Relevance of Photocatalysis prior to Biological Treatment of Organic Pollutants – Selection Criteria

The relevance of a photocatalytic pretreatment prior to a biological process for removal of organic pollutants was examined. Owing to the significant residual amount and toxicity, amitrole was not relevant. High mineralization allowed to remove bisphenol A and 2,4‐dichlorophenoxyacetic acid. Isoproturon and diuron cannot be considered due to the slight evolution of chemical oxygen demand/total organic carbon (COD/TOC) and average oxidation state during irradiation. After photocatalysis, the ratio of biological oxygen demand (BOD₅)/COD remained below the biodegradability limit (0.4) for the rest of the molecules. A favorable COD/TOC trend (decrease during irradiation) was recorded for dimethoate and antibiotics. However, dimethoate and sulfamethoxazole seemed not pertinent due to the long time span for their removal. Since a decrease of toxicity was only recorded for tylosine, it can be selected for subsequent tests.     

硼酸镁晶须在聚丙烯中的应用

以硼酸、乙醇胺、甲基丙烯酰氯为主要原料,合成了新型可聚合硼酸酯偶联剂BE-1。利用BE-1在硼酸镁晶须表面引发聚合形成有机涂层,并用改性后的硼酸镁晶须制备了硼酸镁晶须/聚丙烯(PP)复合材料。检测结果如下:由红外测试结果可以推断,合成产物即为可聚合硼酸酯偶联剂BE-1;在水解稳定性测试中BE-1稳定时间大于960 h,BE-1具有良好的溶解性及贮存性能;有机涂层形成的最佳反应温度为78℃,最佳反应时间为6 h;BE-1改性硼酸镁晶须/PP复合材料拉伸强度、弯曲强度、热变形温度分别比纯PP提高了30%、40%和104%,分别比未改性硼酸镁晶须/PP复合材料提高了11.05%、23.52%、15.29%。     

Transformation in Bulk and Trace Organics during Ozonation of Wastewater

The aim of this paper is to determine the ozone dosages needed to oxidize bulk and trace organics. Treated effluent from eight full-scale wastewater treatment plants was collected and subjected to lab-scale ozonation. Because both organics and inorganics exert ozone demand, an approach was developed to calculate only the ozone demand associated with organics. This method allowed normalization of dosing parameters to correlate with removal of color, UV absorbance, plus oxidation of trace organics and nitrosamine precursors. We also showed that ozonation effectively reduces the fraction of organic matter characterized as “colloidal organic matter,” thereby reducing the potential for membrane fouling.     

Removal of Alkaline Catalysts from Polyols by Ion Exchange

Abstract

Resin regeneration is crucial in the feasibility of polyol purification by ion exchange. In order to get an economically viable commercial process, a new regeneration process, including initial and final methanol flushing steps and treating with a 4.5 M aqueous mineral acid solution, has been investigated. An important reduction in regeneration costs was reached by minimizing the amount of acid used and recycling one part of the regenerant solution to the process. The composition of regeneration effluents has been studied in order to recover their valuable components. This simple resin regeneration technique lends itself to a technically and economically viable commercial process for the treatment of polyol products.     

Phase Separation of Lactan Gum from Fermentation Broths by Addition of Water-Miscible Organic Solvents

Abstract

A microbial polysaccharide (lactan gum) produced by bacterium ATCC 55046 was precipitated from fermentation broths by the addition of ethanol, acetone, isopropanol, or tert-butanol. Compositions of the precipitate and supernatant phases were determined as a function of organic solvent concentration and used to construct binodal solubility curves. Lactan did not precipitate at bulk-mixture organic solvent concentrations below 35% (wt) ethanol, 35% acetone, 33% isopropanol, or 25% tert-butanol. At organic solvent concentrations just exceeding the solubility transition point, the precipitates were soft, moist, and sponge-like in texture, with low lactan concentrations. At higher organic solvent concentrations the precipitates were compact and dense. The maximum lactan concentration in the precipitate was 25–37%, depending on the organic solvent type and concentration. Increasing the organic solvent concentration beyond 50% for ethanol, or 70% for acetone, decreased the lactan concentration in the precipitate. No such decrease occurred for isopropanol and tert-butanol. Thus, organic solvent usage, from greatest to least, was in the order ethanol, acetone, isopropanol, and tert-butanol, but the maximum lactan concentration in the precipitate, from greatest to least, was in the order acetone, isopropanol, ethanol, and tert-butanol.     

