Characterization, catalytic, and recyclability studies of nano-sized spherical palladium particles synthesized using aqueous poly-extract (turmeric, neem, and tulasi)

Green synthesis of noble metal nanoparticles (NPs) has gained immense significance compared to other metal ions owing to their unique properties. Among them, palladium 'Pd' has been in the spotlight for its stable and superior catalytic activity. This work focuses on the synthesis of Pd NPs using the combined aqueous extract (poly-extract) of turmeric (rhizome), neem (leaves), and tulasi (leaves). The bio-synthesized Pd NPs were characterized to study its physicochemical and morphological features using several analytical techniques. Role of Pd NPs as nano-catalysts in the degradation of dyes (1 mg/2 mL stock solution) was evaluated in the presence of a strong reducing agent (sodium borohydride; SBH). In the presence of Pd NPs and SBH, maximum reduction of methylene blue (MB), methyl orange (MO), and rhodamine-B (Rh-B) dyes was observed under 20nullmin (96.55 ± 2.11%), 36nullmin (96.96 ± 2.24%), and 27nullmin (98.12 ± 1.33%), with degradation rate of 0.1789 ± 0.0273 min^-1, 0.0926 ± 0.0102 min^-1, and 0.1557 ± 0.0200 min^-1, respectively. In combination of dyes (MB + MO + Rh-B), maximum degradation was observed under 50nullmin (95.49 ± 2.56%) with degradation rate of 0.0694 ± 0.0087 min^-1. It was observed that degradation was following pseudo-first order reaction kinetics. Furthermore, Pd NPs showed good recyclability up to cycle 5 (72.88 ± 2.32%), cycle 9 (69.11 ± 2.19%) and cycle 6 (66.21 ± 2.72%) for MB, MO and Rh-B dyes, respectively. Whereas, up to cycle 4 (74.67 ± 0.66%) during combination of dyes. As Pd NPs showed good recyclability, they can be used for several cycles thus influencing the overall economics of the process.

Antimicrobial, antioxidant, cytotoxicity and photocatalytic performance of Co doped ZnO nanoparticles biosynthesized using Annona Muricata leaf extract

In the present study, ZnO nanoparticles doped with 3%, 5% and 7% of cobalt have been synthesized by green method using Annona muricata leaf extract. The obtained nanopowder was characterised by XRD, FTIR, XPS, HRTEM, SAED, SEM, EDAX and UV-Visible spectroscopy techniques. XRD patterns confirm the formation of pure and Co doped ZnO nanoparticles with a hexagonal wurtzite structure with high phase purity. FTIR spectra indicate the stretching vibration of Zn-O at 495 cm-1. The incorporation of Co2+ ions into the ZnO lattice was identified by XPS analysis. EDX spectra confirm the existence of Co, Zn and O elements. The SEM and HRTEM micrographs show morphology of nanoparticles. The optical study specifies a decrease in energy band gap with an increase in Co-doping concentration. The photocatalytic performance of ZnO and Zn0.93Co0.07O has been examined for the degradation of methylene blue (MB) under sunlight irradiation. The antimicrobial activity of synthesized nanoparticles against s.aureus, p.aeruginosa, b.subtilis bacterial strains c.albicans and a.niger fungal strains as investigated. The Zn0.93Co0.07O nanoparticles exhibit good antioxidant properties. Moreover, the cytotoxicity of ZnO nanoparticles was evaluated against L929 normal fibroblast cells. So, this work suggests that Annona muricata leaf extract mediated pure and Co-doped ZnO nanoparticles are a potential candidate for biomedical and photocatalytic applications.

Cationic distributions and dielectric properties of magnesium ferrites fabricated by sol-gel route and photocatalytic activity evaluation

Sol-gel auto combustion method was adopted to fabricate magnesium ferrite (MgFe2O4) nanoparticles. The structural and morphological properties was studied by XRD, FTIR, and SEM analysis. The average particle sizes of MgFe2O4 was in the range of 35–55 nm. The octahedral & Tetrahedral bond lengths, R AE (tetrahedral edge length), R BE (shared octahedral edge length) and R BEU (individual octahedral edge length), cationic radii (tetra and octa-sites) were also determined. The magnetic strength also showed direct reliance on bond angle and indirect to bond length. Hoping length L a and L b and bond angles are also measured. The frequency dependent conductivity and dielectric properties of MgFe2O4 were investigated by Impedance analyzer. The photocatalytic activity (PCA) is appraised against MB (methylene blue) dye and MgFe2O4 calcined at 800 °C showed promising degradation (78%) under visible light irradiation. The findings revealed that MgFe2O4 is can harvest the solar light, which could be employed for the remediation of wastewater contains textile dyes.

