Development of Novel Bioadsorbents for Heavy Metal Removal

EPA Grant Number: R827227
Title: Development of Novel Bioadsorbents for Heavy Metal Removal
Investigators: Chen, Wilfred , Mehra, Rajesh , Mulchandani, Ashok
Institution: University of California - Riverside
EPA Project Officer: Lasat, Mitch
Project Period: December 1, 1998 through November 30, 2001
Project Amount: $360,818
RFA: Exploratory Research - Environmental Engineering (1998) RFA Text |  Recipients Lists
Research Category: Engineering and Environmental Chemistry , Sustainability , Land and Waste Management

Description:

Conventional technologies such as precipitation-filtration, ion exchange, reverse osmosis, oxidation-reduction, and membrane separation are often inadequate to reduce heavy metal concentrations in waste water to acceptable regulatory standards, and recent research has been focusing on the development of novel materials with increased affinity, capacity, and selectivity for target metals. The overall objective of this research is to develop high-affinity microbial bioadsorbents for heavy metal removal. Genetically engineered E. coli with surface-expressed peptide analogues (ECs) of phytochelatin will be utilized as microbial bioadsorbents for the removal of heavy metals such cadmium, mercury and lead. A series of synthetic genes encoding ECs ranging two to twenty cysteine will be expressed on the cell surface, and their metal binding capability will be investigated. Recombinant bacteria which exhibit the best selectivity and affinity for heavy metal accumulation will be co-expressed with the Cellulose binding domain protein on the cell surface and use for developing bioadsorbent columns with cellulose-based support.

Approach:

Synthetic genes encoding for (Glu-Cys)2-20Gly (EC2 to EC20) was synthesized and cloned into pUC18. The Lpp-OmpA fusion system, which has been used by us to express organophosphorus hydrolase on the cell surface, will be used to anchored the various ECs to the surface. Experiments will be conducted to determine the selectivity and metal uptake capacity of the recombinant cells expressing different ECs on the surface. Selected ECs with the greatest affinity and selectivity towards Cd, Hg, and Pb will be co-expressed with the cellulose-binding domain (CBD) on the cell surface. The resulting recombinant cells will be immobilized onto various cellulose-based supports and tested for heavy metal removal in continuous column operations. The potential of the novel bioadsorbents for repeated metal removal will be investigated by subjecting to several cycles of binding and stripping. The bioadsorbent column will be evaluated for the metal removal from the wastewaters of electroplating, mining and metallurgy and chlor-alkali process industries and the performance compared to the three commercially available sorbents such as Duolite GT-73, Amberlite IRC-718, and BIO-FIX in order to compare the utility the bioadsorbents in large-scale column operations.

Expected Results:

Although existing technologies are adequate to remove the bulk of the heavy metal contamination, they fail to meet the low concentration limits required by regulatory standard. It becomes clear that a secondary, polishing operation is needed for this purpose. In this research, novel bioadsorbents based on recombinant E. coli with surface-expressed ECs (synthetic phytochelatins) will be developed with high specificity and affinity for Cd, Hg, and Pb. Co-expression of the Cellulose binding domain on the cell surface enables the bioadsorbents to immobilize tightly onto cellulosic materials. The resulting bioadsorbent column can be applied continuously with other existing technologies for bulk heavy metal removal to comply with regulatory standards. This operation is environmentally friendly since no toxic chemical is required for synthesis of the bioadsorbents and regeneration can be achieved easily. This strategy if successful, will provide a low-cost and environmentally benign technology for heavy metal removal.

Publications and Presentations:

Publications have been submitted on this project: View all 18 publications for this project

Journal Articles:

Journal Articles have been submitted on this project: View all 10 journal articles for this project

Supplemental Keywords:

environmental biotechnology, bioremediation, pollution prevention, waste reduction, Scientific Discipline, Air, Toxics, Waste, Water, Ecosystem Protection/Environmental Exposure & Risk, Bioavailability, National Recommended Water Quality, Environmental Chemistry, Bioremediation, Engineering, Chemistry, & Physics, Mercury, fate and transport, bioadsorption, aquatic, wastewater treatment, bioremediation model, waste reduction, chemical speciation, phytochelation, cellulose binding, lead, chemical transport, metal binding, biological attenuation, bioadsorbent, organophospherous hydrolase, synthetic genes, water quality, wetland, cadmium, heavy metals, mercury concentrations

Progress and Final Reports:

  • 1999 Progress Report
  • 2000 Progress Report
  • Final Report