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• Novel BiOCl/TiO 2 /clinoptilolite composite photocatalyst was synthesized. • BiOCl/TiO 2 /clinoptilolite displayed excellent visible photocatalytic activity. • Carrier effect and heterojunction charged for photocatalytic enhancement. • This study provides a novel idea for ternary heterojunction construction. Novel BiOCl/TiO 2 /clinoptilolite composite was prepared via a homogeneous precipitation and calcination-crystallization process in this study. Through structural design and spatial assembly, the ternary composite based on clinoptilolite layer as well as the TiO 2 nano particles and BiOCl nano sheets was successfully synthesized. The prepared composite was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscope (HRTEM), X-ray photoelectron spectroscopy (XPS), N 2 isothermal adsorption-desorption test and electrochemical measurement, respectively. Compared with bare photocatalysts (i.e. TiO 2 and BiOCl), the composite exhibited enhanced photoactivity under visible light irradiation towards rhodamine B (RhB). Based on the pseudo-first-order kinetic constants, the photocatalytic performance of BiOCl/TiO 2 /clinoptilolite composite is around 48 and 11 times higher than that of pure TiO 2 and BiOCl, respectively. The enhanced photocatalytic properties of the composite should be attributed to the improved adsorption ability and the formation of the n -p heterojunction between BiOCl and TiO 2 , which is beneficial to establish the rapid adsorption-desorption system and promote the efficient separation of the photogenerated electron-hole pairs. The excellent visible-light-driven performance makes the BiOCl/TiO 2 /clinoptilolite composite possible to be utilized in the field of industrial wastewater treatment. [ABSTRACT FROM AUTHOR]

Graphical abstract Novel ternary heterogeneous BiOCl/TiO 2 /sepiolite composite with enhanced visible-light-induced photoactivity towards TC was successfully fabricated by a mild hydrolysis precipitation method followed by the calcination crystallization process. The present study would inspire the exploration of similar novel design to synthesize other highly efficient visible-light photocatalysts for better applications in addressing environmental pollution issues. Abstract In this study, the novel ternary heterogeneous BiOCl/TiO 2 /sepiolite composite with enhanced visible-light-induced photocatalytic activity was synthesized via the hydrolysis precipitation method followed by a calcination crystallization process. The as-prepared samples were characterized by X-ray diffraction (XRD), UV–VIS diffused reflectance spectroscopy (DRS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N 2 adsorption-desorption, X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL), respectively. Compared with bare BiOCl and TiO 2 , the ternary heterogeneous structure in BiOCl/TiO 2 /sepiolite significantly improved the visible-light-induced photocatalytic performance towards tetracycline (TC), and also contributed to the separation efficiency and recyclability of the photocatalyst. In addition, the influence of the mass ratio of BiOCl in the composites was also discussed, and the optimal mass ratio is identified as 50% (m BiOCl /(m TiO2 + m BiOCl). Furthermore, TC degradation by-products were further detected by HPLC-MS/MS, and a possible degradation pathway was proposed. Besides, ESR (Electron spin resonance) results indicated that the main active radical species were photo-induced holes (h+) and superoxide radical (O 2 −) in the TC degradation process. Hence, the enhanced photocatalytic activity of the prepared ternary composite was mainly attributed to the remarkable synergistic effect within the BiOCl/TiO 2 /sepiolite ternary heterogeneous system, resulting in the superior adsorption activity, the outstanding visible-light response performance and the efficient separation of the photogenerated electron-hole pairs. It is speculated that the novel ternary heterogeneous BiOCl/TiO 2 /sepiolite composite would have a broad application prospect in the field of wastewater treatment. [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]

To overcome rapid electron-hole recombination and low adsorption capacity of single g-C 3 N 4 photocatalyst, the present work reports on the fabrication of two kinds of visible-light-driven composite photocatalysts (g-C 3 N 4 /kaolinite and g-C 3 N 4 /illite composites). 2D/2D assembly was successfully achieved in this work. Furthermore, the as-synthesized composites exhibited significantly enhanced photocatalytic activity under visible-light irradiation, whose reaction rate constants were almost 4.13 times (g-C 3 N 4 /kaolinite) and 3.18 times (g-C 3 N 4 /illite) that of pure g-C 3 N 4 . A plausible reaction mechanism over the as-prepared composite photocatalysts was also proposed based on the experimental results obtained. The photocatalytic enhancement of synthesized composites should be attributed to the intimate interface contact between g-C 3 N 4 and layered minerals, resulting in better dispersion performance, higher charge separation efficiency as well as stronger adsorption ability. [ABSTRACT FROM AUTHOR]

Diatomite, a porous non-metal mineral, was used as support to prepare TiO 2 /diatomite composites by a modified sol–gel method. The as-prepared composites were calcined at temperatures ranging from 450 to 950 °C. The characterization tests included X-ray powder diffraction (XRD), scanning electron microscopy (SEM) with an energy-dispersive X-ray spectrometer (EDS), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption/desorption measurements. The XRD analysis indicated that the binary mixtures of anatase and rutile exist in the composites. The morphology analysis confirmed the TiO 2 particles were uniformly immobilized on the surface of diatom with a strong interfacial anchoring strength, which leads to few drain of photocatalytic components during practical applications. In further XPS studies of hybrid catalyst, we found the evidence of the presence of Ti–O–Si bond and increased percentage of surface hydroxyl. In addition, the adsorption capacity and photocatalytic activity of synthesized TiO 2 /diatomite composites were evaluated by studying the degradation kinetics of aqueous Rhodamine B under UV-light irradiation. The photocatalytic degradation was found to follow pseudo-first order kinetics according to the Langmuir–Hinshelwood model. The preferable removal efficiency was observed in composites by 750 °C calcination, which is attributed to a relatively appropriate anatase/rutile mixing ratio of 90/10. [ABSTRACT FROM AUTHOR]

Over the past decades, inspired by the outstanding properties of clay minerals such as abundance, low-cost, environmental benignity, high stability, and regularly arranged silica-alumina framework, researchers put much efforts on the interface assembly and surface modification of natural minerals with bare photocatalysts, i.e. TiO 2 , g-C 3 N 4 , ZnO, MoS 2 , etc. The clay-based hybrid photocatalysts have resulted in a rich database for their tailor-designed microstructures, characterizations, and environmental-related applications. Therefore, in this study, we took a brief introduction of three representative minerals, i.e. kaolinite, montmorillonite and rectorite, and discussed their basic merits in photocatalysis applications. After that, we summarized the recent advances in construction of stable visible-light driven photocatalysts based on these minerals. The structure-activity relationships between the properties of clay types, pore structure, distribution/dispersion and light absorption, carrier separation efficiency as well as redox performance were illustrated in detail. Such representative information would provide theoretical basis and scientific support for the application of clay based photocatalysts. Finally, we pointed out the major challenges and future directions at the end of this review. Undoubtedly, control and preparation of novel photocatalysts based on clays will continue to witness many breakthroughs in the arena of solar-driven technologies. [Display omitted] • Kaolinite, montmorillonite and rectorite based photocatalysts were well reviewed. • The role of clay in composite photocatalysts was illustrated in detail. • We point out the major challenges and direction of clay based photocatalysts. • This review is meaningful for energy crisis and environmental remediation. [ABSTRACT FROM AUTHOR]