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.     

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     

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...     

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.     

A CALCULATION OF THE THRESHOLD STRESS INTENSITY RANGE FOR FATIGUE CRACK PROPAGATION IN METALS

Abstract— In this paper the strain distribution and the plastic zone size at a fatigue crack tip are discussed. From this analysis and considering the critical condition for plastic-blunting, a simple analytical formula for calculating the threshold stress intensity range for fatigue crack propagation at R= 0 is proposed. It is found that calculated values are in good agreement with existing experimental results.     

高密度聚乙烯在砂浆中磨蚀的研究

自制了一台有６只臂的旋臂式磨蚀仪，旋臂上的样条座可使样条只在指定的有效磨蚀面积上发生磨蚀。磨蚀试验相对误差约为３０％。实验结果在明，高密度聚乙烯５０００Ｓ、６０９８的磨蚀无差别，仅为Ａ３钢的１／８。这３种样品皆在３０～４５°冲击角度时有最大磨蚀。     

HOLOGRAPHIC STUDY OF FATIGUE DEFORMATION AND CRACK GROWTH IN METALS

Abstract— Changes in optical correlation intensity ( I _c) are observed during fatigue cycling of 2024-T3 aluminum alloy. Topographic changes such as slip band development, microcracking, and crack propagation, observed in situ during fatigue cycling cause corresponding changes in correlation intensity. A three-stage curve of log ( I _c) vs number of fatigue cycles is observed. Metallographic observations show that region A corresponds to progressive roughening of the specimen surface caused by slip together with a rapid increase in the number of microcracks up to about 10 μm in length. Few metallographic changes are observed during region B where the correlation intensity remains relatively constant. The metallographic observations show that the accelerating loss of correlation intensity during region C is caused by propagation of cracks more than about 10 μm in length. The loss in correlation intensity during region C arises from the elastic and plastic displacements which occur as the crack length increases. At the present sensitivity of the experiments, crack growth to a length of a few hundred microns causes correlation intensity losses as great as four orders of magnitude or more. The correlation intensity readings during region C are sensitive to factors such as crack branching and crack-tip plasticity as well as to the overall increase in crack length. The total loss in correlation intensity from the beginning of a test to a crack length of about 800 μm can be more than eight orders of magnitude. The optical correlation technique is an extremely sensitive method of detecting remotely, in air, both deformation and fatigue crack growth.     

一种带边柱的钢筋混凝土剪力墙空间非线性分析模型

基于纤维模型概念,提出了一种便于钢筋混凝土高层框架-剪力墙结构空间非线性分析的带边柱剪力墙单元模型。将墙体和边柱视作一个整体单元,导出了相应刚度矩阵。用细分的纤维元模拟混凝土和钢筋的线性和非线性特性,墙元用平面纤维元模拟,柱元用空间纤维元模拟,在考虑墙、柱构件各自受力特点的同时,保证了模型的整体协调性。编制了可应用于钢筋混凝土高层框架-剪力墙结构空间分析的计算机程序。两个算例证明了该文模型的正确性和有效性。     

大型支承辊置裂原因分析

大型支承辊在放置时自然断裂，采用化学分析、金相检验和扫描电镜等手段对断裂支承辊进行了套料取样分析，结果表明．辊身心部较高的内应力和在带状碳化物中存在严重的网状碳化物是造成大型支承辊置裂的主要原因。     

STRESSES IN A RAPID, SIMPLE SHEAR FLOW OF GRANULAR MATERIALS WITH MULTIPLE GRAIN SIZES

A dense mixture of multiple-size disks or spheres are considered to flow in a simple shear motion. The stresses generated by the binary collisions among the particles are derived. It is quantitatively shown that as the size gradation widens, the stress reduction increases. A log-normal size distribution is used to demonstrate the effect of increasing standard deviation.