废电池中氧化锰还原冶炼锰钢的实验研究

为促进我国锌锰废电池集中资源化处理,开发了一种高温回收废电池中锰的新工艺.废电池分选后,破碎和筛分,其中二氧化锰与还原剂碳制成球团,烧结后在感应炉中还原锰,制成锰钢.实验表明,球团中不加表面活性剂的二氧化锰还原率为34%,球团中加入硫化物表面活性剂促进二氧化锰在钢中的还原率,达到80%,钢液中锰含量可达3.97%,本实验条件下,还原最佳时间为20 min.在铸钢生产中可以直接应用该工艺处理废电池.     

巢湖湖岸砂石的磷吸附特性研究

以巢湖湖岸上富含铁、铝、锰等元素的砂石为实验材料,研究其对水体中磷的吸附效果。实验表明:在砂石对磷的吸附过程中,同时存在着物理吸附和化学吸附,且以化学吸附作用为主,符合准二级动力学模型;砂石对磷的作用与溶液初始磷浓度有关,磷释放与吸附的临界浓度点约为0.04 mg/L;砂石对磷的吸附符合Langmuir等温吸附方程,最大吸附量约为1 428.57 mg/kg,对磷的吸附效果比普通沙石要好,且经济易得。     

微波法处理含铬废渣的可行性分析

微波辐照解毒铬渣是一项新技术,为考察该技术应用的可行性,本文对铬渣解毒前后性状的变化进行了讨论。结果表明,该技术能较完全地使高价铬转化为低价铬,解毒渣中铬主要以三价形态存在,铬渣毒性得到消除;解毒渣浸出液中Cr6+浓度远低于国家危险废物鉴别标准,解毒渣已不属于危险固体废弃物,其在环境条件下可安全存放。说明该技术具有应用前景。     

UASB反应器处理生活污水的试验研究

采用UASB中试(100 m3/d)对生活污水处理进行了研究。试验结果表明,采用此系统处理生活污水,出水水质良好。COD的去除率在52%~83%,出水的COD值<100 mg/L以下,SS的去除率在95%左右,UASB处理生活污水的最佳停留时间为6 h。产气率在0.1 m3/d。不管停留时间在10 h、5 h,出水的氨氮、乙酸值比进水的高;钙、镁、总氮、总磷、硫酸根和硝酸根离子出水值比进水值低。     

Some Factors in Minimizing Precipitator Costs

This paper is directed to those individuals involved in design of electrostatic precipitators. The Deutsch-Anderson model is usually employed by industry for the design of electrostatic precipitators. The so-called process design variable in this approach is the total capture area in the precipitator. Unfortunately, little is available on the equipment design of this unit, i.e., the geometric arrangement of the plates that constitute the capture area and the external dimensions of the physical structure that houses the precipitator components. These are important economic considerations, and it is to this subject that this paper is directed. It is relatively easy to predict equipment costs for “off-the-shelf” electrostatic precipitators; it is more difficult to closely predict the cost for a custom-made unit, which is more often the case encountered in practice. Once the capture area is calculated, the total precipitator cost becomes a strong function of the outer casing and outer accessories of the physical system. In this paper, a model is presented that can help minimize precipitator cost. An illustrative example complements the development of the model.     

Seasonal influences on PCB retention and biotransformation in fish

There is extensive evidence that fish from waters with polychlorinated biphenyls (PCB)-contaminated sediments accumulate PCBs and related chemicals and that people who eat fish from contaminated waters have higher body burdens of PCBs and PCB metabolites than those who do not. PCBs and their metabolites are potentially toxic; thus, it is important to human health to understand the uptake, biotransformation, and elimination of PCBs in fish since these processes determine the extent of accumulation. The intestinal uptake of PCBs present in the diet of fish into fish tissues is a process that is influenced by the lipid composition of the diet. Biotransformation of PCBs in fish, as in mammals, facilitates elimination, although many PCB congeners are recalcitrant to biotransformation in fish and mammals. Sequential biotransformation of PCBs by cytochrome P450 and conjugation pathways is even less efficient in fish than in mammalian species, thus contributing to the retention of PCBs in fish tissues. A very important factor influencing overall PCB disposition in fish is water temperature. Seasonal changes in water temperature produce adaptive physiological and biochemical changes in fish. While uptake of PCBs from the diet is similar in fish acclimated to winter or summer temperatures, there is evidence that elimination of PCBs occurs much more slowly when the fish is acclimated at low temperatures than at warmer temperatures. Research to date suggests that the processes of elimination of PCBs are modulated by several factors in fish including seasonal changes in water temperature. Thus, the body burden of PCBs in fish from a contaminated location is likely to vary with season.     

