Visible light assisted photocatalytic degradation of Rhodamine B dye on CdSe-ZnO nanocomposite: Characterization and kinetic studies

Optimization of reduced Graphene oxide synthesis using central composite design analysis-A waste to value approach

In recent times, reduced graphene oxide has gained more attention in various fields. In our study, a direct synthesis of reduced graphene oxide using a novel carbon-rich agro-waste from Pennisetum glaucum was used. Ferrocene acted as an oxidizing agent during thermal degradation at 300 °C for 15 and 20 min to promote graphene oxide and reduced graphene oxide formation. The X-ray diffraction peak at 2θ indicating a shift from 16.86 to 24.28°, presence of functional groups like -OH stretching, -C = C-, C = O, C-O, and C-OH by Fourier transmission infrared spectroscopy, prominent D and G bands at 1308 cm^-1 and 1578 cm^-1 by Raman spectra and UV-visible spectroscopy peak shift from 235 to 245 nm (π-π*, C = C bonds) confirmed the reduction of graphene oxide to reduced graphene oxide. The average particle size values 233.3 nm for graphene oxide and 63.57 nm for reduced graphene oxide illustrate the nanoscale range of our synthesized material. The negative zeta potential values in the range - 45.5 mV and - 29.5 mV for graphene oxide and its reduced forms infer the dispersion stability along with surface oxygen group presence. We have also highlighted the formation of graphene oxide quantum dots by magnetic stirring and confirmed by UV transilluminator and photoluminescence spectra. The photodegradation efficiency was optimized using central composite design for dosage, dye concentration, pH, and time for both malachite green and reactive blue dye. The kinetic studies report pseudo-first-order kinetic model for catalytic degradation and statistical Analysis of variance proved the significance of the process for p value < 0.05. Thus, the synthesized graphene materials could be used as a potential candidate for environmental applications.

Enhanced visible light-driven photocatalytic performance of CdSe nanorods

Cadmium selenide (CdSe) semiconductor nanorods are prepared in hydrothermal process using hydrazine hydrate (N₂H₄.H₂O) and ammonia (NH₃.H₂O) as reducing agents. The reaction time is increased to 7 h and the amount of hydrazine hydrate used is also increased to 15 mL which have resulted in diminished stacking faults in the CdSe nanorods prepared. The crystal structure, morphological variations, and size of the prepared CdSe nanorods are examined by XRD analysis. The crystalline size of the CdSe nanorods is 20-30 nm in diameter. HRTEM images reveal the formation of high order CdSe nanorods of the length about 25-40 nm. The bandgap in the CdSe nanoparticles is determined to be 2.17 eV. The peak at 595 nm in photoluminescence (PL) spectrum indicates oxygen vacancy defects in the prepared CdSe sample. The variation of dielectric properties with respect to temperature and frequency of pelletized CdSe is studied. High photocatalytic efficiency (98%) of catalyst/H₂O₂ is also achieved for decomposition of Rhodamine-B dye.

Facile sonochemical method for preparation of Cs2HgI4 nanostructures as a promising visible-light photocatalyst

Attempts are continuing to discover novel and efficient solutions to promote water grade and industrial sewage treatment. For the first time, we present a novel Cs₂HgI₄ photocatalyst functional below visible radiation. Cs₂HgI₄ nano photocatalyst has been prepared via an accelerated sonochemical approach to examine its photocatalytic progression. Several construction circumstances, including variations of power and time of sonication and performance of different surfactant types, were conducted to produce fine particles with uniform morphology. FESEM images attested that the presence of surfactant had an adverse and destructive effect on the morphology of products. The bandgap for Cs₂HgI₄ nanostructures was determined to be approximately 2.3 eV, making these nanostructures desirable for photocatalytic applications. The photocatalytic data confirmed that Cs₂HgI₄ could destroy acidic coloring agents greater than basic ones. The highest photodegradation was observed for methyl orange with 76.8%.

A new phase transfer nanocatalyst NiFe2O4-PEG for removal of dibenzothiophene by an ultrasound assisted oxidative process: kinetics, thermodynamic study and experimental design

In this study, NiFe₂O₄–PEG, an effective nanocatalyst was synthesized via a hydrothermal method using different PEG concentrations and synthesis times. The synthesized nanocatalyst was used in the ultrasound assisted oxidative desulfurization (UAOD) of model fuels (e.g. n-hexane and dibenzothiophene (DBT)) for the first time. The nanocatalyst was then characterized by XRD, FTIR, BET, SEM, VSM and TEM analyses. In addition, central composite design was used to evaluate the effective variables on the UAOD process. The optimal values of effective factors such as catalyst dose, oxidant amount, irradiation time and ultrasonic power to maximize of the percentage of sulfur removal were 0.149 g, 15 mL, 11.96 min, and 70 MHz, respectively. Moreover, the kinetic aspects of the oxidation reaction of DBT in the UAOD process were investigated using a pseudo-first-order model. Furthermore, using the Arrhenius equation, an activation energy of 35.86 kJ mol⁻¹ was obtained. Additionally, thermodynamic analysis showed that the oxidation reaction of DBT was endothermic with a positive Gibbs free of energy, indicating the non-spontaneity of oxidation of DBT in the UAOD process. Moreover, the conversion rate of DBT has increased from 57% at 35 °C to 85% at 65 °C.

In this study, NiFe₂O₄–PEG, an effective nanocatalyst was synthesized via a hydrothermal method using different PEG concentrations and synthesis times.

Facile preparation and characterization of a novel visible-light-responsive Rb2HgI4 nanostructure photocatalyst

Visible photocatalytic procedures exhibit encouraging potential in water purification by increasing the photocatalytic performance. Therefore, the improvement of low-cost and efficient photocatalysts for environmental remediation is an increasing demand, and photocatalysts based on semiconductors have gained considerable attention due to their superior stability and activity. In the current study, novel Rb₂HgI₄ nanostructures were prepared via a simple, low-cost, and low-temperature solid-state method. The effects of different parameters such as type of surfactants, reaction temperature, and reaction time were studied on the structure, crystallinity, particle size, and shape of nanostructures. This new compound has a suitable band gap (2.6 eV) in the visible region. The photocatalytic performance of Rb₂HgI₄ was examined for the removal of coloring agents under visible light irradiation and it was found that this compound could degrade and eliminate acid black 1 by about 72.1%.