1 --- Effect of biomass weight --- p.106 / Chapter 4.1.2 --- Selection of biomass --- p.107 / Chapter 4.2 --- Effect of pH --- p.109 / Chapter 4.3 --- Effect of retention time --- p.112 / Chapter 4.4 --- Effect of metal ions concentration --- p.114 / Chapter 4.4.1 --- Relationship of removal capacity with initial concentration of metal ions --- p.114 / Chapter 4.4.2 --- Langmuir adsorption isotherm --- p.114 / Chapter 4.4.3 --- Freundlich adsorption isotherm --- p.115 / Chapter 4.4.4 --- Insights from isotherm study --- p.117 / Chapter 4.5 --- Effect of mix-cations and mix-anions on the removal capacity of selected metal ions by Ulva lactuca --- p.118 / Chapter 4.5.1 --- Effect of mix-cations --- p.118 / Chapter 4.5.2 --- Effect of mix-anions --- p.120 / Chapter 4.6 --- Recovery of adsorbed metal ions from Ulva lactuca (I): screening of suitable desorbing agents --- p.122 / Chapter 4.7 --- Recovery of adsorbed metal ions from Ulva lactuca (II): multiple adsorption-desorption cycles of selected metal ions --- p.124 / Chapter 4.8 --- Removal and recovery of selected metal ions from electroplating effluent by Ulva lactuca --- p.126 / Chapter 5. --- Conclusion --- p.131 / Chapter 6. --- Summary --- p.134 / Chapter 7. --- References --- p.134 / Chapter 8. --- Appendixes --- p.144

Thesis (MEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: The main purpose of the base metal refinery (BMR) as operated by Lonmin at their Western Platinum Ltd BMR, is to remove base metals – such as copper and nickel – from a platinum group metal (PGM) containing matte. The leaching processes in which this is done pose several challenges to the control of the process. The most significant of these is the slow dynamics of the process, due to large process units, as well as the continuously changing composition of the first stage leach residue, which is not measured on-line. This is aggravated by the fact that the exact leaching kinetics (and therefore the effect of the disturbances) are not understood well fundamentally. The slow process dynamics mean that controllers cannot be tuned aggressively, resulting in slow control action. The large residence times and off-line composition analyses of major controlled variables also mean that the effects of operator set point changes are visible only the following day, often by a different shift of operators. Dorfling (2012) recently developed a fundamental dynamic model of the pressure leach process at Lonmin‟s BMR. This dynamic model incorporates 21 chemical reactions, as well as mass and energy balances, into a system of 217 differential equations. The model provides a simulation framework within which improved control strategies can be investigated. The primary aims of this study are twofold. The first is to validate the model for the purpose of the investigation and development of control structure improvements. This is done by comparing the model to plant data, and adapting it if necessary. The second aim to reconsider the current control philosophy to the extent that is allowed by the model‟s determined validity. The current plant control philosophy aims to maintain a PGM grade of 65%, while the copper in the solids products of the second and third leaching stages should be below 25% and 3.5% by mass, respectively. Two areas of particular concern in this process that have been raised by Lonmin are the control of the temperature of the first compartment and the addition of pure sulphuric acid to control the acid concentration in the second stage leach. Dynamic plant data were used to calibrate the model, which was migrated from its received MATLAB platform to Simulink, to assist with control development. Flow rates were imported from the data, with some data values adapted for this purpose, due to mass balance inconsistencies. The outputs from the calibrated model were compared with corresponding data values. The model was found to be suitable for the investigation and development of the control structures of pressure, temperatures and inventories (termed basic regulatory control) and the acid concentration and solids fraction in the preparation tanks (termed compositional regulatory control). It was, however, found to be inadequate for the investigation and development of supervisory control, since it does not provide accurate compositional results. The leaching of copper is especially under-predicted, with the predicted copper concentration in the second stage product being approximately 46% lower than data values. The basic and compositional regulatory control structures were investigated. For each of these a base case was developed which aimed to represent the relevant current control