HEAVY METALS REMOVAL IN A RAPID INFILTRATION SAND COLUMN

ABSTRACT

Sand filtration has been used as a cost-effective tertiary treatment process for sewage and wastewaters. However, little information is available on the performance of the process for heavy metals removal. In this project, the effect of a rapid infiltration sand filtration system on the removal of total organic carbon (TOC) phosphorus, Cd, Cu, Pb, and Zn from a mixed industrial and domestic wastewater was evaluated. To facilitate observation of the system behavior under varied conditions, the influent samples were also subjected to extreme pH values. Further studies were conducted to determine the effects of calcium carbonate addition for heavy metals precipitation prior to application onto the sand column. The results revealed that sand filtration was remarkably successful in removing phosphorus from wastewater under all conditions. The data further confirmed that in a sand filtration process, the mechanism of phosphorus removal was mainly due to chemical precipitation. Under neutral pH conditions, TOC, Cd, and Cu, were removed in the order of 20%, and Pb, and Zn were about 35–40% removed. Addition of a chemical precipitant such as calcium carbonate increased the pollutant removal to about 50%. At pH values below 2.4 and above 11.0, the TOC and all the metals showed an increase in concentration in passing through the sand column.     

化学液气相渗透致密快速制备炭/炭复合材料

探索了一种的炭/炭制备方法-快速化学液气相渗透致密(CLVD),沉积时间3h内可获得密度达1.74g/cm3的炭/炭材料.预制体为环形炭毡制件(160mm×80mm×10mm),以液态低分子有机物(CYH和KEE)作炭源前躯体,将预制体浸泡在液体炭源前驱体中,利用辐射加热,在预制体范围内造成由内而外的温度梯度.研究表明,在900℃～1100℃沉积温度范围内,炭纤维表面最大沉积速率为64μm/h,比等温CVI的沉积速率 (0.1μm/h～0.25μm/h)快2个数量级以上.同时,分析并提出了该方法快速致密多孔预制体的机理.     

腊山残留巨石柱超深孔控制爆破

在城市内破损山体治理中,通过采用深孔控制爆破、毫秒延时起爆网路及合理的爆破参数,防止了爆破飞石、降低了爆破振动,保证了爆破效果。本工程成功地对残留巨石柱进行了一次性爆破,可供类似工程借鉴。     

腊山残留巨石柱超深孔控制爆破

在城市内破损山体治理中,通过采用深孔控制爆破、毫秒延时起爆网路及合理的爆破参数,防止了爆破飞石、降低了爆破振动,保证了爆破效果。本工程成功地对残留巨石柱进行了一次性爆破,可供类似工程借鉴。     

THE EFFECT OF TARTRATE, A WEAK COMPLEXING AGENT, ON THE REMOVAL OF HEAVY METALS BY SULFIDE AND HYDROXIDE PRECIPITATION

Industrial vastevaters generated in the electroplating and metal finishing industries typically contain toxic heavy metals. Depending on their origin, these wastewaters may also contain chelating agents, such as EDTA, NTA, citrate, tartrate, and gluconic acid. Although the major effect of complexation is an increase in the solubility of complexed metal ions, significant changes in the precipitation kinetics and particle size distribution may also contribute to the observed precipitation behavior.

This paper addresses the effect of a weak complexing agent, tartrate, on the removal of zinc and cadmium using both hydroxide and sulfide treatment. Results are presented on the removal of heavy metals from synthetic plating wastewaters. Poor zinc removals were observed in the presence of tartrate, particularly when larger filter pore sizes were employed. The results suggest that tartrate severely hinders both zinc hydroxide and zinc sulfide precipitation, resulting in the formation of very fine precipitates; this was confirmed when no zinc removal occurred even with a settling time of 30 min. For removal of cadmium, virtually no change in residual cadmium concentration was observed in the presence of tartrate (compared to the case of no complexing agents present) due to the formation of low-stability complexes.     

