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Chapter 18 Recovery of silver from used X-ray film for Sphingomonas paucimobilis MX8

  • Rosalba Argumedo-Delira and Janeth Alducin-Ruiz
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Biomedical Waste Management
This chapter is in the book Biomedical Waste Management

Abstract

X-ray films are used for mammograms, CT scans, chest X-rays, and dental X-rays. It is estimated that approximately 2 billion X-ray films are generated worldwide each year. However, there is little information on the final disposition of the X-ray films generated worldwide, and whether all these films have been processed for Ag recovery, as X-ray films contain between 1.5% and 2% (w/w) of this precious metal. Among the processes reported for the recovery of silver from X-ray films are pyrometallurgical, hydrometallurgical, and biological processing, which have advantages and disadvantages. In biological processing, the use of bacterial and fungal enzymes such as gelatinases and alkaline proteases for the recovery of Ag from X-ray films predominates. Therefore, this research aimed to determine the effect of the number of inoculations on the bioleaching of Ag from X-ray films by the bacteria Sphingomonas paucimobilis MX8. S. paucimobilis MX8 was grown in Petri dishes with nutrient agar at 28 °C for 4 days; then, a bacterial suspension of 108 CFU mL−1 was prepared. Then, 30 mL of sterile mineral medium (g L−1) was added: 1.5 (NH4)2SO4; 0.5 Na2 SO4; 0.25 MgCl2; 0.25 CaCl2; and 10 glucose; pH 7 to plastic tubes with a capacity of 50 mL. Subsequently, 0.1 g of X-ray film powder and 2 mL of the bacterial suspension were added to the tubes with culture medium. The following treatments had culture medium + X-ray film, culture medium + bacteria, and treatments with culture medium + bacteria + X-ray film - having treatments with initial inoculation, treatments with a second inoculation after 5 days, and treatments with a third inoculation after 10 days. The treatments were allowed to incubate at room temperature at 500 rpm for 20 days. After the incubation time, the dry biomass of the bacteria, pH, and the content of Ag bioleached from the X-ray films were determined. The results indicate that the dry biomass of S. paucimobilis MX8 increases by increasing the number of inoculations in the X-ray film treatments, doubling, and tripling the dry biomass of the bacteria. Likewise, the bioleaching of Ag from the X-ray films carried out by S. paucimobilis MX8 increases with increasing bacterial inoculum, obtaining a bioleaching of 90% of Ag with a third inoculation. Therefore, S. paucimobilis MX8 could be used for the bioleaching of Ag from X-ray films. However, more studies are needed to find the secondary metabolites or enzymes that are involved in the bioleaching mechanism of Ag from this medical waste.

Abstract

X-ray films are used for mammograms, CT scans, chest X-rays, and dental X-rays. It is estimated that approximately 2 billion X-ray films are generated worldwide each year. However, there is little information on the final disposition of the X-ray films generated worldwide, and whether all these films have been processed for Ag recovery, as X-ray films contain between 1.5% and 2% (w/w) of this precious metal. Among the processes reported for the recovery of silver from X-ray films are pyrometallurgical, hydrometallurgical, and biological processing, which have advantages and disadvantages. In biological processing, the use of bacterial and fungal enzymes such as gelatinases and alkaline proteases for the recovery of Ag from X-ray films predominates. Therefore, this research aimed to determine the effect of the number of inoculations on the bioleaching of Ag from X-ray films by the bacteria Sphingomonas paucimobilis MX8. S. paucimobilis MX8 was grown in Petri dishes with nutrient agar at 28 °C for 4 days; then, a bacterial suspension of 108 CFU mL−1 was prepared. Then, 30 mL of sterile mineral medium (g L−1) was added: 1.5 (NH4)2SO4; 0.5 Na2 SO4; 0.25 MgCl2; 0.25 CaCl2; and 10 glucose; pH 7 to plastic tubes with a capacity of 50 mL. Subsequently, 0.1 g of X-ray film powder and 2 mL of the bacterial suspension were added to the tubes with culture medium. The following treatments had culture medium + X-ray film, culture medium + bacteria, and treatments with culture medium + bacteria + X-ray film - having treatments with initial inoculation, treatments with a second inoculation after 5 days, and treatments with a third inoculation after 10 days. The treatments were allowed to incubate at room temperature at 500 rpm for 20 days. After the incubation time, the dry biomass of the bacteria, pH, and the content of Ag bioleached from the X-ray films were determined. The results indicate that the dry biomass of S. paucimobilis MX8 increases by increasing the number of inoculations in the X-ray film treatments, doubling, and tripling the dry biomass of the bacteria. Likewise, the bioleaching of Ag from the X-ray films carried out by S. paucimobilis MX8 increases with increasing bacterial inoculum, obtaining a bioleaching of 90% of Ag with a third inoculation. Therefore, S. paucimobilis MX8 could be used for the bioleaching of Ag from X-ray films. However, more studies are needed to find the secondary metabolites or enzymes that are involved in the bioleaching mechanism of Ag from this medical waste.

