Nanoscale Biopolymers with Tunable Properties for Improved Decontamination and Recycling of Heavy MetalsEPA Grant Number: R829606
Title: Nanoscale Biopolymers with Tunable Properties for Improved Decontamination and Recycling of Heavy Metals
Investigators: Chen, Wilfred , Matsumoto, Mark , Mulchandani, Ashok
Institution: University of California - Riverside
EPA Project Officer: Lasat, Mitch
Project Period: February 1, 2002 through January 31, 2005
Project Amount: $390,000
RFA: Exploratory Research: Nanotechnology (2001) RFA Text | Recipients Lists
Research Category: Nanotechnology , Safer Chemicals
Description:Nanoscale materials have been gaining increasing interest in the area of environmental remediation because of their unique physical, chemical and biological properties. One emerging area of research has been the development of novel materials with increased affinity, capacity, and selectivity for heavy metals because conventional technologies are often inadequate to reduce concentrations in wastewater to acceptable regulatory standards. Genetic and protein engineering have emerged as the latest tools for the construction of nanoscale materials that can be controlled precisely at the molecular level. With the advent of recombinant DNA techniques, it is now possible to create "artificial" protein polymers with fundamentally new molecular organization. The most significant feature of these nanoscale biopolymers is that they are specifically pre-programmed within a synthetic gene template and can be controlled precisely in terms of sizes, compositions and functions at the molecular level. In this manner, it is possible to specifically design protein-based nano-biomaterials with both metal-binding and tunable properties that can be used to selectively remove heavy metals from dilute solutions in one single process. The overall objective of this research is to develop high-affinity, nanoscale biopolymers with tunable properties for the selective removal of heavy metals such as cadmium, mercury and arsenic.
Approach:The elastin domain, which has been shown to undergo a reversible phase transition upon temperature changes, will be used to generate fusion biopolymers with various metal-binding domains. Several metal-binding domains such as Gly-His-His-Pro-His-Gly, MerR (a repressor for the mercury resistance operon), and ArsR (a repressor for the arsenic resistance operon) will be used to provide high affinity and selective removal of mercury and arsenic. Synthetic genes encoding for the tunable biopolymers will be specifically tailored for the desired properties. By tuning the process pH and temperature, reversible network formation between the individual biopolymers will then enable the recovery of sequestered metals by precipitation. The use of these metal-binding domains has significant advantages over existing chemical chelators, including higher specificity and affinity. The potential lower limit for heavy metal removal could be on the order of 10-10M, or about 8 parts per trillion, depending on the metal-binding domain employed.
The ability of these biopolymers to self assemble as aggregates and their metal binding capability will be elucidated. Experiments will be conducted to determine the selectivity and metal uptake capacity of the tunable biopolymers. The potential of the biopolymers for repeated metal removal will be investigated by subjecting to several cycles of binding and stripping. The performance of the tunable biopolymers for heavy metal removal will be compared to the commercially available ion exchange sorbents such as Duolite GT-73, Amberlite IRC-718, Dowex SBR-1 and Amberlite IRA 900X.