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Cyanide is a highly toxic substance present in wastewater from various industries. This study investigates the removal of cyanide species (CS) from aqueous solutions using the ZnTiO3/TiO2/H2O2/UVB system. ZnTiO3/TiO2 nanoparticles synthesized by the sol-gel method were characterized by powder X-ray diffractometry (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The adsorption capacity of nanoparticles was tested by varying the pH of the solution, adsorbent concentration, and contact time. The adsorption of CS on ZnTiO3 and TiO2 surfaces was verified by Density Functional Theory (DFT) calculations. Photocatalytic experiments were achieved under UVB irradiation (λ = 310 nm). The response surface methodology (RSM) was used to optimize the CS removal efficiency. The detoxification effect was evaluated by acute toxicity tests with brine shrimp. The theoretical results show that the adsorption of CS is energetically more favorable on the ZnTiO3 surface than on the TiO2 surface. The experimental results show that the system consisting of ZnTiO3/TiO2 (200 mg L−1), H2O2 (0.1%), and UVB light removes 99% of CS from aqueous solutions after 60 min and reduces the mortality of nauplii in 90% after 90 min. This system was reused in five consecutive cycles with a total loss of efficiency of 30%. [ABSTRACT FROM AUTHOR]

In this study, GP (geopolymer) and GTA (geopolymer/ZnTiO3/TiO2) geopolymeric materials were prepared from metakaolin (MK) and characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), energy dispersive X-rays (EDX), specific surface area (SSA), and point of zero charge (PZC). The adsorption capacity and photocatalytic activity of the compounds prepared in the form of pellets was determined by degradation of the methylene blue (MB) dye in batch reactors, at pH = 7.0 ± 0.2 and room temperature (20 °C). The results indicate that both compounds are highly efficient at adsorbing MB, with an average efficiency value of 98.5%. The Langmuir isotherm model and the pseudo second order kinetic model provided the best fits to the experimental data for both compounds. In the MB photodegradation experiments under UVB irradiation, GTA reached an efficiency of 93%, being higher than that achieved by GP (4%). Therefore, the incorporation of ZnTiO3/TiO2 in the geopolymeric matrix allowed GTA to achieve higher overall efficiency, by combining adsorption and photocatalysis, compared to the GP compound. The results indicate that the synthesized compounds could be used for up to five consecutive cycles for the removal of MB from wastewater through adsorption and/or photocatalysis processes. [ABSTRACT FROM AUTHOR]

In this study, zeolites prepared by the hydrothermal method from Ecuadorian clay were combined with the precursor clay and with the semiconductor ZnTiO3/TiO2 prepared by the sol-gel method to adsorb and photodegrade cyanide species from aqueous solutions. These compounds were characterized by X-ray powder diffraction, X-ray fluorescence, scanning electron microscopy, energy-dispersive X-rays, point of zero charge, and specific surface area. The adsorption characteristics of the compounds were measured using batch adsorption experiments as a function of pH, initial concentration, temperature, and contact time. The Langmuir isotherm model and the pseudo-second-order model fit the adsorption process better. The equilibrium state in the reaction systems at pH = 7 was reached around 130 and 60 min in the adsorption and photodegradation experiments, respectively. The maximum cyanide adsorption value (73.37 mg g−1) was obtained with the ZC compound (zeolite + clay), and the maximum cyanide photodegradation capacity (90.7%) under UV light was obtained with the TC compound (ZnTiO3/TiO2 + clay). Finally, the reuse of the compounds in five consecutive treatment cycles was determined. The results reflect that the compounds synthesized and adapted to the extruded form could potentially be used for the removal of cyanide from wastewater. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) is a widely used method for studying matter at the quantum level. In this study, the surface (101) of TiO2 (anatase phase) was considered to develop DFT calculations and explain the effect of lanthanum ion (La3+) on the electronic properties, adsorption capacity, and photocatalytic activity of this semiconductor. Due to the presence of the La3+ ion, the bandgap energy value of La/TiO2 (2.98 eV) was lower than that obtained for TiO2 (3.21 eV). TDOS analysis demonstrated the presence of hybrid levels in La/TiO2 composed mainly of O2p and La5d orbitals. The chemical nature of the La-O bond was estimated from PDOS analysis, Bader charge analysis, and ELF function, resulting in a polar covalent type, due to the combination of covalent and ionic bonds. In general, the adsorption of the methylene blue (MB) molecule on the surface (101) of La/TiO2 was energetically more favorable than on the surface (101) of TiO2. The thermodynamic stability of doping TiO2 with lanthanum was deduced from the negative heat-segmentation values obtained. The evidence from this theoretical study supports the experimental results reported in the literature and suggests that the semiconductor La/TiO2 is a potential catalyst for applications that require sunlight. [ABSTRACT FROM AUTHOR]

