Chemical recycling of polyester textile wastes using silver-doped zinc oxide nanoparticles: an economical solution for circular economy.

The waste management of polyethylene terephthalate (PET)-derived polyester (PES) textile is a global issue, and material recovery through chemical recycling can restore a circular economy. In our investigation, microwave-induced catalytic aminolysis and glycolysis of PES textile wastes using Ag-doped ZnO nanoparticles have been proposed. Ag-doped ZnO is prepared by the sol-gel method and characterised by XRD, FT-IR, UV-Vis, SEM-EDX and TEM. The reaction parameters such as PET-to-catalyst ratio, microwave power and irradiation time, temperature and catalyst recycling have been optimised. The catalyst was found to be more stable and could be recycled up to six times without losing its activity. Both the aminolysis and glycolysis of PES showed 100% conversion and afforded of bis (2-hydroxy ethylene) terephthalamide (BHETA) and bis (2-hydroxy ethylene) terephthalate (BHET), respectively. The depolymerisation of PES wastes using Ag-doped ZnO afforded BHETA and BHET for about 95 and 90%, respectively. The monomers BHET and BHETA confirmed by FT-IR, 1H NMR and mass spectroscopy. According to the findings, 2 mol% Ag-doped ZnO has higher catalytic activity.

All-alike hollow nanotubes of g-C3N4 converting photons into fuel by splitting water.

In this article, we present a sapiential method for producing highly effective oxygen-containing CN with hierarchical porous hollow nanotubes (HTCN) using thermal polycondensation of oxalic acid-assisted supramolecular aggregates. As a result of the synergistic effect of spatial charge separation and optical absorption ability, HTCN outperforms pristine CN nanosheets (NSCN) in photocatalytic hydrogen production. This research will provide a novel cognitive perspective and understanding for constructing contemporary hydrogen production photocatalysts.

A Z-scheme BiYO3/g-C3N4 heterojunction photocatalyst for the degradation of organic pollutants under visible light irradiation.

Photocatalysis is one of the fascinating fields for the wastewater treatment. In this regard, the present study deals with an effective visible light active BiYO3/g-C3N4 heterojunction nanocomposite photocatalyst with various ratios of BiYO3 and g-C3N4 (1:3, 1:1 and 3:1), synthesised by a wet chemical approach. The as-synthesised nanocomposite photocatalysts were investigated via different physicochemical approaches like Fourier transform infrared (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electrons microscopy (TEM), UV-vis diffuse reflectance spectroscopy (DRS), photoluminescence (PL) and photoelectrochemical studies to characterise the crystal structure, morphology, optical absorption characteristics and photoelectrochemical properties. The photocatalytic degradation ability of the prepared photocatalytic samples was also analysed through the degradation of RhB in the presence of visible light irradiation. Of all the synthesised photocatalysts, the optimised CB-1 composite showed a significant photocatalytic efficiency (88.7%), with excellent stability and recyclability after three cycles. O2•- and •OH radicals were found to act a major role in the RhB degradation using optimised CB-1 composite, and it possessed ~ 1 times greater photocurrent intensity than the pristine g-C3N4 and BiYO3. In the present work, a direct Z-scheme heterojunction BiYO3/g-C3N4 with a considerably improved photocatalytic performance is reported.

Construction of direct Z-scheme g-C3N4/BiYWO6 heterojunction photocatalyst with enhanced visible light activity towards the degradation of methylene blue.

Construction of the Z-scheme heterojunction photocatalyst achieved highly improved photocatalytic ability by its high redox ability of the photoinduced e--h+ pairs. In the study, Z-scheme g-C3N4/BiYWO6 heterojunction photocatalyst is prepared by the single-step hydrothermal method. Further, its photocatalytic ability was assessed by degrading methylene blue under visible light exposure. Particularly, the optimized 30 wt% of g-C3N4 in the g-C3N4/BiYWO6 composite exposes almost complete degradation after 90 min, that is ~ 3.0 times greater than the bare BiYWO6 and g-C3N4 with the rate constant value 0.032 min-1. Experimentally, the radical trapping studies indicate O2·- and ·OH radicals are playing a vital role in the photocatalytic degradation process. Also, the Z-scheme g-C3N4/BiYWO6 heterojunction photocatalyst exhibits excellent photoelectrochemical property and it is stable after 5 cycles, which indicates its good reusability nature. These enhancements are due to the newly formed heterostructure that facilitates the migration and separation efficiency of the photoproduced e--h+ pairs. Hence, the synthesized Z-scheme g-C3N4/BiYWO6 heterostructure could be an excellent material for wastewater remediation works.

