Synthesis and characterization of chitosan-supported Fe2O3 nanohybrids for rapid sonophotocatalytic degradation of 2,4,6-trichlorophenol.

The present study reports the design of heterogeneous photocatalytic system using Fe2O3 with chitosan (CS) as a matrix for the sonophotocatalytic degradation of 2,4,6-trichlorophenol (2,4,6-TCP). CS was chosen as a polymer matrix as it is abundant in nature, eco-friendly, and can be easily processed into microparticles, nanofibers, as well as nanoparticles and shows the tendency of adhesion towards a vast range of solid substrates besides serving as a chelating agent toward metallic oxides. The nanohybrids were characterized via Fourier transformation infrared spectrum (FT-IR), X-ray diffraction (XRD), scanning electron microscopy coupled with electron dispersive spectrum (SEM-EDS), thermogravimetric analysis (TGA), and UV-visible diffuse reflectance (UV-Vis-DRS) analyses. Infrared spectroscopy (IR) studies confirmed synergistic interaction between Fe2O3 and CS. The XRD measurements confirmed the crystalline morphology while SEM revealed formation of rod-like structures. The TGA studies confirmed higher thermal stability of CS/Fe2O3 as compared to pure CS. The optical band gap for CS and CS/Fe2O3 was calculated to be 3 eV and 2.25 eV, respectively, from diffuse reflectance spectral (DRS) studies. Rapid photocatalytic degradation of 2,4,6-TCP was observed under UV light irradiation in presence of CS and CS/Fe2O3 nanohybrids which revealed 83.19% and 95.20% degradation within a short span of 60 min. The degraded fragments were identified using liquid chromatography-mass spectrometry (LC-MS). The present study on the development of ecofriendly nanohybrid photocatalyst is expected to provide experimental basis for the future development of CS-based photocatalysts which can be easily processed into membranes/filters for the industrial scale degradation of toxic organic pollutants.

Highly efficient degradation of metronidazole drug using CaFe2O4/PNA nanohybrids as metal-organic catalysts under microwave irradiation.

Catalytic degradation based on microwave irradiation is an emerging technique which promises prompt and efficient catalytic degradation of organic pollutants. Calcium ferrite (CaFe2O4), poly(1-napththylamine) (PNA), and PNA/CaFe2O4 nanohybrids were synthesized via microwave-assisted technique. The properties of the as-prepared CaFe2O4, PNA, and PNA/CaFe2O4 nanohybrids were characterized by the thermogravimetric analysis (TGA), FTIR, XRD, SEM, and ultraviolet-visible spectrophotometry (UV-vis) analyses. The formation of inorganic-organic hybrids was confirmed by the FTIR and XRD studies. Loading of PNA was confirmed to be 8%, 16%, 32%, and 40% in CaFe2O4 which was established by TGA studies and the thermal stability was found to follow the order: CaFe2O4 > 8-PNA/CaFe2O4 > 16-PNA/CaFe2O4 > 32-PNA/CaFe2O4 > 40-PNA/CaFe2O4 > PNA. CaFe2O4 and PNA revealed band gap values of 3.42 eV and 2.60 eV respectively while for the PNA/CaFe2O4 nanohybrids, the values were found to be ranging between 2.46 and 3.00 eV. The PNA modified CaFe2O4 nanohybrids showed higher degradation efficiency towards metronidazole (MTZ) drug as compared with PNA and pure CaFe2O4. MTZ drug showed around 94% degradation within 21 min of microwave irradiation using 40-PNA/CaFe2O4 as catalyst. The enhanced catalytic activity was attributed to the high surface area of the nanohybrid catalyst as well as improved microwave catalytic activity of PNA. The reactive species responsible for degradation were confirmed by scavenger studies which formation of ·OH and O2·- radicals. Recyclability tests showed that the 40-PNA/CaFe2O4 nanohybrid exhibited 86% degradation of MTZ (90 mg/l) even after the third cycle, which reflected higher reusability of the catalyst. The MTZ fragments were identified using liquid chromatography-mass spectrometry (LC-MS).

Microwave-Assisted Degradation of Paracetamol Drug Using Polythiophene-Sensitized Ag-Ag2O Heterogeneous Photocatalyst Derived from Plant Extract.

Ag-Ag2O nanoparticles were synthesized using Osmium sanctum plant extract. The nanoparticles were sensitized with polythiophene (PTh) and were characterized via scanning electron microscopy with energy dispersive X-ray and elemental mapping, transmission electron microscopy, X-ray diffraction (XRD), Fourier-transform infrared, and UV-vis spectroscopy analyses. The elemental mapping results revealed that the samples were composed of C, S, Ag, and O elements which were uniformly distributed in the nanohybrid. XRD analysis confirmed the crystalline nature of Ag-Ag2O nanoparticles, and the average particle size was found to be ranging between 36 and 40 nm. The optical band gap of Ag-Ag2O, PTh, and Ag-Ag2O/PTh was found to be 2.49, 1.1, 1.5, and 0.68 eV. The catalytic activity of Ag-Ag2O, PTh, and Ag-Ag2O/PTh was investigated by degrading paracetamol drug under microwave irradiation. Around 80% of degradation was achieved during 20 min irradiation. All degradation kinetics were fitted to the pseudo-first-order model. A probable degradation pathway for paracetamol degradation was proposed based on liquid chromatography mass spectrometry analysis of degraded fragments.

