Search

• TiO 2 nanoparticles were rationally monodispersed on the kaolinite surface. • The composite's reaction rate constant is about 6.90 times higher than that of pure TiO 2. • The synergistic effect between kaolinite and TiO 2 charged for performance enhancement. • This study provides a promising candidate for wastewater treatment. Lamellar kaolinite supported monodispersed TiO 2 was prepared through rational design and 0D/2D structural assembly, which showed significantly improved photocatalytic performance towards ciprofloxacin. After systematic evaluation, the pseudo-first-order kinetic constant rate of TiO 2 /kaolinite composite can reach to 0.04549 min−1, which was 6.90 and 1.81 times higher than that of pure TiO 2 and P25, respectively. The nano-TiO 2 /kaolinite composite photocatalyst also displayed good reusability performance, only a slight decline occurred after four repeated experiments, which is beneficial for the large-scale application of photocatalysts. Various characterizations indicated that enhanced photocatalytic performance can be ascribed to the synergistic effect between natural kaolinite and the well distributed TiO 2 , which enhanced the light absorption ability, assisted the dispersion of pure TiO 2 , resulted in co-catalysis effect, improved the separation facilitation of photo-induced carriers and promoted the stronger adsorption capacity, etc. These merits effectively regulated the carriers' lifetime and migration velocity of the photogenerated charge carriers. Considering the excellent properties of natural kaolinite (low cost, abundance, stability, etc.), our study provides a promising candidate for effective degradation of trace amounts of pharmaceutical and personal care product (PPCP) or contaminants with potential high-toxic risk. [ABSTRACT FROM AUTHOR]

Natural minerals are generally accepted as one of the most suitable carriers to support TiO 2 in photocatalytic and other applications because of their abundance, low cost, large surface area, and easy recyclability. Hence, in this work, a novel 0D/2D TiO 2 /kaolinite composite endowed with presence of oxygen vacancies and surface defect sites was synthesized through a mild sol-gel method combining with nitrogen induction. Ciprofloxacin (CIP) was taken as the main target organic pollutant to study the photocatalytic performance of the synthesized catalyst. The results showed that the nitrogen treated TiO 2 /kaolinite composite exhibited improving degradation performance for adsorption-photocatalytic elimination of CIP within broad radiation spectrum (200–800 nm). The synthesized composite exhibited enhanced reaction rate constant which is nearly 7.00, 2.54 and 3.13 times higher than that of bare TiO 2 treated with air under UV, solar, and visible light, respectively. Moreover, the newly prepared composite also exhibited significant enhancement towards the removal of formaldehyde under both UV and visible light. Radical scavenger experiments and ESR results indicated that holes should be the main oxidizing species within broad spectrum in the degradation system. The enhanced activity of nitrogen treated composite is mainly attributed to the induced oxygen vacancies as well as the intimate interface contact between TiO 2 and kaolinite, resulting in smaller grain size, higher light absorption ability, and faster carrier separation efficiency. It is expected that this high-efficiency composite photocatalyst based on natural minerals will be a promising candidate for the elimination of pharmaceutical and personal care products and volatile organic compounds within broad radiation spectrum. [ABSTRACT FROM AUTHOR]

