Carbonaceous adsorbents from sewage sludge and their application in a combined activated sludge-powdered activated carbon (AS-PAC) treatment

In this study, waste biological sludge is converted to an adsorbent by chemical activation with sulphuric acid. The adsorbent obtained is then applied to the aerated vessel of an activated sludge process treating glucose and phenol to improve the quality of the treated effluent. The sludge-based carbonaceous adsorbent was found to be mesoporous in nature, with a good adsorption capacity for large molecular weight compounds and limited removal efficiency for smaller molecules such as phenol. The addition of carbon, either sludge-based or commercial, enhanced phenol removal from 58% to 98.7% and from 87% to 93% the organic matter removal as measured by the chemical oxygen demand (COD) when operated with feed concentrations of 100 mg phenol/l and 2500 mg COD/l. No differences were found between the activated sludge-activated carbon bench scale continuous reactors operating with either commercial or sludge-based adsorbents in spite of the higher adsorption capacity of the former. It is suggested that powdered adsorbent bioregeneration in the combined AS-PAC system may be impaired by the obstruction of pores due to bacterial growth, the effect being more important for the commercial activated carbon with a narrower pore size distribution.     

Synthesis and characterization of cleavable surfactants derived from poly(ethylene glycol) monomethyl ether

A series of noncyclic acetal-linked cleavable surfactants were simply prepared by condensation of aldehydes with poly(ethylene glycol) monomethyl ethers. All of the products were characterized by¹H nuclear magnetic resonance. Their hydrophile-lipophile balance, surface tension, cloud point, critical micelle concentration, and foam height were determined. Hydrolysis kinetic studies, followed by gas chromatography, showed that they had higher hydrolytic reactivity in acidic solution than cyclic acetal-linked cleavable surfactants.     

Particle-Substrate Collisions, Particle Rebound and Removal

Recent progress in particle capture and rebound and its effect on the adhesion force is reviewed in this paper. Particles rebound when the incident velocity is greater than a characteristic critical velocity. Lower impaction velocity particles experience elastic and plastic deformation. Recent models for particle rebound and capture are discussed and evaluated in terms of their restrictive assumptions and results. Recent experimental data of particle rebound and capture is also discussed, as is the hydrodynamic removal of captured particles. The removal of particles occurs when the applied hydrodynamic removal force overcomes the adhesion force. The effect of adhesion-induced deformation on the removal of particles is introduced and discussed.     

High molecular weight polypropylene nanospheres: Synthesis and characterization

The high molecular weight (MW) polypropylene with average particle size of 60 nm was synthesized by controlled growth mechanism using Ziegler–Natta catalyst. The atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) studies showed that PP nanoparticles were spherical in shape. Structure and crystallinity were concomitantly studied through Fourier transform infrared spectroscopy and X‐ray diffraction, respectively. It shows nanospherical PP particles with more crystallinity (～ 75%) compared with macrosized PP (～ 59%). In addition, differential scanning calorimetry studies revealed the finite particle size effect on T_g and the scale dependence T_g followed a first order exponential trend. As particle size goes down to nano‐ scale from macrosize, continuous elevation of T_g's were observed from ?25 to ?11°C. This phenomenon was directed to configuration entropy of single spherical nanoparticles of PP. The mechanical properties and surface roughness were also evaluated through AFM. At last, the properties of nanosized PP were compared with micron and macrosized particles. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

The effect of fibre-matrix interactions on structure and property changes during the fabrication of unidirectional carbon/carbon composites

This paper reports the systematic characterisation of changes in the structure and properties of a series of unidirectional carbon-carbon composites at key stages of processing. The composites were fabricated from PAN-based carbon fibres (surface treated and untreated) and two carbon matrix systems (graphitising and non-graphitising). The effects of matrix shrinkage, together with thermal expansion mismatch and interfacial bonding, established the composite structure and hence the composite properties. The morphology and interconnectivity of the shrinkage cracks, the strength and nature of the fibre-matrix interfacial interaction and the development of matrix texture were identified as key structural features. These features were characterised and their effect on subsequent processing stages (densification) and composite properties was determined.     