Study of the effect of mechanically treated CeO2 and SiO2 pigments on the corrosion protection of painted galvanized steel

The effectiveness of mechanically treated CeO₂ particles and SiO₂ particles as active fillers into an organic coating was investigated. For this purpose, different combinations of CeO₂ and SiO₂ particles were added to an epoxy-polyester polymeric matrix: mechanically treated CeO₂ particles, mechanically treated CeO₂/SiO₂ particles and mechanically treated SiO₂ powders (used for comparison). The particles were dispersed into the polymeric matrix and HDG steel panels were coated with the different paints. A strontium chromates containing paint was used as a reference to compare the performances of the other samples. The salt spray results proved the good performance of coatings containing combinations of ceria and silica especially where these had been mechanically treated in a co-milling operation. The paint containing only the mechanically treated SiO₂ particles showed a fairly good resistance in the salt spray chamber considering the scratched samples. The EIS measurements evidenced the good corrosion protection properties of the paints containing the different combinations of mechanically treated CeO₂ and SiO₂ particles. After about 1000 h of immersion in 0.1 M NaCl solution, the samples containing the mix of mechanically treated CeO₂/SiO₂ particles showed impedance values which were comparable with the chromate control sample. The cathodic polarization tests evidenced the low extent of detachment of the coating containing the mix of mechanically treated CeO₂/SiO₂ particles. The electrochemical characterization and neutral salt spray test results proved the effectiveness of the mechanical treated cerium (IV) oxides treated together with SiO₂ as active pigments to improve the corrosion protection of the substrate. The reasons for the synergistic effect of the milled (together or separately) SiO₂ and CeO₂ particles was not clear at all, but a few hypothesis were discussed.     

气相色谱-质谱联用法测定PVC塑料制品中的微量有机锡

建立了一种可同时测定聚氯乙烯(PVC)塑料制品中一丁基锡、二丁基锡、三丁基锡、四丁基锡、一辛基锡、二苯基锡和三苯基锡等7种有机锡化合物的气相色谱-质谱(GC-MS)检测方法。利用三水合二乙基二硫代氨基甲酸钠(NaDDTC)与有机锡的螯合作用,以甲醇-NaDDTC水溶液(2%,m/v)的混合溶液浸取PVC样品中的有机锡,经四乙基硼酸钠(NaBEt4)水溶液衍生化后,用正己烷萃取分离,再进行GC-MS的定性定量分析。对样品前处理过程、衍生化条件、色谱条件等进行了优化,并考察了方法的线性关系、检出限、回收率和精密度等。方法的线性范围为0.1～50.0 mg/L,线性相关系数为0.999 0～0.999 8。有机锡化合物的检出限为0.005～0.025 mg/L,样品加标回收率为87.64%～110.16%,相对标准偏差皆小于10%。结果表明,该法简便、灵敏,能很好地应用于PVC制品中微量有机锡的测定。     

Nanostructured materials with biomimetic recognition abilities for chemical sensing

