Lead oxide hydroxide clusters in Pb9O(OH)4A,zeolite A exchanged with Pb2+ at Ph 6.0

The crystal structure of Pb₉O(OH)₄A, zeolite 4A exchanged with Pb²⁺ at pH 6.0 and evacuated at 26°C, has been determined by single-crystal X-ray crystallography. Two separate (Pb²⁺, OH⁻, O²⁻) clusters were found. In each sodalite unit, a (Pb²⁺)₃(O²⁻)(OH⁻)₃ cluster, a distorted Pb₄O₄ cube with one Pb²⁺ missing, coordinates via its oxygens to four Pb²⁺ ions at 6-ring sites to give [Pb₇O(OH)₃]⁹⁺. In half of the large cavities, a [Pb₂(OH)₂]²⁺ cluster may have formed. The remaining Pb²⁺ ion is near the center of an 8-ring. The oxygen positions are somewhat uncertain, and the presence of hydrogen atoms is inferred.     

Inhibitory effects of odor substances,geosmin and 2-methylisoborneol,on early development of sea urchins

Geosmin (1α,10β-dimethyl-9α-decanol) and 2-methylisoborneol ((1-R-exo)-1,2,7,7-tetramethyl-bicyclo-(2,2,1)-heptan-2-ol) (MIB) are volatile terpene derivatives, and have received a great deal of attention because they can cause musty/muddy off-flavor in water and food resources. By the Ames test, these metabolites showed no mutagenicity but antimicrobial activity toward tester strains. While these compounds are produced by various organisms living in aquatic environments, there are few reports of their effects on aquatic organisms. The effects of geosmin and MIB on sea urchin development were examined. The estimated IC₅₀ (50% inhibitory concentration) values for the formation of the fertilization membrane were 16.67 mg geosmin l⁻¹ and 68.77 mg MIB l⁻¹; those for the cell cleavage were 16.58 mg geosmin l⁻¹ and 66.86 mg MIB l⁻¹, suggesting that the toxicity of geosmin and MIB toward sea urchins are comparable to their toxicity toward Salmonella tester strains in the Ames test. These values are far greater than concentrations of these substances observed in aquatic environments with severe muddy off-flavor problems.     

Degradation of pentachlorophenol (PCP) by Arthrobacter strain ATCC 33790 in biofilm culture

Degradation of pentachlorophenol (PCP) by Arthrobacter strain ATCC 33790 naturally immobilized on glass beads in a column was studied. PCP was removed from mineral salts medium 4–5 d after inoculation of the column with PCP-acclimated cells grown in batch culture. Adherence to the glass occurred with production of extracellular polymer. The laboratory reactor operated without aseptic precaution for over 300 d employing a feed containing 12–366 mg/l PCP as the predominant carbon source. Transient studies were done with both ammonia and nitrate in the feed. With ammonia in the feed the system lost its ability to respond effectively to step increases in PCP feed concentration from 12–170 mg/l within 4 months. After 6 months, even at very low flow rate, the column was unable to efficiently remove PCP after 2 abrupt increases in hydraulic load. The presence of 120 mg/l nitrite in the effluent indicated that nitrification caused deterioration in column performance. Replacement of the ammonia in the feed with nitrate reestablished PCP removal efficiency. Effluent concentrations were typically less than 1 mg/l with 20 mg/l in the feed. In transient studies the amplitude of response to 5 step increases in feed concentration of 20–150 mg/l decreased in time from 91.5 to 11 mg/l. The column responded well to a step increase from 20 to 366 mg/l but was stunned following a subsequent step change from 20 to 1000 mg/l.     

给水管网硝化作用控制方法研究进展

介绍了氯胺消毒管网中的硝化作用及其控制方法,并对控制方法进行了总结和展望。在采用氯胺消毒的给水管网中,存在着硝化反应发生的可能性。硝化作用会造成出水亚硝酸盐含量升高、消毒剂含量降低、异养菌繁殖等危害。国内外对氯胺消毒管网中硝化作用控制方法的研究主要集中在改变出厂水水质条件-pH、提高消毒剂的浓度、优化氯胺投加方式、管道冲洗、硝化潜能曲线及投加亚氯酸根控制硝化作用。目前以上的控制方法对硝化作用起到了一定的抑制作用,但是存在控制效果不确定、不具有长期性或者增加生成消毒副产物的风险。因此,对硝化作用的控制方法有待深入研究。笔者提出了氯胺、二氧化氯联合消毒控制硝化作用的方法。     

Experimental determination and numerical prediction of mechanical properties of injection molded self-reinforcing polymer composites

A novel method to calculate the distribution of tensile modulus of injection molded PET/LCP blends across the thickness of the mold cavity has been developed, based on the generalized Halpin–Tsai composite model, but with a variable fiber aspect ratio. Using this method, we are able to make a number of predictions regarding the effects of melt temperature, mold temperature, injection speed, and LCP volume fraction on the moduli of the injection molded blends. Our predictions show that in order to optimize the reinforcement effect of the in-situ formed LCP fibers in the blends, low mold temperature and low injection speed are required. These results are in good agreement with experimental results.     

巯基修饰的超高交联树脂对酚类化合物的吸附

对超高交联聚苯乙烯树脂进行巯基修饰,对比大孔吸附树脂(Amberlite XAD-4)对苯酚、对甲苯酚、对氯苯酚、对硝基苯酚在水溶液中进行吸附研究。经过巯基修饰的超高交联聚苯乙烯树脂(JN-8)具有亲水性高、对酚类化合物吸附容量大的优点,该树脂可望在高浓度含酚废水治理中得到应用。     

Effect of flow conditioners on water sorption and flow properties of egg powder

Water sorption and flow properties of whole egg powder with and without flow conditioners were studied. Flow conditioner silica and sodium silico-aluminate improved the egg powder's flowability due to particle surface modification. Addition of the conditioners appears to eliminate the hysteresis loop. Moisture uptake by powders with flow conditioners was greater than by those without.     

Development of a novel modified EGSB reactor for municipal sewage treatment at ambient temperatures

A novel modified expanded granular sludge bed(EGSBm) reactor was developed for anaerobic treatment of municipal sewage with mixed liquid recirculation instead of effluent recirculation commonly adopted by a conventional EGSB(EGSBc) reactor.Performances of these two reactors were compared in treating municipal sewage at ambient temperatures ranging from 8 to 26 ℃.At an upflow liquid velocity(Vup) of 10.3 m/h,the mean concentrations of filtrated COD(CODfilt) and COD of the EGSBm effluent were determined to be 59.4 and 95.9 mg/L,respectively,which were significantly lower than those of the EGSBc effluent operated under identical experimental conditions.When the organic loading rate was suddenly increased from 1.2 to 7.2 kg COD/(m3·d),the EGSBm regained the removal efficiency of previous operation phase in 10 d.Hydrodynamic characteristics of the reactors were compared using the residence time distribution(RTD) model.It was found that the treatment efficiency of EGSBm kept increasing as the Vup increased.The polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis(PCR-DGGE) technique was used to analyze the microbial diversity in EGSBm.Fingerprinting pattern indicated that some species in the inoculating sludge were still reserved in the granular sludge of EGSBm,moreover,several new species occurred.