structure, assuming optimal tuning. The variable pairings for the basic regulatory control were reconsidered using a method proposed by Luyben and Luyben (1997), since this part of the process does not permit the generation of a relative gain array (RGA) for variable pairing. The resulting pairing corresponds with Lonmin‟s current practice. Considering the temperature control of compartment 1, it was found that the addition of feed-forward control to the feedback control of the level of the flash tank improves the temperature control. More specifically, during an evaluation where the temperature‟s set point is varied up to 1%, the IAE of the temperature of compartment 1 was decreased with 7.5% from the base case, without disturbing the flash tank. The addition of feed-forward control allows for more rapid control and more aggressive tuning of this temperature, removing the current limit on ratio between the flash recycle stream and the autoclave feed. The compositional control was investigated for the second stage leach only, due to insufficient flow rate and compositional information around the third stage preparation tank. Variable pairing showed that three additive streams are available for the preparation tanks of the second and third stage leach to control the acid concentration and solids fraction in those tanks. Focussing on the second stage, the aim was to determine whether the acid concentration in the flash tank can be successfully controlled without the addition of pure acid to the tank. With four streams available around the second stage preparation tank to control its mass/level, the acid concentration and solids fraction, three manipulated variables were derived from these streams. The resulting pairings were affirmed by an RGA. Control loops for the control of acid concentration and solids fraction in the flash tank were added as cascade controllers, using the preparation tank‟s control as secondary loops. The added compositional control was evaluated in two tests. The first of these entailed the adding of typical disturbances, being the flash recycle rate, the solids and water in the feed to the second stage preparation tank and the acid concentration in copper spent electrolyte. In the second test the control system was tested for tracking an acid concentration set point. It was found that the cascade structure controls the acid concentration in the flash tank less tightly than the base case (with an IAE that is 124% and 80.6% higher for the two tests), but that it decreases the variation of solids fraction (lowering the IAE with 40.8% with the first test) in the same tank and of the temperature in the first compartment (lowering the IAE with 73.6% in the second test). It is recommended that the relative effects of these three variables on leaching behaviour should be investigated with an improved model that is proven to accurately predict leaching reactions in the autoclave. / AFRIKAANSE OPSOMMING: Die hoofdoel van die basismetaal-raffinadery (BMR), soos dit bestuur word deur Lonmin by hulle Western Platinum Ltd BMR, is om basismetale – soos koper en nikkel – te verwyder uit 'n mat wat platinum groep metale (PGM) bevat. Die logingsprosesse waarin dit gedoen word hou talle uitdagings in vir die beheer van die proses. Die mees beduidende hiervan is die proses se stadige dinamika, wat veroorsaak word deur groot proseseenhede, sowel as die deurlopend veranderende samestelling van die eerste stadium residue (wat nie aanlyn gemeet word nie). Dit word vererger deur die feit dat die presiese logingskinetika (en daarom ook die effek van versteurings) nie fundamenteel goed verstaan word nie. Die stadige dinamika beteken dat die beheerders die aggressief verstel kan word nie, en dit lei tot stadige beheeraksies. Die groot verblyftye en aflyn samestellingsanalises van die belangrikste beheerde veranderlikes beteken dat die gevolge van 'n operateur se stelpunt veranderinge slegs die volgende dag sigbaar is – dikwels in die skof van 'n ander operateur. Dorfling (2012) het onlangs 'n fundamentele, dinamiese model van die drukloog proses by Lonmin se BMR ontwikkel. Hierdie dinamiese model inkorporeer 21 chemiese reaksies, sowel as massa- en energiebalanse, in ‟n stelsel van 217 differensiaalvergelykings. Die model bied 'n simulasie-raamwerk waarbinne verbeterde beheerstrategieë ondersoek kan word. Die hoofdoel van hierdie studie is tweeledig. Die eerste hiervan is om die model te valideer vir die ondersoek en ontwikkelling van beheerstruktuur verbeteringe. Dit is gedoen deur die model met aanlegdata te vergelyk en dit aan te pas, indien nodig. Die tweede doel is om die huidige beheerfilosofie te heroorweeg tot op 'n punt wat