Inorganic greywater matrix impact on photocatalytic oxidation : does flocculation of TiO₂ nanoparticles impair process efficiency?

Journal
Water science and technology  
Volume
63
Issue
12
Start Page
2808
End Page
2813
Citation
Water Science and Technology 63 (12): 2808-2813 (2011)
Publisher DOI
10.2166/wst.2011.614
Scopus ID
2-s2.0-79959715941
PubMed ID
22049703
Publisher
IWA Publishing
This study was conducted in order to clarify whether photocatalyst flocculation - as observed in biologically pretreated greywater - contributes to photocatalytic oxidation (PCO) efficiency impairment. Aqueous solutions of tetraethyleneglycol dimethylether spiked with different inorganic salts in concentrations as found in biologically treated greywater were investigated with respect to TiO 2 flocculation and PCO mineralisation kinetics. Flocculation of the photocatalyst primarily depended on pH (which was affected by the salts) and how close pH was to the point of zero charge (PZC). Photocatalyst agglomeration was maximum at pH 5.5. With salt concentrations >7 mmol L -1, flocculation was strong even at pH far above PZC due to electric double layer compression. PCO rate constants were not unequivocally related to flocculation. Increasing pH was observed as the clearest factor deteriorating PCO efficiency. This was interpreted to result from impaired adsorbability of negatively charged oxidation intermediates as well as from enhanced CO 2 absorption with increasing pH and subsequent formation of HCO 3- anions which are OH radical scavengers. © IWA Publishing 2011.
Subjects
Greywater
Inorganic matrix
Photocatalyst flocculation
Photocatalytic oxidation
DDC Class
600: Technik
620: Ingenieurwissenschaften