Graphical abstract Novel CH 3 COOH functionalized TiO 2 /kaolinite composite was facilely prepared through a typical sol-gel method modified with CH 3 COOH treatment. Weak acid (CH 3 COOH) was utilized to activate the TiO 2 surface and generate more hydroxyl groups. Taken ciprofloxacin (CIP) as the target pollutant, both strongest adsorption ability and highest degradation efficiency were obtained compared with bare TiO 2 or TiO 2 /kaolinite composite under UV light and visible light, especially under UV light. Furthermore, density functional theory (DFT) calculations demonstrated that CH 3 COOH treatment might exert effect towards the transition and lifetime of electrons as well as contribute to the enhancement of the reactivity ability of TiO 2 and increase the catalytic properties. Enhancement mechanism and possible radicals' migration pathway was illustrated based on the characterizations (i.e. XRD, BET, UV–Vis, FTIR, Raman, etc.). Our study provides new insights into composite photocatalysts' surface adjustment and functional groups construction based on natural minerals. Highlights • Acetic acid was used to functionalize the TiO 2 /kaolinite surface. • Enhanced photocatalytic activity for ciprofloxacin within broad light spectrum was obtained. • DFT was used to explore the interface effect and the hydrogen function. • The enhancement mechanism was elucidated in this work. • This study provides novel idea for the synthesis of photocatalysts based on natural minerals. Abstract In this study, sol-gel method modified with acetic acid (CH 3 COOH) was employed to facilely synthesize hydrogen functionalized TiO 2 /kaolinite composite. Weak acid (CH 3 COOH) was used to modify the surface of TiO 2 /kaolinite composite in order to activate TiO 2 surface and generate more hydroxyl groups. The modified surface can act as Lewis acid sites to allow the physisorption of uncharged carboxyl acid groups, which is believed to be beneficial for electron injection and transfer. Using ciprofloxacin (CIP) as the target pollutant, in comparison with the use of strong acid such as hydrochloric acid (HCl) or sulfuric acid (H 2 SO 4), it was found that CH 3 COOH functionalized TiO 2 /kaolinite composite possessed the strongest adsorption ability and exhibited highest degradation efficiency under broad spectrum (200–800 nm). Moreover, the concentration of CH 3 COOH required is low (0.1 mol/L) in this work. The results show that the CH 3 COOH treated sample exhibited much higher degradation rates than bare TiO 2 or TiO 2 /kaolinite composite under both UV light and visible light. The kinetic constants under UV light were almost 2.61 and 1.57 times higher than those of TiO 2 and TiO 2 /kaolinite, respectively. According to the X-ray diffraction (XRD), N 2 adsorption-desorption isotherms, X-ray photoelectron spectroscopy (XPS), Fourier Transform infrared spectroscopy (FTIR) as well as Raman characterization results, it is revealed that the improved photocatalytic activity can be mainly attributed to the CH 3 COOH functionalization towards the TiO 2 /kaolinite composite. Furthermore, density functional theory (DFT) calculations were employed to explore the interface effect between TiO 2 and kaolinite as well as the function of newly introduced hydrogen on the surface of the composite, which significantly contributes to better understanding the function of CH 3 COOH in the constructed system. On the other hand, electron spin resonance (ESR) analysis suggests that the main oxidation species in the degradation process under broad light spectrum illumination was the holes. This study also provides information about the enhancement mechanism. New insights in photocatalysts synthesis and properties adjustment based on natural minerals for the elimination of organic contaminants of emerging concern in water was successfully introduced in the present study. [ABSTRACT FROM AUTHOR]

A novel 3D heterogeneous g-C 3 N 4 /TiO 2 /kaolinite composite with enhanced visible light activity was fabricated via a mild sol-gel method associated with chemical stripping and self-assembly. Compared with bare photocatalysts, the g-C 3 N 4 /TiO 2 /kaolinite 3D structure exhibits enhanced adsorption-photocatalytic degradation ability for the removal of ciprofloxacin (CIP) under visible-light irradiation, and also facilitate the recyclability of the photocatalyst as demonstrated from the reusability test. The apparent rate constant of the composite is up to around 5.35 times, 6.35 times and 4.49 times that of bare TiO 2 , g-C 3 N 4 and P25, respectively, and a possible degradation pathway was also proposed. On the other hand, the as-received composite also exhibited enriched disinfection ability towards S. aureus . It is indicated that the superoxide radical ( O 2 − ) is the main active species in the degradation process, and the superior photocatalytic performance of composite should be mainly attributed to both the improvement of light harvesting as well as the enhanced separation and transfer efficiency. It is expected that this novel ternary visible-light responding composite would be a promising candidate material for the organic pollutants degradation and bacteria inactivation. [ABSTRACT FROM AUTHOR]

• Carbon doped TiO 2 /kaolinite composite was rationally designed and assembled. • The composite's reaction rate constant is about 25 times higher than that of pure TiO 2. • TiIII defects and localized occupied states are responsible for performance enhancement. • Kaolinite induced carrier effect plays important role in catalytic activity enhancement. • The composite material might be a promising candidate for degrading trace amounts of pollutants. In this work, kaolinite supported monodispersed TiO 2 with carbon regulation was prepared through rational design and different dimensions' assembly, leading to generation of TiIII species in carbon doped TiO 2 /kaolinite (C-TiO 2 /kaolinite) composite. The C-TiO 2 /kaolinite composite exhibited improved degradation performance towards ciprofloxacin under visible light, with a reaction rate constant of 0.00597 min−1, which is about 3.24 and 24.88 times higher than that of 2.0C-T (2.0% carbon-doped TiO 2) and pure TiO 2 , respectively. Based on various materials characterization methods and DFT calculations, it was indicated that the electronic structure was correlated with the changes in light absorption, charge carrier lifetime, and reactive oxygen species (ROS). The enhanced visible light responding ability could be attributed to the synergistic effect between natural kaolinite and nanosized TiO 2 , the formation of localized occupied states in the gap, and the formation of TiIII defects consisted of surface oxygen vacancies. All of them effectively increase the separation efficiency, migration velocity, and lifetime of the photoinduced charge carriers under visible-light irradiation. Overall, our study provides a promising candidate for effective degradation of trace amounts of pharmaceutical and personal care products and other highly toxic contaminants with the assistance of solar light. [ABSTRACT FROM AUTHOR]