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A novel membrane distillation concentration method was used to prepare high concentration polyaluminum chloride (PACl) with
high content of Alb or Alc. 2.52 mol/L PACl1 with 88% Alb and 2.38 mol/L PACl2 with 61% Alc were successfully prepared. Three
coagulants, AlCl3, PACl1 and PACl2 were investigated on their hydrolysis behavior and speciation under di erent conditions. The
e ects of pH and dilution ratio on Al species distribution were investigated by ferron assay. Experimental result showed that pH had a
significant e ect on Al species distribution for the three coagulants. Dilution ratio had little e ects on Alb and Alc distribution in whole
dilution process except the beginning for PACl1 and PACl2. The results indicated that transformation of Al depends largely on their
original composition. AlCl3 was the most unstable coagulant among these three coagulants during hydrolysis process. PACl1 and PACl2
with significant amounts of highly charged and stable polynuclear aluminum hydrolysis products were less a ected by the hydrolysis
conditions and could maintain high speciation stability under various conditions. 相似文献
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混凝过程产生的絮体会对后续膜过滤性能产生一定的影响。实验中利用激光粒度仪研究2种混凝剂(AlCl3和PAC)在不同投加量下的絮体性质,混凝出水(不经过沉淀)直接进入纳滤膜(NF270)装置进行过滤实验。研究表明,投加量低(<0.20 mmol/L)的情况下,混凝出水反而使纳滤通量衰减发生恶化,随着投加量的增加,纳滤膜通量衰减得到有效的减缓。直接过滤腐殖酸(HA)的膜通量衰减(J/J0)为0.65,投加量为0.50 mmol/L时,AlCl3和PAC 2种混凝剂产生的通量衰减(J/J0)分别为0.78和0.75。滤饼层阻力受到絮体尺寸的影响较大,絮体尺寸越大,形成的滤饼层透水性更好。通过污染模型分析,混凝出水的纳滤膜污染机理主要是滤饼层阻力。 相似文献
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广州市夏、冬季室内外PM2.5质量浓度的特征 总被引:5,自引:1,他引:5
2004年7月2日至8月13日和2004年11月29日至2005年1月6日分别在广州市3种类型区域(一般城市区域、道路旁、工业源附近)9个居民住宅的室内和室外同步采集了PM2.5颗粒.采用标准称重法测定PM2.5质量浓度,得到广州市夏季住宅室内外PM2.5平均质量浓度分别为67.7、74.5 μg/m3,冬季室内外PM2.5平均质量浓度分别为109.9、123.7 μg/m3.广州市PM2.5平均质量浓度,与美国PM2.5标准相比,与国内PM10标准基础上假设的PM2.5限值相比,与其他一些国内、亚洲和欧美城市的文献记录相比,结果均显示广州市PM2.5处于相当严重污染状态.广州市PM2.5质量浓度呈现明显的空间分布特征和季节变化特征;PM2.5室内质量浓度并不总是低于室外质量浓度,反映了室内空气污染的存在. 相似文献
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Copper and zinc induction of lipid peroxidation and effects on antioxidant enzyme activities in the microalga Pavlova viridis (Prymnesiophyceae) 总被引:2,自引:0,他引:2
The metal-induced lipid peroxidation and response of antioxidative enzymes have been investigated in the marine microalga Pavlova viridis to understand the mechanisms of metal resistance in algal cells. We have analyzed superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX) activities and glutathione (GSH) contents in microalgal cells grown at different concentrations of copper and zinc. In response to each metal, lipid peroxidation was enhanced with the increase of concentrations, as an indication of the oxidative damage caused by metal concentration assayed in the microalgae cells. Exposure of P. viridis to the two metals caused changes in enzyme activities in a different manner, depending on the metal assayed: after copper treatments, total SOD activity was enhanced, while it was reduced after zinc exposure. Copper and zinc stimulated the activities of CAT and GSH whereas GPX showed a remarkable increase in activity in response to copper treatments and decrease after zinc treatments. These results suggest that an activation of some antioxidant enzymes was enhanced to counteract the oxidative stress induced by the two metals. 相似文献
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A novel polyamide (PA) thin film nanocomposite (TFN) membrane modified with Beta (β) zeolite was prepared by interfacial polymerization on a poly (ether sulfone) (PES) ultrafiltration membrane. Compared with the PA thin film composite (TFC) membrane, the introduction of β zeolite with porous structure notably increased the water flux of TFN membrane. Because the β zeolite with tiny-sized and well-defined inner-porous acted as prior flow channels for water molecules and a barrier for the sulfate ions. The successful introduction of β zeolite into the (PA) selective layer and their dispersion in the corresponding layer were verified by scanning electron microscope (SEM) and atomic force microscopy (AFM). Water contact angle, zeta potential measurements were used to characterize the changes of membrane surface properties before and after incorporating the β zeolite. With the β zeolite introducing, the water contact angle of modified TFN membrane was decreased to 47.8°, which was benefited to improve the water flux. Meanwhile, the negative charges of the modified TFN membrane was increased, resulting in an enhancement of separation effect on SO42? and Cl?. In term of nanofiltration (NF) experiments, the highest pure water flux of the TFN membranes reached up to 81.22 L m?2 hr?1 under operating pressure of 0.2 MPa, which was 2.5 times as much as the pristine TFC membrane. 相似文献
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外港河是秦淮河重要支流,长期以来遭受严重污染。2006年4月份起对外港河进行了综合生态治理。在前期清淤和截污的基础上,7月份开始引种凤眼莲。在上游排污口附近和外港河河口段分别设置的4个生态区以及河面上布设的水面载体内全面放养以凤眼莲为主的浮水植物。经过5个多月的初步治理,外港河水体透明度从40cm以下提高到120cm左右,COD下降了70.4%,TSS、TN和NH3-N分别下降了39.6%、49.7%和21.8%。结果证明,凤眼莲在净化严重污染的河道方面起到了良好的效果,引种凤眼莲治理城市重污染河道是切实可行的;此外,用PVC管设计制作的水面载体来放养浮水植物可以点缀水面环境,美化城市河道景观。 相似文献
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