Journal of Water and Environmental Nanotechnology
Volume:8 Issue: 1, Winter 2023

Catalysis for environmental remediation is becoming of paramount importance as industrial and urban activities multiply, and by-products contaminate soils and wastewater. Effluents from industrial and urban activities have led to many environmental problems involving water contamination. Here, we propose a new iron-incorporated metal-organic framework (MOF) photocatalyst to decontaminate water. The nanocatalyst was synthesized by the solvothermal method, and Fe was added to the structure as a promoter and active phase. In this study, we examined the degradation of methylene blue (MB) as a cationic azo dye. The nanocatalysts were characterized by XRD, FE-SEM, BET, NH3-TPD, and FTIR techniques. The results showed high crystallinity, a large specific surface area, and a uniform promoter distribution. At a pH = 9, a catalyst amount of 110 mg and an initial MB concentration in the effluent of 2 ppm resulted in the highest removal percentage (98 %). The kinetic analysis provided a quasi-first-order model that reasonably matched the experimental data (R2 = 95 %). The results verified the catalyst’s great capability for efficient and fast MB removal in 60 minutes of photocatalytic processing.

In the current work, a novel ZnO-Cu2O heterojunction was synthesized from ZnO nanorods and Cu2O nanoparticles via hydrothermal route and was applied for the first time as a visible light active photocatalyst for decomposition of Paraoxon insecticide. Crystallinity, shape and size of particles, and optical properties of the synthesized heterojunction nanocomposites were evaluated by XRD, FESEM, EDS, Mott-Schottky, photocurrent analysis and UV-Visible spectroscopy analyses. Based on the obtained results the ZnO-Cu2O heterojunction nanocomposite was successfully synthesized and compared to pure ZnO semiconductor has the enhanced photocatalytic efficiency. The nanocomposite with 40% weight percentage of Cu2O has the best photocatalytical activity of 0.0201 min-1, which could be related to the improvement of optical properties (increasing of the visible light harvesting ability) and the reduction of the recombination of the photoinduced electron-hole pairs. In addition, according to the radical trapping tests and Mott-Schottky experiments, superoxide radical was determined as the main oxidizing species for photocatalytic degradation of Paraoxon, and a type II charge transfer process was proposed for the improved photocatalytic activity.

In this paper, we report, the synthesis of conducting polymer nanocomposites of nickel oxide polypyrrole (NiO-PPy) doped with dodecyl benzene sulphonic acid for its application as a photocatalyst. In-situ polymerization of the pyrrole technique was employed along with oxidant ammonium persulphate and dodecyl benzene sulphonic acid as a dopant. The nanostructures were synthesized at different concentrations of NiO nanoparticles viz. 0.05 wt.%, 0.1 wt.%, 0.2 wt.% and 0.3 wt.%. The development of nanostructures was explored by Fourier Transform Infrared Spectrophotometer, Field Emission Scanning Electron Microscope, X-ray diffraction spectrometer, and electrical conductivity measurements. FTIR studies revealed a shift in the absorption band when pure PPy and NiO-PPy nanocomposites were studied, exhibiting the substantial interaction between the PPy network and the NiO. FE-SEM analysis demonstrated the consistent distribution of NiO with globular-shaped metal oxide materials in the PPy host template. The XRD studies for pure PPy revealed its amorphous nature while nanocomposites indicated the prominent NiO peaks arising from (111), (200) and (220) planes. The nanocomposites' direct electrical conductivity at room temperature was much higher than pure PPy. It was observed that the electrical conductivity for pure PPy was 0.409×10-5 S/cm while it substantially increased to 4.2×10-5 (S/cm) for 0.3% nanocomposite. The electrical studies revealed that the electrical conductivity goes on increasing with increased NiO concentration and then after a saturation point more PPy encapsulates the NiO and in turn reduces the electrical conductivity. With 50 mg of 0.3% nanocomposite, the photocatalytic degradation of the Methylene-Blue dye was 84.98%.

The recent theoretical investigation has advocated the Al2O3 monolayer as a stable atomic configuration. This work deals with the interaction of NH3 and PH3 towards this monolayer configuration. Structural and electronic investigation suggests a strong affinity of the monolayer towards the NH3 and PH3 molecules. PDOS analysis reveals hybridization between the molecular orbital of NH3/PH3 and Al2O3-monolayer. The electronic energy bandgap of the Al2O3 monolayer gets reduced by 0.26eV and 0.21eV respectively, on NH3 and PH3 adsorption. In the bandstructure analysis of the Al2O3-monolayer, the energy band dispersion got flattened after the toxic molecular gas (NH3/PH3) adsorption, suggesting strong sensitivity towards the toxicants. Mulliken population analysis witnessed a robust amount of charge transferred from the toxic molecules to the Al2O3-nanosheet. A competency in electrical conductivity and energy-band gap flattening of the NH3/PH3-Al2O3 configurations is an interesting outcome of the present work. All these findings suggest strong sensitivity of the 2D-monolayer for NH3/PH3.