Construction of direct FeMoO4/g-C3N4-2D/2D Z-scheme heterojunction with enhanced photocatalytic treatment of textile wastewater to eliminate the toxic effect in marine environment.

A novel FeMoO4/g-C3N4-2D/2D Z-scheme heterojunction photocatalyst was prepared via wet chemical method. The observed structural morphology of FeMoO4/g-C3N4 reveals the 2D-iron molybdate (FeMoO4) nanoplates compiled with the 2D-graphitic carbon nitride (g-C3N4) nanosheets like structure. The photocatalytic activity of the g-C3N4, FeMoO4, and FeMoO4/g-C3N4 composites were studied via the degradation of Rhodamine B (RhB) as targeted textile dye under visible light irradiation (VLI). The optimal FeMoO4/g-C3N4 (1:3 ratio of g-C3N4 and FeMoO4) composite show an enhanced degradation performance with rate constant value of 0.02226 min-1 and good stability even after three cycles. Thus, the h+ and O2•－are the key radicals in the degradation of RhB under VLI. It is proposed that the FeMoO4/g-C3N4 Z-scheme heterojunction effectively enhances the transfer and separation ability of e-/h+ pairs, by the way increasing the photocatalytic efficiency towards the RhB degradation. Thus, the newly constructed Z-scheme FeMoO4/g-C3N4 heterojunction photocatalyst is a promising material for the remediation of wastewater relevant to elimination of toxic effect in marine environment.

A facile synthesis of visible light driven Ni3V2O8 nano-cube/BiVO4 nanorod composite photocatalyst with enhanced photocatalytic activity towards degradation of acid orange 7.

Photocatalysis is one of the promising method to degrade harmful organic pollutants under visible light exposure. In this work, a novel Ni3V2O8/BiVO4 nanocomposite has been prepared by one-pot hydrothermal method, and investigated through X-ray diffraction, FT-IR, UV-visible diffuse reflectance spectroscopy, scanning and transmission electron microscopy and photoluminescence techniques. Subsequently, the photocatalytic performance of Ni3V2O8/BiVO4 nanocomposite has been examined by degrading AO7 under visible light illumination. The photocatalytic efficiency of the optimized 1:2 ratio of Ni3V2O8/BiVO4 nanocomposite photocatalyst is found to be 87% with a rate constant value of 0.03387 min-1 which are higher than those of other prepared photocatalysts. This nanocomposite exhibits excellent stability even after 3 three cycles, and shows 1.135- and 1.17-times higher photocurrent intensity than pure BiVO4 and Ni3V2O8 respectively. The mechanism for the degradation of AO7 over Ni3V2O8/BiVO4 nanocomposite photocatalyst has been proposed.

Revealing the charge transfer mechanism in magnetically recyclable ternary g-C3N4/BiOBr/Fe3O4 nanocomposite for efficient photocatalytic degradation of tetracycline antibiotics.

Pharmaceutical compounds in water bodies pose hazards to the ecosystem because of their biotoxicity potency. To eradicate such pharmaceutical compounds, a novel g-CN/BiOBr/Fe3O4 nanocomposites was prepared using a simplistic route and appraised for photodegradation of model tetracycline antibiotics. The g-CN/BiOBr/Fe3O4 nanocomposites exhibited complete tetracycline degradation in just 60 min exposure of simulated light irradiation, which is 6 times higher than the g-CN. Under the analogous condition, the tetracycline mineralization ability of the g-CN/BiOBr/Fe3O4 nanocomposites was evaluated to be 78% of total organic carbon removal. The superior photocatalytic performance is ascribed to the extended visible light harvesting ability and enhanced charge carrier separation/transfer with impeded recombination rate in light of effective indirect Z-scheme heterojunction construction. Based on band-edge potential and radical trapping studies indicate that h+ > â€¢O2- > â€¢OH are the active species responsible for photodegradation. Furthermore, the ternary nanocomposites are magnetically retrievable and recyclable while retaining their stable photocatalytic performance. This work endows a new perspective on the rational design and construction of magnetically recoverable ternary nanocomposite for environmental remediation.

Complete photocatalytic degradation of tetracycline by carbon doped TiO2 supported with stable metal nitrate hydroxide.

