Grantee Research Project Results
2019 Progress Report: Mesoporous Adsorbents for Perfluorinated Compounds
EPA Grant Number: SU839448Title: Mesoporous Adsorbents for Perfluorinated Compounds
Investigators: Vasiliev, Aleksey , Mohseni, Ray , Lotsi, Bertha , Saul Garcia, Anastasia Kuvayskaya
Current Investigators: Vasiliev, Aleksey , Mohseni, Ray
Institution: East Tennessee State University
EPA Project Officer: Page, Angela
Phase: I
Project Period: December 1, 2018 through November 30, 2019 (Extended to August 30, 2020)
Project Period Covered by this Report: December 1, 2018 through November 30,2019
Project Amount: $15,000
RFA: P3 Awards: A National Student Design Competition Focusing on People, Prosperity and the Planet (2018) RFA Text | Recipients Lists
Research Category: P3 Challenge Area - Safe and Sustainable Water Resources , P3 Awards
Objective:
In this project we plan to develop porous adsorbents for cleanup of water contaminated by perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid. Most of existing technologies are expensive and insufficiently efficient. The proposed materials with high adsorption capacity (up to 6.8 mmol/g) will be used for reversible adsorption of these contaminants from drinking water or wastewater. The innovative aspect of the project is the use of bridged polysilsesquioxanes combining high structural stability with high concentration of surface amino-groups serving as adsorption sites. The project is based on the hypothesis that porous hybrid materials containing bridged amines can adsorb PFOA and PFOS from contaminated water with significantly enhanced adsorption capacity.
The specific aims of the project were:
- Synthesis of mesoporous bridged amino-functionalized materials;
- Characterization of the obtained materials;
- Study of PFOA and PFOS adsorption;
- Development of a recyclable efficient adsorbent for cleanup of contaminated water.
Application of the developed adsorbent in water filters will significantly reduce the exposure
of people in affected areas to PFOA and PFOS. It will improve public health by reducing the rate
of related illnesses, i.e. developmental effects, cancer, immune and thyroid effects, etc.
Progress Summary:
During Phase I of the project, novel mesoporous adsorbents were synthesized and successfully tested in adsorption of PFOS and PFOA. The project is conducted in four steps. On the first step, mesoporous bridged polysilsesquioxanes were synthesized by sol-gel method from bis[3-(trimethoxysilyl)- propyl]amine and N-Methyl-3,3'-bis(trimethoxysilyl)-dipropylamine at variable conditions. Different surfactants were used as pore-forming agents: sodium dodecylsulfate, octadecyltriammonium chloride, dodecylamine and Pluronic P123. These surfactants demonstrated different types of interaction between functional groups of the adsorbent (hydroxyl groups) and the head groups of the surfactants in acidic and basic media. Thus, in acidic media we employed S+X-I+ and S-I+ interactions, while in basic media S+I- and S M+I- interactions take place. In the case of nonionic Pluronic P123, the interaction involves hydrogen bonds. The structure of the final product depended on the surfactant type. On the second step, the materials were tested in adsorption of PFOS and PFOA from aqueous solutions. All obtained adsorbents demonstrated high effectiveness in the adsorption. Their adsorption capacity reached about 80% of the mass of adsorbent. It was shown that the adsorption is irreversible at studied conditions and polyfluorinated substances did not desorb up to 180 °C. The materials were characterized by elemental analysis, reversed titration, FT-IR, porosimetry, DLS, TGA and DSC techniques. They proved high porosity of the adsorbents and high contents of basic adsorption sites. Adsorption of PFOS and PFOA decreased porosity and resulted in agglomeration of the particles. High amount of adsorbed species transformed hydrophilic suraces of the materials to hydrophobic.
- Novel mesoporous materials with high concentration of basic adsorption sites were synthesized by sol-gel method using bridged bis-trimethoxysilanes.
- Obtained materials with particle size up to 300 nm had high BET surface area (up to 189 m2/g) that provides easy access of adsorbing molecules to the adsorption sites.
- The materials demonstrated high adsorption capacity to PFOA and PFOS. The highest amount of adsorbed polyfluorinated compounds was about 90% of the mass of adsorbent.
- Adsorbed acids are bonded to the surface strongly and remain on the adsorbents at heating up to 180 °C.
- After adsorption, the materials agglomerated and became hydrophobic that makes easy its separation from water.
- Further study of adsorption at different temperatures and concentrations will demonstrate a possibility to use the adsorbent in different climatic conditions.
- Regeneration study will confirm a possibility of recycling the adsorbent without loss of its adsorption capacity.
In summary, proposed adsorbents for treatment of PFOA/PFOS-contaminated waste waters will have the following advantages over existing materials: they are easy to prepare, easy to use, and easy to recycle. Currently, most of existing technologies of cleanup of water from polyfluorinated substances involve materials whose synthesis is difficult and expensive, their use require complicated equipment and often energy-consuming.
Future Activities:
The adsorbent developed will have high adsorption capacity in powder form, however, the particle might be highly cohesive that makes an industrial application impractical. For field application it should be converted to mid-size granules with high mechanical stability. On this step of the project we will manufacture and study adsorbent formulations with binders: charcoal, clay and γ-Al2O3.
The formulations with be prepared by wet granulation method with various contents of the binder. The perfluorinated alkylated substances (PFAS) adsorption kinetics on the formulation will be studied using the methodology described in the Phase I. The mechanical strengths of the granulated formulations will be determined in accordance with American Society for Testing Materials (ASTM) standards.
The bound adsorbents will be studied in column and batch tests to determine kinetics and diffusion parameters of the adsorption. In general, the Phase II is based on the hypothesis that granulated bound adsorbents will have high effectiveness in filtration devices for cleanup of contaminated water from polyfluorinated compounds.
- Granulation of mesoporous bridged amino-functionalized materials with binders;
- Characterization of the obtained materials;
- Study of PFOA and PFOS adsorption on bound materials;
- Development of a filtration device for cleanup of contaminated water from polyfluorinated compounds.
Journal Articles:
No journal articles submitted with this report: View all 2 publications for this projectSupplemental Keywords:
Water, perfluorinated compounds, waste reduction, cleanup, environmental chemistry.Progress and Final Reports:
Original AbstractThe 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.