This research focused on the synthesis, characterization, and performance testing of a novel Magnéli phase (TinO2n-1), n = 4 to 6, reactive electrochemical membrane (REM) for water treatment. The REMs were synthesized from tubular asymmetric TiO2 ultrafiltration membranes, and optimal reactivity was achieved for REMs composed of high purity Ti4O7. Probe molecules were used to assess outer-sphere charge transfer (Fe(CN)6(4-)) and organic compound oxidation through both direct oxidation (oxalic acid) and formation of OH(•) (coumarin, terephthalic acid). High membrane fluxes (3208 L m(-2) h(-1) bar(-1) (LMH bar(-1))) were achieved and resulted in a convection-enhanced rate constant for Fe(CN)6(4-) oxidation of 1.4 × 10(-4) m s(-1), which is the highest reported in an electrochemical flow-through reactor and approached the kinetic limit. The optimal removal rate for oxalic acid was 401.5 ± 18.1 mmol h(-1) m(-2) at 793 LMH, with approximately 84% current efficiency. Experiments indicate OH(•) were produced only on the Ti4O7 REM and not on less reduced phases (e.g., Ti6O11). REMs were also tested for oxyanion separation. Approximately 67% removal of a 1 mM NO3(-) solution was achieved at 58 LMH, with energy consumption of 0.22 kWh m(-3). These results demonstrate the extreme promise of REMs for water treatment applications.
This study investigated the use of a sub-stoichiometric TiO2 reactive electrochemical membrane (REM) for the inactivation of a model Escherichia coli (E. coli) pathogen in chloride-free solutions. The filtration system was operated in dead-end, outside-in filtration model, using the REM as anode and a stainless steel mesh as cathode. A 1-log removal of E. coli was achieved when the electrochemical cell was operated at the open circuit potential, due to a simple bacteria-sieving mechanism. At applied cell potentials of 1.3 and 3.5V neither live nor dead E. coli cells were detected in the permeate stream (detection limit of 1.0 cell mL(-1)), which was attributed to enhanced electrostatic bacteria adsorption at the REM anode. Bacteria inactivation in the retentate solution increased as a function of the applied cell potential, which was attributed to transport of E. coli to the REM and stainless steel cathode surfaces, and direct contact with the local acidic and alkaline environment produced by water oxidation at the anode and cathode, respectively. Clear evidence for an E. coli inactivation mechanism mediated by either direct or indirect oxidation was not found. The low energy requirement of the process (2.0-88Whm(-3)) makes the REM an attractive method for potable water disinfection.
In this study, a novel substoichiometric TiO 2 ultrafiltration reactive electrochemical membrane (REM) was synthesized and used for electrochemical regeneration of membranes fouled by humic acid (HA) and polystyrene beads (PS). A non-invasive and non-destructive electrochemical impedance spectroscopy (EIS) characterization technique was used to spatially characterize fouling at the REM and data were successfully interpreted by a transmission line model. Based on these analyses, a chemical free electrochemical regeneration (CFER) scheme in backwash mode was developed. The CFER in anodic treatment mode recovered the flux of a HA fouled REM from 3.0% to between 76% and 99% of the initial flux over 5 continuous fouling/regeneration cycles. Full flux recovery of a PS fouled REM (fouling 31% to 38%) was achieved when using either cathodic or anodic CFER. By contrast, regeneration without an applied potential showed only partial flux recovery of 66% and 62% on HA fouled and PS fouled membranes, respectively. The operating cost of CFER was $0.04 m-2 to $0.06 m-2 per regeneration cycle, which is only 1.3% the cost of NaOH cleaning. Results suggest that the REM can provide an efficient and cost effective regeneration scheme that allows it to function in a diverse set of water treatment applications.
Efficient algal harvesting, cell pretreatment and lipid extraction are the major steps challenging the algal biofuel industrialization. To develop sustainable solutions for economically viable algal biofuels, our research aims at devising innovative reactive electrochemical membrane (REM) filtration systems for simultaneous algal harvesting and pretreatment for lipid extraction. The results in this work particularly demonstrated the use of the Ti4O7-based REM in algal pretreatment and the positive impacts on lipid extraction. After REM treatment, algal cells exhibited significant disruption in morphology and photosynthetic activity due to the anodic oxidation. Cell lysis was evidenced by the changes of fluorescent patterns of dissolved organic matter (DOM) in the treated algal suspension. The lipid extraction efficiency increased from 15.2 ± 0.6 g-lipidg-algae(-1) for untreated algae to 23.4 ± 0.7 g-lipidg-algae(-1) for treated algae (p<0.05), which highlights the potential to couple algal harvesting with cell pretreatment in an integrated REM filtration process.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.