toegelaat word deur die bepaalde geldigheid van die model. Die huidige beheerfilosofie van die aanleg mik om 'n gehalte van 65% te handhaaf, terwyl die koper in die vastestof produk van die tweede en derde logingsstadia onderskeidelik onder 25% en 3.5% op 'n massa basis moet wees. Twee probleem-areas, soos ge-opper deur Lonmin, is die beheer van die temperatuur in die eerste kompartement en die byvoeging van suiwer swaelsuur om die suurkonsentrasie van die tweede stadium te beheer. Dinamiese aanlegdata is gebruik om die model te kalibreer. Hierdie model is van die oorspronklike MATLAB platform na Simulink gemigreer, ten einde beheerontwikkelling te vergemaklik. Vloeitempo's is van die data af ingevoer na die model toe, met sekere data waardes wat aangepas is vanweë massabalans inkonsekwenthede. Die uitsette van die gekalibreerde model is met die ooreenstemmende data waardes vergelyk. Daar is bevind dat die model geskik is vir die ondersoek en ontwikkelling van die beheer van druk, temperature en tenks (basiese reguleringsbeheer), sowel as die beheer van suurkonsentrasies en vastestoffraksies in die bereidingstenks (reguleringsbeheer van die samestelling). Daar is egter bevind dat die model nie geskik is vir die ondersoek en ontwikkelling van toesigbeheer nie, aangesien dit nie akkurate samestellingsresultate genereer nie. Die voorspelde loging van koper is veral te laag, met die model wat koperkonsentrasies vir die tweede stadium voorspel wat ongeveer 46% laer is as ooreenstemmende data waardes. Die basiese en samestelling reguleringsbeheer strukture is ondersoek. Vir elkeen is ‟n basisgeval ontwikkel wat poog om die huidige beheerstruktuur te verteenwoordig, met optimale verstellings aanvaar. Die paring van veranderlikes vir die basiese reguleringsbeheer is heroorweeg met deur middel van ‟n metode wat deur Luyben en Luyben (1997) voorgestel is, aangesien hierdie deel van die proses nie die opstel van ‟n relatiewe winsmatriks (RWM) vir die paring toelaat nie. Die uiteindelike paring stem ooreen met Lonmin se huidige praktyk. Met die heroorweging van die temperatuurbeheer van kompartement 1 is daar bevind that die byvoeging van vooruitvoer beheer by die terugvoerbeheer van die flitstenk die temperatuurbeheer verbeter. Meer spesifiek het die IAE van hierdie temperatuur met 7.5% verlaag van die basisgeval af nadat die temperatuur se stelpunt tot met 1% gevariëer is – sonder om die flitstenk te versteur. Die byvoeging van vooruitvoer beheer laat vinniger beheer en meer aggressiewe verstellings van die temperatuur toe, aangesien die huidige beperking op die verhouding tussen die flitsstroom en die outoklaaf voer verwyder word. Die samestellingsbeheer is slegs ondersoek in die geval van die tweede loogstadium as gevolg van onvoldoende vloeitempo- en samestellingsinligting om die bereidingstenk van die derde stadium. Die paring van veranderlikes het gewys dat drie voerstrome onderskeidelik beskikbaar is vir beide die bereidingstenks van die tweede en derde stadia, om die suurkonsenstrasies en vastestoffraksies in hierdie tenks te beheer. Met die fokus op die tweede stadium was die doel om te bepaal of die suurkonsentrasie in die flitstenk suksesvol beheer kan word sonder dat suiwer suur by hierdie tenk gevoeg word. Met vier strome beskikbaar rondom die bereidingstenk van die tweede stadium om die massa/vlak, die suurkonsentrasie en die vastestoffraksie te beheer, is drie manipuleerde veranderlikes vanuit hierdie strome afgelei. Die uiteindelike paring is bevestig deur 'n RWM. Beheerlusse is ingevoeg vir die beheer van die suurkonsentrasie en vastestoffraksie in die flitstenk, met die bereidingstenk se beheer wat dien as sekondêre lusse in kaskadebeheer. Die kaskadebeheer is geëvalueer in twee toetse. Die eerste hiervan behels die invoer van tipiese versteurings, soos die vloeitempo van die flitsstroom, die vastestof en water in die voer na die tweede stadium se bereidingstenk en die suurkonsentrasie in die gebruikte elektroliet. In die tweede toets is die vermoë van die beheerstelsel om 'n suurkonsentrasie stelpunt te volg getoets. Daar is bevind dat die kaskadestruktuur die suurkonsentrasie minder nougeset beheer as die basisgeval (met 'n IAE wat 124% en 80.6% hoër is vir die twee toetse), maar dat dit die variasie in die vastestoffraksie in dieselfde tenk (40.8% vermindering van die IAE in die eerste toets) en in die temperatuur van die eerste kompartement (73.6% vermindering van die IAE in die tweede toets) beduidend verminder. Daar word aanbeveel dat die relatiewe effekte van hierdie drie veranderlikes op logingsoptrede ondersoek moet word, met die gebruik van 'n model wat logingsreaksies in die outoklaaf akkuraat voorspel.

