Characterization of primary precipitate composition formed during co-removal of Cr(VI) with Cu(II) in synthetic wastewater

BACKGROUND, AIMS AND SCOPE: Hexavalent chromium [Cr(VI)] cannot react with either carbonate or hydroxide to form chromium precipitates. However, by using a precipitation technology to treat plating wastewater containing Cr(VI), Cu(II), Ni(II) and Zn(II), approximately 78% of Cr(VI) (initial 60 mg/L) was co-removed with the precipitation of Cu(II), Ni(II) and Zn(II) (each 150 mg/L) by dosing with Na2CO3 (Sun 2003). Direct precipitation by forming Cu(II)-Cr(VI) precipitates followed by adsorption of Cr(VI) onto freshly formed Cu-precipitates was subsequently found to be the main mechanism(s) involved in Cr(VI) co-removal with Cu(II) precipitation by dosing Na2CO3 stepwise to various pH values (Sun et al. 2003). This study was. carried out to further characterize the formation of primary precipitates during the early stages of copper precipitation and simultaneous removal of Cr(VI) with Cu(II). METHODS: Test metal-solutions were prepared with industrial grade chemicals: CuCl2 x 2H2O, Na2SO4 and K2Cr2207. NaCO3 was added drop-wise to synthetic metal-solution to progressively increase pH. For each pH increment, removal of soluble metals was detected by atomic absorption spectrophotometer (AAS) and surface morphology of precipitates was analyzed by scanning electron microscope (SEM). To further characterize the formation of primary precipitates, a series of MINEQL+ thermodynamic calculations/analyses and equilibrium calculations/ analyses were conducted. RESULTS AND DISCUSSION: MINEQL+ thermodynamic calculation indicated that, for a system containing 150 mg/L Cu(II) and 60 mg/L Cr(VI) with gradual Na2CO3 dosing, if any precipitates can be formed at pH 5.0 or lower, it should be in the form of CuCrO4. Comparison tests using systems containing the same equivalent of Cu(II) plus Cr(VI) and Cu(II) plus SO4(2-) showed that the precipitation occurred at a pH of around 5.0 in the Cu(II)-Cr(VI) system and around 6.0 in the Cu(II)-SO4(2-) system. The discrepancy of the precipitation was indeed caused by the formation of Cu-Cr precipitates. The initiation of copper removal at pH around 5.0 for the Cu-Cr co-removal test was not attributable to the formation of Cu-CO3 precipitates, instead, it was most likely through the formation of insoluble Cu-Cr precipitates, such as CuCrO4 and CuCrO4 x 2Cu(OH)2. Experimental tests, equilibrium calculations, MINEQL+ thermodynamic calculations and surface morphologies for systems using higher concentrations of Cu(II) and Cr(VI) further verified the most probable composition of primary precipitates is copper-chromate. CONCLUSION: In the Cu-Cr co-removal test with Na2O3 dosing to increase pH and induce metal precipitation, copper-chromate precipitates are the primary precipitates produced and contribute to the initial simultaneous removal of copper and chromium.     

有机高分子絮凝剂AUF的研制及其除油效果测定

以尿素、甲醛为原料合成脲醛树脂，加入环氧氯丙烷对树脂进行改性，再加入三乙铵进行季胺化，得到改性脲醛树脂季铵盐絮凝剂AUF。在WEMCO浮选机上考察AUF的除油性能及最佳合成条件。结果表明：AUF投药量为10mg／L时，出水中油浓度达到国家排放标准；当甲醛、尿素、环氧氯丙烷三者的摩尔比为2：1：0.5，季铵化温度为80～110C，反应时间为4～5h时，得到的絮凝剂AUF除油效果最好。     

水煤浆加压气化制合成氨系统的三废排放情况及治理措施

简述了水煤浆加压气化制合成氨系统的特点，着重介绍了该系统制气工段和净化工段的三废排放情况及治理措施，并对仍存在的问题提出了看法。     

基于BP神经网络的垃圾堆放场稳定化程度的综合判别

分析和判别垃圾堆放场的稳定化程度直接关系到是否需要采取加快稳定化进程，缩短垃圾堆放场的稳定化周期以及是否需要采取措施减少它们对环境的不利影响。本文根据我国垃圾堆放场的具体情况，提出稳定化程度的判别评价指标体系，并且确定稳定化程度的判别标准，运用BP神经网络建立垃圾堆放场稳定化程度的综合判别模型。以三峡库区的一个小型垃圾堆放场为例，采用本文所提出的综合评价模型确定它的稳定化程度，演示模型的运行过程，并为三峡库区的环境保护提供帮助。     

SYL-01破乳剂的合成及性能测试

在国内外研究的基础上通过实验以MAA、AA、BuAc、MMAc为原料，采用乳液聚合的方法合成了一种新型的不含烷氧基的水溶性W／O原油破乳剂SYL-01。反应条件与反应物的用量研究表明：反应物最佳配比为AA：MAA：BuAc：MMAC＝0．75：0．25：10：4。对原油乳液的破乳实验说明：SYL－01与目前使用的9901破乳剂性能相当，脱水率较高。SYL－01原料价廉易得，不使用易燃易爆的气体原料，工艺简单，有较好的开发应用前景。     

CM-3絮凝剂的室内研制及在含油污水处理中的应用

介绍复合高分子絮凝剂CM─3的研制。CM─3是以无机高分子聚合铝（PAC）、有机高分子改性聚丙烯酰胺（APAM）为主，添加少量的硫酸根离子及破乳剂复配而成的。经室内实验研究确定了适合的PAM分子量、改性PAM的胺甲基化度、PAM与PAC的比例以及其他组分的添加量，并与PAC比较进行了室内及现场应用试验，结果表明CM─3投药量为20～30mg／L时，炼油厂含油污水处理后的水质符合GB8978─88的标准。     

Making decisions about environmental management when conventional economic analysis cannot be used

A process is described for making comparative valuations of a wide range of environmental management activities when the combined social, economic, managerial, and political benefits of some (but not all) of these activities cannot be adequately described in economic terms and when budgetary constraints do not permit funding of all activities under consideration. The process accounts for subjective judgment and contains a formal rigorous decision strategy that takes the place of intuition when quantitative and qualitative values of environmental activities need to be evaluated.     

APPLICATION OF A LOW-FLOW ASSESSMENT MODEL FOR THE MONONGAHELA RIVER BASIN1

ABSTRACT: The application of a low-flow assessment model is illustrated for the Monogahela River Basin. The model simulates the impact of reservoir operating rules and consumptive use limitation policies on low-flow frequency at downstream locations in the basin. Policies are evaluated using an observed flow sequence and synthetic flow inputs. The paper reviews the historical development of flow management on the Monogahela to provide background for the current study.     

贵阳市人工边坡稳定性模糊综合评判

在充分考虑了影响人工边坡稳定性的自然地质条件、诱发因素、人类工程活动等多项指标的基础上,用模糊综合评判方法对贵阳市近十年来发生的崩滑灾害和典型人工边坡的稳定性进行了综合分析和评价,评判结果与实际一致。     

库水作用下公路土质岸坡稳定性影响因素综合评判

以三峡库区公路土质岸坡为研究对象,通过对库水作用的影响效应分析,建立了岸坡稳定性评价的参数指标评价体系以及相应的分级标准.在此基础上,应用影响因素综合评判方法,对实例岸坡进行了稳定性分级评价,评价结果与实际情况基本相符.