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Objective:
This project aims to develop a new functionalized sawdust anion exchange resin for PFAS removal and to develop new cost-effective treatment processes using functionalized sawdust (FS). The hypothesis of this research is that cellulose-based sawdust can be functionalized into anion exchange resin, which can remove negatively charged PFAS in drinking water. This research will improve water management practices, and technical methods to minimize the PFAS risks to human, ecosystem and the environment. The specific research objectives of the proposed work are to: 1) Functionalize sawdust into biomass-based anion exchange resin; 2) Determine PFOA and PFOS removal from drinking water using functionalized sawdust column tests. The first objective helps students to understand the natural biomass (sawdust) from planet can be used for cleaning drinking water, which is related to people’s health. The second objective helps student to understand how much of PFAS existing in tap water, which is related to the polymer production from industries. This will help students to recognize the critical balance between prosperity of industry and protection of human health and the ecosystem. This project enables the student team to identify the community issues in our drinking water system. Undergraduate students will be trained in the area of sustainability, analytical chemistry, process design and environmental protection.
Summary/Accomplishments (Outputs/Outcomes):
In this Phase I project, functionalized sawdust has been chemically synthesized with epichlorohydrin and dimethylamine and characterized by Fourier transform infrared spectroscopy. The kinetic and isothermal adsorption experiments with FS have been performed and samples have been collected for liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (LC-QToF) analysis. It has been observed that the functionalized sawdust can remove 93% of PFOA and 84% of PFOS in batch process. For the adsorption kinetics, the adsorption sorption rate constant of PFOA and PFOS is 0.1739 g/mg/h and 0.1022 g/mg/h respectively. The initial adsorption rate of PFOA and PFOS is 15.12 mg/g/h and 7.25 mg/g/h, respectively. The results suggested that the adsorption of PFOA and PFOS on FS was very fast and majority of adsorption can be completed within 2 h. The results have been summarized in the 2020 Progress Report.
Adsorption isotherm is critical to evaluate the sorption capacity of adsorbents as well as understand the PFAS and FS interactions. For the adsorption isotherm, series concentrations (ranging from 5-250 mg/L) of PFOA and PFOS solutions were absorbed with 0.2 g FS, respectively. The bottles were maintained on the shaker (200 rpm) for 120 h. The residual concentration of PFAS compounds have been quantified by LC-QToF analysis. As showed in Fig. 1, two commonly used models, the Langmuir and Freundlich were adopted to describe the experimental data and assess the adsorption behavior of the PFAS on each media. The adsorption isotherms show that the FS possesses high adsorption capacity 209.26 mg/g for PFOA and 161.80 mg/g for PFOS according to the Langmuir fitting (Table 1). The Langmuir adsorption model is based on the assumption of a structurally homogeneous adsorbent, monolayer adsorption and equivalent adsorption sites. The Freundlich model assumes adsorption on a heterogeneous surface. A good fit with the Langmuir model indicated monolayer adsorption of PFAS on the FS. The adsorption isotherm results in this study suggested that the synthesized FS showed high adsorption capacity for PFOA and PFOS removal…
Conclusions:
Our goal for the Phase I project is to develop a new functionalized sawdust anion exchange resin for PFAS (especially PFOA and PFOS) removal and to develop new cost-effective treatment processes using FS. To achieve this goal, the commercial sawdust has been functionalized by reaction with epichlorohydrin and dimethylamine. FTIR was used to characterize the functional groups changes along with the functionalization reactions. It can be observed that functional groups (such as hydroxyl group) have been significantly changed after functionalization, which indicated the occurrence of functionalization reactions. To assess the efficiency of FS in PFAS removal, we also adsorption kinetic and adsorption isotherm of PFOA and PFOS in batch process. Based on the adsorption kinetics, we found that adsorption of PFOA and PFOS on FS was very fast and majority of adsorption can be completed within 2 h in batch condition. Based on Langmuir and Freundlich model, we also determine adsorption isotherms to assess the adsorption behavior of the PFAS on each media. The result suggested that the synthesized FS showed high removal efficiency and high adsorption capacity for PFOA and PFOS removal according to the Langmuir fitting. Through this study, we believe that we have successfully synthesized sawdust-based anion exchange resin, which possessed high adsorption capacity of PFOA and PFOS removal from water system. We recommend that more PFAS compounds should be tested with this new developed technology and a techno-economic analysis is needed to assess the cost of advantages of FS for PFAS removal.