In the present research, the essential oil from Piper ecuadorense was analysed by GC/MS and GC/FID techniques. A total of forty-four chemical compounds were identified which represent 98.65% of the essential oil composition. The main compounds were bicyclogermacrene (12.98%), 3-thujopsanone (11.59%), α-phellandrene (6.89%), (E)-nerolidol (6.88%), δ-elemene (6.83%) and shyobunol (5.79%). The essential oil from P. ecuadorense exerted a strong activity against Gram-positive bacterium Staphylococcus aureus (ATCC 25923) with an MIC of 250 μg/mL, and a very strong activity against Trichophyton rubrum (ATCC 28188) and Trichophyton mentagrophytes (ATCC 28185) with an MIC of 62.5 μg/mL in both cases. The antioxidant activity of essential oil was explored using DPPH and ABTS method, through ABTS assay. The oils showed an IC50 of 1.81 ± 0.09 mg/mL. This is the first report on the chemical composition and biological activity of essential oil from this species. [ABSTRACT FROM AUTHOR]

Phytochemical study of P. lanceifoluim, used in the traditional medicine in the South of Ecuador, resulted in the isolation of one flavone called Sakuranetin (1), two benzoic derivative acid knows called: lanceaefolic acid methyl ester (2), and cyclolanceaefolic acid methyl ester (3). The structures of compounds were established by means of 1H- and 13C-NMR and MS data, and compared with literature data. The essential oils were obtained by hydrodistillation and then analysed by gas chromatography/flame ionization detector (GC/FID) and gas chromatography/mass spectrometry (GC/MS), a total of 35 constituents were identified, representing the 97.3% of the chemical composition. Safrole was the most abundant compound in the plant with 48.3%. Monoterpene hydrocarbons and oxygenated monoterpenes are the most important groups of compounds in the essential oil of P. lanceifolium, this oil exhibited a moderate antibacterial effect against Klebsiella pneumoniae (ATCC 9997). [ABSTRACT FROM AUTHOR]

In the present research the essential oil from aerial parts of Gnaphalium elegans was extracted by hydrodistillation and analyzed by Gas Chromatography coupled to mass spectroscopy (GC/MS) and Gas Chromatography flame ionization detector (GC-FID) techniques, twenty-one chemical compounds were identified which represent a 96.33 % of the total essential oil. The main compounds were: γ-curcumene (55.61 %), Italicene (4.69 %), α-cubebene (4.45 %), δ-cadinene (4.28 %) and α-pinene (3.57 %). The antimicrobial activity and antifungal activity of this essential oil was assayed against two Gram positives bacterium: Enterococcus faecalis and Staphylococcus aureus; five Gram negatives bacterium: Pseudomonas aeruginosa, Klebsiella pneumoniae, Proteus vulgaris, Escherichia coli and Salmonella Tiphymurium; and three fungi: Tricophyton mentagrophytes, Tricophyton rubrum and Aspergillus niger. The essential oil was inactive against all bacterium at the maximum concentration tested 1000 μg/mL. However, the essential oil from G. elegans presented a moderate activity against Trichophyton rubrum and Trichophyton mentagrophytes with a MIC of 500 μg/mL and 1000 μg/mL, respectively. This is the first report on the chemical composition and biological activity of essential oil from this species. [ABSTRACT FROM AUTHOR]