Visible light-driven carbon-doped TiO2 supported with metal nitrate hydroxide (CT-Ni/Co/Cu) nanocomposites were prepared and characterized by various studies. It is fascinating to note that particle size of TiO2 was substantially reduced from 5 µm to 50 nm after doping of carbon which was confirmed by FESEM. Moreover, the incorporation of stable metal (Cu) nitrate hydroxide further enhanced the visible light absorption up to 800 nm as evident by UV-DRS. The carbon doping and copper nitrate formation are validated by the Ti-O-C and N-O bonds using XPS and FTIR spectra. The photocatalytic activity of as-prepared photocatalyst was tested for the tetracycline degradation (TC, 10 mg/mL) under light irradiation. Significantly, 3 wt% carbon-doped TiO2 (31CT) with Cu (II) hydroxide nitrate nanocomposite photocatalyst exhibited an excellent photocatalytic activity (97%, within 1 h), and the corresponding reaction rate was around 2 times higher than bare TiO2. The excellent photocatalytic activity of 31CT-Cu nanocomposite was due to enhanced adsorbent of TC via carbon doping, visible light absorption, improved photo-generated carrier separation and migration by metal nitrate hydroxide as a support. This work may promote the development of a new carbon-doped TiO2 supported with highly stable metal nitrate hydroxide nanocomposite by facile method and used as an efficient photocatalyst for photodegradation of environmental pollutants.

Complete removal of Tetracycline by sonophotocatalysis using ultrasound-assisted hierarchical graphitic carbon nitride nanorods with carbon vacancies.

Tuning a graphitic carbon nitride (CN) structure is an effective strategy to advance its physicochemical and electronic properties. Herein, hierarchical CN nanorods with carbon vacancy were synthesized via ultrasound-assisted thermal polycondensation method wherein melamine-HONH2·HCl complex acts as a template. The hierarchical CN nanorods can facilitate multiple light scattering, provide large specific surface area with extensive reactive sites and endow abundant mass-transport channels for charge migration. The existence of carbon vacancies can serve as shallow charge trapping sites and prompt charge separation. Consequently, hierarchical CN nanorod possessed excellent sonophotodegradation efficiency of ∼100% towards Tetracycline (TC) antibiotic within 60 min under ultrasonic irradiation and visible light illumination. Moreover, the sonophotocatalytic degradation was higher than the sum of sonocatalytic and photocatalytic TC degradation using hierarchical CN nanorods due to its synergistic performance. A plausible sonophotocatalytic mechanism and TC degradation pathway using hierarchical CN nanorod were proposed. Lastly, hierarchical CN nanorod is durable and stable which can withstand the sonophotocatalytic condition even after the fifth run. This work offers an insight into hierarchical CN nanorod to advance sonophotocatalytic degradation performance for highly efficient removal of various recalcitrant pollutants.

Construction of S-scheme 1D/2D rod-like g-C3N4/V2O5 heterostructure with enhanced sonophotocatalytic degradation for Tetracycline antibiotics.

Pharmaceutically active compounds are an emerging water contaminant that resists conventional wastewater treatments. Herein, the sonophotocatalytic degradation of Tetracycline (TC) antibiotics as a model contaminant was carried out over a rod-like g-C3N4/V2O5 (RCN-VO) nanocomposite. RCN-VO nanocomposite was synthesized via ultrasound-assisted thermal polycondensation method. The results showed that the RCN-VO nanocomposite could completely remove the TC in water within 60 min under simultaneous irradiation of visible light and ultrasound. Moreover, the sonophotocatalytic TC degradation (a synergy index of ∼1.5) was superior to the sum of individual sonocatalytic and photocatalytic degradation using RCN-VO nanocomposite. Besides, the enhanced sonophotocatalytic activity of RCN-VO can be attributed to the 1D/2D nanostructure and the S-scheme heterojunction formation between RCN and VO where the electrons migrated from RCN to VO across the RCN-VO interface. Under irradiation, the built-in electric field, band edge bending and Coulomb interaction can synergistically facilitate the unavailing electron-hole pair recombination. Thereby, the cumulative electron in RCN and holes in VO can actively take part in the redox reaction which generates free radicals and attack the TC molecules. This study provides insight into a novel S-Scheme heterojunction photocatalyst for the removal of various refractory contaminants via sonophotocatalytic degradation.