Binding features found in biological systems can be implemented into man-made materials to design nanostructured artificial receptor matrices which are suitable, e.g., for chemical sensing applications. A range of different non-covalent interactions can be utilized based on the chemical properties of the respective analyte. One example is the formation of coordinative bonds between a polymerizable ligand (e.g., N-vinyl-2-pyrrolidone) and a metal ion (e.g., Cu(II)). Optimized molecularly imprinted sensor layers lead to selectivity factors of at least 2 compared to other bivalent ions. In the same way, H-bonds can be utilized for such sensing purposes, as shown in the case of Escherichia coli. The respective molecularly imprinted polymer leads to the selectivity factor of more than 5 between the W and B strains, respectively. Furthermore, nanoparticles with optimized Pearson hardness allow for designing sensors to detect organic thiols in air. The ‘harder’ MoS₂ yields only about 40% of the signals towards octane thiol as compared to the ‘softer’ Cu₂S. However, both materials strongly prefer molecules with -SH functionality over others, such as hydrocarbon chains. Finally, selectivity studies with wheat germ agglutinin (WGA) reveal that artificial receptors yield selectivities between WGA and bovine serum albumin that are only about a factor of 2 which is smaller than natural ligands.     

α-Bi2O3/β-Ni(OH)2 composites: Effective solar light photocatalysts for organic pollutants degradation

α-Bi₂O₃/β-Ni(OH)₂ composites exhibited perfect photocatalytic properties for organic pollutants degradation under sunlight irradiation. Pure α-Bi₂O₃ and β-Ni(OH)₂ were prepared by coprecipitation method and then mechanically mixed in different proportions to form α-Bi₂O₃/β-Ni(OH)₂ composites. The XRD and FTIR analyses have well emphasized the formation of monoclinic α-Bi₂O₃ and hexagonal β-Ni(OH)₂ phases with high crystallinity. The SEM micrographs of α-Bi₂O₃ and β-Ni(OH)₂ powders displayed a rod and sheet shaped grains, respectively. The band gap of the pure α-Bi₂O₃ was estimated to be 2.87 eV. Pure β-Ni(OH)₂ revealed three absorption bands in the UV–visible light region. α-Bi₂O₃/β-Ni(OH)₂ composites have a more intense absorption in the visible light region compared to pure α-Bi₂O₃ sample. Modification of α-Bi₂O₃ by β-Ni(OH)₂ induced a superior photocatalytic activity especially at β-Ni(OH)₂ content of 12 wt% in α-Bi₂O₃ (BN-12 composite). This composite showed high efficiencies of 99%, 96%, 91% and 90% for methylene blue, Congo red, methyl orange and 4-niropheniol degradation in 80, 80, 180 and 300 min under sunlight irradiation, respectively. The remarkable photocatalytic activity of the α-Bi₂O₃/β-Ni(OH)₂ composite was attributed to the new states in charge separation, charge transportation and the intensive absorption of visible light. α-Bi₂O₃/β-Ni(OH)₂ composite (BN-12) has a great potential in removing of cationic and anionic dyes beside phenolic compounds from wastewater.     

DyCrxFe(1-x)O3 nanoparticles prepared by wet chemical technique for photocatalytic applications

DyCr_xFe_(1-x)O₃ (0 ≤ x ≥ 0.4) nanoparticles were prepared using facile chemical route. Structural and morphological evaluation was carried out using X-ray diffraction (XRD) and electron microscopy. Formation of orthorhombic DyFeO₃ nanoparticles was confirmed by XRD with crystallite size of 9–10 nm. FESEM images revealed nearly spherical morphology of the fabricated nanoparticles. Energy dispersive X-ray (EDX) technique was employed to confirm the presence of Dy, Cr, Fe and O elements in DyCr_xFe_(1-x)O₃ nanoparticles. FTIR studies illustrated the presence of characteristics stretching and bending vibrations. UV–visible spectroscopy was used to analyze the photocatalytic performance of the DyFeO₃ and Cr-substituted DyFeO₃ nanoparticles and optical band gap measurements. Photocatalytic activities of the prepared substituted and un-substituted DyFeO₃ nanoparticles were conducted using three different dyes. These dyes were (i) methyl orange, (ii) rhodamine B and (iii) methylene blue. Lower band gap and higher photocatalytic performance was observed for Cr-substituted DyFeO₃ nanoparticles with methylene blue dye.