低温等离子体氧化水中难降解有机物研究

实验将介质阻挡放电与电晕放电组合在同一个反应器内,实验废水为直接大红染料溶液,将高压电极上通人50 Hz交流高压电,介质阻挡放电系统的电极间距为30 mm、电晕放电系统电极间距为25 mm、电源电压20 kV,利用常压空气中形成的雾化水电极介质阻挡放电/电晕放电低温等离子体及其活性基团作用于难降解有机物分子.实验分析了...     

Small-scale spatial and temporal variance in the concentration of heavy metals in aquatic sediments: a review and some new concepts.

Uncertainty associated with data derived by the analyses of heavy metals in aquatic sediment is due to variance produced in the laboratory (precision), plus 'natural', small-scale spatial variance, (or field variance) at the sampling site. Precision is easily determined and is usually reported in contaminant studies, but field variance is poorly understood and seldom documented. It is important to have an understanding of the field variance because if small-scale spatial variance in the concentration of heavy metals is excessive, regional trends may be limited value. Similarly, if temporal change is large, the results of single synoptic surveys may be questionable and the ability to demonstrate anthropogenic contributions over time will be difficult. However, it is evident from the literature that the information needed to address problems of spatial and temporal variance in the field is beyond the resources of most researchers. Analytical precision of about 5% relative standard deviation (RSD) for heavy metal analysis is typical of a well-managed laboratory. Many studies of small-scale spatial variability made during the current investigation indicate that field variance is related to ambient energy and to the type of sedimentological environment. Total variance (analytical plus field variance) is approximately 10% RSD (mean for a suite of nine trace elements) for depositional parts of estuaries and the marine environment, but increases to about 20-35% RSD for the more dynamic parts of the estuarine environment and the fluvial system. Repeated sampling over periods of up to 7 years undertaken during the present study, indicate a similar order of magnitude for temporal variability in these sedimentological environments. A proposed scheme to provide information on field variance is to undertake small-scale spatial and temporal studies in discrete sedimentological environments in the study area after sediment sampling and characterisation has been completed. The comparatively large proportion of total variance associated with small-scale spatial and temporal variability in the field questions the often excessive cost and effort made in attempting minor reductions in analytical precision in contaminant investigations.     

Degradation reactions of a carbamate herbicide, chlorbufam: effect of soil factors

Kinetics of degradation of chlorbufam is determined in aqueous solution, in aqueous solution with humic acids, argilo-humic complexes, soil and sterile soil. The adsorption is also evaluated in this different fractions. The adsorption process has a protecting effect and the chlorbufam is not chemically degraded when it is adsorbed on organic matter. The biodisponibility is also decreased by adsorption.     

用呼吸速率控制SBR反应时问的基础研究

以人工配水为对象，研究了SBR工艺反应过程中呼吸速率的变化规律，探讨了用呼吸速率控制SBR反应时间长度的可行性，结果证明，呼吸速率在SBR反应过程中有明显特征变化可以作为SBR反应结束的标志。把呼吸速率与其他物理变量结合起来可以更加有效地控制SBR，提高其运行效率。     

Perchlorate as an environmental contaminant

Perchlorate anion (ClO4-) has been found in drinking water supplies throughout the southwestern United States. It is primarily associated with releases of ammonium perchlorate by defense contractors, military operations, and aerospace programs. Ammonium perchlorate is used as a solid oxidant in missile and rocket propulsion systems. Traces of perchlorate are found in Chile saltpeter, but the use of such fertilizer has not been associated with large scale contamination. Although it is a strong oxidant, perchlorate anion is very persistent in the environment due to the high activation energy associated with its reduction. At high enough concentrations, perchlorate can affect thyroid gland functions, where it is mistakenly taken up in place of iodide. A safe daily exposure has not yet been set, but is expected to be released in 2002. Perchlorate is measured in environmental samples primarily by ion chromatography. It can be removed by anion exchange or membrane filtration. It is destroyed by some biological and chemical processes. The environmental occurrence, toxicity, analytical chemistry, and remediative approaches are discussed.     