化学液气相渗透致密快速制备炭/炭复合材料(英)

探索了一种的炭／炭制备方法快速化学液气相渗透致密（ Ｃ Ｌ Ｖ Ｄ）,沉积时间３ ｈ 内可获得密度达１．７４ ｇ／ｃｍ ３ 的炭／炭材料。预制体为环形炭毡制件（１６０ ｍ ｍ ×８０ ｍ ｍ ×１０ ｍ ｍ ）,以液态低分子有机物（ Ｃ Ｙ Ｈ 和 Ｋ Ｅ Ｅ）作炭源前躯体,将预制体浸泡在液体炭源前驱体中,利用辐射加热,在预制体范围内造成由内而外的温度梯度。研究表明,在９００℃～１ １００℃沉积温度范围内,炭纤维表面最大沉积速率为 ６４ μｍ ／ｈ ,比等温 Ｃ Ｖ Ｉ的沉积速率 （０．１ μｍ ／ｈ～０．２５ μｍ ／ｈ）快２ 个数量级以上。同时,分析并提出了该方法快速致密多孔预制体的机理。     

SELECTIVE REMOVAL OF METALS FROM WASTEWATER USING AFFINITY DIALYSIS

ABSTRACT

In this paper, a new technique called “Affinity Dialysis” has been studied for removal of metal ions from solution using a membrane reactor. The basic technique requires a solution of macromolecular agents in water, which are capable of rapidly complexing metal ions. The macromolecular agent solution flows through the tube side of a hollow fiber dialysis membrane unit, with wastewater flowing through the shell side. Quantitative removal rates for metal ions can be achieved in a compact unit. The macromolecular agent can be regenerated by changing the pH of the solution. An experimental study and a detailed mathematical model for the affinity dialysis system are presented with examples using actual kinetic and permeation data.     

SELECTIVE REMOVAL OF METALS FROM WASTEWATER USING AFFINITY DIALYSIS

In this paper, a new technique called “Affinity Dialysis” has been studied for removal of metal ions from solution using a membrane reactor. The basic technique requires a solution of macromolecular agents in water, which are capable of rapidly complexing metal ions. The macromolecular agent solution flows through the tube side of a hollow fiber dialysis membrane unit, with wastewater flowing through the shell side. Quantitative removal rates for metal ions can be achieved in a compact unit. The macromolecular agent can be regenerated by changing the pH of the solution. An experimental study and a detailed mathematical model for the affinity dialysis system are presented with examples using actual kinetic and permeation data.     

楼板系统对去柱后钢框架梁的轴向约束刚度研究

钢梁两端约束刚度对其悬链线效应影响很大,因此钢梁悬链线效应中约束刚度的研究是一个重要的内容。该文研究“双跨钢梁”两端的钢梁、楼板以及栓钉连接件对钢梁的轴向约束作用。首先,提出提供约束的钢梁、楼板以及栓钉连接件的非线性位移和变形函数。其次,利用最小势能原理,推导楼板系统对去柱钢框架梁轴向约束刚度的计算公式。考虑提供约束的楼板总是局限在一定范围内,提出并使用楼板“临界长度”对理论公式进行了修正。最后,采用20 个有限元算例对理论公式进行算例验证,证明了该文研究结论的可靠性。     

纳晶金属材料氢脆的微观力学模型

针对纳晶金属材料的氢脆问题,该文提出一个新的理论模型。在该模型的理论框架内,认为堆积在距裂纹尖端最近晶界上的氢原子会阻止位错从裂纹尖端的发射,从而抑制裂纹的钝化,同时促进纳晶金属材料的脆性断裂。该文在有氢和无氢两种条件下,对纳晶镍的临界应力强度因子与晶粒尺寸之间的相互关系进行了对比。结果表明：由于氢原子的脆化作用,纳晶镍的临界应力强度因子下降30％之多,这种氢致纳晶金属材料脆化的现象随其晶粒尺寸的变小而愈加显著。     

基于抽柱法的无粘结预应力装配式框架结构连续倒塌分析

为研究无粘结预应力装配式框架结构的防连续倒塌性能,首先采用有限元软件OpenSees中的梁柱节点单元模拟无粘结预应力梁柱节点,并与试验结果进行对比,然后采用抽柱法对一栋6层无粘结预应力装配式框架结构和现浇框架结构进行连续倒塌分析,得到了抽柱后关键构件的内力时程曲线和失效点的竖向位移时程曲线,最后模拟了无粘结预应力装配式框架结构和现浇框架结构的连续倒塌过程。研究结果表明：在抽除中柱后,无粘结预应力装配式框架结构的倒塌荷载极限值比现浇框架结构高24.2%;在抽除边柱后,无粘结预应力装配式框架结构的倒塌荷载极限值比现浇框架结构则高35.7%。在柱截面尺寸和配筋相同、梁截面尺寸和受弯承载力相同的情况下,无粘结预应力装配式框架结构防连续倒塌性能优于现浇框架结构。     

