Novel polypropylene-TiO2:Bi spherical floater for the efficient photocatalytic degradation of the recalcitrant 2,4,6-TCP herbicide

In this work, spherical photocatalytic floaters were fabricated by depositing TiO2:Bi (TBi) particles on poly-propylene (PP) spheres (recycled from beer cans). These particles were deposited on the sphere (TBi-sphere) by the spray coating technique and evaluated their performance for the photocatalytic degradation of 2,4,6-trichlorophenol (2,4,6-TCP) herbicide. SEM images demonstrated that the BTi powders consisted in conglomerated grains with sizes of 20-80 nm and the analysis by X-ray diffraction confirmed the presence of rutile and anatase phases in the BTi. The photocatalytic experiments showed that the TBi and TBi-sphere produced maximum degradation of 90 and 97% for 2,4,6-TCP, respectively, after 4 h under UV-Vis light. The photocatalytic powders/composites were reused 3 times and the loss of degradation efficiency was 3 and 16% for the TBi powder and TBi-sphere, respectively. This means that the TBi-sphere is more stable for the continuous degradation of the 2,4,6-TCP contaminant. The TiO2:Bi powder was compared with the commercial TiO2 (P25) and found that the TiO2:Bi powder had higher light absorption (approximate to 42%) and higher surface area (approximate to 105%) than the P25. Therefore, the degradation percentage for the 2,4,6-TCP was 52% higher in the sample doped with Bi. Also, scavenger experiments were carried out and found that the main oxidizing agents produced for the degradation of 2,4,6-TCP were (OH-)-O-center dot radicals and O-center dot(2)- anions. Other species such as h(+) were also produced at lower amount. Hence, our results demonstrated that spherical/floatable photocatalytic composites are a viable option to remove herbicide residuals from the water, which is of interest in water-treatment-plants.

Automated summary

Spherical photocatalytic floaters containing TiO2:Bi particles were fabricated and evaluated for the degradation of 2,4,6-trichlorophenol (2,4,6-TCP) herbicide. The TBi-sphere showed higher degradation efficiency and stability compared to TBi powder. TiO2:Bi powder exhibited higher light absorption and surface area than commercial TiO2 (P25), resulting in a 52% higher degradation percentage for 2,4,6-TCP. The main oxidizing agents produced during degradation were (OH-)-O-center dot radicals and O-center dot(2)- anions.