Grantee Research Project Results
Final Report: Water quality monitoring at hydraulic fracturing sites using molecularly imprinted porous hydrogels
EPA Grant Number: SU836124Title: Water quality monitoring at hydraulic fracturing sites using molecularly imprinted porous hydrogels
Investigators: Fidalgo, Maria
Institution: University of Missouri - Columbia
EPA Project Officer: Page, Angela
Phase: I
Project Period: September 1, 2015 through August 31, 2016
Project Amount: $14,997
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2015) RFA Text | Recipients Lists
Research Category: P3 Awards , Pollution Prevention/Sustainable Development , Sustainable and Healthy Communities , P3 Challenge Area - Safe and Sustainable Water Resources
Objective:
The long-term objective of this project is to develop a highly sensitive and specific monitoring device capable of simultaneously detecting a group of contaminants in water associated with hydraulic fracturing operations that have been identified as endocrine disruptors (EDC). The proposed device includes several individual chemical sensors fabricated from molecularly imprinted polymers (MIPs), and can be deployed in the environment to determine single concentration levels and/or average concentrations throughout the deployment period. The advancement of unconventional oil and gas (UOG) extraction technologies has led to their abundance in the United States, and the trend is expected to continue for the next few decades. However, environmental concerns have been raised since UOG operations can contaminate surface and ground water with chemicals known to have negative health effects. There is no current mechanism to detect this contamination for people living in affected areas. Development of MIPs for remote sensing of a UOG chemical fingerprint would allow for rapid detection and remediation of water contamination. This would limit the potential negative impact of this process, thus making it much more sustainable. Sustainability challenges cannot be solved with today’s technologies within any one given discipline. Within this project, students were trained professionally in an interdisciplinary, collaborative environment. The PIs worked with a diverse group of students representing a unique mix of disciplines: environmental engineering, chemical engineering, chemistry, and biological sciences.
The team met monthly to share results and discuss project challenges. These meetings provided opportunities for interdisciplinary learning and discussion, through presentations of their own results and reviews of recent literature. PIs actively participated in all meetings to provide advise and diverse scientific points of view to the students. The student research team was composed by graduate and undergraduate students, from the departments of Biochemistry, Environmental Science, Civil and Environmental Engineering, and Biological Sciences. Doctoral students participating in the team are: Jingjing Dai, Civil and Environmental Engineering, has expertise in nanoparticle synthesis and polymer chemistry; and Victoria Balise, Biological Sciences, has expertise in hormone action, particularly ligand receptor binding. Undergraduate students from the Department of Civil and Environmental Engineering (Emily Kahanic, Darryl Rockfield) participated in the MIPs fabrication and evaluation. The use of MIPs and MIP-enabled devices in natural waters is recognized as a significant challenge and is still unsolved. MIPs can be engineered not only to very specifically capture and concentrate organic contaminants in water at extremely low concentration (i.e., below current gold standard analytical techniques), but also can be designed to quantify the capture level and produce a signal proportional to the captured contaminant mass that can be transmitted in real time from remote sites to a central monitoring facility. Such a device will constitute an innovative and transformative approach to environmental monitoring and sensing. Moreover, the high specificity allows for the fabrication of MIPs arrays targeting a definite group of contaminants. Careful selection of contaminants present in effluents from certain industrial activity and their simultaneously detection combined with their relative concentration can be regarded as a “fingerprint” of contamination from a particular source.
