Coated Photocatalysts on Supporters or Substrates
Coating of a photocatalyst as a thin layer on supporting materials is an effective
strategy to overcome the limitation of nanostructured photocatalyst powders involving the post-separation of slurry catalysts from the treated wastewater. Recent
approaches for treatments of organic pollutants are as follows.
Treatments of Pharmaceuticals and Personal Care Products
Photocatalytic removal of pharmaceuticals and personal care products in water using
photocatalysts coated on various support materials has been investigated, e.g.,
removal of salicylic acid, naproxen, diclofenac, and ibuprofen by TiO 2 (P25)/
tetraethyl orthosilicate coated on glazed ceramics (Zhang et al. 2015); removal of
ibuprofen by micro-TiO 2 on coated glass rings (Czech and Tyszczuk-Rotko 2018);
and removal of a wide variety of pharmaceuticals and personal care products and
their metabolites [i.e., pharmaceuticals (carbamazepine, venlafaxine, fluoxetine,
atenolol, sulfamethoxazole, ibuprofen, atorvastatin, and naproxen) and personal
care products (triclosan and triclocarban)] by TiO 2 coated on quartz fiber filters
(Arlos et al. 2016). Dip-coating technique is mostly used for the photocatalyst
coatings in wide areas.
Treatments of Persistent Organic Pollutants
Photocatalytic removal of persistent organic pollutants in water is widely carried out
using photocatalysts coated on solid substrates, especially glass substrates. The
commercial TiO 2 -coated glass microrods were applied to degrade phenol in water.
The adherence of TiO 2 to glass microrods was proved to be good. The powder
suspension of TiO 2 in bulk solution was not observed after experimental runs
(Medina-Valtierra et al. 2006). Glass tubes and glass beads were used as supporting
materials of TiO 2 thin film for degradation of paraquat in water. In the case of glass
tubes, the photocatalytic activity of three different types of TiO 2 was compared,
including commercial TiO 2 (P25), TiO 2 synthesized by hydrothermal method, and
TiO 2 synthesized by sol–gel method. It was found that TiO 2 synthesized by hydrothermal method exhibited the highest paraquat herbicide removal efficiency (99%),
followed by commercial TiO 2 (75%) and TiO 2 synthesized by sol–gel method
(65%), respectively. The reason was that anatase phase of TiO 2 transformed to rutile
phase during sol–gel preparation method with heat treatment above 400
C (Lee
et al. 2002). In the case of glass beads, paraquat can be efficiently degraded by N, S
codoped TiO 2 -coated glass beads under sunlight and visible light irradiation. The
paraquat removal efficiencies could maintain after ten consecutive runs (Zahedi et al.
2015). Furthermore, photocatalytic removal of mixed pesticides (methyl parathion,
dichlorvos, and lindane) in water using TiO 2 -coated glass plates is presented in the
28
P. Kemacheevakul and S. Chuangchote
Coating of a photocatalyst as a thin layer on supporting materials is an effective
strategy to overcome the limitation of nanostructured photocatalyst powders involving the post-separation of slurry catalysts from the treated wastewater. Recent
approaches for treatments of organic pollutants are as follows.
Treatments of Pharmaceuticals and Personal Care Products
Photocatalytic removal of pharmaceuticals and personal care products in water using
photocatalysts coated on various support materials has been investigated, e.g.,
removal of salicylic acid, naproxen, diclofenac, and ibuprofen by TiO 2 (P25)/
tetraethyl orthosilicate coated on glazed ceramics (Zhang et al. 2015); removal of
ibuprofen by micro-TiO 2 on coated glass rings (Czech and Tyszczuk-Rotko 2018);
and removal of a wide variety of pharmaceuticals and personal care products and
their metabolites [i.e., pharmaceuticals (carbamazepine, venlafaxine, fluoxetine,
atenolol, sulfamethoxazole, ibuprofen, atorvastatin, and naproxen) and personal
care products (triclosan and triclocarban)] by TiO 2 coated on quartz fiber filters
(Arlos et al. 2016). Dip-coating technique is mostly used for the photocatalyst
coatings in wide areas.
Treatments of Persistent Organic Pollutants
Photocatalytic removal of persistent organic pollutants in water is widely carried out
using photocatalysts coated on solid substrates, especially glass substrates. The
commercial TiO 2 -coated glass microrods were applied to degrade phenol in water.
The adherence of TiO 2 to glass microrods was proved to be good. The powder
suspension of TiO 2 in bulk solution was not observed after experimental runs
(Medina-Valtierra et al. 2006). Glass tubes and glass beads were used as supporting
materials of TiO 2 thin film for degradation of paraquat in water. In the case of glass
tubes, the photocatalytic activity of three different types of TiO 2 was compared,
including commercial TiO 2 (P25), TiO 2 synthesized by hydrothermal method, and
TiO 2 synthesized by sol–gel method. It was found that TiO 2 synthesized by hydrothermal method exhibited the highest paraquat herbicide removal efficiency (99%),
followed by commercial TiO 2 (75%) and TiO 2 synthesized by sol–gel method
(65%), respectively. The reason was that anatase phase of TiO 2 transformed to rutile
phase during sol–gel preparation method with heat treatment above 400
C (Lee
et al. 2002). In the case of glass beads, paraquat can be efficiently degraded by N, S
codoped TiO 2 -coated glass beads under sunlight and visible light irradiation. The
paraquat removal efficiencies could maintain after ten consecutive runs (Zahedi et al.
2015). Furthermore, photocatalytic removal of mixed pesticides (methyl parathion,
dichlorvos, and lindane) in water using TiO 2 -coated glass plates is presented in the
28
P. Kemacheevakul and S. Chuangchote