Biosorption of precious metals from synthetic and refinery wastewaters by immobilized saccharomyces cerevisiae
- Authors: Mack, Cherie-Lynn
- Date: 2008
- Subjects: Metals -- Refining Metals -- Absorption and adsorption Saccharomyces cerevisiae Factory and trade waste Water reuse Platinum
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4071 , http://hdl.handle.net/10962/d1006977
- Description: The process of precious metal refining can be up to 99.99% efficient at best, and although it may seem small, the amount of valuable metal lost to waste streams is appreciable enough to warrant recovery. The method currently used to remove entrained metal ions from refinery wastewaters, chemical precipitation, is not an effective means for selective recovery of precious metals from a wastewater. Biosorption, the ability of certain types of biomass to bind and concentrate metals from even very dilute aqueous solutions, may be an effective point-source metal recovery strategy. The yeast, Saccharomyces cerevisiae, has been found capable of sorbing numerous precious and base metals, and is a cheap and abundant source of biomass. As such, it represents a possible precious metal sorbent for application to refining wastewaters. In this investigation, S. cerevisiae biomass was immobilized, using polyethyleneimine and glutaraldehyde, to produce a suitable sorbent, which was found to be capable of high platinum uptake (150 to 170 mg/g) at low pH (< 2). The sorption mechanism was elucidated and found to be a chemical reaction, which made effective desorption impossible. The sorption process was investigated in a packed bed column conformation, the results of which showed that the diameter and height of the column require further optimization in order to attain the metal uptake values achieved in the batch studies. When applied to a refinery wastewater, two key wastewater characteristics limited the success of the sorption process; the high inorganic ion content and the complex speciation of the platinum ions. The results proved the concept principle of platinum recovery by immobilized yeast biosorption and indicated that a more detailed understanding of the platinum speciation within the wastewater is required before the biosorption process can be applied. Overall, the sorption of platinum by the S. cerevisiae sorbent was demonstrated to be highly effective in principle, but the complexity of the wastewater requires that pretreatment steps be taken before the successful application of this process to an industrial wastewater.
- Full Text:
- Date Issued: 2008
- Authors: Mack, Cherie-Lynn
- Date: 2008
- Subjects: Metals -- Refining Metals -- Absorption and adsorption Saccharomyces cerevisiae Factory and trade waste Water reuse Platinum
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4071 , http://hdl.handle.net/10962/d1006977
- Description: The process of precious metal refining can be up to 99.99% efficient at best, and although it may seem small, the amount of valuable metal lost to waste streams is appreciable enough to warrant recovery. The method currently used to remove entrained metal ions from refinery wastewaters, chemical precipitation, is not an effective means for selective recovery of precious metals from a wastewater. Biosorption, the ability of certain types of biomass to bind and concentrate metals from even very dilute aqueous solutions, may be an effective point-source metal recovery strategy. The yeast, Saccharomyces cerevisiae, has been found capable of sorbing numerous precious and base metals, and is a cheap and abundant source of biomass. As such, it represents a possible precious metal sorbent for application to refining wastewaters. In this investigation, S. cerevisiae biomass was immobilized, using polyethyleneimine and glutaraldehyde, to produce a suitable sorbent, which was found to be capable of high platinum uptake (150 to 170 mg/g) at low pH (< 2). The sorption mechanism was elucidated and found to be a chemical reaction, which made effective desorption impossible. The sorption process was investigated in a packed bed column conformation, the results of which showed that the diameter and height of the column require further optimization in order to attain the metal uptake values achieved in the batch studies. When applied to a refinery wastewater, two key wastewater characteristics limited the success of the sorption process; the high inorganic ion content and the complex speciation of the platinum ions. The results proved the concept principle of platinum recovery by immobilized yeast biosorption and indicated that a more detailed understanding of the platinum speciation within the wastewater is required before the biosorption process can be applied. Overall, the sorption of platinum by the S. cerevisiae sorbent was demonstrated to be highly effective in principle, but the complexity of the wastewater requires that pretreatment steps be taken before the successful application of this process to an industrial wastewater.
- Full Text:
- Date Issued: 2008
Screening of technologies for the recovery of rhodium (III) metal ions from a precious metal refinery wastewater
- Authors: Mack, Cherie-Lynn
- Date: 2005
- Subjects: Rhodium , Metal ions , Sewage -- Purification -- Metals removal , Platinum group
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3987 , http://hdl.handle.net/10962/d1004046 , Rhodium , Metal ions , Sewage -- Purification -- Metals removal , Platinum group
- Description: 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.
- Full Text:
- Date Issued: 2005
- Authors: Mack, Cherie-Lynn
- Date: 2005
- Subjects: Rhodium , Metal ions , Sewage -- Purification -- Metals removal , Platinum group
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3987 , http://hdl.handle.net/10962/d1004046 , Rhodium , Metal ions , Sewage -- Purification -- Metals removal , Platinum group
- Description: 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.
- Full Text:
- Date Issued: 2005
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