Selective growth of Ti3+/TiO2/CNT and Ti3+/TiO2/C nanocomposite for enhanced visible-light utilization to degrade organic pollutants by lowering TiO2-bandgap

Modified hydrothermal method for synthesizing titanium dioxide-decorated multiwalled carbon nanotube nanocomposites for the solar-driven photocatalytic degradation of dyes

This study aimed to address the issue of rapid electron-hole recombination in photocatalysis by exploiting multi-phase TiO2 decorated on multiwalled carbon nanotubes (MWCNTs) to improve the photocatalytic degradation of dyes. A simple and eco-friendly one-pot method was utilized to create the TiO2/MWCNT nanostructure using glucose as both a structure-directing agent and a carbon source without requiring any prior covalent or non-covalent functionalization of the MWCNTs at 160 °C. Furthermore, it was found that the average width of the nanocomposites changed from 20 ± 1 and 42 ± 2 nm to 56 ± 3 nm, corresponding to MWCNT contents of 1.0, 2.0, and 3.0 (wt%), respectively. Specifically, TiO2/MWCNTs with a low content of MWCNTs demonstrated enhanced performance for the photocatalytic degradation of dyes, with the bandgap of the nanocomposites decreasing to 2.5 eV with 1.0% MWCNTs and 2.4 eV with 2.0% MWCNTs. The TiO2/MWCNT-1.0 catalyst demonstrated high photocatalytic efficiency for methylene blue (MB) degradation with a rate constant of 0.0051 min-1. TiO2/MWCNT-2.0 was more effective for rhodamine (RhB) degradation than pristine TiO2, with a rate constant of 0.0065 min-1 within 120 min of solar-light exposure. This novel modified approach can be used to synthesize nanocomposites simply and is potentially feasible for efficient dye degradation and beyond, offering a promising solution for water-pollution treatment.

Preparation of MWCNT/CoMn2O4 nanocomposite for effectual degradation of picric acid via peroxymonosulfate activation

In recent years, using nanomaterials based on multi-wall carbon nanotubes (MWCNT) through the activation of peroxymonosulfate (PMS) has attracted more attention to the degradation of organic pollutants. This research presented a new route for the synthesis of MWCNT/CoMn2O4 nanocomposite for the degradation of picric acid using advanced oxidation processes (AOPs). Firstly, CoMn2O4 nanoparticles were prepared and then loaded on MWCNT using ultrasonic waves. The results of various analyzes confirmed the successful loading of nanoparticles on carbon nanotubes. As the degradation process proceeds through oxidation processes, the high electronic conductivity of MWCNT and the active sites of Mn and Co in the nanocomposite play an essential role in activating PMS to generate reactive oxygen species (ROS). An investigation of the reaction mechanism in different conditions showed that the highest speed of picric acid decomposition in the presence of nanocomposite (98%) was in 47 min. However, the scavenger test showed that HO· and SO4·- radicals are more important in the degradation process. Meanwhile, the results showed that removing picric acid using MWCNT/CoMn2O4 was more effective than CoMn2O4 alone and confirmed the interaction effect of MWCNT nanotubes with AB2O4 nanocatalyst.

In Situ Quantitative Study of Single-Molecule Photoreduction Activities and Kinetics on 1D-1D Heterostructure

Understanding the underlying catalytic mechanisms with nanometer resolution is of critical importance to the rational design of 1D heterogeneous catalysts. However, a fundamental investigation of photocatalytic activities and kinetics at their individual sites is still challenging. Herein, in situ single-molecule fluorescence microscopy is employed to study the site-specific catalytic activities and dynamics on 1D-1D heterostructure for the first time. For carbon nanotube (CNT)/CdS nanorod composites, it is found that the CdS end with heterojunction exhibits the highest catalytic conversion rate constant of resazurin photoreduction, which is 30%, 7%, and 19% higher than those of the middle segment and the bare end of CdS, and the CNT end with heterojunction, respectively. A similar trend of adsorption abilities is observed in these structures. Such phenomena can be attributed to the different content of defects in these structures. Regarding the dissociation behaviors, the dissociation rate constants of all structures exhibit an opposite trend to those of adsorption and conversion. The direct and indirect dissociation are found to be predominant on CdS and CNT, respectively. Such investigation provides a deep insight into the understanding of site-specific properties on 1D heterogeneous catalysts and helps construct the "structure-dynamics" correlations at the nanoscale.