Chapters in this book

  1. Frontmatter I
  2. Contents V
  3. List of contributing authors IX
  4. Chapter 1 Current status of biomedical waste generation in the world 1
  5. Chapter 2 Conventional and modern biomedical waste management technologies 15
  6. Chapter 3 Biomedical waste management: challenges and opportunities 39
  7. Chapter 4 Technological advancements for biomedical waste management 51
  8. Chapter 5 Segregation of biomedical waste: methodologies and importance 65
  9. Chapter 6 Metal recovery from biomedical waste: prospects and Perspectives 85
  10. Chapter 7 Biomedical waste treatment and energy generation 103
  11. Chapter 8 Biomedical waste and bioenergy: prospects and challenges 115
  12. Chapter 9 Utilization of biomedical waste as construction substitute 131
  13. Chapter 10 Segregation of biomedical waste: methodologies and importance 147
  14. Chapter 11 Biomedical waste management strategies: prospects and future scenario 161
  15. Chapter 12 The significance of information technology in enhancing revenue generation from biomedical waste management 179
  16. Chapter 13 Economics and market scenario of biomedical waste management 193
  17. Chapter 14 Biomedical waste: economics and market trends 207
  18. Chapter 15 Government initiatives and futuristic plans for waste management and revenue generation 219
  19. Chapter 16 Biomedical waste: environmental impacts and sustainable management 231
  20. Chapter 17 Environmental impact of diverse biomedical waste and their sustainable management strategies 261
  21. Chapter 18 Recovery of silver from used X-ray film for Sphingomonas paucimobilis MX8 273
  22. Index 283
https://doi.org/10.1515/9783111305288-018

Chapters in this book

  1. Frontmatter I
  2. Contents V
  3. List of contributing authors IX
  4. Chapter 1 Current status of biomedical waste generation in the world 1
  5. Chapter 2 Conventional and modern biomedical waste management technologies 15
  6. Chapter 3 Biomedical waste management: challenges and opportunities 39
  7. Chapter 4 Technological advancements for biomedical waste management 51
  8. Chapter 5 Segregation of biomedical waste: methodologies and importance 65
  9. Chapter 6 Metal recovery from biomedical waste: prospects and Perspectives 85
  10. Chapter 7 Biomedical waste treatment and energy generation 103
  11. Chapter 8 Biomedical waste and bioenergy: prospects and challenges 115
  12. Chapter 9 Utilization of biomedical waste as construction substitute 131
  13. Chapter 10 Segregation of biomedical waste: methodologies and importance 147
  14. Chapter 11 Biomedical waste management strategies: prospects and future scenario 161
  15. Chapter 12 The significance of information technology in enhancing revenue generation from biomedical waste management 179
  16. Chapter 13 Economics and market scenario of biomedical waste management 193
  17. Chapter 14 Biomedical waste: economics and market trends 207
  18. Chapter 15 Government initiatives and futuristic plans for waste management and revenue generation 219
  19. Chapter 16 Biomedical waste: environmental impacts and sustainable management 231
  20. Chapter 17 Environmental impact of diverse biomedical waste and their sustainable management strategies 261
  21. Chapter 18 Recovery of silver from used X-ray film for Sphingomonas paucimobilis MX8 273
  22. Index 283
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