We report the results of the application of UiO-66 derivates for dye removal. This complex process includes two parallel mechanisms. The first one is the adsorption of the dye into the pores of MOF. ...The second one is photocatalytic degradation. We used two linkers for MOF synthesis: 1,4-benzene dicarboxylate and 1,4-naphthalene dicarboxylate. The introduction of these molecules in various ratios into the UiO-66-type structure allowed us to trace the effect of naphthalene species on the methylene blue removal. It was shown that a conjugated π-system of naphthalene rings led to charge transfer from linker to zirconium ions. It reduces the bandgap of the material and, therefore, results in higher photocatalytic performance. We also traced the effect of defects in the MOF structure on methylene blue degradation. It was shown that unsaturated zirconium ions in defect pores effectively catalyze dye cleavage and direct this process to the oxidative demethylation pathway. Obtained results could be applied to improve the photocatalytic properties of UiO-66 derivates.
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•We report UiO-66 derivates for dye removal.•This process could be considered as adsorption and photocatalytic degradation.•The introduction of naphthalene rings into the UiO-66 reduces the bandgap and enhanced photocatalytic performance.•Unsaturated zirconium ions in defect pores effectively catalyze dye cleavage as well.•Proposed catalysts work under visible light.
► Electrochemical oxidation of ILs at PbO2 anode was very effective. ► ILs were mainly oxidized in indirect way. ► The mineralization process was more effective for ILs with the shorter side chain. ► ...Intermediates were produced by hydroxyl radical substitution to side chain of ILs. ► Another pathway of degradation was oxidative cleavage of the imidazolium ring.
Advanced oxidation processes can assist in the elimination of imidazolium-based ionic liquids (ILs) from water. With the aid of electrocatalytic degradation at a lead dioxide anode, it was shown that the degradation rate of these ILs from aqueous solutions was dependent on a change in the nature of the side chains in the cation. All the ionic liquids were efficiently oxidized within 240min. Even the mineralization of ILs was high up to 97% depending on structure. Cyclic voltammetry indicated that ILs were oxidized indirectly by radicals generated on the anode surface. HPLC-UV and electrospray mass spectroscopy analysis suggest that ILs undergo degradation along a pathway involving intermediates produced as a result of hydroxyl radical substitution to side chain and by oxidative cleavage of the imidazolium ring. The probability of imidazolium core attack by OH radicals increased with decreasing length of the substituted side chain.
Full-Scale Study to Treat Hydrogen Sulfide with Biofilter Zhang, Chao; Li, Bo Fu; Jiang, Ying He
Applied Mechanics and Materials,
10/2013, Letnik:
443, Številka:
Computer-Aided Design, Manufacturing, Modeling and Simulation III
Journal Article
Recenzirano
With the development of urbanization, the odor from municipal wastewater treatment plants has disturbed the neighborhood and the control of odor has become an urgency research subject. The H2S odor ...was treated by the biofilter. The removal load of the biofilter, end products of H2S degradation, and operation process were studied in this paper. The results of removal H2S odor with the biofilter were as follows: When the gas flow rate was 1000m3/h (resident time 16.2s) and 1250m3/h (resident time 13.0s), and the inlet concentration of H2S ranged from 1.876 to 34.705mg/m3, the removal rate maintained above 99.92%, and the average outlet concentration was 0.001 mg/m3 which was far lower than the national level of discharge standard. The relationship between removal rate and temperature satisfied with the formula , and for H2S, θ=1.016. Furthermore, the end products of H2S degradation were only sulfate without sulfide. With the increase of sulfate, the removal of H2S was not affected. The study of operating parameters with the biofilter provided the necessary technical support for industrial design and operation control.
Many compounds are resistant to biodegradation and photolysis processes in the environment. These compounds are known as persistent pollutants. Analytical efforts have shown that compounds released ...into the environment tend to accumulate more in one medium than in others. As a result, the paritioning, transport, and transformation rates of any given compound will differ between different environmental media. Under these conditions, degradation processes in the dominant medium have the strongest role in determining overall persistence. Biodegradation is typically considered the dominant degradation process of contaminants in diverse environmental media. Scientists review data detailing photodegradation and biodegradation processes for several organic pollutants.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Chemical, biological, and photochemical reactions can contribute to changes in chemical compounds in the environment. The types of changes occurring in chemical compounds are governed by the ...environmental compartment in which they occur, such as soil, benthic sediments, surface waters, and groundwaters. A review considered the most important factors governing these changes. Researchers examined problems associated with the formation of intermediate products during the degradation of pollutants. Issues associated with the toxicity of substances produced during the process of organic compound degradation are reviewed. Techniques that have proven useful for the identification of these types of substances are investigated.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
An improved method of degradation diagnosis for medium‐size distribution transformers is described. The proposed method uses refined criteria of degradation for specific application for 200‐ to ...1000‐kVA range transformer diagnostics. The new criteria were established with a 95 percent confidence limit of data after extensive case studies focusing on the relationship between the amounts of CO and CO2 generated in transformer oil and the length of operating time of the transformer. Another feature of this diagnostic technique is the provision of a capability to estimate the thermal history of the insulation material by examining the amounts of certain trace products of decomposition present in the transformer oil. For this purpose, a thermal history discriminant chart was devised by application of a canonical discriminant analysis method.
The two major routes of degradation of phenylbutazone (I) are oxidation and hydrolysis. Hydrolysis gives rise to n-butylmalonic acid mono(N,N'-diphenyl)hydrazide (II). Oxidation at the C-4 position ...yields 1,2-diphenyl-4-n-butyl-4-hydroxpyrazolidine-3,5-dione (III), which is readily hydrolyzed to n-butyltartronic acid mono-(N,N'-diphenyl)hydrazide (IV). Whereas the mass spectra of I, III, and the methyl esters of carboxylic acids II and IV all demonstrate major peaks corresponding to their respective molecular ions, the mass spectrum of II is essentially identical with that of I, suggesting facile dehydration. In the mass spectrum of IV, the peak of highest mass is found at m/e 205; no peak could be perceived corresponding to the molecular ion or to loss of water, carbon dioxide, or both of these elements from the molecular ion. Under normal pyrolytic conditions, II is decarboxylated to N-caproylhydrazobenzene (V) and IV is readily dehydrated to yield III. The mass spectral fragmentation of IV was successfully simulated in the laboratory to give an excellent yield of aniline and alpha-keto-N-caproylaniline (VI) (mol. wt. 205). The probable course of this unusual transformation was elucidated from studies of the accelerated decomposition of IV and derivatives considered as possible intermediates in the degradation process.
ABSTRACT
The stability of a model protein, bovine serum albumin (BSA), either in solid state or entrapped in polymer matrices, was studied. A series of copolymers consisting of lactide (LA) or ...caprolactone (CL) with 6-methyl-2, 5-morpholinedione (MMD) were synthesized and used as the matrices. Size exclusion chromatography assay revealed that covalent aggregation of BSA occurred during the incubation of BSA or BSA-polymer matrices under certain water content. The amount of aggregate was shown to be dependent on the water content, pH value, and composition of the polymer. The content of MMD in the copolymer greatly affected properties of the material, such as hydrophilicity, water absorption, and degradation, which determined the biocompatibility of the material. In the copolymer of CL and MMD, the incorporation of glycine and lower water absorption improved the BSA stability. In the copolymer of LA and MMD, higher water absorption and glycine incorporation acted on the opposite way and the BSA stability was dependent on the overall effects of both.
