TiO₂-Based Photocatalytic Degradation of 2-Chlorophenol Adsorbed on Hydrophobic Clay

Abstract

The combination of adsorption and heterogeneous photocatalysis has been investigated as a promising technology for the removal of organic water pollutants. A laboratory study of the removal and decomposition of 2-chlorophenol (2-CP) as a toxic organic pollutant was carried out under various conditions with an organophilized clay mineral (hexadecylpyridinium chloride-modified montmorillonite; HDPM) as adsorbent and Degussa P25 TiO2 as photocatalyst. Three different oxidation processes leading to the degradation of 2-CP were compared: direct photolysis, heterogeneous photocatalysis in a TiO2 suspension, and the decomposition of substrate adsorbed on HDPM in the presence of TiO2. Both the degradation of 2-CP and the formation of intermediates were analyzed by HPLC, the total organic carbon content and the total organic and inorganic chloride contents were measured to monitor the mineralization process, and X-ray diffraction and thermoanalytical measurements were made to characterize the hydrophobic clay adsorbent. The heterogeneous photocatalytic degradation of dissolved (2-CP/UV/TiO2) and desorbed 2-CP (2-CP/HDPM/UV/TiO2) appeared to be equally efficient, whereas direct photolysis of 2-CP was far less efficient in the oxidative destruction. HDPM proved to be a suitable adsorbent, capable of adsorbing toxic organics from water. It was demonstrated that the adsorbent (at relatively high concentration) did not decrease the rate of mineralization of 2-CP. The results confirmed that the adsorbent retains its structure and composition during the mineralization process, and thus it can be reused without regeneration. The combination of adsorption and heterogeneous photocatalysis studied may be an efficient and economical means of accumulating, removing, and oxidizing organic water contaminants, and its application is in accordance with the growing environmental demands.

Titania/C TAB Nanoskeleton as adsorbent and photocatalyst for removal of alkylphenols dissolved in water

“…Furthermore, combining of titania (TiO 2 ) with organic/inorganic hybrid porous materials is expected to enhance the removal of organic contaminants from water due to the synergistic effect of adsorption and photocatalytic degradation of organic contaminants [22][23][24][25][26][27][28][29].…”

Synthesis of hectorite–TiO2 and kaolinite–TiO2 nanocomposites with photocatalytic activity for the degradation of model air pollutants

“…In aqueous dispersions, clays have been used in combination with TiO 2 photocatalytic degradation to enhance the removal of organic pollutants (Mogyorósi et al, 2002).…”

Growth of TiO2 nanocrystals in the presence of alkylpyridinium salts: the interplay between hydrophobic and hydrophilic interactions

“…1 -6 In the case of photovoltaic devices, for example, the TiO 2 anatase polymorph is reported to exhibit the highest activity, 1,4 while in the photodegradation of environmental pollutants a controlled mixture of anatase and rutile is suggested to produce the best results. 7 Further, in all the above-mentioned applications, the nanometer scale of the crystals is reported to play a key role in determining the performance of the material. 1,4 -6 Thus, it is important to develop synthetic methods in which the crystalline form as well as the size and shape of the TiO 2 nanocrystals can be controlled.…”