Dynamic mechanical properties of polycarbonate and acrylonitrile–butadiene–styrene copolymer blends

Blends of polycarbonate (PC) and poly(acrylonitrile‐co‐butadiene‐co‐styrene) (ABS) with different compositions are characterized by means of dynamic mechanical measurements. The samples show phase separation. The shift in the temperatures of the main dynamic mechanical relaxation shown by the blend with respect to those of the pure components is attributed to the migration of oligomers present in the ABS toward the PC in the melt blending process. A comparison with other techniques (dielectric and calorimetric analysis) and the application of the Takayanagi three block model confirm this hypothesis. In all the studied blend compositions (ABS weight up to 28.6%) the PC appears as the matrix where a disperse phase of ABS is present. The scanning and transmission electron microscopy micrographs show that the size of the ABS particles increases when the proportion of ABS in the blend increases. The FTIR results indicate that the interaction between both components are nonpolar in nature and can be enhanced by the preparation procedure. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1507–1516, 2002     

The Effects of Phenyltrimethoxysilane Coupling Agents on the Properties of PTFE/Silica Composites

A study on PTFE reinforced with SiO₂ was described. This study included the manufactural process of SiO₂-reinforced PTFE and the effects of the content of silane (Z6124) on the properties of the composites material, such as thermal, dielectric properties, tensile strength and morphology, etc. PTFE/silica composites of 60 wt% SiO₂ loaded with a different coupling agent content were mixed by a high-speed dispersion machine and prepared by a two-roll milling machine. Our results show that the sample treated with 3 wt% silane has the highest tensile strength and optimum dielectric properties. Furthermore, the tensile strength and coefficient of thermal expansion (CTE) increase, and the water absorption decreases, with an increasing silane content. These experiments reveal that silane treatment can reduce the overall hydrophilicity of the composites. Finally, predictions on dielectric and CTE properties are discussed. It has been found that experimental values of the dielectric constant agree well with those predicted by the rule of mixture.     

Evaluation of the thermal and mechanical properties of poly(ε‐caprolactone), low‐density polyethylene,and their blends

The thermal and mechanical properties of low‐density polyethylene (LDPE), poly(ε‐caprolactone) (PCL), and their blends were evaluated. Differential scanning calorimetry showed that increasing the PCL content of the blend did not change the LDPE melting temperature, but reduced the crystallinity by up to 16.8%. This behavior was related to interactions between the PCL chains and the crystalline phase of LDPE. Tensile strength and elongation at break values for the blends were lower than those for the pure polymers, which suggested an incompatibility between the polymers. The values for Young's modulus under tensile increased when PCL was added to LDPE. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91:3909–3914, 2004     

强震区土石坝筑坝材料动力特性试验研究(投稿研究生论坛)

土石坝筑坝材料的动力特性是进行坝工设计和动力评价的基础。以西部强震区某土石坝工程为研究对象,采用室内动三轴试验,对其坝壳料、心墙料和坝基断层料进行动力特性试验研究,并以Hardin-Drnevich模型为基础,确定筑坝材料的动弹模、阻尼比等特性参数,试验表明：在动应变在10-6 ～ 10-5 范围内,动模量与围压、固结比成正相关;随动模量的增大,相关性降低;动应变和振级的拟合指数模型则表明不同围压、固结比的心墙料的应变-振级曲线趋势一致,坝壳料较为离散;试验中固结围压对粗骨料阻尼比-应变曲线的影响较固结比大,可为强震区土石坝的动力稳定评价提供可靠的理论依据。     

对震后沙牌拱坝坝肩动力稳定性的再分析

沙牌RCC拱坝是少数经受了大地震考验的百米级高坝实例之一,对其坝肩动力稳定性的再研究意义重大。本文综合有限元法与刚体极限平衡法的优势,提出极限累积位移公式作为滑块失稳判据,开展了两种地震波作用下的沙牌坝肩动力稳定分析并对5.12地震反演的人工波开展了拱坝坝肩稳定性超载分析。结果表明,在反映5.12地震的人工波（ah=2.05 m/s2）作用下,沙牌左右坝肩稳定,与实际地震效应一致。在设计波（ah=5.31m/s2）作用下,沙牌左岸坝肩将失稳,而右岸仍稳定。进行人工波超载分析时,左岸坝肩滑块L1、L2分别经受3.2、3.6倍人工超载波时会发生滑移失稳;右岸坝肩滑块则在4.2倍超载波作用下滑移失稳。此次沙牌坝肩动力稳定再分析考虑了滑块滑移方向及安全系数瞬态变化对滑块累积位移的影响,更真实地反映了沙牌拱坝坝肩滑块滑移规律,为工程实际中的坝肩动力稳定分析提供了一个新思路。