N-Doped TiO₂-Coated Ceramic Membrane for Carbamazepine Degradation in Different Water Qualities.

Enbal Luster,Hadas Mamane,Rossana Grilli,Inna Horovitz,Luca Lozzi,Dror Avisar,Mark A Baker

doi:10.3390/nano7080206

Enbal Luster, Hadas Mamane + Show 5 more

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https://doi.org/10.3390/nano7080206

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Abstract

The photocatalytic degradation of the model pollutant carbamazepine (CBZ) was investigated under simulated solar irradiation with an N-doped TiO2-coated Al2O3 photocatalytic membrane, using different water types. The photocatalytic membrane combines photocatalysis and membrane filtration in a single step. The impact of each individual constituent such as acidity, alkalinity, dissolved organic matter (DOM), divalent cations (Mg2+ and Ca2+), and Cl− on the degradation of CBZ was examined. CBZ in water was efficiently degraded by an N-doped TiO2-coated Al2O3 membrane. However, elements added to the water, which simulate the constituents of natural water, had an impact on the CBZ degradation. Water alkalinity inhibited CBZ degradation mostly due to increase in pH while radical scavenging by carbonate was more dominant at higher values (>200 mg/L as CaCO3). A negative effect of Ca2+ addition on photocatalytic degradation was found only in combination with phosphate buffer, probably caused by deposition of CaHPO4 or CaHPO4·2H2O on the catalyst surface. The presence of Cl− and Mg2+ ions had no effect on CBZ degradation. DOM significantly inhibited CBZ degradation for all tested background organic compounds. The photocatalytic activity of N-doped TiO2-coated Al2O3 membranes gradually decreased after continuous use; however, it was successfully regenerated by 0.1% HCl chemical cleaning. Nevertheless, dissolution of metals like Al and Ti should be monitored following acid cleaning.

Highlights

Public health concerns, increased worldwide environmental awareness and improved analytical and technological capabilities are the main driving forces in improving water quality
The water pH was adjusted by 1 mM phosphate buffer saline (PBS) to obtain a pH range between 6 and 7, and by 2 mM borate buffer saline (BBS) to obtain a pH value of 8.5
The current study showed that both the hardness cations in water (Ca2+ or Mg2+) and the pH are critical parameters to determine the CBZ degradation efficacy via photocatalytic membrane reactors (PMR)

Summary

Introduction

Public health concerns, increased worldwide environmental awareness and improved analytical and technological capabilities are the main driving forces in improving water quality. The presence of anions (e.g., bicarbonate and chloride), cations (e.g., calcium, magnesium), and natural organic matter (NOM) can enhance or suppress the photocatalytic efficiency through mechanisms such as competition for surface adsorption or for hydroxyl radicals and light screening by organic substances [2]. At high concentrations these radicals may prove significant in the photocatalytic reaction due to their stability and longer lifetime [9] Another route to inhibit the photocatalytic process is the adsorption of ions at the active sites, which depends on the species concentration as well as type, solution pH, and the isoelectric point (IEP) of the catalyst. Natural organic matter (NOM) in water can enhance the photocatalytic reaction through its photosensitization properties [10] or inhibit by scavenging of surface generated hydroxyl radicals [11]

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