Efficient Treatment of Toxic Organic Wastewaters by Hybrid Photocatalysis and Nanofiltration/Ultrafiltration Processes

Project: National Science and Technology CouncilNational Science and Technology Council Academic Grants

Project Details

Abstract

Each existing method used for wastewater treatment has limitations and drawbacks. For example, chemical precicipation and activated carbon adsorption merely transfers the pollutants from liquid phase to solid phase, leading to secondary pollution. Filtration can hinder suspended solids but not microsolids unless the use of polymer membranes with sufficiently small pore sizes. In that case, the efficiency and economics will largely reduce due to the phenomena of membrane fouling and pore blockage. Biological method can degrade organic pollutants in a greener manner; however, the degradation of some synthetic organics is much slow, making the process efficient only under well controlled temperature and/or pH environments. Photocatalysis under UV irradiation has received much attention recently due to no need of the oxidants added, fast reaction, and low operating cost. However, the degradation rate will largely decrease during the process because it essentially contains many successive chemical reactions. This evitably increases the “time” cost. In this regards, more efficient treatment methods are highly desired. In this project, a hybrid UV/photocatalysis and NF/UF process is proposed because this process has the synergistic effect based on both single processes; for example, the level of pollutant in the retentate can be maintained because water passes through the membrane, resulting into a nearly constant reaction rate. Also, membrane self-cleaning is observed because the pollutant(s) adjacent to membrane surface can be degraded by UV/photocatalysis, leading to the less membrane fouling. Several dyes with a molar mass beyond 300 g/mol are selected here as model organic pollutants. In the first year, the parameters that are defined in single process are first obtained including the apparent degradation rate constant and solute rejection by the original and prepared membranes. The degradation of dye and flux decline in a hybrid UV/photocatalysis with TiO2 suspension and NF/UF with original membrane is then tested. Moreover, the TiO2/carbon nanotube (CNT) composite membrane with a diameter of 30 mm will be prepared and its physicochemical properties including crystalline phase, absorption wavelength, surface structure, and pore size are characterized. In the second year, the TiO2/CNT composite membrane with a diameter of 47 mm is prepared. The reaction rate and flux decline in a hybrid UV/photocatalysis and NF/UF with TiO2/CNT composite membrane are measured to check membrane self-cleaning ability. In the third year, a larger size of TiO2/CNT composite membrane is prepared. Dynamic behavior of this hybrid process is then analyzed and the operating parameters are optimized. Due to its high specific surface area and excellent photocatalytic activity, TiO2/CNT is capable of facilitating photodegradation and NF/UF for organic wastewater. It is hence expected that the present project allows us to realize the application potentials and limitations of this hybrid process. The solutions that can overcome such limitations will be suggested.

Project IDs

Project ID:PB10501-2673
External Project ID:MOST103-2221-E182-073-MY3
StatusFinished
Effective start/end date01/08/1631/07/17

Keywords

  • Photocatalysis
  • Membrane filtration
  • Organic wastewater
  • TiO2 suspension
  • TiO2-coated composite membrane
  • TiO2/carbon nanotube-functionalized composite membrane

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