高温铝熔液在旋转多孔介质内的渗透与瞬态固化和再熔过程

针对离心渗铸板材工艺中金属铝熔液在旋转的Al₂O₃预型体内的充型过程,考虑离心惯性力对金属铝熔液的瞬态固化与再熔过程的影响,研究了伴随有瞬态固化和再熔现象的流场温度分布以及熔融区长度和固化率瞬态变化规律,推导了渗透界面和再熔界面移动速度计算公式,建立了界面速度与温度的耦合关系。结果表明:当Al₂O₃颗粒预热温度低于铝熔化温度时,渗透过程出现了瞬态固化和再熔现象,液固共熔区随渗透过程不断向前推进,共熔区长度和固化率随渗透过程而增长。随着孔隙率和转速的减小,共熔区内固化率提高,渗透前沿和再熔前沿界面移动速度减小。但孔隙率的减小使两种界面移动速度差值增大,液固共熔区长度增长;而转速的减小使两种界面移动速度差值缩小,液固共熔区长度缩短。     

快速凝固对Ni基高温合金中碳化物的影响

对常规铸态凝固和快速凝固高温合金中 MC 型碳化物的观察、分析表明,快速凝固后碳化物的形态、尺寸、成分和分布都发生了明显变化,这些变化对合金的高温力学性能有可能产生重要影响。     

FAILURE MECHANISMS IN IMPACT FATIGUE OF METALS

Abstract Impact fatigue tests were performed with smooth and notched specimens of low carbon steels under various impact loading conditions. The characteristic failure mechanisms in impact fatigue was discriminated by comparison with those in non-impact, ordinary fatigue. The fatigue life of smooth specimens was uniquely related to the range of plastic strain at the middle of the fatigue life in both impact and non-impact fatigue, although the characteristics of micro-structural deformation and cyclic stress-strain relationships were markedly different. The growth rate of a fatigue crack in impact fatigue of notched specimens was higher than that in non-impact fatigue when compared at the same stress intensity factor. Fractographic observations with scanning electron microscopy and the X-ray diffraction technique revealed more abundant cleavage facets and a smaller spread of the plastic zone beneath the fracture surface made by impact fatigue. Both nucleation and propagation lives in notched specimens were much shorter in impact fatigue than in non impact fatigue when compared at the same values of nominal stress and stress concentration factor.     

爆炸复合材料中金属的强化

用大量的强度性能数据讨论了爆炸复合材料中金属的强化问题。指出 ,这种强化是明显的 ,表现在复合材料总体强度的提高和基材各自强度的提高两个方面 ;这种强化的程度与爆炸焊接工艺参数和基材本身的强化趋势有关 ;这种强化的合理利用、减轻和消除的方法 ,以及引起强化的原因和规律的探讨 ,是爆炸焊接应用和理论研究的重要课题     

STRESSES IN A RAPID FLOW OF SPHERICAL SOLID WITH TWO SIZES

Existing theories that predict the stress-strain rate relationship in a rapidly sheared granular flow can only treat materials that are made of single-size particles. However, granular flows usually involve materials of mixed sizes. It has been observed in many laboratory studies that size distribution has a significant effect on the flow of a granular material. Despite its importance, there has been no quantitative theory that can explain the effect of size distribution. An analytical model is developed here to quantify the stresses in a mixture of spheres with two different sizes and identical material properties. Binary collisions between adjacent particles are considered as the dominating stress-generating mechanism. Comparisons between the theoretical results and the existing laboratory data show good agreement.     

DISLOCATION-FREE ZONE AHEAD OF CRACK-TIP IN METALS

本文对材料断裂研究中的裂纹尖端形变行为,特别是裂纹尖端无位错区的研究作了简要评述。其中包括:一些薄膜金属,如Al,Cu,Nb,Fe,W 和Mo 等,裂纹尖端在变形时的位错发射和无位错区存在的实验事实;裂纹尖端位错的屏蔽与反屏蔽概念的引进;材料断裂研究中无位错区模型的引进和描述;延-脆断裂转变的判据。     

天然混合沙运动速度特征的风洞PIV实验

采用PIV（Particle Image Velocimetry）系统测量了天然混合沙风沙两相流中沙粒的速度分布特征,得到了沙粒入射以及起跳的速度分布情况,并且分析了沙波纹对风沙运动的影响。结果表明：沙粒运动过程中的速度分布与沙粒起跳速度的分布可以应用对数正态分布来表明;当有沙波纹存在时,沙粒总体速度分布与平坦沙床面差...