State of energy consumption and CO2 emission in Bangladesh

Carbon dioxide (CO2) is one of the most important gases in the atmosphere, and is necessary for sustaining life on Earth. It is also considered to be a major greenhouse gas contributing to global warming and climate change. In this article, energy consumption in Bangladesh is analyzed and estimates are made of CO2 emission from combustion of fossil fuel (coal, gas, petroleum products) for the period 1977 to 1995. International Panel for Climate Change guidelines for national greenhouse gas inventories were used in estimating CO2 emission. An analysis of energy data shows that the consumption of fossil fuels in Bangladesh is growing by more than 5% per year. The proportion of natural gas in total energy consumption is increasing, while that of petroleum products and coal is decreasing. The estimated total CO2 release from all primary fossil fuels used in Bangladesh amounted to 5072 Gigagram (Gg) in 1977, and 14 423 Gg in 1995. The total amounts of CO2 released from petroleum products, natural gas, and coal in the period 1977-1995 were 83 026 Gg (50% of CO2 emission), 72 541 Gg (44% of CO2 emission), and 9545 Gg (6% CO2 emission), respectively. A trend in CO2 emission with projections to 2070 is generated. In 2070, total estimated CO2 emission will be 293 260 Gg with a current growth rate of 6.34% y . CO2 emission from fossil fuels is increasing. Petroleum products contribute the majority of CO2 emission load, and although the use of natural gas is increasing rapidly, its contribution to CO2 emission is less than that of petroleum products. The use of coal as well as CO2 emission from coal is expected to gradually decrease.     

The study of lag phase and rate improvement of TCE decay in UV/surfactant systems

The photodegradation of trichloroethene (TCE) in surfactant micelles was investigated. The decay of TCE was studied in the Rayonet RPR-200 merry-go-round photoreactor, at 253.7 nm monochromatic ultraviolet (UV) lamps, in the presence of surfactants. Surfactants are used as additional hydrogen sources to improve the photodegradation rates of TCE. About three times the rate increment is observed in the presence of Brij 35 surfactant micelles than in water alone. The increasing concentrations of H+ and Cl- indicate that they are the final products of TCE photodegradation (i.e. photodechlorination is the dominant mechanism in this system). A lag phase is observed at the beginning of the degradation, but the duration of the lag phase is apparently reduced as the initial pH increases. Because the overall decay of TCE is also found faster at higher pH levels, it is suggested that the free radical reaction is dominant at high pH levels, and the formation of lag phases is mainly due to the deficiency of free radicals at lower pH levels. The photodecomposition of TCE in surfactant micelles is also proven to be a clean and effective process. It generates no chlorinated by-products or intermediates during the process, and TCE is fully decomposed within a reasonable time.     

三相生物流化床处理炼油厂含酚废水的实验研究

酚是一类剧毒性物质 ,是我国重点控制的污染物之一。本文利用三相生物流化床对人工含酚废水和燕山石化集团炼油厂含酚废水进行实验室模拟降解实验 ,生物颗粒使用海藻酸钠、氯化钙和从活性污泥筛选驯化的四种细菌用微生物包埋法制作。结果显示 ,在 3h时段内对酚的降解显著 ,t testP <0 .0 1。在三相生物流化床中使用微生物包埋法制作的生物颗粒处理含酚废水 ,处理效果良好 ,并且用海藻酸钠、氯化钙为主要原料制作生物颗粒可以大大降低处理成本。     

Scavenging of soluble trace gases by falling rain droplets in inhomogeneous atmosphere

We analyze non-isothermal absorption of trace gases by the rain droplets with internal circulation which is caused by interfacial shear stresses. It is assumed that the concentration of soluble trace gases and temperature in the atmosphere varies in a vertical direction. The rate of scavenging of soluble trace gases by falling rain droplets is determined by solving heat and mass transfer equations. In the analysis we accounted for the accumulation of the absorbate in the bulk of the falling rain droplet. The problem is solved in the approximation of a thin concentration and temperature boundary layers in the droplet and in the surrounding air. We assumed that the bulk of a droplet, beyond the diffusion boundary layer, is completely mixed and concentration of the absorbate and temperature are homogeneous and time-dependent in the bulk. By combining the generalized similarity transformation method with Duhamel's theorem, the system of transient conjugate equations of convective diffusion and energy conservation for absorbate transport in liquid and gaseous phases with time-dependent boundary conditions is reduced to a system of linear convolution Volterra integral equations of the second kind which is solved numerically. Calculations are performed using available experimental data on concentration and temperature profiles in the atmosphere.It is shown than if concentration of a trace gas in the atmosphere is homogeneous and temperature in the atmosphere decreases with height, beginning from some altitude gas absorption is replaced by gas desorption. Neglecting temperature inhomogenity in the atmosphere described by adiabatic lapse rate leads to essential overestimation of the trace gas concentration in a droplet on the ground.     