Submitted in partial fulfillment of the requirements for the degree in Masters of Technology: Chemistry, ML Sultan Technikon, Durban, 2003. / The pollution of water bodies by heavy metals is a serious threat to humanity. The technique known as phytoremediation is used to clean up these polluted water bodies. The accumulation of heavy metals by aquatic plants is a safer, . cheaper and friendlier manner of cleaning the environment. The aquatic plants -studied in this project are A.sessilis, P.stratiotes, R.steudelii and T.capensis. The accumulation of heavy metals in aquatic plants growing in waste water treatment ponds was investigated. The water, sludge and plants were collected from five maturation ponds at the Northern Waste Water Treatment Works, Sea Cow Lake, Durban. The samples were analysed for Zn, Mn, Cr, Ni, Pb and Cu using ICP-MS. In general it was found that the concentrations of the targeted metals were much lower in the water (0.002 to 0.109 mg/I) compared to sediment/sludge (44 to 1543mg/kg dry wt) and plants (0.4 to 2246 mg/kg dry wt). These results show that water released into the river from the final maturation pond has metal concentrations well below the maximum limits set by international environmental control bodies. It also shows that sediments act as good sinks for metals and that plants do uptake metals to a significant extent. Of the four plants investigated it was found that }t.sessi[ir (leaves, roots and stems) and }A.sessilis (roots and stems) are relatively good collectors of Mn and Cu respectively. These findings are described in the thesis. The concentration of heavy metals in the stems, leaves and roots of the three plants were compared to ascertain if there were differences in the ability of the plant at different parts of the plant to bioaccumulate the six heavy metals studied. / M

A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Engineering, 2016 / The aim of this research was to reduce heavy metal and sulfate content of acid mine drainage (AMD) through the methods of passive filtration by combining permeable concrete and organic materials. This was to achieve a low cost, yet effective temporary treatment method for rural/poor communities who are affected by AMD. The acids are filtered through layers of alternating pervious concrete and biological composting layers. The concrete layers target removal of heavy metals such as iron, manganese, potassium, and magnesium, etc. through precipitation as well as reduce sulfate content to a small degree along with total dissolved solids. The concrete layers also aid in raising the pH of the AMD to more acceptable levels. The biological layers achieve sulfate remediation through the metabolism of sulfatereducing- bacteria (SRB). This process however required time and the organic layers were thus thicker and less permeable than the concrete layers in order to allow seepage to take place at a reduced rate. A wide variation of composting layers were tested, including cow manure, chicken manure, sawdust, straw, zoo manure, and leaf compost to find an optimum mix of materials which allows for the greatest sulfate reduction through sulfate reducing bacteria in the shortest possible time. Short as well as Long-term testing of rigs was undertaken to establish effectiveness, limitations and lifespan of the filtration systems. AMD from a mine in the Mpumalanga coal fields with exceptionally high sulfate content was used to test effectiveness of the organic materials over a short period of time. With long term testing conducted with a synthetic AMD, due to limited supply from the mine. The short term testing yielded removal of sulfates in the order of 56% when using kraal manure as the biological reagent mixed with sawdust for added organic carbon. The mix percentages by volume were 80%Sawdust to 20%manure and this setup was able to achieve the 56% removal of sulfates within 14 days. The filter also successfully raised the pH to 8 while removing a significant portion of heavy metals. The long term tests showed complete (100%) remediation of sulfates after a period of approximately sixty days. The tests are continuing to determine their finite lifespan and limitations. The results show promise for using the technology as a low cost, temporary measure to protect locally impacted groundwater, especially for isolated and/or rural communities while a permanent long term solution is sought.