Synthesis of nanohybrids of polycarbazole with α-MnO2 derived from Brassica oleracea: a comparison of photocatalytic degradation of an antibiotic drug under microwave and UV irradiation.

The present work describes the synthesis of α-MnO2 nanorods using a natural extract of Brassica oleracea (cabbage) and the formulation of its nanohybrids with polycarbazole, i.e., α-MnO2/PCz. Synergistic interaction between PCz and MnO2 is revealed from infrared spectroscopy (IR) studies while the composition is determined by X-ray photoelectron spectroscopy (XPS). The formation of α-MnO2 nanorods is confirmed via high-resolution transmission electron microscopy (HRTEM). The indirect bandgap of α-MnO2 is reported as 2.5 eV while for the nanohybrids it is found to be ranging between 2.3 and 2.5 eV. Results show that 91% and 89% of degradation is achieved within 30 min and 90 min under the microwave and UV irradiation respectively. Hydroxyl radicals (•OH) and superoxide (•O2-) radicals are responsible for photocatalytic degradation of the drug Bactrim DS which is confirmed by radical scavenging experiments. The nanohybrids show promising catalytic activity under UV as well as microwave irradiation.

Microwave-assisted rapid degradation of DDT using nanohybrids of PANI with SnO2 derived from Psidium Guajava extract.

The present work reports microwave-assisted synthesis of SnO2 nanoparticles via green route using Psidium Guajava extract. For the enhancement of catalytic activity, nanohybrids of SnO2 were formulated using different ratios of polyaniline (PANI) via ultrasound-assisted chemical polymerization. Formation of nanohybrids was confirmed via IR and XPS studies. The UV-vis DRS spectra of PANI/SnO2 revealed significant reduction in the optical band gap upon nanohybrid formation. Microwave-assisted catalytic efficiency of pure SnO2, PANI, PANI/SnO2 nanohybrids was investigated using DDT as a model persistent organic pollutant. The degradation efficiency of PANI/SnO2 was found to increase with the increase in the loading of PANI. Around 87% of DDT degradation was achieved within a very short period of 12 min under microwave irradiation using PANI/SnO2-50/50 as catalyst. The effect of DDT concentration was explored and the degradation efficiency of PANI/SnO2-50/50 catalyst was noticed to be as high as 82% in presence of 100 mg/L of DDT. The effect of microwave power on the degradation efficiency revealed 79% degradation using the same nanohybrid when exposed to microwave irradiation for 5 min under 1110 W microwave power. Scavenging studies confirmed the generation of OH, O2- radicals. The fragments with m/z values as low as 86 and 70 were confirmed by LCMS analysis. Recyclability tests showed that PANI/SnO2-50/50 nanohybrid exhibited 81% degradation of DDT (500 mg/L) even after the third cycle, which reflected high catalytic efficiency as well as remarkable stability of the catalyst. This green nanohybrid could therefore be effectively utilized for the rapid degradation of persistent organic pollutants.

Visible-light driven photocatalytic degradation of bisphenol-A using ultrasonically synthesized polypyrrole/K-birnessite nanohybrids: Experimental and DFT studies.

Although manganese oxides are known for their semiconductor characteristics, the photocatalytic performance of conducting polymer intercalated K-Birnessite (K-Bi) has not been explored till date. With the view to design a visible light driven organic-inorganic hybrid photocatalyst for rapid degradation of Bisphenol A (BPA), the present work reports the ultrasound-assisted green synthesis of K-Bi/polypyrrole (Ppy) nanohybrids. The loading of Ppy in K-Bi was confirmed by thermogravimetric analysis while the formation of organic-inorganic hybrid was confirmed by infrared spectroscopy. K-Bi revealed a band gap of 2.8 eV while for the nanohybrids it was found to be ranging between 2.4 and 1.6 eV. X-ray diffraction studies confirmed partial intercalation of Ppy chains in the inter-layer space of K-Bi. High resolution transmission electron microscopy and scanning electron microscopy studies showed mixed morphology of K-Birnessite/Ppy nanohybrids. Rapid degradation of BPA was observed under visible irradiation in presence of K-Bi/Ppy nanohybrids and almost 90% degradation of 20 mg/L BPA solution was achieved within 120 min. The degradation was found to follow pseudo-first order kinetics and the degraded fragments were identified using liquid chromatography-mass spectrometry. Degradation pathway was proposed based on density-functional theory calculations of fukui index predicting the radical easy-attacking (f0) and (f-) sites in BPA.