In the current work synthesis and modification of graphene oxide with Nickel Hexa Ferrocyanide (NiHCF) nanoparticles has been reported. The Graphene oxide- Nickel Hexa Ferrocyanide (GO-NiHCF) was used as an adsorbent to remove Cesium (Cs) ions from a simulated solution. The obtained product was characterized with XRD, SEM, TGA, FTIR, and BET techniques. The SEM images and XRD pattern confirms the successful immobilization of Nickel Hexa Ferrocyanide on graphene oxide sheet. The cesium removal ability of GO-NiHCF was evaluated in batch mode. Effect of various parameters such as pH, initial concentration, contact time, and interferences ions were studied. The results cleared that the maximum adsorption for Cs removal was 240 mg g-1. Equilibrium modeling studies suggest that the data are reasonably and relatively fitted well to the Langmuir adsorption isotherm. Kinetic studies show that sorption process is fairly rapid and the kinetic data are fitted well to the pseudo-second order rate model. This composite offers strong potential in the field of elimination of Cs that requires rapid and complete decontamination.

In this work, hydrothermal technique and precursor materials obtained from the wastes of filtration unit of gas pressure reduction station were used to create ZnO-Fe2O3 nanocomposite. FT-IR, FE-SEM, XRD and TEM analyzes were used to investigate the properties of the produced nanocomposite. XRD analysis showed the structure of ZnO and Fe2O3 without impurities. The crystal size of ZnO-Fe2O3 nanocomposite was determined to be about 53 nm. FE-SEM images showed a nanocomposite pattern with an approximate diameter of 50 nm. Finally, visual decomposition of anionic and cationic dyes under visible light was used to study the photocatalytic activity of ZnO-Fe2O3 nanocomposite. By exposing a metal halide lamp to light and darkness for 60 minutes and 150 minutes, respectively, it was possible to study the photocatalytic activity of the synthesized nanocomposite in removing anionic and cationic dyes from aqueous medium. In the photocatalytic degradation of anionic and cationic dyes, the following factors were considered as essential variables: pH, initial dye concentration, nanocomposite content and exposure time. In this study, the degradation percentage of anionic and cationic dyes of ZnO-Fe2O3 nanocomposite with a ratio of 0.75:1 was 99.89 and 99.9%, respectively. The amount of band gap was calculated by Tack plot method and electrical conductivity was calculated using electrochemical impedance spectroscopy, which reduced the band gap. And the resistance increases. Due to the acceleration of charge transfer at the heterogeneous junction surface and the suppression of electron/hole pairs from recombination, the ZnO-Fe2O3 nanocomposite significantly increased the visible light current response.

Metal nanoparticles incorporated conducting polymer nanocomposites have outstanding properties and potential applications in various fields and significant research has been carried out over the last two decades for the development of efficient methods for their synthesis. The current study describes a microwave-assisted, rapid, and environmentally friendly method for depositing silver nanoparticles (AgNPs) over poly(1-naphthylamine) (PNA) using clammy cherry (Cordia Obliqua willd) extract as a reductant to create silver/nanocomposites (Gr-Ag/PNA) with varying silver contents. Thermal stability and charge transfer kinetics of PNA was significantly improved upon introducing AgNPs, as evidenced by the thermogravimetric analysis and electrochemical investigations, respectively. All prepared Gr-Ag/PNA nanocomposites could show improved catalytic activity towards the borohydride-aided reduction of 4-nitrophenol (4-NP) and the pseudo-first-order rate constants showed a direct relationship with the percent of silver incorporated over PNA. Additionally, for the first time, the Gr-Ag/PNA modified carbon paste electrode (Gr-Ag/PNA/CPE) was utilized to validate its usefulness and applicability in the electrocatalytic reduction of 4-NP. A low-cost enzymeless voltammetric 4-NP sensor based on Gr-Ag/PNA/CPE was fabricated and it showed excellent selectivity for 4-NP, as well as a strong linear response over a wide range of 4-NP concentrations (30-1000 𝜇M) and a detection limit of 6.25 𝜇M.

The purpose of this study was to determine the adsorptive characteristics of a MnWO4/ZnS nanocomposite for removing Amaranth dye from aqueous solution. A simple chemical precipitation approach was used to make the MnWO4/ZnS nanocomposite. The crystal structure, morphology, and pore size of the resulting nanocomposites were evaluated by UV-vis-DRS, FT-IR, XRD, SEM, EDAX and BET. In a laboratory batch adsorption experiment, the effect of operational parameters such as adsorbent dose, starting dye concentration, agitation speed, contact time, and temperature was investigated to optimise the conditions for maximum amaranth removal. To reduce the number of trials and the associated costs, an artificial neural network (ANN) was used to forecast dye removal effectiveness. For amaranth dye, a contact time of 180 minutes, an adsorbent dosage of 0.35 g/l, and an initial dye concentration of 10 M resulted in a 96 percent dye removal. Different models were used to fit the equilibrium isotherm data. Langmuir and Temkin models have high R2 and are in good agreement with the experimental data (0.9966 and 0.9927). T and film diffusion may be involved in the sorption process, according to the kinetic analysis. When the experimental data was compared to the dye adsorption efficiency predicted by the artificial neural network model, it was discovered that this model can accurately predict the behaviour of the amaranth dye adsorption process on MnWO4/ZnS under various conditions.