Selectivity of Sol-Gel and Hydrothermal TiO2 Nanoparticles towards Photocatalytic Degradation of Cationic and Anionic Dyes

Titanium dioxide (TiO2) nanoparticles have been extensively studied for catalyzing the photo-degradation of organic pollutants, the photocatalyst being nonselective to the substrate. We, however, found that TiO2 nanoparticles prepared via the sol-gel and hydrothermal synthetic routes each possess a definite specificity to the charge of the substrate for photodegradation. The nanoparticles were characterized by SEM, FTIR, XRD, TGA, and UV-visible spectra, and the photocatalytic degradation under UV-B (285 nm) irradiation of two model compounds, anionic methyl Orange (MO) and cationic methylene blue (MB) was monitored by a UV-visible spectrophotometer. Untreated sol-gel TiO2 nanoparticles (Tsg) preferentially degraded MO over MB (90% versus 40% in two hours), while after calcination at 400 °C for two hours (Tsgc) they showed reversed specificity (50% MO versus 90% MB in one hour). The as-prepared hydrothermal TiO2 nanoparticles (Tht) behaved in the opposite sense of Tsg (41% MO versus 91% MB degraded in one and a half hours); calcination at 400 °C (Thtc) did not reverse the trend but enhanced the efficiency of degradation. The study indicates that TiO2 nanoparticles can be made to degrade a specific class of organic pollutants from an effluent facilitating the recycling of a specific class of pollutants for cost-effective effluent management.

Harnessing Bio-Immobilized ZnO/CNT/Chitosan Ternary Composite Fabric for Enhanced Photodegradation of a Commercial Reactive Dye

Growing demand for sustainable wastewater treatment drives interest in advanced photocatalytic materials. Immobilized photocatalysts hold potential for addressing industrial wastewater organic pollutants, offering substantial surface area, agglomeration prevention, and easy removal. In this study, we successfully immobilized ZnO and carbon nanotubes onto a textile substrate through bilateral esterification and explored their effectiveness as a potent photocatalyst for degrading of commercial textile colorant reactive blue 4 (RB-4) colorant. Findings demonstrated significant improvements in photocatalytic performance upon integrating ZnO and CNTs into the fabric, coupled with chitosan immobilization. The immobilization process of ZnO and CNTs onto the substrate was elucidated through a proposed reaction mechanism, while the appearance of carbonyl peaks at 1719.2 cm-1 in the composite fabric further confirmed bilateral esterification. The as-developed immobilized nano-catalyst exhibited remarkable photocatalytic efficiency with an impressive 93.54% color degradation of RB-4. This innovative approach underscores the immense potential of the ternary immobilized (ZnO/fCNT/chitosan) composite fabric for efficient photocatalytic degradation in textile coloration processes. Exploring the early-stage development of immobilized photocatalysts contributes to safer and more eco-friendly practices, addressing pressing environmental challenges effectively.

Investigating the thermal and mechanical properties of novel LDPE/TiO2 and LDPE/TiO2/CNT composites for 3D printing applications

The development of new materials is essential for advancing technology and improving the quality of life. With new materials, we can create products that are stronger, more durable, and more efficient. The ongoing research and development of new materials for 3D printing applications continue to drive innovation in various fields, leading to improved products and processes with great benefits. The main goal of this work was to produce a functional filament with a 1.75-mm diameter that may be used for 3D printing. Composite materials were prepared using a low-density polyethylene (LDPE) resin as polymer matrix, and titanium dioxide (TiO₂) and carbon nanotubes (CNT) as fillers in various ratios. Up to 15 wt% of TiO₂ and 0.25 wt% of CNT were added. Some of the greatest difficulties with high filler content composites are achieving good homogeneity, and in the case of the 3D printing, greatest difficulties are producing the filament with a specific and stable filament diameter. During the 3D printing itself, the fillers can also often cause the nozzle clogging. This paper reports findings of thermal and mechanical properties of the LDPE/TiO₂/CNT composites which are significant for the 3D printing process and the applicability of the composite materials. All of the planed composite materials are successfully prepared and 3D printed into the tensile test specimens. The melting point shift caused by the addition of fillers did not show consistent pattern at differential scanning calorimetry, as all of the samples had melting temperatures around 113.5 ± 1.4 °C. The addition of filler, according to the TGA, increased the threshold temperature for the material decomposition, in case of TiO₂ 5.4 °C increase, while TiO₂ and CNT combination increased the threshold temperature for 6.8 °C. The results of the tensile test show a general increase trend with addition of TiO₂ filler but do not show to a trend for the tensile strength as a result of the addition of CNT filler. The sample with highest TiO₂ filler ratio of 15% (LDPE 15T0C) showed the greatest tensile strength of 14.5 MPa, compared to the 13.0 MPa of pure LDPE. The sample with 5% of TiO₂ filler and 0.1% of CNT filler (LDPE 5T0.1C) showed the greatest elongation of 73.9%, compared to the 68.9% of pure LDPE.

