Grantee Research Project Results
Final Report: Keratin-based Adsorbent for Drinking Water Filtration
EPA Grant Number: SU836769Title: Keratin-based Adsorbent for Drinking Water Filtration
Investigators: Almquist, Catherine B
Institution: Miami University - Oxford
EPA Project Officer: Page, Angela
Phase: I
Project Period: September 1, 2016 through August 31, 2017
Project Amount: $13,939
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2016) RFA Text | Recipients Lists
Research Category: Sustainable and Healthy Communities , P3 Awards , P3 Challenge Area - Safe and Sustainable Water Resources
Objective:
This project aims to design, construct, and demonstrate a drinking water purification process that couples sand filtration with the natural protein, keratin, which will act as an adsorbent for removing heavy metals from water. Keratin is a protein that occurs naturally, for example, in skin, hair, nails, hooves, horns, and bird feathers. Keratin has chemical and structural characteristics that allow it to bind with heavy metals. The challenges lie in creating a keratin adsorbent material with high porosity and surface area suitable for water filtration without degrading the adsorption sites on which heavy metals bind.
The experimental plan for Phase I will have answered the following questions:
- To what extent can our filtration system remove heavy metals from water?
- How fast are heavy metals adsorbed onto the keratin-based adsorbent?
- How long can our sustainable drinking water system operate before it needs to be cleaned or regenerated?
- How do other contaminants that are typical of surface waters (minerals, organic concentrations) affect the efficiency of our sustainable water treatment system?
Summary/Accomplishments (Outputs/Outcomes):
The following are our results thus far:
- We constructed two different sand beds using fine sand as our filtration media: 1) 28 cm high x 20 cm2 cross-sectional area; and 2) 50 cm high x 50 cm2 cross-sectional area. Using Darcy’s Law, we calibrated the flow through the sand beds as a function of pressure head, and we found the permeability of the fine sand to be 1.4x10-7 cm2. This value is supported by reported values of sand permeability. Based upon the sand permeability and Darcy’s Law, we can scale the sand bed to a desired water treatment capacity.
- We synthesized keratin aerogels from purchased hair keratin (KeraNetics). The method required that a 15 wt% keratin solution in deionized water be prepared. The solution gelled, and the gel was frozen at -80°C overnight, followed by freeze drying until the material was dry.
- We extracted keratin from chicken feathers using two methods from the published literature. Briefly, the chicken feathers were soaked in highly basic solutions at elevated temperature for several hours to extract the keratin from the feathers. The undissolved material was separated from the dissolved material, and the keratin was precipitated out of the dissolved material using a strong acid. This material was washed and dried before use.
- We characterized the keratin samples using Fourier Transform Infrared spectroscopy (FTIR), thermogravimetric analyses (TGA) and differential scanning calorimetry (DSC) in an effort to assess differences in chemical structure of the purchased hair keratin and the keratin extracted from chicken feathers. Our goal is to assess which functional groups are responsible for adsorbing the heavy metals and whether those functional groups are available or retained in the keratin from chicken feathers.
- We obtained an adsorption isotherm for copper metal ion in water using the keratin aerogel at pH = 6. Based upon several trials, the adsorption capacity for the keratin aerogel sample is approximately 400 mmoles Cu ion/kg keratin aerogel.
- We obtained an adsorption isotherm for keratin aerogel at three different temperatures: 25°C, 35°C, and 45°C. Based upon only one trial each at the higher temperatures, there appears to be little effect of temperature on the adsorption capacity of keratin aerogels for copper ion in this temperature range. However, these results will be verified with subsequent trials to reproduce the data.
- We attempted to obtain adsorption isotherms for extracted keratin samples. There was little to no adsorption of copper ion on these samples. However, the pH of the solutions in these trials was very low (~3.5). It is hypothesized that the low pH of these trials was the reason for the low adsorption of copper ion. We recently purchased buffers to control the pH of the solutions during adsorption trials. The buffered adsorption isotherm trials will be done this summer.
- We obtained an adsorption isotherm for activated carbon for copper ion for comparison with the keratin aerogel. The activated carbon adsorbed approximately 150 mmoles copper ion/kg adsorbent compared with ~400 mmoles copper ion/kg keratin aerogel. Thus, the keratin aerogel adsorbs approximately three times more copper ion from water than activated carbon.
Conclusions:
The conclusions made regarding the Phase I efforts so far are:
- Keratin aerogels prepared from hair keratin can be used to adsorb copper metal ions from water at a capacity of 400 mmoles Cu2+/kg keratin aerogel. The adsorption capacity of keratin aerogel for copper metal ion is approximately three times that of activated carbon (BPL, Calgon Carbon).
- The adsorption capacity of copper ion on keratin aerogel does not appear to be a function of temperature, and so it should be just as effective in very warm climates, where water may become very warm during the day.
- Fine sand can be used as a slow sand filter, and the intrinsic permeability of the sand (1.4x10-7 cm2) that we measured can be used to scale the sand bed to a desirable water treatment capacity for either individual families or for communities of several hundred people.
As we continue to work on this project to complete our Phase I objectives, we will assess the effects of pH and contact time on the uptake of heavy metals with both hair keratin aerogel and the keratin that we extracted from chicken feathers. In addition, we anticipate using at least two other metals (lead (Pb) and Arsenic (As)) in addition to copper metal ion to investigate the uptake of these metals on keratin aerogel.
Journal Articles:
No journal articles submitted with this report: View all 4 publications for this projectSupplemental Keywords:
Keratin aerogel; heavy metals; sand filtration; water treatment; adsorptionThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.