Wet hydrogen peroxide catalytic oxidation (WHPCO) is one of the most importantindustrially applicable advanced oxidation processes (AOPs) for the decomposition of organic pollutants in water. It is demonstrated that manganese functionalized silicate nanoparticles with interparticle porosity act as a superior Fenton-type nanocatalyst in WHPCO as they can decompose 80% of a test organic compound in 30 minutes at neutral pH and room temperature. By using X-ray absorption spectroscopic techniques it is also shown that the superior activity of the nanocatalyst can be attributed uniquely to framework manganese, which decomposes H2O2 to reactive hydroxyls and, unlike manganese in Mn3O4 or Mn2O3 nanoparticles, does not promote the simultaneous decomposition of hydrogen peroxide. The presented material thus introduces a new family of Fenton nanocatalysts, which are environmentally friendly, cost-effective, and possess superior efficiency for the decomposition of H2O2 to reactive hydroxyls (AOP), which in turn readily decompose organic pollutants dissolved in water.
COBISS.SI-ID: 4863514
Effects of four different nanocrystalline CeO2-based catalysts on crustaceans Daphnia magna and early-life stages of zebrafish Danio rerio were studied. Pure CeO2 and CuO-CeO2 mixed oxides with a nominal 10, 15 and 20 mol. % CuO content were tested. Pure CeO2 provoked no effects, but CuO-CeO2 mixed oxides induced some sublethal effects on fish and affected daphnidsć survival. The most pronounced effects were found on fish body growth, which was reduced at 10 mg/L in case of CuCe20 and 50 mg/L in cases of CuCe10 and CuCe15. Daphnidsćsurvival was affected above 80 mg/L of CuCe20, while CuCe10 and CuCe15 did not affect daphnids. None of the materials was highly toxic to daphnids and fish in comparison to some other environmental pollutants. Differences in effects between the materials could not be explained by their specific physicochemical properties. This work indicates that more attention should be placed at potential toxicity of nanostructured materials, such as nanocrystalline mixed-oxides.
COBISS.SI-ID: 4936474
Titanate nanotube based catalysts were prepared via alkaline hydrothermal synthesis route followed by heat treatment at different temperatures, ranging from 300 to 700 oC. The resulting metal-free solids were then applied as a catalyst in a threephase trickle-bed reactor, where catalytic wet air oxidation (CWAO) reactions of model aqueous bisphenol A (BPA) solution were performed. Mainly, the CWAO experiments were conducted at 200 oC with oxygen partial pressure of 10 bar over 300 mg of a catalyst. It was observed in the given range of operating conditions that BPA undergoes both noncatalytic as well as catalytic oxidation routes, while the latter is far more pronounced. At 210 oC and in the presence of 0.5 g of titanate nanotube-based catalyst, which was annealed at 600 oC, complete BPA removal was obtained. From TOC point of view, approximately 70 % conversion was achieved indicating the persistence of refractory intermediates of lower carboxylic acids. The cross-section of results derived from various analytical techniques, which were used to identify surface, textural and morphological properties, revealed that balanced physico-chemical properties are required to achieve meaningful extent of BPA removal. During 24-day time on stream, no catalyst deactivation occurred that could be attributed to the dissolution of active powders, or to the carbonaceous deposits accumulated on the catalyst surface. Therefore, these nanotubular materials can be regarded as innocuous and efficient long-term catalysts for oxidation of hazardous organic compounds (such as BPA) in the CWAO process.
COBISS.SI-ID: 5149722
Our work was focused on investigation of different treatment procedures for the removal of toxic fractions from a landfill leachate. The applied methods were air stripping, adsorption to activated carbon and zeolite clinoptilolite and Fenton oxidation. Air stripping at pH 11 was a viable treatment option for the removal of ammonia nitrogen (up to 94 %) and reduction of toxicity to microorganisms. In the column experiments with clinoptilolite 45/93/100 % of NH4+-N as well as 25/32/39 % of COD removal was attained. Fenton oxidation at molar ratio Fe2+:H2O2 = 1.0:10.0 assured 70-85 % removal of COD.
COBISS.SI-ID: 33885701
A method is proposed for on-line UV spectroscopy and data analysis are applied to determine nitrate and nitrite nitrogen (NOx-N) in various waste water matrices. Comparison with standard analytical method was performed. Sensor calibration with pure substance reference materials delivered sufficient results for characteristic municipal waste water matrix, but for waste water with substantual industrial contribution and for landfill leachate matrix match calibration was required to enhance trueness. The described method concept is well suited for on-line monitoring.
COBISS.SI-ID: 33738245