A research project submitted to the Faculty of Sciences, University of the Witwatersrand, in partial fulfilment of the requirements for the degree of Master of Science in Environmental Sciences (Coursework and Research Report). Johannesburg, 2016. / Paenibacillus castaneae isolated from acid mine decant (Gauteng, South Africa) was previously shown to tolerate high concentrations of lead (Pb). The ability of the bacterium to tolerate/resist other heavy metals is probable and suggests a role for P. castaneae as a biosorbent for their removal from contaminated wastewaters. The current study aimed at determining whether the bacterium is also resistant to other common metal contaminants specifically, zinc (Zn) and nickel (Ni), found in South African wastewaters for biosorption by P. castaneae. Additionally, the influence of the external factors pH and competing cations on the uptake of these metals by the bacterium was evaluated. Specific rates of metal uptake (Q) were calculated indirectly from quantifying (by spectroscopy) the residual ion concentrations post exposure to 3 mM metal after various treatments. P. castaneae was found to tolerate Zn but showed vulnerability towards Ni. In a binary metal system, the bacterium showed a preferential metal uptake in the order Zn>>Co> Mn with a highest Q of 26 mg Zn/g biosorbent biomass recorded in the presence of Mn at pH 7. On the contrary, in a multimetal complex solution, the order of preference shifted to Co>>Zn with no absorption of Mn at the same pH. The results indicate that both pH and the presence of cations have an effect on the uptake of Zn by P. castaneae that could favour or inhibit its biosorption. The present study confirms the ability of P. castaneae to remove additional metals such as Zn, Mn and Co. These findings further suggest the potential of P. castaneae as a biosorbent for greener clean-up strategies of contaminated water facilities around Gauteng in the way of bioremediation. Keywords: P. castaneae, biosorption, specific metal uptake, zinc, lead, nickel / LG2017

A dissertation submitted to the Faculty of Engineering and the Built Environment, University of Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Master of Science in Engineering. Johannesburg, 2016 / The remediation of acid mine drainage (AMD) has received much attention over the years due to the environmental challenges associated with its toxic constituents. Although, the current methods are able to remediate AMD, they also result in the loss of valuable products which could be recovered and the financial benefits used to offset the treatment costs. Therefore, this research focused on the removal of toxic heavy metals as well as the recovery of acid using a low cost adsorbent and acid retardation process, respectively. In the first aspect of the study, three low cost adsorbents namely zeolite, bentonite clay and cassava peel biomass were evaluated for metal uptake. The adsorption efficiencies of zeolite and bentonite, was found to be less than 50% for most metal ions, which was lower compared to the 90% efficiency obtained with cassava peel biomass. Subsequently, cassava peel biomass was chosen for further tests. The metal removal efficiency using the cassava biomass was in the order Co2+> Ni2+> Ca2+> Mn2+> Fe3+> Mg2+. The highest metal removal was attained at 2% adsorbent loading and 30 ˚C solution temperature. Amongst the equilibrium models tested, the experimental data was found to fit well with the Langmuir isotherm model. Column studies using the immobilized cassava waste biomass suggested that the breakthrough curves of most metal ions did not resemble the ideal breakthrough curve, due to the competitive nature of the ions present in the AMD used in this study. However, the experimental data from the column tests was found to correlate well with the Adam-Bohart model. Sulphuric acid recovery from the metal barren solution was evaluated using Dowex MSA-1 ion exchange resins. The results showed that sulphuric acid can be recovered by the resins via the acid retardation process, and could subsequently be upgraded to near market values of up to 70% sulphuric acid using an evaporator. Water of re-usable quality could also be obtained in the acid upgrade process. An economic evaluation of the proposed process also showed that it is possible to obtain revenue from sulphuric acid which could be used to offset some of the operational costs. / M T 2016