Superfund Research Program
Chloro-Organic Degradation by Polymer Membrane Immobilized Iron-Based Particle Systems
Project Leader: Dibakar Bhattacharyya
Grant Number: P42ES007380
Funding Period: 2000-2019
Several types of polymer/membrane platforms (including hydrogels and flat sheet (FS) or hollow fiber (HF) membranes) have been developed in both bench-scale and large-scale (40 inches wide). Dibakar Bhattacharyya, Ph.D., and his research group have directly synthesized zero-valent and oxidized iron nanoparticles (NPs) within to prevent their agglomeration and reduce the metal leaching. These NPs, immobilized in pH/temperature responsive materials (polyacrylic acid/poly(N-isopropylacrylamide)), remediate toxic organic/inorganic contaminated water by reductive and/or oxidative pathways. Spongy polyvinylidene fluoride (PVDF) FS with high porosity and large internal pore volume was modified with stimuli-responsive and different functionality polymers resulting in tunable pore size and ion-exchange capacity. These membranes have shown higher ion exchange capacity, from 10 to 80 times than non-spongy (Xiao et al. 2015, Davenport et al. 2016). These membranes functionalized with PAA and synthesized Fe/Pd NPs show that 40% of trichloroethylene (TCE) was adsorbed in 15 min and then degraded with a significant production of chloride (55% of the calculated) (Davenport et al. 2016). In the same way, PVDF HF membranes were manufactured at the Singapore Membrane Technology Center and with spongy-like FS were functionalized (PAA and Fe/Pd NPs). The HF membranes, originally hydrophobic, were hydrophilized using water-based green chemistry. Nanoparticle size characterization using image analyses was applied for pictures developed in a FIB equipment. The NP distribution was not only on the membrane surface but also in depth through the membrane. The reactivity of HF degrading TCE is almost doubled than reported works using the same concentrations of Pd. FS reactivity, on the other hand, is almost four times higher with similar iron loadings to previous studies (Hernández et al., 2015).
Model mixtures of PCB 126 have been studied in both batch and convective flow mode. For batch mode, 96% PCB 126 was consumed, and almost 55% of it was converted to biphenyl after 5 hours. In convective flow, almost all PCB 126 is consumed within the membrane in 28 seconds. Through predictive models followed by partitioning, adsorption, and dechlorination experiments with PCBs using immobilized Fe/Pd nanoparticles, the temperature responsive behavior of polyacrylic acid/poly (N-isopropylacrylamide) polymer has achieved contaminant degradation of PCBs.
Iron oxide NPs in the membrane matrix can decompose oxidizing agents like hydrogen peroxide and persulfate salt, generating free radicals as it was presented in a previous work. Through joint work with a petroleum company and a membrane manufacturer, the researchers leveraged their NIEHS work to degrade organic acids (naphthenic acids) by sulfate radical reaction involving iron functionalized membranes. The persulfate based oxidation (5000 mg/L potassium persulfate) at 45°C with iron functionalized membrane was very effective in reducing the final organic concentration below water discharge limit.