A novel and stretchable carbon-nanotube/Ni@TiO2:W photocatalytic composite for the complete removal of diclofenac drug from the drinking water

We present the structural, morphological and photocatalytic properties of stretchable composites made with carbon nanotubes (CNTs), silicon rubber and Ni@TiO₂:W nanoparticles (TiWNi NPs) with average size of 37 ± 2 nm. Microscopy images showed that the TiWNi NPs decorated the surface of the CNT fibers, which are oriented in a preferential direction. TiWNi NPs presented a mixture of anatase/rutile phases with cubic structure. The performance of the TiWNi powders and stretchable composites was evaluated for the photocatalytic degradation of diclofenac (DCF) anti-inflammatory drug under ultraviolet-visible light. The results revealed that the maximum DCF degradation percentages were 34.6%, 91.9%, 97.1%, 98.5% and 100% for the CNT composite (stretched at 0%), TiWNi powders, CNT + TiWNi (stretched at 0%), CNT + TiWNi (stretched at 50%) and CNT + TiWNi (stretched at 100%), respectively. Thus, stretching the CNT + TiWNi composites was a good strategy to enhance the DCF degradation percentage from 97.1% to 100%, since stretching created additional defects (oxygen vacancies) that acted as electron sink, delaying the electron-hole recombination, and favors the DCF degradation. Raman/absorbance measurements confirmed the presence of such defects. Moreover, the reactive oxygen species (ROS) were determined by the scavenger's experiments and found that the main ROS were the ·OH and O₂^- radicals, which attacked the DCF molecules, causing their degradation. The results of this investigation confirmed that the stretchable CNT/TiWNi-based composites are a viable alternative to remove pharmaceutical contaminants from water and can be manually separated from the decontaminated water, which is unviable using photocatalytic powders.

Photocatalytic Degradation of Caffeine in a Solar Reactor System

In this paper, solar photodegradation of caffeine in aqueous solution was studied, this organic compound is the most consumed stimulant around the world. The degradation experiments were carried outdoors in a solar reactor and Evonik-Degussa P25 TiO2was used as catalyst. The photochemical and photocatalytic effect were tested in aqueous solutions of caffeine. Experimental results indicate that the organic compound is easily degraded over a very short period of time using 0.5 g L-1of catalyst. The kinetic analysis indicates that the initial reaction rate of caffeine is described by the LH-HW model. However, the original compound cannot be mineralized very fast, caffeine is converted to other organic compounds with a longer lifetime before the mineralization, converting caffeine CO2and water.