Control of Membrane Fouling in Organics Filtration Using Ce-Doped Zirconia and Visible Light

Abstract

Membrane fouling has been a major issue in the development of more efficient water treatment processes. Specifically in surface waters filtration, organic matter, such as humic-like substances, can cause irreversible fouling. Therefore, this study evaluates the activity of a photocatalytic layer composed of Ce-doped zirconia nanoparticles in improving the fouling resistance during filtration of an aqueous solution of humic acid (HA). These nanoparticles were prepared by hydrothermal and sol–gel processes and then characterized. Before the filtration experiments, the photodegradation of HA catalyzed by Ce-doped zirconia nanoparticles in dispersion was studied. It was observed that the sol–gel prepared Ce-ZrO2 exhibited higher HA removal in practically neutral pH, achieving 93% efficiency in 180 min of adsorption in the dark followed by 180 min under visible-light irradiation using light-emitting diodes (LEDs). Changes in spectral properties and in total organic carbon confirmed HA degradation and contributed to the proposal of a mechanism for HA photodegradation. Finally, in HA filtration tests, Ce-ZrO2 photocatalytic membranes were able to recover the flux in a fouled membrane using visible-light by degrading HA. The present findings point to the further development of anti-fouling membranes, in which solar light can be used to degrade fouling compounds and possibly contaminants of emerging concern, which will have important environmental implications.

Photocatalytic Reduction of Cr(VI) in the Presence of Humic Acid Using Immobilized Ce–ZrO2 under Visible Light

“…This catalyst was tested as a suspended powder or immobilized on a support. In the first case, Ce-ZrO 2 nanopowder was synthesized by a sol-gel route developed in previous work [25]. In brief, for the synthesis processes, 5 mL of zirconium propoxide Zr(OC 3 H 7 ) 4 (CAS 23519-77-9, 70 wt %, Sigma-Aldrich, St. Louis, MO, United States) were mixed with 5 mL of 2-propanol (CAS 67-63-0, 99.5%, Sigma-Aldrich, St. Louis, MO, United States).…”

“…In previous works [22][23][24][25][26], the development and testing of Ce-ZrO 2 nanoparticles was studied. An extensive characterization of the material was performed, including XRD, SEM, TEM, N 2 adsorption/desorption, diffusive reflectance, and photo-electronic characterization.…”

“…In a "double jump" mechanism, low-energy photons (visible light) is absorbed, leading to the excitation of electrons from the valence band to the conduction band [22,23]. This material found applications in degrading pollutants [23][24][25] and promoting water splitting [26].…”

Engineered Nanoparticles with Decoupled Photocatalysis and Wettability for Membrane-Based Desalination and Separation of Oil-Saline Water Mixtures

“…The utility of surfaces with selective wettability can be further extended by incorporating them with photocatalytic nanoparticles that can degrade organic substances upon light irradiation [23][24][25]. Such a photocatalytic surface with selective wettability has demonstrated the potential for a wide range of practical applications, including anti-fouling [26,27], self-cleaning [28,29], and bactericidal coating [30]. Recent studies [31][32][33][34] have revealed that membranes with selective wettability can further benefit by incorporating photocatalytic nanoparticles that can radically transform physical filtration into chemically reactive processes.…”

“…Luster et al [36] fabricated an N-doped, TiO 2 -coated alumina membrane and demonstrated the photocatalytic degradation of carbamazepine (CBZ) as a model pollutant under simulated solar irradiation. Further, Coelho et al [26] coated a filter paper with zirconia-doped cerium to prepare a photocatalytic membrane. The membrane demonstrated flux recovery by photocatalytic degradation of humic acid as a foulant.…”