Summary/Accomplishments (Outputs/Outcomes):
In the selection of the target contaminants for the sensor array, data collected by the PIs from hydraulic fracturing wastewaters and contaminated ground and surface water was considered, as well as the toxic effects of those compounds, primarily their potential as EDCs, given their environmental and human health implications. The chemical selected for Phase I research is 2-butoxyethanol due to its presence in high concentrations in the wastewaters and high water solubility. The sensor consists in molecularly imprinted porous polymeric films with highly ordered structures. The fabrication protocol includes the synthesis of silica particles with narrow size distribution and submicron diameters, the deposition of the silica particles as colloidal crystals structures on suitable support materials, the infiltration of the crystal with a solution containing the monomer, polymerization, and removal of the sacrificial silica particles to reveal the porous structure. Silica particles were fabricated following the Stober method. Colloidal crystals are ordered arrays of colloidal particles whose structures resemble standard crystals but are composed of particles instead of atoms. Formation of colloidal crystalline deposits demand very uniformly sized particles, which can be obtained by strict control of the synthesis conditions. Only particles with a standard deviation within 5% of the mean particle size were used for the deposits. The colloidal crystals were fabricated by vertical deposition onto microscope slides used as supports. Deposits made on glass slides led to self-standing films; polymethylmethacrylate (PMMA) slides were used to fabricate supported MIPs. The self-standing films were prepared work in the laboratory (characterization, incubation experiments), while the supported configuration will be used in actual applications of the sensor Polymerization mixtures were prepared by adding the monomer, the crosslinker agent, the initiator of polymerization reaction, and in the case of the imprinted polymers, the target molecule 2-butoxyethanol (2BE). Glass slides were placed on both sides of the support with the colloidal crystal and assembly was held firmly together. One end of the 3-slide assembly was put in contact with the polymerization mixture and let it to rise above the deposit top line, filling the void spaces within the colloidal crystal. Polymerization was performed under UV light and then silica particles were removed by submerging in 5% hydrofluoric acid (HF) solution. The films were characterized by a variaty of techniques: electron microscopy, differential scanning calorimetry, N2 adsorption isotherms and swelling properties. Microcopy images revealed the porous morphology, while differential scanning calorimetry indicated a glass trasition temperature of 50.3°C. The specific surface area given by the N2 adsorption isotherms was determined to be 2.1 m2g−1, and a high swelling ratio hinted to a relatively low crosslinking of the polymeric molecules and an elevated water adsorption capacity. The films were incubated in sealed containers. Approximately 8 mg of MIPs and NIPs self-standing films were suspended in 50 mL of 10 ppm solutions of 2BE. After 24 hrs contact time, the solution was sampled and analyzed for 2BE concentration by liquid-liquid extraction followed by GC-MS. A decrease in concentration was observed of 54% of the initial values. Alternatively, optical methods were explored to quantify the capture of 2BE by the MIPs, due to the uniformly ordered porous structure that confers light reflection properties of the sensor. If the molecular recognition process produced the swelling or shrinkage of the MIP, the readable optical signal is detectable.
Conclusions:
The sensor porous morphologies were successfully obtained by bulk polymerization inside a colloidal crystal void space. Molecularly imprinting with 2BE did not alter the structure of the film, as evidenced by the results of the characterization work on imprinted and nonimprinted films. Preliminary results on contaminant capture by the film yielded a moderate imprinting efficiency (IE), given by the relative absorbance of 2BE on the imprinted versus the non-imprinted polymer. More rigid MIP structures form better-shaped captured sites and contribute to higher IE; this can be obtained by increasing the amount of crosslinker in the polymerization mixture. The analytical determinations are also challenging due to the complexity of the technique: increasing the mass of film used in the incubation and decreasing the initial concentration produced significant improvements. In summary, the results demonstrate the feasibility of the proposed approach and constitute the foundation for the fabrication of the sensor array in Phase II.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
Other project views: | All 1 publications | 1 publications in selected types | All 1 journal articles |
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Dai J, Vu D, Nagel S, Lin C, de Cortalezzi M. Colloidal crystal templated molecular imprinted polymer for the detection of 2-butoxyethanol in water contaminated by hydraulic fracturing. MICROCHIMICA ACTA 2017;185(1):32. |
SU836124 (Final) |
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Supplemental Keywords:
Water, health effects, pollution prevention, petroleum industryThe 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.