Efficient degradation of nonylphenol and 2,4-dinitrophenol by sunlight responsive hexacyanocobaltates nanostructures

A facile method for synthesis rGO/Ag nanocomposite and its uses for enhancing photocatalytic degradation of Congo red dye

The enhancing breakdown of dyes using facile, novel and eco-friendly photocatalyst without remaining any hazards secondary intermediates from the dye species regarded one of the most challenges to the healthy world. A novel facile method was used to synthesize reduced graphene oxide (rGO) with various doping ratios of silver nanoparticles (Ag NPs) and applied as photocatalyst to enhancing removal of Congo red (CR) dye using UV light irradiation from aqueous solution. Some characterization features such as UV-diffuse reflectance spectra, TEM, SEM, FTIR, X-ray diffraction, and EDX were measured to demonstrate the energy gap, morphology, size distribution, crystalline nature, phase structure, and elemental compositions of as-synthesized nanoparticles. The effect of some important factors such as pH of solution, initial CR concertation (Co), amount of rGO@Ag (g) and contact time (t) were studied to detect the optimum adsorption condition. The results indicated that, the maximum CR dye photodegradation is obtained at pH 7, 120 min, 50 mg/L initial CR concentration and 0.4 g/L photocatalyst dosage. The photodegradation data declared that, the higher the Ag doping ratio, the higher the degrading efficiency. Isotherm and kinetic studies showed that Langmuir and Freundlich models and the pseudo-second-order model are well fitting the adsorption process with maximum CR adsorption values ranging between 86.95 and 98.04 mg/L with corresponding R2 > 0.99.

Sunlight-induced photocatalytic degradation of organic pollutants by biosynthesized hetrometallic oxides nanoparticles

Dyes and phenols are extensively used chemicals in petrochemicals, pharmaceuticals, textile, and paints industries. Due to high persistence, bioaccumulation, and toxicity, their removal from the environment is highly imperative by advanced techniques. Single metal oxide nanomaterials are generally associated with limitations of large bandgap (> 3eV) and charge recombination. Therefore, heterometallic oxides (HMOs) as CuFe₂O₄, CuMn₂O₄, and MnZn₂O₄ have been synthesized via green route by employing leaf extract of Azadirachta indica. XRD revealed the crystalline nature of HMOs nanospheres with particle size less than 100 nm. Subsequently, HMOs nanocatalysts were used as photocatalyst for removal of 3-amino phenols (3-AP) and eriochrome black T (EBT) from water under sunlight. Reaction parameters namely pollutant concentration (50-130 mgL^-1), catalyst dose (20-100 mg), and pH (3-11) were optimized in order to get best results. Substantial degradation (80-95%) of pollutants (50 mgL^-1) by HMOs (80 mg) was achieved at neutral pH under sunlight exposure. Highest removal by CuFe₂O₄ might be due to its high surface area (35.7 m²g^-1), low band gap (2.4 eV), larger particle stability (Zeta potential: -22.0 mV), and lower photoluminescence intensity. Sharp declines in curves were visually confirmed by color change and indicated for first-order kinetics of degradation with initial Langmuir adsorption. Spectrophotometric analysis revealed that half-life (t_1/2) of 3-AP (0.9-1.7 h) and EBT (0.6-0.8 h) were significantly reduced. Faster degradation of EBT than 3-AP was because of less electronegative N-atom at the diazo group. Scavenger analysis indicated the presence of active radicals in photo-catalytic degradation of 3-AP and EBT. All HMOs have shown high reusability (n=8) which ensures their stability, sustainability, and efficiency. Overall, green synthesized HMOs nanoparticles with prominent surface characteristics offer a viable alternative photocatalyst for industrial applications.

Insight in to sunlight-driven rapid photocatalytic degradation of organic dyes by hexacyanoferrate-based nanoparticles

Release of colouring agents into the environment alarms the need to design a cheap, quick and safe process. Owing to environmental safety concern, synthesis of two metal hexacyanoferrates (MHCFs) based on cadmium (CdHCF) and manganese (MnHCF) was carried out using natural plant extract of Azadirachta indica and water as a solvent. Synthesized MHCFs were utilized for the removal of an acid dye (fuchsin acid, FA) and a xanthenes dye (rhodamine B, RB). The reactions were optimized at various conditions of dye concentration, catalyst dose, reaction pH, time and source of light. The MHCFs showed excellent results with both the dyes within very limited span of time (2 h). Consequently, 98% of FA and 97% of RB were degraded with 10 mg of CdHCF, at neutral pH and under sunlight. The degradation process followed the first-order reaction kinetics having t_1/2 around 0.3 min. The MHCFs exhibited difference of only little percentage in degradation owing to a very slight difference between their surface areas (CdHCF: 54.1 m² g^-1; MnHCF: 49.7 m² g^-1). The synthesised nanocatalysts were stable as indicated by their higher negative zeta potential values. The adsorption of dyes was found to be maximum with CdHCF having X_m value 19.69 mg g^-1 and 18.15 mg g^-1 for FA and RB, respectively. Photocatalytic degradation involved the main role of hydroxyl radical as indicated by decline in activity of nanocatalyst in the presence of scavengers. All in all, this study presents highly active nanomaterials with higher surface area, stability and semiconducting properties under natural conditions.