Ultrasonic supported dye removal by a novel biomass

Sumac Leaves (Rhus Coriaria L), were used as a possible adsorbent of Basic Blue 3 (BB3) removal. The main affecting parameters on adsorption such as concentration, pH and temperature were investigated. Adsorption equilibrium was reached in 30 min. The ultrasonic effect was also enhanced the dyestuff removal. Adsorption capacity was rised from 0.566 to 1.826 mg/g, as rising the concentration from 4 μg/mL to 10 μg/mL. Several isotherm models including Langmuir, Freundlich and Temkin were applied for explaining the adsorption mechanism. Temkin and Langmuir isotherm models describe the system well. Pseudo first order, pseudo second order and intra particle kinetics were evaluated. Pseudo second order diffusion model supports the adsoprption and also intra particle diffusion plays an important role for BB3 removal. Thermodynamics of the adsorption were commented. −2219.5 J/mol of Gibbs energy showed us a spontaneous and physical adsorption.

Photocatalytic hydrogen generation using TiO2: a state-of-the-art review

This review is focusing on photocatalytic hydrogen (H2) production as a viable fuel. The limitations of different production methods for H2 generation and the importance of photocatalytic process are discussed, which renders this process as highly promising to meet the future energy crises. TiO2 is one of most effective material to generate the H2 via photocatalytic processes. Therefore, advantages of the catalyst over other semiconductors have been thoroughly analyzed. Starting from synthesis of TiO2 and factors affecting the whole process of photocatalytic H2 production have been discussed. Modifications for improvement in TiO2 and the photocatalytic reaction are critically reviewed as well as the mechanism of TiO2 modification has been described. Metal doping, non-metal doping, impurity addition and defect introduction processes have been analyzed and the comparison of experimental results is developed based on H2 production efficiency. A critical review of the literature from 2004 to 2021 concludes that H2 production as fuel using TiO2 photocatalytic method is efficient and environment friendly, which have potential for practical applications for H2 generation.

Ionizing radiation based advanced oxidation process for reactive orange 122 dye degradation and kinetics studies

In the current study, the degradation of reactive orange 122 (RO 122) dye was carried out under UV and gamma irradiation in presence of H2O2. The effect of variables such as UV exposure time, gamma-ray absorbed dose, initial concentration of dye and oxidant dose were investigated. The removal of 64.10, 58.84 and 55.46 (%) was observed for 50, 100 and 150 (mg/L) dye concentrations, respectively using UV radiation time of 150 (min). The degradation was enhanced to 80.39, 69.95 and 67.01 (%) when UV radiation was employed in the presence of H2O2 (0.5 mL/L) for above concentrations respectively. The degradation was further improved to 97, 92.54 and 81.32 (%) using 5 kGy absorbed dose along with H2O2 (0.5 mL/L). The reduction in chemical oxygen demand (COD) was 77, 64 and 57 (%) using UV/H2O2 (0.5 mL/L), while 63, 56 and 53 (%) in case of gamma/H2O2 for aforementioned concentrations. The removal efficiency (G-value), dose constants (k), dose indispensable for 50, 90 and 99 (%) degradation (D 0.5, D 0.90, and D 0.99) after the treatment with gamma radiation were determined. The G-value was noted as 0.46–0.0711 for 50–150 mg/L dye concentration for gamma irradiated samples which improved to 0.57–0.1204 for above mentioned concentrations in presence of H2O2. The FTIR analysis showed that all the peaks were disappeared using gamma/H2O2 at 5 kGy absorbed dose except a minor peak of −CO stretching. The degradation mechanism of dye followed pseudo-first-order kinetics. A significant decrease in peak area was observed by the HPLC analysis after treating the dye samples with gamma/H2O2 (0.5 mL/L) at absorbed dose of 5 kGy which has proven the process efficiency for dye degradation.

Green synthesis of iron nanoparticles and photocatalytic activity evaluation for the degradation of methylene blue dye

The present study focuses on iron nanoparticles (Fe NPs) biosynthesis, characterization and photocatalytic activity (PCA) appraisal for methylene blue dye degradation. A green rapid biogenic synthesis route was employed for synthesis of Fe NPs using banana peel extract. The synthesized Fe NPs was characterized by XRD (X-ray diffraction), SEM (scanning electron microscopy) and EDX (energy dispersive X-ray) techniques. These analysis confirmed the synthesis of zero valent Fe NPs with high crystallinity, purity and semi spherical in shape. The photocatalytic activity was assessed under ultra violet irradiation and under optimum conditions, 87% degradation of MB dye was obtained for 72 min of irradiation, which revealed promising catalytic efficiency of the Fe NPs. The result shows that photocatalytic activity of Fe NPs is promising and could possibly be used to treat dyes in industrial effluents and the use of green synthetic protocol is suggested due to its ecofriendly nature.