Beneficial reuse of PCBs (poly-chlorinated biphenyls) as new materials through a low cost processEPA Grant Number: SV839354
Title: Beneficial reuse of PCBs (poly-chlorinated biphenyls) as new materials through a low cost process
Investigators: Lu, Mingming
Institution: University of Cincinnati - Main Campus
EPA Project Officer: Page, Angela
Project Period: March 1, 2018 through February 29, 2020
Project Amount: $74,958
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet - Phase 2 (2017)
Research Category: Sustainability , P3 Awards , P3 Challenge Area - Materials & Chemicals
Even though PCBs (poly-chlorinated biphenyls) production has ceased due to their high toxicity and bio-accumulation, PCB contamination remains a challenging problem to solve worldwide.
There has been a lot of progress made over the years in PCB treatment, via chemical, biological and thermal desorption, etc.. However, there are challenges in adopting these technologies due to the following reasons: high temperature, longer duration, and high initial cost, etc. Therefore, there is the constant need to seek low cost and yet effective technologies.
The overall objective of the research was to develop a low cost technology for PCB decontamination. Phase I tested the feasibility of catalytic hydrodechlorination by converting select PCBs into non-chlorine containing chemicals. Parametric study was carried out to understand what factors, and how the factors affect the reaction. Reaction kinetics will also be studied with the time remained to prepare for future scale up. Phase I (this proposal) is a proof of concept of the proposed technology. In Phase II, the team planned to test with more complex PCBs including some commonly used in the past, such as Aroclor 1254, 1248 and Askarel. With the help of their partners, they will modify the design based on test results as well as the real world oil or sediment matrixes. If Phase II is successful, they will pursue SBIR or contract opportunities to do a pilot test with the actual site conditions. The possibility of patenting the technology will also be pursued, to obtain license opportunities from companies.
In Phase II, the team plans to test on PCBs with more chlorine substitutions, such as aroclor (1254) and (1248) to better understand the chlorine position vs. dechlorination, and the reaction kinetics. Reaction kinetics is essential parameters for scaling up.
The proposal team has studied the effectiveness of catalytic de-coloration at low temperatures and atmospheric pressure under hydrogen environment. The catalyst responsible for dechlorination is palladium on carbon (Pd/C) with triethylamine (Et3N) serving as an electronic donor and acid neutralizer. Both 3-PCB and 2,3- PCB are being studied, with respect to the reaction time, catalyst dosage, hydrogen partial pressure, mixing effects and temperature, etc. The reaction kinetics is also being investigated.
The experimental setup is designed as a batch process. 50 mg of reactants (AccuStandard), the catalyst Pd/C (with Pd content varying from 0.5% to 10% by weight), and Et3N and 50 ml toluene were placed in a flask. This flask is sealed with a cork with a carrier gas tube passing through. Before reaction, N2 gas was passed into the flask for 15 minutes to get rid of air inside the flask.
Then a mixture of N2 and H2 (with a H2 partial pressure varying from 0.41 to 0.5) was passed through the suspension at room temperature ( 25°C ) and atmospheric pressure. The carrier gas has two functions. It both supplied the hydrogen and also mixes the suspension. After reaction, the products were washed with magnetic stirs, filtered using vacuum filtration, and an aliquot of the filtered liquid was diluted 50 times for GC-MS (gas chromatography and mass spectroscopy) analysis. Both 3 chloronbiphenyl (3-PCB) and 2,3-dichloronbiphenyl (2,3-PCB) were tested. The reaction time was varied from 0.5hrs to 6hrs.
The Phase I goal was divided into three specific aims. 1) Study the optimum conditions for catalytic dechlorination. 2) Research on the optimum conditions for bipehneyl conversion, 3) public outreach: disseminate research results at various venues to educate the public about waste reuse in environmentally friendly ways.
For specific aim 1, studying the optimum conditions for catalytic dechlorination has been carried out, and is in healthy progress that may result in a journal publication. New findings include a better solvent than reported from literature, much lower temperatures and much shorter time used. In our study, toluene as identified as a better solvent than methanol, by having higher product recovery (not much difference with regard to dechlorination), and also more sensitive for instrumentation (peak area in toluene is 6.08 times larger).
A few tests were performed on specific aim 2. But after discussion with the ETSC (Engineering Technology Support Center) of the US EPA and one of the executive secretaries of the PEN (PCB Elimination Network), we decided to stop this goal since it is “not practical” based on the feedback from the experts above.
Specific aim 3, student mentoring and outreach, has being carried out and is on a healthy pace. An interdisciplinary team of students has been formed, which consists of two graduate students (environmental and materials engineering) and three undergraduate students (one in Chemical Engineering and two in Chemistry). Also a visiting faculty mentor has been co-leading this project, who is an expert in environmental catalysis. The team developed best practices through working together. They made a few binders to document experimental conditions, one for instrumental analysis and a third one for literature on sustainability and technology related publications. They also established a shared Google Drive for literature and results. Students developed effective management skills for documentation/research.
The PI has worked with partners in student recruitment and making business connections, and will work with newly developed partners to guide the team through the Phase II project on what are needed to move the technology to a pilot demonstration. New partnership has been established with the ETSC (Engineering Technology Support Center) of the US EPA and the PEN (PCB Elimination Network) under the Stockholm Convention.