Introduction: The removal of natural organic matter (NOM) from water is becoming increasingly important in order to prevent the formation of carcinogenic disinfection by-products. The inadequate removal of NOM has a bearing on the capacity of the other treatment processes to remove organic micro-pollutants or inorganic species that may be present in the water. New methods are therefore currently being sought to effectively characterise NOM and also to ensure that it is sufficiently removed from drinking water sources.
Methodology: Nitrogen- and palladium-co-doped TiO(2) was synthesised by a modified sol-gel method and evaluated for its photocatalytic degradation activity on NOM fractions under simulated solar radiation. The photocatalyst was characterised by FT-IR, Raman, XRD, DRUV-vis, SEM, TEM, EDS, XPS and TGA. FT-IR confirmed the presence of OH groups on thermally stable, nearly spherical anatase nanoparticles with an average diameter of 20 nm. PdO species appeared on the surface of the TiO(2) as small uniformly dispersed particles (2 to 3 nm). A red shift in the absorption edge compared to commercial anatase TiO(2) was confirmed by DRUV-vis. In order to gain a better insight into the response of NOM to photodegradation, the NOM was divided into three different fractions based on its chemical nature.
Results and discussion: Photodegradation efficiencies of 96, 38 and 15 % were realised for the hydrophobic, hydrophilic and transphilic NOM fractions, respectively. A reasonable mechanism was proposed to explain the photocatalytic degradation of the NOM fractions. The high photocatalytic activity could be attributed to the larger surface area, smaller crystalline size and synergistic effects of the co-dopants N and Pd in the TiO(2) crystal.