Potential protective effects of Spirulina platensis on liver,kidney, and brain acrylamide toxicity in rats

Environmental Science and Pollution Research - Acrylamide (AA) is a hazardous chemical that is widely used in industrial practices. Spirulina platensis (SP) is a blue green alga that is rich in...     

Determination of total arsenic content in water by atomic absorption spectroscopy (AAS) using vapour generation assembly (VGA)

Analysis of arsenic in water is important in view of contamination of ground water with arsenic in some parts of the world including West Bengal in India and neighboring country Bangladesh. WHO has fixed the threshold for arsenic in drinking water to 10ppb (microg/l) level, hence the methodology for determination of arsenic is required to be sensitive at ppb level. Atomic absorption spectrophotometry with vapour generation assembly (AAS-VGA) is well known technique for the trace analysis of arsenic. However, total arsenic analysis [As(III)+As(V)] is very crucial and it requires reduction of As(V) to As(III) for correct analysis. As(III) is reduced to AsH3 vapours and finally to free As atoms, which are responsible for absorption signal in AAS. To accomplish this the vapour generation assembly attached to AAS has acid channel filled with 10 M HCl and the reduction channel with sodium borohydride. Further sample can be reduced either before aspiration for analysis, using potassium iodide (KI) or the sample can be introduced in the instrument directly and KI can be added in the reduction channel along with the sodium borohydride. The present work shows that samples prepared in 3 M HCl can be reduced with KI for 30 min before introduction in the instrument. Alternatively samples can be prepared in 6 M HCl and directly aspirated in AAS using KI in VGA reduction channel. The latter methodology is more useful when the sample size is large and time cycle is difficult to maintain. It is observed that the acid concentration of the sample in both the situations plays an important role. Further reduction in acid concentration and analysis time is achieved for the arsenic analysis by using modified method. Analysis in both the methods is sensitive at ppb level.     

Simultaneous estimation of effective and apparent diffusion coefficients in compacted bentonite

Effective diffusion coefficients (D(e)) are usually measured by means of "through-diffusion" experiments in which steady state is reached, and the "time-lag" methods are used to estimate the apparent diffusion coefficient (D(a)). For sorbing radionuclides (as caesium), the time needed to reach steady-state conditions is very large, and the precision in D(a) determinations is not satisfactory. In this paper, a method that allows determining simultaneously effective and apparent diffusion coefficients in compacted bentonite without reaching steady-state conditions is described. Basically, this method consists of an "in-diffusion" experiment in which the concentration profile in the bentonite sample is used to estimate D(a), and the temporal evolution of the solute concentration in the reservoir is used to estimate D(e). This method has several advantages over the typical "through-diffusion" experiments, in particular: (a) experiment duration is significantly shorter, (b) D(a) values are measured with greater precision and (c) it is not necessary to maintain a constant solute concentration in the reservoir. This new method has been used to estimate the effective and apparent diffusion coefficients for caesium in FEBEX bentonite and in order to validate it, the results have been compared with results previously obtained with standard methods. Experimental results have been satisfactorily modelled using a simple model of diffusion in porewater and the measured value of D(e)(Cs) is very similar to D(e)(HTO) in the same bentonite. There is no evidence of "surface diffusion" in FEBEX bentonite for caesium.     

Optimization of Flow for Forcing Stack Wastes to High Altitudes

It is difficult to control the emission of waste products from large stacks because of the large volume of material to be handled. However, if the waste gas is projected to relatively high altitudes, the problem is less severe in that pollution products are carried to regions of low pollution density. It is especially helpful to accomplish this high altitude dispersal during periods when the air is stable and pollution buildup is most severe. In this paper it is shown that dramatic improvements in the altitude to which stack wastes rise may be obtained by emitting the effluent in discrete vortex rings rather than in steady plumes or forced jets. The parameters of vortex rings required to reach given altitudes under given conditions are calculated. The flow at the stack required to give specific vortex ring parameters is also calculated. Some comments on the type of stack needed to create the desired flow are presented.     

用呼吸速率控制SBR反应时间的基础研究

以人工配水为对象,研究了SBR工艺反应过程中呼吸速率的变化规律,探讨了用呼吸速率控制SBR反应时间长度的可行性,结果证明,呼吸速率在SBR反应过程中有明显特征变化可以作为SBR反应结束的标志.把呼吸速率与其他物理变量结合起来可以更加有效地控制SBR,提高其运行效率.