Fabrication of Robust and Stable N-Doped ZnO/Single-Walled Carbon Nanotubes: Characterization, Photocatalytic Application, Kinetics, Degradation Products, and Toxicity Analysis

The production of effective visible-light (VL) photocatalysts for the elimination of noxious organic pollutants from wastewater has attracted considerable interest owing to increasing awareness worldwide. Despite the large number of photocatalysts reported, the selectivity and activity of photocatalysts still need to be developed. The goal of this research is to eliminate toxic methylene blue (MB) dye from wastewater through a cost-effective photocatalytic process using VL illumination. A novel N-doped ZnO/carbon nanotube (NZO/CNT) nanocomposite was successfully synthesized via a facile cocrystallization method. The structural, morphological, and optical properties of the synthesized nanocomposite were systematically investigated. The as-prepared NZO/CNT composite exhibited remarkable photocatalytic performance (96.58%) within 25 min of VL irradiation. The activity was 92, 52, and 27% greater than that of photolysis, ZnO, and NZO, respectively, under identical conditions. The enhanced photocatalytic efficiency of NZO/CNT was attributed to the N atom and CNT involvement: N contributes to narrowing the band gap of ZnO, and CNT captures the electrons and maintains the electron flow in the system. The reaction kinetics of MB degradation, catalyst reusability, and stability were also investigated. In addition, the photodegradation products and their toxicity effects in our environment were analyzed using the liquid chromatography-mass spectrometry and ecological structure activity relationships programs, respectively. The findings of the current study demonstrate that the NZO/CNT nanocomposite can be utilized to remove contaminants in an environmentally acceptable manner, thereby providing a new window for practical applications.

Photocatalytic VOCs Degradation Efficiency of Polypropylene Membranes by Incorporation of TiO2 Nanoparticles

A class of serious environmental contaminants related to air, namely volatile organic compounds (VOCs), has currently attracted global attention. The present study aims to remove harmful VOCs using as-prepared polypropylene membrane + TiO₂ nanoparticles (PPM + TiO₂ NPs) via the photocatalytic gas bag A method under UV light irradiation. Here, formaldehyde was used as the target VOC. The PPM + TiO₂ NPs material was systematically characterized using various microscopic and spectroscopic techniques, including field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy, photoluminescence spectroscopy, and contact angle measurements. These results confirm the successful preparation of PPM + TiO₂ NPs, which can be applied to the degradation of VOCs. Photocatalytic degradation of formaldehyde gas reached 70% within 1 h of UV illumination. The energy bandgap and photoluminescence intensity reductions are responsible for the improved photocatalytic activity. These characteristics increase the charge transport while decreasing the recombination of electron-hole pairs.

Boosting the Visible Light Photocatalytic Activity of ZnO through the Incorporation of N-Doped for Wastewater Treatment

In the present work, we prepared N-doped ZnO by a facile chemical vapor deposition method and used it for the degradation of wastewater containing noxious rose bengal (RB) dye under visible-light stimulation. The as-prepared N-doped ZnO and the undoped ZnO (used as a control sample) were characterized by numerous spectroscopic and microscopic methods. These analyzing results confirmed the successful formation of the N-doped ZnO compound and it could be implemented for wastewater treatment. Interestingly, the N-doped ZnO material confirmed the maximum RB dye degradation efficiency (96.90%) and was shown to be 154% more efficient than undoped ZnO (62.95%) within 100 min of visible-light irradiation. The bandgap energy was considerably decreased after the incorporation of N onto the ZnO matrix compared to undoped ZnO. The improved photocatalytic performance is because of the reduction of bandgap energy, which suppressed the electron–hole pair recombination. In addition, a plausible photodegradation mechanism of RB dye was discussed employing N-doped ZnO under visible light. The findings show that our as-synthesized product can be used to eliminate contaminants, which provides a new avenue for effective implications.

Highly Efficient and Sustainable ZnO/CuO/g-C3N4 Photocatalyst for Wastewater Treatment under Visible Light through Heterojunction Development

Dye-containing pollutants are currently a threat to the environment, and it is highly challenging to eliminate these dyes photocatalytically under visible light. Herein, we designed and prepared a ZnO/CuO/g-C3N4 (ZCG) heterostructure nanocomposite by a co-crystallization procedure and applied it to eliminate pollutants from wastewater via a photocatalytic scheme. The structural and morphological features of the composite confirmed the formation of a ZCG nanocomposite. The photocatalytic capability of the ZCG photocatalyst was investigated via the decomposition of methylene blue dye. The outstanding activity level of 97.46% was reached within 50 min. In addition, the proficiency of the ZCG composite was 753%, 392%, 156%, and 130% higher than photolysis, g-C3N4, CuO, and ZnO, respectively. Furthermore, the photodeterioration activity on Congo red was also evaluated and found to be excellent. The enhanced catalytic achievement is attributed to the construction of heterojunctions among the constituent compounds. These properties boost the charge transfer and decrease the recombination rate. Moreover, the reusability of the ZCG product was explored and a negligible photoactivity decline was detected after six successful runs. The outcomes suggest the as-prepared nanocomposite can be applied to remove pollutants, which opens a new door to practical implementation.