Catalytic wet air oxidation (CWAO) is classified as an advanced oxidation process, which proved to be highly efficient for the removal of emerging organic pollutant bisphenol A (BPA) from water. In this study, BPA was successfully removed in a batch-recycle trickle-bed reactor over bare titanate nanotube-based catalysts at very short space time of 0.6 min gCAT g−1. The as-prepared titanate nanotubes, which underwent heat treatment at 600 °C, showed high activity for the removal of aqueous BPA. Liquid-phase recycling (5- or 10-fold recycle) enabled complete BPA conversion already at 200 °C, together with high conversion of total organic carbon (TOC), i.e., 73 and 98 %, respectively. The catalyst was chemically stable in the given range of operating conditions for 189 h on stream.
COBISS.SI-ID: 5490202
Complex waste streams originating from extraction processes containing residual organic solvents and increased C/N ratios have not yet been considered as feedstock for biogas production to a great extent. In this study, spent rosehip (Rosa canina L.) solid residue (64% VS, 22 MJ/kg HHV, 30C/1N) was obtained from an industrial ethanol aided extraction process, and extensively examined in an automated batch bioreactor system for biogas production. Fraction separation of the compact lignocellulosic seeds increased the available sugar and ethanol content, resulting in high biogas potential of the sieved residue (516 NL/kg VS’). In co-digestion of spent rosehip substrate with non-deactivated nitrogen rich microbial co-substrates, methanogenesis was favored (Ym ) 68 % CH4). In individual digestion of microbial co-substrates, this was not the case, as biogas with 28 vol.% N2 was produced from activated sludge supplement. Therefore, effective inhibition of exogenous microbiota was achieved in the presence of carbonaceous spent rose hip.
COBISS.SI-ID: 37567749
Ceria zirconia solid solution with a high specific surface area and oxygen storage capacity was used to support NiCo bimetallic nanoparticles and was successfully employed as a catalyst in the methane–CO2 reforming reaction. During the reforming test with an equimolar CH4/CO2 ratio at 1023 K, an initial catalyst deactivation was observed, which was followed by a slow self-reactivation. The catalyst reached its initial activity after approximately 400 h TOS with negligible carbon accumulation and H2 and CO yields of 71 and 85 %, respectively. Catalyst deactivation in the initial 25 h of reaction could be correlated to the oxidation of nanosized NiCo particles by water produced through the reversed water gas shift reaction pathway. With prolonged time on stream, sintering and growth of nanosized NiCo particles occurs, which makes them less susceptible to oxidation and slowly leads to their reduction and reactivation. In parallel, recrystallization of Ce0.8Zr0.2O2 support from cubic crystallites to a more irregular polyhedral shape occurs, which improves the oxygen storage capacity of the material and significantly contributes to the catalyst regeneration. The rate of catalyst regeneration mainly depends on the rate of Ce0.8Zr0.2O2 support recrystallization, which is driven by sintering, and is consequently much slower than the initial deactivation. Upon increasing the CH4/CO2 feed ratio to 1.5 and 2.33, water yields were significantly reduced and the previously observed catalyst deactivation could be strongly decreased or even completely avoided.
COBISS.SI-ID: 37294341
Zinc(II) oxide nanoparticles were used for the stabilization of dicyclopentadiene (DCPD)−water-based high internal phase emulsions (HIPEs), which were subsequently cured using ring-opening metathesis polymerization (ROMP). The morphology of the resulting ZnO-pDCPD nanocomposite foams was investigated in correlation to the nanoparticle loading and nanoparticle surface chemistry. While hydrophilic ZnO nanoparticles were found to be unsuitable for stabilizing the HIPE, oleic acid coated, yet hydrophobic, ZnO nanoparticles were effective HIPE stabilizers, yielding polymer foams with ZnO nanoparticles located predominately at their surface. These inorganic/organic hybrid foam-materials were subsequently calcined at 550 °C for 15 min to obtain inorganic macroporous ZnO foams with morphology reminiscent to the original hybrid foam, and a specific surface area of 1.5 m2 g−1. Longer calcination time (550 °C, 15 h) resulted in a sea urchin like morphology of the ZnO foams, characterized by higher specific surface area of 5.5 m2 g−1. The latter foam type showed an appealing catalytic performance in the catalytic wet air oxidation (CWAO) process for the destruction of bisphenol A.
COBISS.SI-ID: 5593626
The aim of this study was to compare the efficiency of BPA removal from aqueous samples with photolytic, photocatalytic, and UV/H2O2 oxidation. BPA solutions were illuminated with different bulbs (halogen; 17 W UV, 254 nm; and 150 W UV, 365 nm) with or without the TiO2 P-25 catalyst or H2O2 (to accelerate degradation). Acute toxicity and oestrogenic activity of treated samples were determined using luminescent bacteria (Vibrio fischeri), water fleas (Daphnia magna), zebrafish embryos (Danio rerio), and Yeast Estrogen Screen (YES) assay with genetically modified yeast Saccharomyces cerevisiae. The results confirmed that BPA is toxic and oestrogenically active. Chemical analysis showed a reduction of BPA levels after photolytic treatment and 100 % conversion of BPA by photocatalytic and UV/H2O2 oxidation. The toxicity and oestrogenic activity of BPA were largely reduced in photolytically treated samples. Photocatalytic oxidation, however, either did not reduce BPA toxic and oestrogenic effects or even increased them in comparison with the baseline, untreated BPA solution. Our findings suggest that chemical analysis is not sufficient to determine the efficiency of advanced oxidation processes in removing pollutants from water and needs to be complemented with biological tests.
COBISS.SI-ID: 3069007